Add char rules + fix unit test setup

See:
- https://github.com/dawidd6/action-download-artifact/compare/v2.28.0...v2.28.1

.github/ISSUE_TEMPLATE/bug_report.md

@@ -42,7 +42,7 @@ Please replace this sentence with log output, if applicable.
 <!-- Please complete the following information: -->
 
 - Operating system (e.g. MacOS Monterey).
-- Java version (i.e. `java --version`, e.g. `17.0.7`).
+- Java version (i.e. `java --version`, e.g. `17.0.8`).
 - Error Prone version (e.g. `2.18.0`).
 - Error Prone Support version (e.g. `0.9.0`).
 

.github/workflows/build.yml

@@ -10,16 +10,16 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-22.04 ]
-        jdk: [ 11.0.19, 17.0.7, 20.0.1 ]
+        jdk: [ 11.0.20, 17.0.8, 21.0.0 ]
         distribution: [ temurin ]
         experimental: [ false ]
         include:
           - os: macos-12
-            jdk: 17.0.7
+            jdk: 17.0.8
             distribution: temurin
             experimental: false
           - os: windows-2022
-            jdk: 17.0.7
+            jdk: 17.0.8
             distribution: temurin
             experimental: false
     runs-on: ${{ matrix.os }}
@@ -31,11 +31,11 @@ jobs:
       # additionally enabling all checks defined in this project and any Error
       # Prone checks available only from other artifact repositories.
       - name: Check out code
-        uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
         with:
           persist-credentials: false
       - name: Set up JDK
-        uses: actions/setup-java@cd89f46ac9d01407894225f350157564c9c7cee2 # v3.12.0
+        uses: actions/setup-java@387ac29b308b003ca37ba93a6cab5eb57c8f5f93 # v4.0.0
         with:
           java-version: ${{ matrix.jdk }}
           distribution: ${{ matrix.distribution }}

.github/workflows/codeql.yml

@@ -22,23 +22,23 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Check out code
-        uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
         with:
           persist-credentials: false
       - name: Set up JDK
-        uses: actions/setup-java@cd89f46ac9d01407894225f350157564c9c7cee2 # v3.12.0
+        uses: actions/setup-java@387ac29b308b003ca37ba93a6cab5eb57c8f5f93 # v4.0.0
         with:
-          java-version: 17.0.7
+          java-version: 17.0.8
           distribution: temurin
           cache: maven
       - name: Initialize CodeQL
-        uses: github/codeql-action/init@5b6282e01c62d02e720b81eb8a51204f527c3624 # v2.21.3
+        uses: github/codeql-action/init@407ffafae6a767df3e0230c3df91b6443ae8df75 # v2.22.8
         with:
           languages: ${{ matrix.language }}
       - name: Perform minimal build
         if: matrix.language == 'java'
-        run: mvn -T1C clean install -DskipTests -Dverification.skip
+        run: mvn -T1C clean package -DskipTests -Dverification.skip
       - name: Perform CodeQL analysis
-        uses: github/codeql-action/analyze@5b6282e01c62d02e720b81eb8a51204f527c3624 # v2.21.3
+        uses: github/codeql-action/analyze@407ffafae6a767df3e0230c3df91b6443ae8df75 # v2.22.8
         with:
           category: /language:${{ matrix.language }}

.github/workflows/deploy-website.yml

@@ -12,15 +12,15 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Check out code
-        uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
         with:
           persist-credentials: false
-      - uses: ruby/setup-ruby@250fcd6a742febb1123a77a841497ccaa8b9e939 # v1.152.0
+      - uses: ruby/setup-ruby@8575951200e472d5f2d95c625da0c7bec8217c42 # v1.161.0
         with:
           working-directory: ./website
           bundler-cache: true
       - name: Configure Github Pages
-        uses: actions/configure-pages@f156874f8191504dae5b037505266ed5dda6c382 # v3.0.6
+        uses: actions/configure-pages@1f0c5cde4bc74cd7e1254d0cb4de8d49e9068c7d # v4.0.0
       - name: Generate documentation
         run: ./generate-docs.sh
       - name: Build website with Jekyll
@@ -48,4 +48,4 @@ jobs:
     steps:
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@9dbe3824824f8a1377b8e298bafde1a50ede43e5 # v2.0.4
+        uses: actions/deploy-pages@13b55b33dd8996121833dbc1db458c793a334630 # v3.0.1

.github/workflows/openssf-scorecard.yml

@@ -21,16 +21,16 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Check out code
-        uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
         with:
           persist-credentials: false
       - name: Run OpenSSF Scorecard analysis
-        uses: ossf/scorecard-action@08b4669551908b1024bb425080c797723083c031 # v2.2.0
+        uses: ossf/scorecard-action@0864cf19026789058feabb7e87baa5f140aac736 # v2.3.1
         with:
           results_file: results.sarif
           results_format: sarif
           publish_results: ${{ github.ref == 'refs/heads/master' }}
       - name: Update GitHub's code scanning dashboard
-        uses: github/codeql-action/upload-sarif@5b6282e01c62d02e720b81eb8a51204f527c3624 # v2.21.3
+        uses: github/codeql-action/upload-sarif@407ffafae6a767df3e0230c3df91b6443ae8df75 # v2.22.8
         with:
           sarif_file: results.sarif

.github/workflows/pitest-analyze-pr.yml

@@ -12,14 +12,14 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Check out code
-        uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
         with:
           fetch-depth: 2
           persist-credentials: false
       - name: Set up JDK
-        uses: actions/setup-java@cd89f46ac9d01407894225f350157564c9c7cee2 # v3.12.0
+        uses: actions/setup-java@387ac29b308b003ca37ba93a6cab5eb57c8f5f93 # v4.0.0
         with:
-          java-version: 17.0.7
+          java-version: 17.0.8
           distribution: temurin
           cache: maven
       - name: Run Pitest
@@ -32,7 +32,7 @@ jobs:
       - name: Aggregate Pitest reports
         run: mvn pitest-git:aggregate -DkilledEmoji=":tada:" -DmutantEmoji=":zombie:" -DtrailingText="Mutation testing report by [Pitest](https://pitest.org/). Review any surviving mutants by inspecting the line comments under [_Files changed_](${{ github.event.number }}/files)."
       - name: Upload Pitest reports as artifact
-        uses: actions/upload-artifact@0b7f8abb1508181956e8e162db84b466c27e18ce # v3.1.2
+        uses: actions/upload-artifact@a8a3f3ad30e3422c9c7b888a15615d19a852ae32 # v3.1.3
         with:
           name: pitest-reports
           path: ./target/pit-reports-ci

.github/workflows/pitest-update-pr.yml

@@ -20,17 +20,17 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Check out code
-        uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
         with:
           persist-credentials: false
       - name: Set up JDK
-        uses: actions/setup-java@cd89f46ac9d01407894225f350157564c9c7cee2 # v3.12.0
+        uses: actions/setup-java@387ac29b308b003ca37ba93a6cab5eb57c8f5f93 # v4.0.0
         with:
-          java-version: 17.0.7
+          java-version: 17.0.8
           distribution: temurin
           cache: maven
       - name: Download Pitest analysis artifact
-        uses: dawidd6/action-download-artifact@246dbf436b23d7c49e21a7ab8204ca9ecd1fe615 # v2.27.0
+        uses: dawidd6/action-download-artifact@f29d1b6a8930683e80acedfbe6baa2930cd646b4 # v2.28.1
         with:
           workflow: ${{ github.event.workflow_run.workflow_id }}
           name: pitest-reports

.github/workflows/run-integration-tests.yml

@@ -0,0 +1,43 @@
+# If requested by means of a pull request comment, runs integration tests
+# against the project, using the code found on the pull request branch.
+# XXX: Generalize this to a matrix build of multiple integration tests,
+# possibly using multiple JDK or OS versions.
+# XXX: Investigate whether the comment can specify which integration tests run
+# run. See this example of a dynamic build matrix:
+# https://docs.github.com/en/actions/learn-github-actions/expressions#example-returning-a-json-object
+name: "Integration tests"
+on:
+  issue_comment:
+    types: [ created ]
+permissions:
+  contents: read
+jobs:
+  run-integration-tests:
+    name: On-demand integration test
+    if: |
+      github.event.issue.pull_request && contains(github.event.comment.body, '/integration-test')
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Check out code
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
+        with:
+          persist-credentials: false
+          ref: refs/pull/${{ github.event.issue.number }}/head
+      - name: Set up JDK
+        uses: actions/setup-java@387ac29b308b003ca37ba93a6cab5eb57c8f5f93 # v4.0.0
+        with:
+          java-version: 17.0.8
+          distribution: temurin
+          cache: maven
+      - name: Install project to local Maven repository
+        run: mvn -T1C install -DskipTests -Dverification.skip
+      - name: Run integration test
+        run: xvfb-run ./integration-tests/checkstyle-10.12.4.sh "${{ runner.temp }}/artifacts"
+      - name: Upload artifacts on failure
+        if: ${{ failure() }}
+        uses: actions/upload-artifact@a8a3f3ad30e3422c9c7b888a15615d19a852ae32 # v3.1.3
+        with:
+          name: integration-test-checkstyle-10.12.4
+          path: "${{ runner.temp }}/artifacts"
+      - name: Remove installed project artifacts
+        run: mvn build-helper:remove-project-artifact

.github/workflows/sonarcloud.yml

@@ -16,14 +16,14 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Check out code
-        uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
         with:
           fetch-depth: 0
           persist-credentials: false
       - name: Set up JDK
-        uses: actions/setup-java@cd89f46ac9d01407894225f350157564c9c7cee2 # v3.12.0
+        uses: actions/setup-java@387ac29b308b003ca37ba93a6cab5eb57c8f5f93 # v4.0.0
         with:
-          java-version: 17.0.7
+          java-version: 17.0.8
           distribution: temurin
           cache: maven
       - name: Create missing `test` directory

.gitignore

@@ -9,3 +9,6 @@
 target
 *.iml
 *.swp
+
+# The Git repositories checked out by the integration test framework.
+integration-tests/.repos

.renovaterc.json

@@ -12,10 +12,11 @@
       "separateMinorPatch": true
     },
     {
-      "matchPackagePatterns": [
-        "^ruby\\/setup-ruby$"
+      "matchDepNames": [
+        "github/codeql-action",
+        "ruby/setup-ruby"
       ],
-      "schedule": "* * 1 * *"
+      "schedule": "every 4 weeks on Monday"
     }
   ],
   "reviewers": [

CONTRIBUTING.md

@@ -80,6 +80,6 @@ Some pointers:
 [error-prone-support-developing]: https://github.com/PicnicSupermarket/error-prone-support/tree/master#-developing-error-prone-support
 [error-prone-support-full-build]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/run-full-build.sh
 [error-prone-support-issues]: https://github.com/PicnicSupermarket/error-prone-support/issues
-[error-prone-support-mutation-tests]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/run-mutation-tests.sh
+[error-prone-support-mutation-tests]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/run-branch-mutation-tests.sh
 [error-prone-support-patch]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/apply-error-prone-suggestions.sh
 [error-prone-support-pulls]: https://github.com/PicnicSupermarket/error-prone-support/pulls

README.md

@@ -15,9 +15,11 @@ focussing on maintainability, consistency and avoidance of common pitfalls.
 > Error Prone is a static analysis tool for Java that catches common
 > programming mistakes at compile-time.
 
-Read more on how Picnic uses Error Prone (Support) in the blog post [_Picnic
-loves Error Prone: producing high-quality and consistent Java
-code_][picnic-blog-ep-post].
+To learn more about Error Prone (Support), how you can start using Error Prone
+in practice, and how we use it at Picnic, watch the conference talk
+[_Automating away bugs with Error Prone in practice_][conference-talk]. Also
+consider checking out the blog post [_Picnic loves Error Prone: producing
+high-quality and consistent Java code_][picnic-blog-ep-post].
 
 [![Maven Central][maven-central-badge]][maven-central-search]
 [![Reproducible Builds][reproducible-builds-badge]][reproducible-builds-report]
@@ -223,10 +225,13 @@ Other highly relevant commands:
   Before running this command, make sure to have installed the project (`mvn
   clean install`) and make sure that the current working directory does not
   contain unstaged or uncommited changes.
-- [`./run-mutation-tests.sh`][script-run-mutation-tests] runs mutation tests
-  using [Pitest][pitest]. The results can be reviewed by opening the respective
-  `target/pit-reports/index.html` files. For more information check the [PIT
-  Maven plugin][pitest-maven].
+- [`./run-branch-mutation-tests.sh`][script-run-branch-mutation-tests] uses
+  [Pitest][pitest] to run mutation tests against code that is modified relative
+  to the upstream default branch. The results can be reviewed by opening the
+  respective `target/pit-reports/index.html` files. One can use
+  [`./run-mutation-tests.sh`][script-run-mutation-tests] to run mutation tests
+  against _all_ code in the current working directory. For more information
+  check the [PIT Maven plugin][pitest-maven].
 
 When running the project's tests in IntelliJ IDEA, you might see the following
 error:
@@ -262,6 +267,7 @@ channel; please see our [security policy][security] for details.
 [bug-checks-identity-conversion]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/IdentityConversion.java
 [codeql-badge]: https://github.com/PicnicSupermarket/error-prone-support/actions/workflows/codeql.yml/badge.svg?branch=master&event=push
 [codeql-master]: https://github.com/PicnicSupermarket/error-prone-support/actions/workflows/codeql.yml?query=branch:master+event:push
+[conference-talk]: https://www.youtube.com/watch?v=-47WD-3wKBs
 [contributing]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/CONTRIBUTING.md
 [contributing-pull-request]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/CONTRIBUTING.md#-opening-a-pull-request
 [error-prone-bugchecker]: https://github.com/google/error-prone/blob/master/check_api/src/main/java/com/google/errorprone/bugpatterns/BugChecker.java
@@ -271,8 +277,8 @@ channel; please see our [security policy][security] for details.
 [error-prone-installation-guide]: https://errorprone.info/docs/installation#maven
 [error-prone-orig-repo]: https://github.com/google/error-prone
 [error-prone-pull-3301]: https://github.com/google/error-prone/pull/3301
-[github-actions-build-badge]: https://github.com/PicnicSupermarket/error-prone-support/actions/workflows/build.yaml/badge.svg
-[github-actions-build-master]: https://github.com/PicnicSupermarket/error-prone-support/actions/workflows/build.yaml?query=branch:master&event=push
+[github-actions-build-badge]: https://github.com/PicnicSupermarket/error-prone-support/actions/workflows/build.yml/badge.svg
+[github-actions-build-master]: https://github.com/PicnicSupermarket/error-prone-support/actions/workflows/build.yml?query=branch:master&event=push
 [google-java-format]: https://github.com/google/google-java-format
 [idea-288052]: https://youtrack.jetbrains.com/issue/IDEA-288052
 [license-badge]: https://img.shields.io/github/license/PicnicSupermarket/error-prone-support
@@ -296,6 +302,7 @@ channel; please see our [security policy][security] for details.
 [reproducible-builds-badge]: https://img.shields.io/badge/Reproducible_Builds-ok-success?labelColor=1e5b96
 [reproducible-builds-report]: https://github.com/jvm-repo-rebuild/reproducible-central/blob/master/content/tech/picnic/error-prone-support/error-prone-support/README.md
 [script-apply-error-prone-suggestions]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/apply-error-prone-suggestions.sh
+[script-run-branch-mutation-tests]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/run-branch-mutation-tests.sh
 [script-run-full-build]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/run-full-build.sh
 [script-run-mutation-tests]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/run-mutation-tests.sh
 [security]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/SECURITY.md

cdg-pitest-licence.txt

@@ -1,7 +1,7 @@
 # Arcmutate license for Error Prone Support, requested by sending an email to
 # support@arcmutate.com.
-expires=07/11/2023
+expires=27/10/2025
 keyVersion=1
-signature=MhZxMbnO6UovNfllM0JuVWkZyvRT3/G5o/uT0Mm36c7200VpZNVu03gTAGivnl9W5RzvZhfpIHccuQ5ctjQkrqhsFSrl4fyqPqu3y5V2fsHIdFXP/G72EGj6Kay9ndLpaEHalqE0bEwxdnHMzEYq5y3O9vUPv8MhUl57xk+rvBo\=
+signature=aQLVt0J//7nXDAlJuBe9ru7Dq6oApcLh17rxsgHoJqBkUCd2zvrtRxkcPm5PmF1I8gBDT9PHb+kTf6Kcfz+D1fT0wRrZv38ip56521AQPD6zjRSqak9O2Gisjo+QTPMD7oS009aSWKzQ1SMdtuZ+KIRvw4Gl+frtYzexqnGWEUQ\=
 packages=tech.picnic.errorprone.*
 type=OSSS

documentation-support/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.12.1-SNAPSHOT</version>
+        <version>0.14.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>documentation-support</artifactId>

documentation-support/src/main/java/tech/picnic/errorprone/documentation/BugPatternExtractor.java

@@ -5,17 +5,19 @@ import static com.google.common.collect.ImmutableList.toImmutableList;
 import static java.util.Objects.requireNonNull;
 
 import com.google.auto.common.AnnotationMirrors;
+import com.google.auto.service.AutoService;
 import com.google.auto.value.AutoValue;
 import com.google.common.collect.ImmutableList;
 import com.google.errorprone.BugPattern;
 import com.google.errorprone.BugPattern.SeverityLevel;
+import com.google.errorprone.VisitorState;
 import com.google.errorprone.annotations.Immutable;
 import com.google.errorprone.util.ASTHelpers;
 import com.sun.source.tree.AnnotationTree;
 import com.sun.source.tree.ClassTree;
 import com.sun.tools.javac.code.Attribute;
 import com.sun.tools.javac.code.Symbol.ClassSymbol;
-import com.sun.tools.javac.util.Context;
+import java.util.Optional;
 import javax.lang.model.element.AnnotationValue;
 import tech.picnic.errorprone.documentation.BugPatternExtractor.BugPatternDocumentation;
 
@@ -23,29 +25,39 @@ import tech.picnic.errorprone.documentation.BugPatternExtractor.BugPatternDocume
  * An {@link Extractor} that describes how to extract data from a {@code @BugPattern} annotation.
  */
 @Immutable
-final class BugPatternExtractor implements Extractor<BugPatternDocumentation> {
-  @Override
-  public BugPatternDocumentation extract(ClassTree tree, Context context) {
-    ClassSymbol symbol = ASTHelpers.getSymbol(tree);
-    BugPattern annotation = symbol.getAnnotation(BugPattern.class);
-    requireNonNull(annotation, "BugPattern annotation must be present");
+@AutoService(Extractor.class)
+@SuppressWarnings("rawtypes" /* See https://github.com/google/auto/issues/870. */)
+public final class BugPatternExtractor implements Extractor<BugPatternDocumentation> {
+  /** Instantiates a new {@link BugPatternExtractor} instance. */
+  public BugPatternExtractor() {}
 
-    return new AutoValue_BugPatternExtractor_BugPatternDocumentation(
-        symbol.getQualifiedName().toString(),
-        annotation.name().isEmpty() ? tree.getSimpleName().toString() : annotation.name(),
-        ImmutableList.copyOf(annotation.altNames()),
-        annotation.link(),
-        ImmutableList.copyOf(annotation.tags()),
-        annotation.summary(),
-        annotation.explanation(),
-        annotation.severity(),
-        annotation.disableable(),
-        annotation.documentSuppression() ? getSuppressionAnnotations(tree) : ImmutableList.of());
+  @Override
+  public String identifier() {
+    return "bugpattern";
   }
 
   @Override
-  public boolean canExtract(ClassTree tree) {
-    return ASTHelpers.hasDirectAnnotationWithSimpleName(tree, BugPattern.class.getSimpleName());
+  public Optional<BugPatternDocumentation> tryExtract(ClassTree tree, VisitorState state) {
+    ClassSymbol symbol = ASTHelpers.getSymbol(tree);
+    BugPattern annotation = symbol.getAnnotation(BugPattern.class);
+    if (annotation == null) {
+      return Optional.empty();
+    }
+
+    return Optional.of(
+        new AutoValue_BugPatternExtractor_BugPatternDocumentation(
+            symbol.getQualifiedName().toString(),
+            annotation.name().isEmpty() ? tree.getSimpleName().toString() : annotation.name(),
+            ImmutableList.copyOf(annotation.altNames()),
+            annotation.link(),
+            ImmutableList.copyOf(annotation.tags()),
+            annotation.summary(),
+            annotation.explanation(),
+            annotation.severity(),
+            annotation.disableable(),
+            annotation.documentSuppression()
+                ? getSuppressionAnnotations(tree)
+                : ImmutableList.of()));
   }
 
   /**

documentation-support/src/main/java/tech/picnic/errorprone/documentation/BugPatternTestExtractor.java

@@ -0,0 +1,229 @@
+package tech.picnic.errorprone.documentation;
+
+import static com.google.errorprone.matchers.Matchers.instanceMethod;
+import static com.google.errorprone.matchers.method.MethodMatchers.staticMethod;
+import static java.util.function.Predicate.not;
+
+import com.google.auto.service.AutoService;
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableList;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.annotations.Immutable;
+import com.google.errorprone.matchers.Matcher;
+import com.google.errorprone.util.ASTHelpers;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.MethodInvocationTree;
+import com.sun.source.util.TreeScanner;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+import org.jspecify.annotations.Nullable;
+import tech.picnic.errorprone.documentation.BugPatternTestExtractor.TestCases;
+
+/**
+ * An {@link Extractor} that describes how to extract data from classes that test a {@code
+ * BugChecker}.
+ */
+// XXX: Handle other methods from `{BugCheckerRefactoring,Compilation}TestHelper`:
+// - Indicate which custom arguments are specified, if any.
+// - For replacement tests, indicate which `FixChooser` is used.
+// - ... (We don't use all optional features; TBD what else to support.)
+@Immutable
+@AutoService(Extractor.class)
+@SuppressWarnings("rawtypes" /* See https://github.com/google/auto/issues/870. */)
+public final class BugPatternTestExtractor implements Extractor<TestCases> {
+  /** Instantiates a new {@link BugPatternTestExtractor} instance. */
+  public BugPatternTestExtractor() {}
+
+  @Override
+  public String identifier() {
+    return "bugpattern-test";
+  }
+
+  @Override
+  public Optional<TestCases> tryExtract(ClassTree tree, VisitorState state) {
+    BugPatternTestCollector collector = new BugPatternTestCollector();
+
+    collector.scan(tree, state);
+
+    return Optional.of(collector.getCollectedTests())
+        .filter(not(ImmutableList::isEmpty))
+        .map(
+            tests ->
+                new AutoValue_BugPatternTestExtractor_TestCases(
+                    ASTHelpers.getSymbol(tree).className(), tests));
+  }
+
+  private static final class BugPatternTestCollector
+      extends TreeScanner<@Nullable Void, VisitorState> {
+    private static final Matcher<ExpressionTree> COMPILATION_HELPER_DO_TEST =
+        instanceMethod()
+            .onDescendantOf("com.google.errorprone.CompilationTestHelper")
+            .named("doTest");
+    private static final Matcher<ExpressionTree> TEST_HELPER_NEW_INSTANCE =
+        staticMethod()
+            .onDescendantOfAny(
+                "com.google.errorprone.CompilationTestHelper",
+                "com.google.errorprone.BugCheckerRefactoringTestHelper")
+            .named("newInstance")
+            .withParameters("java.lang.Class", "java.lang.Class");
+    private static final Matcher<ExpressionTree> IDENTIFICATION_SOURCE_LINES =
+        instanceMethod()
+            .onDescendantOf("com.google.errorprone.CompilationTestHelper")
+            .named("addSourceLines");
+    private static final Matcher<ExpressionTree> REPLACEMENT_DO_TEST =
+        instanceMethod()
+            .onDescendantOf("com.google.errorprone.BugCheckerRefactoringTestHelper")
+            .named("doTest");
+    private static final Matcher<ExpressionTree> REPLACEMENT_EXPECT_UNCHANGED =
+        instanceMethod()
+            .onDescendantOf("com.google.errorprone.BugCheckerRefactoringTestHelper.ExpectOutput")
+            .named("expectUnchanged");
+    private static final Matcher<ExpressionTree> REPLACEMENT_OUTPUT_SOURCE_LINES =
+        instanceMethod()
+            .onDescendantOf("com.google.errorprone.BugCheckerRefactoringTestHelper.ExpectOutput")
+            .namedAnyOf("addOutputLines", "expectUnchanged");
+
+    private final List<TestCase> collectedTestCases = new ArrayList<>();
+
+    private ImmutableList<TestCase> getCollectedTests() {
+      return ImmutableList.copyOf(collectedTestCases);
+    }
+
+    @Override
+    public @Nullable Void visitMethodInvocation(MethodInvocationTree node, VisitorState state) {
+      boolean isReplacementTest = REPLACEMENT_DO_TEST.matches(node, state);
+      if (isReplacementTest || COMPILATION_HELPER_DO_TEST.matches(node, state)) {
+        getClassUnderTest(node, state)
+            .ifPresent(
+                classUnderTest -> {
+                  List<TestEntry> entries = new ArrayList<>();
+                  if (isReplacementTest) {
+                    extractReplacementTestCases(node, entries, state);
+                  } else {
+                    extractIdentificationTestCases(node, entries, state);
+                  }
+
+                  if (!entries.isEmpty()) {
+                    collectedTestCases.add(
+                        new AutoValue_BugPatternTestExtractor_TestCase(
+                            classUnderTest, ImmutableList.copyOf(entries).reverse()));
+                  }
+                });
+      }
+
+      return super.visitMethodInvocation(node, state);
+    }
+
+    private static Optional<String> getClassUnderTest(
+        MethodInvocationTree tree, VisitorState state) {
+      if (TEST_HELPER_NEW_INSTANCE.matches(tree, state)) {
+        return Optional.ofNullable(ASTHelpers.getSymbol(tree.getArguments().get(0)))
+            .filter(s -> !s.type.allparams().isEmpty())
+            .map(s -> s.type.allparams().get(0).tsym.getQualifiedName().toString());
+      }
+
+      ExpressionTree receiver = ASTHelpers.getReceiver(tree);
+      return receiver instanceof MethodInvocationTree
+          ? getClassUnderTest((MethodInvocationTree) receiver, state)
+          : Optional.empty();
+    }
+
+    private static void extractIdentificationTestCases(
+        MethodInvocationTree tree, List<TestEntry> sink, VisitorState state) {
+      if (IDENTIFICATION_SOURCE_LINES.matches(tree, state)) {
+        String path = ASTHelpers.constValue(tree.getArguments().get(0), String.class);
+        Optional<String> sourceCode =
+            getSourceCode(tree).filter(s -> s.contains("// BUG: Diagnostic"));
+        if (path != null && sourceCode.isPresent()) {
+          sink.add(
+              new AutoValue_BugPatternTestExtractor_IdentificationTestEntry(
+                  path, sourceCode.orElseThrow()));
+        }
+      }
+
+      ExpressionTree receiver = ASTHelpers.getReceiver(tree);
+      if (receiver instanceof MethodInvocationTree) {
+        extractIdentificationTestCases((MethodInvocationTree) receiver, sink, state);
+      }
+    }
+
+    private static void extractReplacementTestCases(
+        MethodInvocationTree tree, List<TestEntry> sink, VisitorState state) {
+      if (REPLACEMENT_OUTPUT_SOURCE_LINES.matches(tree, state)) {
+        /*
+         * Retrieve the method invocation that contains the input source code. Note that this cast
+         * is safe, because this code is guarded by an earlier call to `#getClassUnderTest(..)`,
+         * which ensures that `tree` is part of a longer method invocation chain.
+         */
+        MethodInvocationTree inputTree = (MethodInvocationTree) ASTHelpers.getReceiver(tree);
+
+        String path = ASTHelpers.constValue(inputTree.getArguments().get(0), String.class);
+        Optional<String> inputCode = getSourceCode(inputTree);
+        if (path != null && inputCode.isPresent()) {
+          Optional<String> outputCode =
+              REPLACEMENT_EXPECT_UNCHANGED.matches(tree, state) ? inputCode : getSourceCode(tree);
+
+          if (outputCode.isPresent() && !inputCode.equals(outputCode)) {
+            sink.add(
+                new AutoValue_BugPatternTestExtractor_ReplacementTestEntry(
+                    path, inputCode.orElseThrow(), outputCode.orElseThrow()));
+          }
+        }
+      }
+
+      ExpressionTree receiver = ASTHelpers.getReceiver(tree);
+      if (receiver instanceof MethodInvocationTree) {
+        extractReplacementTestCases((MethodInvocationTree) receiver, sink, state);
+      }
+    }
+
+    // XXX: This logic is duplicated in `ErrorProneTestSourceFormat`. Can we do better?
+    private static Optional<String> getSourceCode(MethodInvocationTree tree) {
+      List<? extends ExpressionTree> sourceLines =
+          tree.getArguments().subList(1, tree.getArguments().size());
+      StringBuilder source = new StringBuilder();
+
+      for (ExpressionTree sourceLine : sourceLines) {
+        String value = ASTHelpers.constValue(sourceLine, String.class);
+        if (value == null) {
+          return Optional.empty();
+        }
+        source.append(value).append('\n');
+      }
+
+      return Optional.of(source.toString());
+    }
+  }
+
+  @AutoValue
+  abstract static class TestCases {
+    abstract String testClass();
+
+    abstract ImmutableList<TestCase> testCases();
+  }
+
+  @AutoValue
+  abstract static class TestCase {
+    abstract String classUnderTest();
+
+    abstract ImmutableList<TestEntry> entries();
+  }
+
+  interface TestEntry {
+    String path();
+  }
+
+  @AutoValue
+  abstract static class ReplacementTestEntry implements TestEntry {
+    abstract String input();
+
+    abstract String output();
+  }
+
+  @AutoValue
+  abstract static class IdentificationTestEntry implements TestEntry {
+    abstract String code();
+  }
+}

documentation-support/src/main/java/tech/picnic/errorprone/documentation/DocumentationGeneratorTaskListener.java

@@ -5,10 +5,14 @@ import static java.nio.charset.StandardCharsets.UTF_8;
 import com.fasterxml.jackson.annotation.JsonAutoDetect.Visibility;
 import com.fasterxml.jackson.annotation.PropertyAccessor;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.common.collect.ImmutableList;
+import com.google.errorprone.VisitorState;
 import com.sun.source.tree.ClassTree;
+import com.sun.source.tree.CompilationUnitTree;
 import com.sun.source.util.TaskEvent;
 import com.sun.source.util.TaskEvent.Kind;
 import com.sun.source.util.TaskListener;
+import com.sun.source.util.TreePath;
 import com.sun.tools.javac.api.JavacTrees;
 import com.sun.tools.javac.util.Context;
 import java.io.File;
@@ -19,6 +23,7 @@ import java.net.URI;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
+import java.util.ServiceLoader;
 import javax.tools.JavaFileObject;
 
 /**
@@ -27,6 +32,13 @@ import javax.tools.JavaFileObject;
  */
 // XXX: Find a better name for this class; it doesn't generate documentation per se.
 final class DocumentationGeneratorTaskListener implements TaskListener {
+  @SuppressWarnings({"rawtypes", "unchecked"})
+  private static final ImmutableList<Extractor<?>> EXTRACTORS =
+      (ImmutableList)
+          ImmutableList.copyOf(
+              ServiceLoader.load(
+                  Extractor.class, DocumentationGeneratorTaskListener.class.getClassLoader()));
+
   private static final ObjectMapper OBJECT_MAPPER =
       new ObjectMapper().setVisibility(PropertyAccessor.FIELD, Visibility.ANY);
 
@@ -51,19 +63,25 @@ final class DocumentationGeneratorTaskListener implements TaskListener {
       return;
     }
 
-    ClassTree classTree = JavacTrees.instance(context).getTree(taskEvent.getTypeElement());
     JavaFileObject sourceFile = taskEvent.getSourceFile();
-    if (classTree == null || sourceFile == null) {
+    CompilationUnitTree compilationUnit = taskEvent.getCompilationUnit();
+    ClassTree classTree = JavacTrees.instance(context).getTree(taskEvent.getTypeElement());
+    if (sourceFile == null || compilationUnit == null || classTree == null) {
       return;
     }
 
-    ExtractorType.findMatchingType(classTree)
-        .ifPresent(
-            extractorType ->
-                writeToFile(
-                    extractorType.getIdentifier(),
-                    getSimpleClassName(sourceFile.toUri()),
-                    extractorType.getExtractor().extract(classTree, context)));
+    VisitorState state =
+        VisitorState.createForUtilityPurposes(context)
+            .withPath(new TreePath(new TreePath(compilationUnit), classTree));
+
+    for (Extractor<?> extractor : EXTRACTORS) {
+      extractor
+          .tryExtract(classTree, state)
+          .ifPresent(
+              data ->
+                  writeToFile(
+                      extractor.identifier(), getSimpleClassName(sourceFile.toUri()), data));
+    }
   }
 
   private void createDocsDirectory() {

documentation-support/src/main/java/tech/picnic/errorprone/documentation/Extractor.java

@@ -1,8 +1,9 @@
 package tech.picnic.errorprone.documentation;
 
+import com.google.errorprone.VisitorState;
 import com.google.errorprone.annotations.Immutable;
 import com.sun.source.tree.ClassTree;
-import com.sun.tools.javac.util.Context;
+import java.util.Optional;
 
 /**
  * Interface implemented by classes that define how to extract data of some type {@link T} from a
@@ -13,21 +14,20 @@ import com.sun.tools.javac.util.Context;
 @Immutable
 interface Extractor<T> {
   /**
-   * Extracts and returns an instance of {@link T} using the provided arguments.
+   * Returns the unique identifier of this extractor.
    *
-   * @param tree The {@link ClassTree} to analyze and from which to extract instances of {@link T}.
-   * @param context The {@link Context} in which the current compilation takes place.
-   * @return A non-null instance of {@link T}.
+   * @return A non-{@code null} string.
    */
-  // XXX: Drop `Context` parameter unless used.
-  T extract(ClassTree tree, Context context);
+  String identifier();
 
   /**
-   * Tells whether this {@link Extractor} can extract documentation content from the given {@link
-   * ClassTree}.
+   * Attempts to extract an instance of type {@link T} using the provided arguments.
    *
-   * @param tree The {@link ClassTree} of interest.
-   * @return {@code true} iff data extraction is supported.
+   * @param tree The {@link ClassTree} to analyze and from which to extract an instance of type
+   *     {@link T}.
+   * @param state A {@link VisitorState} describing the context in which the given {@link ClassTree}
+   *     is found.
+   * @return An instance of type {@link T}, if possible.
    */
-  boolean canExtract(ClassTree tree);
+  Optional<T> tryExtract(ClassTree tree, VisitorState state);
 }

documentation-support/src/main/java/tech/picnic/errorprone/documentation/ExtractorType.java

@@ -1,36 +0,0 @@
-package tech.picnic.errorprone.documentation;
-
-import com.google.common.collect.ImmutableSet;
-import com.google.common.collect.Sets;
-import com.sun.source.tree.ClassTree;
-import java.util.EnumSet;
-import java.util.Optional;
-
-/** An enumeration of {@link Extractor} types. */
-enum ExtractorType {
-  BUG_PATTERN("bugpattern", new BugPatternExtractor());
-
-  private static final ImmutableSet<ExtractorType> TYPES =
-      Sets.immutableEnumSet(EnumSet.allOf(ExtractorType.class));
-
-  private final String identifier;
-  private final Extractor<?> extractor;
-
-  ExtractorType(String identifier, Extractor<?> extractor) {
-    this.identifier = identifier;
-    this.extractor = extractor;
-  }
-
-  String getIdentifier() {
-    return identifier;
-  }
-
-  @SuppressWarnings("java:S1452" /* The extractor returns data of an unspecified type. */)
-  Extractor<?> getExtractor() {
-    return extractor;
-  }
-
-  static Optional<ExtractorType> findMatchingType(ClassTree tree) {
-    return TYPES.stream().filter(type -> type.getExtractor().canExtract(tree)).findFirst();
-  }
-}

documentation-support/src/test/java/tech/picnic/errorprone/documentation/BugPatternExtractorTest.java

@@ -1,18 +1,9 @@
 package tech.picnic.errorprone.documentation;
 
-import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 import com.google.common.io.Resources;
-import com.google.errorprone.BugPattern;
-import com.google.errorprone.CompilationTestHelper;
-import com.google.errorprone.VisitorState;
-import com.google.errorprone.bugpatterns.BugChecker;
-import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
-import com.google.errorprone.matchers.Description;
-import com.sun.source.tree.ClassTree;
 import java.io.IOException;
 import java.nio.file.Path;
 import org.junit.jupiter.api.Test;
@@ -45,10 +36,7 @@ final class BugPatternExtractorTest {
         "@BugPattern(summary = \"MinimalBugChecker summary\", severity = SeverityLevel.ERROR)",
         "public final class MinimalBugChecker extends BugChecker {}");
 
-    verifyFileMatchesResource(
-        outputDirectory,
-        "bugpattern-MinimalBugChecker.json",
-        "bugpattern-documentation-minimal.json");
+    verifyGeneratedFileContent(outputDirectory, "MinimalBugChecker");
   }
 
   @Test
@@ -76,10 +64,7 @@ final class BugPatternExtractorTest {
         "    suppressionAnnotations = {BugPattern.class, Test.class})",
         "public final class CompleteBugChecker extends BugChecker {}");
 
-    verifyFileMatchesResource(
-        outputDirectory,
-        "bugpattern-CompleteBugChecker.json",
-        "bugpattern-documentation-complete.json");
+    verifyGeneratedFileContent(outputDirectory, "CompleteBugChecker");
   }
 
   @Test
@@ -99,55 +84,23 @@ final class BugPatternExtractorTest {
         "    documentSuppression = false)",
         "public final class UndocumentedSuppressionBugPattern extends BugChecker {}");
 
-    verifyFileMatchesResource(
-        outputDirectory,
-        "bugpattern-UndocumentedSuppressionBugPattern.json",
-        "bugpattern-documentation-undocumented-suppression.json");
+    verifyGeneratedFileContent(outputDirectory, "UndocumentedSuppressionBugPattern");
   }
 
-  @Test
-  void bugPatternAnnotationIsAbsent() {
-    CompilationTestHelper.newInstance(TestChecker.class, getClass())
-        .addSourceLines(
-            "TestChecker.java",
-            "import com.google.errorprone.bugpatterns.BugChecker;",
-            "",
-            "// BUG: Diagnostic contains: Can extract: false",
-            "public final class TestChecker extends BugChecker {}")
-        .doTest();
-  }
-
-  private static void verifyFileMatchesResource(
-      Path outputDirectory, String fileName, String resourceName) throws IOException {
-    assertThat(outputDirectory.resolve(fileName))
+  private static void verifyGeneratedFileContent(Path outputDirectory, String testClass)
+      throws IOException {
+    String resourceName = String.format("bugpattern-%s.json", testClass);
+    assertThat(outputDirectory.resolve(resourceName))
         .content(UTF_8)
-        .isEqualToIgnoringWhitespace(getResource(resourceName));
+        .isEqualToIgnoringWhitespace(
+            getResource(
+                String.join("-", BugPatternExtractorTest.class.getSimpleName(), resourceName)));
   }
 
   // XXX: Once we support only JDK 15+, drop this method in favour of including the resources as
-  // text blocks in this class. (This also requires renaming the `verifyFileMatchesResource`
-  // method.)
+  // text blocks in this class.
   private static String getResource(String resourceName) throws IOException {
     return Resources.toString(
         Resources.getResource(BugPatternExtractorTest.class, resourceName), UTF_8);
   }
-
-  /** A {@link BugChecker} that validates the {@link BugPatternExtractor}. */
-  @BugPattern(summary = "Validates `BugPatternExtractor` extraction", severity = ERROR)
-  public static final class TestChecker extends BugChecker implements ClassTreeMatcher {
-    private static final long serialVersionUID = 1L;
-
-    @Override
-    public Description matchClass(ClassTree tree, VisitorState state) {
-      BugPatternExtractor extractor = new BugPatternExtractor();
-
-      assertThatThrownBy(() -> extractor.extract(tree, state.context))
-          .isInstanceOf(NullPointerException.class)
-          .hasMessage("BugPattern annotation must be present");
-
-      return buildDescription(tree)
-          .setMessage(String.format("Can extract: %s", extractor.canExtract(tree)))
-          .build();
-    }
-  }
 }

documentation-support/src/test/java/tech/picnic/errorprone/documentation/BugPatternTestExtractorTest.java

@@ -0,0 +1,468 @@
+package tech.picnic.errorprone.documentation;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.google.common.io.Resources;
+import java.io.IOException;
+import java.nio.file.Path;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+final class BugPatternTestExtractorTest {
+  @Test
+  void noTestClass(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerWithoutAnnotation.java",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "public final class TestCheckerWithoutAnnotation extends BugChecker {}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void noDoTestInvocation(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    CompilationTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addSourceLines(\"A.java\", \"// BUG: Diagnostic contains:\", \"class A {}\");",
+        "",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A { /* This is a change. */ }\");",
+        "  }",
+        "}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void nullBugCheckerInstance(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class TestCheckerTest {",
+        "  void m() {",
+        "    CompilationTestHelper.newInstance((Class<BugChecker>) null, getClass())",
+        "        .addSourceLines(\"A.java\", \"// BUG: Diagnostic contains:\", \"class A {}\")",
+        "        .doTest();",
+        "",
+        "    BugCheckerRefactoringTestHelper.newInstance((Class<BugChecker>) null, getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A { /* This is a change. */ }\")",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void rawBugCheckerInstance(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  @SuppressWarnings(\"unchecked\")",
+        "  void m() {",
+        "    @SuppressWarnings(\"rawtypes\")",
+        "    Class bugChecker = TestChecker.class;",
+        "",
+        "    CompilationTestHelper.newInstance(bugChecker, getClass())",
+        "        .addSourceLines(\"A.java\", \"// BUG: Diagnostic contains:\", \"class A {}\")",
+        "        .doTest();",
+        "",
+        "    BugCheckerRefactoringTestHelper.newInstance(bugChecker, getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A { /* This is a change. */ }\")",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void scannerSupplierInstance(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "import com.google.errorprone.scanner.ScannerSupplier;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    CompilationTestHelper.newInstance(",
+        "            ScannerSupplier.fromBugCheckerClasses(TestChecker.class), getClass())",
+        "        .addSourceLines(\"A.java\", \"// BUG: Diagnostic contains:\", \"class A {}\")",
+        "        .doTest();",
+        "",
+        "    BugCheckerRefactoringTestHelper.newInstance(",
+        "            ScannerSupplier.fromBugCheckerClasses(TestChecker.class), getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A { /* This is a change. */ }\")",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void nonCompileTimeConstantStrings(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    CompilationTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addSourceLines(toString() + \"A.java\", \"// BUG: Diagnostic contains:\", \"class A {}\")",
+        "        .addSourceLines(\"B.java\", \"// BUG: Diagnostic contains:\", \"class B {}\", toString())",
+        "        .doTest();",
+        "",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addInputLines(toString() + \"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A { /* This is a change. */ }\")",
+        "        .addInputLines(\"B.java\", \"class B {}\", toString())",
+        "        .addOutputLines(\"B.java\", \"class B { /* This is a change. */ }\")",
+        "        .addInputLines(\"C.java\", \"class C {}\")",
+        "        .addOutputLines(\"C.java\", \"class C { /* This is a change. */ }\", toString())",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void nonFluentTestHelperExpressions(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    CompilationTestHelper testHelper =",
+        "        CompilationTestHelper.newInstance(TestChecker.class, getClass())",
+        "            .addSourceLines(\"A.java\", \"class A {}\");",
+        "    testHelper.doTest();",
+        "",
+        "    BugCheckerRefactoringTestHelper.ExpectOutput expectedOutput =",
+        "        BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "            .addInputLines(\"A.java\", \"class A {}\");",
+        "    expectedOutput.addOutputLines(\"A.java\", \"class A {}\").doTest();",
+        "    expectedOutput.expectUnchanged().doTest();",
+        "  }",
+        "}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void noSource(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    CompilationTestHelper.newInstance(TestChecker.class, getClass()).doTest();",
+        "",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass()).doTest();",
+        "  }",
+        "}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void noDiagnostics(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "TestCheckerTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class TestCheckerTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    CompilationTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addSourceLines(\"A.java\", \"class A {}\")",
+        "        .doTest();",
+        "",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A {}\")",
+        "        .addInputLines(\"B.java\", \"class B {}\")",
+        "        .expectUnchanged()",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void singleFileCompilationTestHelper(@TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "SingleFileCompilationTestHelperTest.java",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class SingleFileCompilationTestHelperTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    CompilationTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addSourceLines(\"A.java\", \"// BUG: Diagnostic contains:\", \"class A {}\")",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    verifyGeneratedFileContent(outputDirectory, "SingleFileCompilationTestHelperTest");
+  }
+
+  @Test
+  void singleFileCompilationTestHelperWithSetArgs(@TempDir Path outputDirectory)
+      throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "SingleFileCompilationTestHelperWithSetArgsTest.java",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class SingleFileCompilationTestHelperWithSetArgsTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    CompilationTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .setArgs(\"-XepAllSuggestionsAsWarnings\")",
+        "        .addSourceLines(\"A.java\", \"// BUG: Diagnostic contains:\", \"class A {}\")",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    verifyGeneratedFileContent(outputDirectory, "SingleFileCompilationTestHelperWithSetArgsTest");
+  }
+
+  @Test
+  void multiFileCompilationTestHelper(@TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "MultiFileCompilationTestHelperTest.java",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class MultiFileCompilationTestHelperTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    CompilationTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addSourceLines(\"A.java\", \"// BUG: Diagnostic contains:\", \"class A {}\")",
+        "        .addSourceLines(\"B.java\", \"// BUG: Diagnostic contains:\", \"class B {}\")",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    verifyGeneratedFileContent(outputDirectory, "MultiFileCompilationTestHelperTest");
+  }
+
+  @Test
+  void singleFileBugCheckerRefactoringTestHelper(@TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "SingleFileBugCheckerRefactoringTestHelperTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class SingleFileBugCheckerRefactoringTestHelperTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A { /* This is a change. */ }\")",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    verifyGeneratedFileContent(outputDirectory, "SingleFileBugCheckerRefactoringTestHelperTest");
+  }
+
+  @Test
+  void singleFileBugCheckerRefactoringTestHelperWithSetArgsFixChooserAndCustomTestMode(
+      @TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "SingleFileBugCheckerRefactoringTestHelperWithSetArgsFixChooserAndCustomTestModeTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper.FixChoosers;",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class SingleFileBugCheckerRefactoringTestHelperWithSetArgsFixChooserAndCustomTestModeTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .setArgs(\"-XepAllSuggestionsAsWarnings\")",
+        "        .setFixChooser(FixChoosers.SECOND)",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A { /* This is a change. */ }\")",
+        "        .doTest(TestMode.TEXT_MATCH);",
+        "  }",
+        "}");
+
+    verifyGeneratedFileContent(
+        outputDirectory,
+        "SingleFileBugCheckerRefactoringTestHelperWithSetArgsFixChooserAndCustomTestModeTest");
+  }
+
+  @Test
+  void multiFileBugCheckerRefactoringTestHelper(@TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "MultiFileBugCheckerRefactoringTestHelperTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class MultiFileBugCheckerRefactoringTestHelperTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A { /* This is a change. */ }\")",
+        "        .addInputLines(\"B.java\", \"class B {}\")",
+        "        .addOutputLines(\"B.java\", \"class B { /* This is a change. */ }\")",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    verifyGeneratedFileContent(outputDirectory, "MultiFileBugCheckerRefactoringTestHelperTest");
+  }
+
+  @Test
+  void compilationAndBugCheckerRefactoringTestHelpers(@TempDir Path outputDirectory)
+      throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "CompilationAndBugCheckerRefactoringTestHelpersTest.java",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class CompilationAndBugCheckerRefactoringTestHelpersTest {",
+        "  private static class TestChecker extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    CompilationTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addSourceLines(\"A.java\", \"// BUG: Diagnostic contains:\", \"class A {}\")",
+        "        .doTest();",
+        "",
+        "    BugCheckerRefactoringTestHelper.newInstance(TestChecker.class, getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A { /* This is a change. */ }\")",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    verifyGeneratedFileContent(
+        outputDirectory, "CompilationAndBugCheckerRefactoringTestHelpersTest");
+  }
+
+  @Test
+  void compilationAndBugCheckerRefactoringTestHelpersWithCustomCheckerPackageAndNames(
+      @TempDir Path outputDirectory) throws IOException {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "CompilationAndBugCheckerRefactoringTestHelpersWithCustomCheckerPackageAndNamesTest.java",
+        "package pkg;",
+        "",
+        "import com.google.errorprone.BugCheckerRefactoringTestHelper;",
+        "import com.google.errorprone.CompilationTestHelper;",
+        "import com.google.errorprone.bugpatterns.BugChecker;",
+        "",
+        "final class CompilationAndBugCheckerRefactoringTestHelpersWithCustomCheckerPackageAndNamesTest {",
+        "  private static class CustomTestChecker extends BugChecker {}",
+        "",
+        "  private static class CustomTestChecker2 extends BugChecker {}",
+        "",
+        "  void m() {",
+        "    CompilationTestHelper.newInstance(CustomTestChecker.class, getClass())",
+        "        .addSourceLines(\"A.java\", \"// BUG: Diagnostic contains:\", \"class A {}\")",
+        "        .doTest();",
+        "",
+        "    BugCheckerRefactoringTestHelper.newInstance(CustomTestChecker2.class, getClass())",
+        "        .addInputLines(\"A.java\", \"class A {}\")",
+        "        .addOutputLines(\"A.java\", \"class A { /* This is a change. */ }\")",
+        "        .doTest();",
+        "  }",
+        "}");
+
+    verifyGeneratedFileContent(
+        outputDirectory,
+        "CompilationAndBugCheckerRefactoringTestHelpersWithCustomCheckerPackageAndNamesTest");
+  }
+
+  private static void verifyGeneratedFileContent(Path outputDirectory, String testClass)
+      throws IOException {
+    String resourceName = String.format("bugpattern-test-%s.json", testClass);
+    assertThat(outputDirectory.resolve(resourceName))
+        .content(UTF_8)
+        .isEqualToIgnoringWhitespace(
+            getResource(
+                String.join("-", BugPatternTestExtractorTest.class.getSimpleName(), resourceName)));
+  }
+
+  // XXX: Once we support only JDK 15+, drop this method in favour of including the resources as
+  // text blocks in this class.
+  private static String getResource(String resourceName) throws IOException {
+    return Resources.toString(
+        Resources.getResource(BugPatternTestExtractorTest.class, resourceName), UTF_8);
+  }
+}

documentation-support/src/test/java/tech/picnic/errorprone/documentation/Compilation.java

@@ -1,5 +1,7 @@
 package tech.picnic.errorprone.documentation;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 import com.google.common.collect.ImmutableList;
 import com.google.errorprone.FileManagers;
 import com.google.errorprone.FileObjects;
@@ -7,39 +9,66 @@ import com.sun.tools.javac.api.JavacTaskImpl;
 import com.sun.tools.javac.api.JavacTool;
 import com.sun.tools.javac.file.JavacFileManager;
 import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+import javax.tools.Diagnostic;
 import javax.tools.JavaCompiler;
 import javax.tools.JavaFileObject;
 
 // XXX: Generalize and move this class so that it can also be used by `refaster-compiler`.
-// XXX: Add support for this class to the `ErrorProneTestHelperSourceFormat` check.
+// XXX: This class is supported by the `ErrorProneTestHelperSourceFormat` check, but until that
+// support is covered by unit tests, make sure to update that logic if this class or its methods are
+// moved/renamed.
 public final class Compilation {
   private Compilation() {}
 
   public static void compileWithDocumentationGenerator(
-      Path outputDirectory, String fileName, String... lines) {
-    compileWithDocumentationGenerator(outputDirectory.toAbsolutePath().toString(), fileName, lines);
+      Path outputDirectory, String path, String... lines) {
+    compileWithDocumentationGenerator(outputDirectory.toAbsolutePath().toString(), path, lines);
   }
 
   public static void compileWithDocumentationGenerator(
-      String outputDirectory, String fileName, String... lines) {
+      String outputDirectory, String path, String... lines) {
+    /*
+     * The compiler options specified here largely match those used by Error Prone's
+     * `CompilationTestHelper`. A key difference is the stricter linting configuration. When
+     * compiling using JDK 21+, these lint options also require that certain JDK modules are
+     * explicitly exported.
+     */
     compile(
-        ImmutableList.of("-Xplugin:DocumentationGenerator -XoutputDirectory=" + outputDirectory),
-        FileObjects.forSourceLines(fileName, lines));
+        ImmutableList.of(
+            "--add-exports=jdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED",
+            "--add-exports=jdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED",
+            "--add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED",
+            "-encoding",
+            "UTF-8",
+            "-parameters",
+            "-proc:none",
+            "-Werror",
+            "-Xlint:all,-serial",
+            "-Xplugin:DocumentationGenerator -XoutputDirectory=" + outputDirectory,
+            "-XDdev",
+            "-XDcompilePolicy=simple"),
+        FileObjects.forSourceLines(path, lines));
   }
 
   private static void compile(ImmutableList<String> options, JavaFileObject javaFileObject) {
     JavacFileManager javacFileManager = FileManagers.testFileManager();
     JavaCompiler compiler = JavacTool.create();
+
+    List<Diagnostic<?>> diagnostics = new ArrayList<>();
     JavacTaskImpl task =
         (JavacTaskImpl)
             compiler.getTask(
                 null,
                 javacFileManager,
-                null,
+                diagnostics::add,
                 options,
                 ImmutableList.of(),
                 ImmutableList.of(javaFileObject));
 
-    task.call();
+    Boolean result = task.call();
+    assertThat(diagnostics).isEmpty();
+    assertThat(result).isTrue();
   }
 }

documentation-support/src/test/java/tech/picnic/errorprone/documentation/DocumentationGeneratorTaskListenerTest.java

@@ -1,19 +1,29 @@
 package tech.picnic.errorprone.documentation;
 
 import static com.google.common.collect.ImmutableList.toImmutableList;
+import static java.nio.charset.StandardCharsets.UTF_8;
 import static java.nio.file.attribute.AclEntryPermission.ADD_SUBDIRECTORY;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.junit.jupiter.api.condition.OS.WINDOWS;
 
+import com.google.auto.service.AutoService;
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Sets;
+import com.google.common.collect.Streams;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.annotations.Immutable;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.tree.Tree;
 import java.io.IOException;
 import java.nio.file.FileSystemException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.attribute.AclEntry;
 import java.nio.file.attribute.AclFileAttributeView;
+import java.util.Optional;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.condition.DisabledOnOs;
 import org.junit.jupiter.api.condition.EnabledOnOs;
@@ -75,4 +85,56 @@ final class DocumentationGeneratorTaskListenerTest {
         .isInstanceOf(IllegalArgumentException.class)
         .hasMessage("Precisely one path must be provided");
   }
+
+  @Test
+  void extraction(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "DocumentationGeneratorTaskListenerTestClass.java",
+        "class DocumentationGeneratorTaskListenerTestClass {}");
+
+    // XXX: Once we support only JDK 15+, use a text block for the `expected` string.
+    assertThat(
+            outputDirectory.resolve(
+                "documentation-generator-task-listener-test-DocumentationGeneratorTaskListenerTestClass.json"))
+        .content(UTF_8)
+        .isEqualToIgnoringWhitespace(
+            "{\"className\":\"DocumentationGeneratorTaskListenerTestClass\",\"path\":[\"CLASS: DocumentationGeneratorTaskListenerTestClass\",\"COMPILATION_UNIT\"]}");
+  }
+
+  @Immutable
+  @AutoService(Extractor.class)
+  @SuppressWarnings("rawtypes" /* See https://github.com/google/auto/issues/870. */)
+  public static final class TestExtractor implements Extractor<ExtractionParameters> {
+    @Override
+    public String identifier() {
+      return "documentation-generator-task-listener-test";
+    }
+
+    @Override
+    public Optional<ExtractionParameters> tryExtract(ClassTree tree, VisitorState state) {
+      return Optional.of(tree.getSimpleName().toString())
+          .filter(n -> n.contains(DocumentationGeneratorTaskListenerTest.class.getSimpleName()))
+          .map(
+              className ->
+                  new AutoValue_DocumentationGeneratorTaskListenerTest_ExtractionParameters(
+                      className,
+                      Streams.stream(state.getPath())
+                          .map(TestExtractor::describeTree)
+                          .collect(toImmutableList())));
+    }
+
+    private static String describeTree(Tree tree) {
+      return (tree instanceof ClassTree)
+          ? String.join(": ", String.valueOf(tree.getKind()), ((ClassTree) tree).getSimpleName())
+          : tree.getKind().toString();
+    }
+  }
+
+  @AutoValue
+  abstract static class ExtractionParameters {
+    abstract String className();
+
+    abstract ImmutableList<String> path();
+  }
 }

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/BugPatternTestExtractorTest-bugpattern-test-CompilationAndBugCheckerRefactoringTestHelpersTest.json

@@ -0,0 +1,24 @@
+{
+  "testClass": "CompilationAndBugCheckerRefactoringTestHelpersTest",
+  "testCases": [
+    {
+      "classUnderTest": "CompilationAndBugCheckerRefactoringTestHelpersTest.TestChecker",
+      "entries": [
+        {
+          "path": "A.java",
+          "code": "// BUG: Diagnostic contains:\nclass A {}\n"
+        }
+      ]
+    },
+    {
+      "classUnderTest": "CompilationAndBugCheckerRefactoringTestHelpersTest.TestChecker",
+      "entries": [
+        {
+          "path": "A.java",
+          "input": "class A {}\n",
+          "output": "class A { /* This is a change. */ }\n"
+        }
+      ]
+    }
+  ]
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/BugPatternTestExtractorTest-bugpattern-test-CompilationAndBugCheckerRefactoringTestHelpersWithCustomCheckerPackageAndNamesTest.json

@@ -0,0 +1,24 @@
+{
+  "testClass": "pkg.CompilationAndBugCheckerRefactoringTestHelpersWithCustomCheckerPackageAndNamesTest",
+  "testCases": [
+    {
+      "classUnderTest": "pkg.CompilationAndBugCheckerRefactoringTestHelpersWithCustomCheckerPackageAndNamesTest.CustomTestChecker",
+      "entries": [
+        {
+          "path": "A.java",
+          "code": "// BUG: Diagnostic contains:\nclass A {}\n"
+        }
+      ]
+    },
+    {
+      "classUnderTest": "pkg.CompilationAndBugCheckerRefactoringTestHelpersWithCustomCheckerPackageAndNamesTest.CustomTestChecker2",
+      "entries": [
+        {
+          "path": "A.java",
+          "input": "class A {}\n",
+          "output": "class A { /* This is a change. */ }\n"
+        }
+      ]
+    }
+  ]
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/BugPatternTestExtractorTest-bugpattern-test-MultiFileBugCheckerRefactoringTestHelperTest.json

@@ -0,0 +1,20 @@
+{
+  "testClass": "MultiFileBugCheckerRefactoringTestHelperTest",
+  "testCases": [
+    {
+      "classUnderTest": "MultiFileBugCheckerRefactoringTestHelperTest.TestChecker",
+      "entries": [
+        {
+          "path": "A.java",
+          "input": "class A {}\n",
+          "output": "class A { /* This is a change. */ }\n"
+        },
+        {
+          "path": "B.java",
+          "input": "class B {}\n",
+          "output": "class B { /* This is a change. */ }\n"
+        }
+      ]
+    }
+  ]
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/BugPatternTestExtractorTest-bugpattern-test-MultiFileCompilationTestHelperTest.json

@@ -0,0 +1,18 @@
+{
+  "testClass": "MultiFileCompilationTestHelperTest",
+  "testCases": [
+    {
+      "classUnderTest": "MultiFileCompilationTestHelperTest.TestChecker",
+      "entries": [
+        {
+          "path": "A.java",
+          "code": "// BUG: Diagnostic contains:\nclass A {}\n"
+        },
+        {
+          "path": "B.java",
+          "code": "// BUG: Diagnostic contains:\nclass B {}\n"
+        }
+      ]
+    }
+  ]
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/BugPatternTestExtractorTest-bugpattern-test-SingleFileBugCheckerRefactoringTestHelperTest.json

@@ -0,0 +1,15 @@
+{
+  "testClass": "SingleFileBugCheckerRefactoringTestHelperTest",
+  "testCases": [
+    {
+      "classUnderTest": "SingleFileBugCheckerRefactoringTestHelperTest.TestChecker",
+      "entries": [
+        {
+          "path": "A.java",
+          "input": "class A {}\n",
+          "output": "class A { /* This is a change. */ }\n"
+        }
+      ]
+    }
+  ]
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/BugPatternTestExtractorTest-bugpattern-test-SingleFileBugCheckerRefactoringTestHelperWithSetArgsFixChooserAndCustomTestModeTest.json

@@ -0,0 +1,15 @@
+{
+  "testClass": "SingleFileBugCheckerRefactoringTestHelperWithSetArgsFixChooserAndCustomTestModeTest",
+  "testCases": [
+    {
+      "classUnderTest": "SingleFileBugCheckerRefactoringTestHelperWithSetArgsFixChooserAndCustomTestModeTest.TestChecker",
+      "entries": [
+        {
+          "path": "A.java",
+          "input": "class A {}\n",
+          "output": "class A { /* This is a change. */ }\n"
+        }
+      ]
+    }
+  ]
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/BugPatternTestExtractorTest-bugpattern-test-SingleFileCompilationTestHelperTest.json

@@ -0,0 +1,14 @@
+{
+  "testClass": "SingleFileCompilationTestHelperTest",
+  "testCases": [
+    {
+      "classUnderTest": "SingleFileCompilationTestHelperTest.TestChecker",
+      "entries": [
+        {
+          "path": "A.java",
+          "code": "// BUG: Diagnostic contains:\nclass A {}\n"
+        }
+      ]
+    }
+  ]
+}

documentation-support/src/test/resources/tech/picnic/errorprone/documentation/BugPatternTestExtractorTest-bugpattern-test-SingleFileCompilationTestHelperWithSetArgsTest.json

@@ -0,0 +1,14 @@
+{
+  "testClass": "SingleFileCompilationTestHelperWithSetArgsTest",
+  "testCases": [
+    {
+      "classUnderTest": "SingleFileCompilationTestHelperWithSetArgsTest.TestChecker",
+      "entries": [
+        {
+          "path": "A.java",
+          "code": "// BUG: Diagnostic contains:\nclass A {}\n"
+        }
+      ]
+    }
+  ]
+}

error-prone-contrib/README.md

@@ -125,9 +125,6 @@ The following is a list of checks we'd like to see implemented:
   statement. Idem for other exception types.
 - A Guava-specific check that replaces simple anonymous `CacheLoader` subclass
   declarations with `CacheLoader.from(someLambda)`.
-- A Spring-specific check that enforces that methods with the `@Scheduled`
-  annotation are also annotated with New Relic's `@Trace` annotation. Such
-  methods should ideally not also represent Spring MVC endpoints.
 - A Spring-specific check that enforces that `@RequestMapping` annotations,
   when applied to a method, explicitly specify one or more target HTTP methods.
 - A Spring-specific check that looks for classes in which all `@RequestMapping`

error-prone-contrib/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.12.1-SNAPSHOT</version>
+        <version>0.14.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>error-prone-contrib</artifactId>
@@ -72,6 +72,11 @@
             <artifactId>auto-service-annotations</artifactId>
             <scope>provided</scope>
         </dependency>
+        <dependency>
+            <groupId>com.google.auto.value</groupId>
+            <artifactId>auto-value-annotations</artifactId>
+            <scope>provided</scope>
+        </dependency>
         <dependency>
             <groupId>com.google.googlejavaformat</groupId>
             <artifactId>google-java-format</artifactId>
@@ -81,11 +86,6 @@
             <artifactId>guava</artifactId>
             <scope>provided</scope>
         </dependency>
-        <dependency>
-            <groupId>com.newrelic.agent.java</groupId>
-            <artifactId>newrelic-api</artifactId>
-            <scope>test</scope>
-        </dependency>
         <dependency>
             <groupId>io.projectreactor</groupId>
             <artifactId>reactor-core</artifactId>
@@ -253,17 +253,6 @@
                         </compilerArgs>
                     </configuration>
                 </plugin>
-                <plugin>
-                    <groupId>org.apache.maven.plugins</groupId>
-                    <artifactId>maven-dependency-plugin</artifactId>
-                    <configuration>
-                        <ignoredUnusedDeclaredDependencies>
-                            <!-- XXX: Figure out why the plugin thinks this
-                            dependency is unused. -->
-                            <ignoredUnusedDeclaredDependency>${project.groupId}:refaster-support</ignoredUnusedDeclaredDependency>
-                        </ignoredUnusedDeclaredDependencies>
-                    </configuration>
-                </plugin>
             </plugins>
         </pluginManagement>
     </build>

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/AutowiredConstructor.java

@@ -9,7 +9,6 @@ import static com.google.errorprone.matchers.Matchers.isType;
 import static tech.picnic.errorprone.bugpatterns.util.Documentation.BUG_PATTERNS_BASE_URL;
 
 import com.google.auto.service.AutoService;
-import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
 import com.google.errorprone.BugPattern;
 import com.google.errorprone.VisitorState;
@@ -17,6 +16,7 @@ import com.google.errorprone.bugpatterns.BugChecker;
 import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
 import com.google.errorprone.matchers.Description;
 import com.google.errorprone.matchers.MultiMatcher;
+import com.google.errorprone.matchers.MultiMatcher.MultiMatchResult;
 import com.google.errorprone.util.ASTHelpers;
 import com.sun.source.tree.AnnotationTree;
 import com.sun.source.tree.ClassTree;
@@ -48,11 +48,9 @@ public final class AutowiredConstructor extends BugChecker implements ClassTreeM
       return Description.NO_MATCH;
     }
 
-    ImmutableList<AnnotationTree> annotations =
-        AUTOWIRED_ANNOTATION
-            .multiMatchResult(Iterables.getOnlyElement(constructors), state)
-            .matchingNodes();
-    if (annotations.size() != 1) {
+    MultiMatchResult<AnnotationTree> hasAutowiredAnnotation =
+        AUTOWIRED_ANNOTATION.multiMatchResult(Iterables.getOnlyElement(constructors), state);
+    if (!hasAutowiredAnnotation.matches()) {
       return Description.NO_MATCH;
     }
 
@@ -61,7 +59,7 @@ public final class AutowiredConstructor extends BugChecker implements ClassTreeM
      * means that the associated import can be removed as well. Rather than adding code for this
      * case we leave flagging the unused import to Error Prone's `RemoveUnusedImports` check.
      */
-    AnnotationTree annotation = Iterables.getOnlyElement(annotations);
+    AnnotationTree annotation = hasAutowiredAnnotation.onlyMatchingNode();
     return describeMatch(annotation, SourceCode.deleteWithTrailingWhitespace(annotation, state));
   }
 }

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/ErrorProneTestHelperSourceFormat.java

@@ -5,6 +5,7 @@ import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
 import static com.google.errorprone.BugPattern.StandardTags.STYLE;
 import static com.google.errorprone.matchers.Matchers.anyOf;
 import static com.google.errorprone.matchers.Matchers.instanceMethod;
+import static com.google.errorprone.matchers.Matchers.staticMethod;
 import static java.util.stream.Collectors.joining;
 import static tech.picnic.errorprone.bugpatterns.util.Documentation.BUG_PATTERNS_BASE_URL;
 
@@ -66,7 +67,12 @@ public final class ErrorProneTestHelperSourceFormat extends BugChecker
               .named("addSourceLines"),
           instanceMethod()
               .onDescendantOf("com.google.errorprone.BugCheckerRefactoringTestHelper")
-              .named("addInputLines"));
+              .named("addInputLines"),
+          // XXX: Add tests for `Compilation.compileWithDocumentationGenerator`. Until done, make
+          // sure to update this matcher if that method's class or name is changed/moved.
+          staticMethod()
+              .onClass("tech.picnic.errorprone.documentation.Compilation")
+              .named("compileWithDocumentationGenerator"));
   private static final Matcher<ExpressionTree> OUTPUT_SOURCE_ACCEPTING_METHOD =
       instanceMethod()
           .onDescendantOf("com.google.errorprone.BugCheckerRefactoringTestHelper.ExpectOutput")
@@ -83,7 +89,8 @@ public final class ErrorProneTestHelperSourceFormat extends BugChecker
     }
 
     List<? extends ExpressionTree> sourceLines =
-        tree.getArguments().subList(1, tree.getArguments().size());
+        tree.getArguments()
+            .subList(ASTHelpers.getSymbol(tree).params().size() - 1, tree.getArguments().size());
     if (sourceLines.isEmpty()) {
       return buildDescription(tree).setMessage("No source code provided").build();
     }
@@ -149,12 +156,13 @@ public final class ErrorProneTestHelperSourceFormat extends BugChecker
     return FORMATTER.formatSource(withOptionallyRemovedImports);
   }
 
+  // XXX: This logic is duplicated in `BugPatternTestExtractor`. Can we do better?
   private static Optional<String> getConstantSourceCode(
       List<? extends ExpressionTree> sourceLines) {
     StringBuilder source = new StringBuilder();
 
     for (ExpressionTree sourceLine : sourceLines) {
-      Object value = ASTHelpers.constValue(sourceLine);
+      String value = ASTHelpers.constValue(sourceLine, String.class);
       if (value == null) {
         return Optional.empty();
       }

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/FormatStringConcatenation.java

@@ -59,6 +59,7 @@ import tech.picnic.errorprone.bugpatterns.util.SourceCode;
 public final class FormatStringConcatenation extends BugChecker
     implements MethodInvocationTreeMatcher {
   private static final long serialVersionUID = 1L;
+
   /**
    * AssertJ exposes varargs {@code fail} methods with a {@link Throwable}-accepting overload, the
    * latter of which should not be flagged.
@@ -68,6 +69,7 @@ public final class FormatStringConcatenation extends BugChecker
           .anyClass()
           .withAnyName()
           .withParameters(String.class.getName(), Throwable.class.getName());
+
   // XXX: Drop some of these methods if we use Refaster to replace some with others.
   private static final Matcher<ExpressionTree> ASSERTJ_FORMAT_METHOD =
       anyOf(

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/IdentityConversion.java

@@ -37,6 +37,8 @@ import tech.picnic.errorprone.bugpatterns.util.SourceCode;
 // the target method such a modification may change the code's semantics or performance.
 // XXX: Also flag `Stream#map`, `Mono#map` and `Flux#map` invocations where the given transformation
 // is effectively the identity operation.
+// XXX: Also flag nullary instance method invocations that represent an identity conversion, such as
+// `Boolean#booleanValue()`, `Byte#byteValue()` and friends.
 @AutoService(BugChecker.class)
 @BugPattern(
     summary = "Avoid or clarify identity conversions",

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/JUnitNullaryParameterizedTestDeclaration.java

@@ -0,0 +1,91 @@
+package tech.picnic.errorprone.bugpatterns;
+
+import static com.google.errorprone.BugPattern.LinkType.CUSTOM;
+import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
+import static com.google.errorprone.BugPattern.StandardTags.SIMPLIFICATION;
+import static com.google.errorprone.matchers.ChildMultiMatcher.MatchType.AT_LEAST_ONE;
+import static com.google.errorprone.matchers.Matchers.annotations;
+import static com.google.errorprone.matchers.Matchers.anyOf;
+import static com.google.errorprone.matchers.Matchers.isType;
+import static tech.picnic.errorprone.bugpatterns.util.Documentation.BUG_PATTERNS_BASE_URL;
+import static tech.picnic.errorprone.bugpatterns.util.MoreMatchers.hasMetaAnnotation;
+
+import com.google.auto.service.AutoService;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
+import com.google.errorprone.fixes.SuggestedFix;
+import com.google.errorprone.fixes.SuggestedFixes;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.google.errorprone.matchers.MultiMatcher;
+import com.google.errorprone.matchers.MultiMatcher.MultiMatchResult;
+import com.sun.source.tree.AnnotationTree;
+import com.sun.source.tree.MethodTree;
+import tech.picnic.errorprone.bugpatterns.util.SourceCode;
+
+/**
+ * A {@link BugChecker} that flags nullary {@link
+ * org.junit.jupiter.params.ParameterizedTest @ParameterizedTest} test methods.
+ *
+ * <p>Such tests are unnecessarily executed more than necessary. This checker suggests annotating
+ * the method with {@link org.junit.jupiter.api.Test @Test}, and to drop all declared {@link
+ * org.junit.jupiter.params.provider.ArgumentsSource argument sources}.
+ */
+@AutoService(BugChecker.class)
+@BugPattern(
+    summary = "Nullary JUnit test methods should not be parameterized",
+    link = BUG_PATTERNS_BASE_URL + "JUnitNullaryParameterizedTestDeclaration",
+    linkType = CUSTOM,
+    severity = SUGGESTION,
+    tags = SIMPLIFICATION)
+public final class JUnitNullaryParameterizedTestDeclaration extends BugChecker
+    implements MethodTreeMatcher {
+  private static final long serialVersionUID = 1L;
+  private static final MultiMatcher<MethodTree, AnnotationTree> IS_PARAMETERIZED_TEST =
+      annotations(AT_LEAST_ONE, isType("org.junit.jupiter.params.ParameterizedTest"));
+  private static final Matcher<AnnotationTree> IS_ARGUMENT_SOURCE =
+      anyOf(
+          isType("org.junit.jupiter.params.provider.ArgumentsSource"),
+          isType("org.junit.jupiter.params.provider.ArgumentsSources"),
+          hasMetaAnnotation("org.junit.jupiter.params.provider.ArgumentsSource"));
+
+  /** Instantiates a new {@link JUnitNullaryParameterizedTestDeclaration} instance. */
+  public JUnitNullaryParameterizedTestDeclaration() {}
+
+  @Override
+  public Description matchMethod(MethodTree tree, VisitorState state) {
+    if (!tree.getParameters().isEmpty()) {
+      return Description.NO_MATCH;
+    }
+
+    MultiMatchResult<AnnotationTree> isParameterizedTest =
+        IS_PARAMETERIZED_TEST.multiMatchResult(tree, state);
+    if (!isParameterizedTest.matches()) {
+      return Description.NO_MATCH;
+    }
+
+    /*
+     * This method is vacuously parameterized. Suggest replacing `@ParameterizedTest` with `@Test`.
+     * (As each method is checked independently, we cannot in general determine whether this
+     * suggestion makes a `ParameterizedTest` type import obsolete; that task is left to Error
+     * Prone's `RemoveUnusedImports` check.)
+     */
+    SuggestedFix.Builder fix = SuggestedFix.builder();
+    fix.merge(
+        SuggestedFix.replace(
+            isParameterizedTest.onlyMatchingNode(),
+            '@' + SuggestedFixes.qualifyType(state, fix, "org.junit.jupiter.api.Test")));
+
+    /*
+     * Also suggest dropping all (explicit and implicit) `@ArgumentsSource`s. No attempt is made to
+     * assess whether a dropped `@MethodSource` also makes the referenced factory method(s) unused.
+     */
+    tree.getModifiers().getAnnotations().stream()
+        .filter(a -> IS_ARGUMENT_SOURCE.matches(a, state))
+        .forEach(a -> fix.merge(SourceCode.deleteWithTrailingWhitespace(a, state)));
+
+    return describeMatch(tree, fix.build());
+  }
+}

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/LexicographicalAnnotationAttributeListing.java

@@ -76,6 +76,7 @@ public final class LexicographicalAnnotationAttributeListing extends BugChecker
   private static final String FLAG_PREFIX = "LexicographicalAnnotationAttributeListing:";
   private static final String INCLUDED_ANNOTATIONS_FLAG = FLAG_PREFIX + "Includes";
   private static final String EXCLUDED_ANNOTATIONS_FLAG = FLAG_PREFIX + "Excludes";
+
   /**
    * The splitter applied to string-typed annotation arguments prior to lexicographical sorting. By
    * splitting on {@code =}, strings that represent e.g. inline Spring property declarations are
@@ -219,7 +220,10 @@ public final class LexicographicalAnnotationAttributeListing extends BugChecker
   private static AnnotationAttributeMatcher createAnnotationAttributeMatcher(
       ErrorProneFlags flags) {
     return AnnotationAttributeMatcher.create(
-        flags.getList(INCLUDED_ANNOTATIONS_FLAG), excludedAnnotations(flags));
+        flags.get(INCLUDED_ANNOTATIONS_FLAG).isPresent()
+            ? Optional.of(flags.getListOrEmpty(INCLUDED_ANNOTATIONS_FLAG))
+            : Optional.empty(),
+        excludedAnnotations(flags));
   }
 
   private static ImmutableList<String> excludedAnnotations(ErrorProneFlags flags) {

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/LexicographicalAnnotationListing.java

@@ -46,6 +46,7 @@ import tech.picnic.errorprone.bugpatterns.util.SourceCode;
 public final class LexicographicalAnnotationListing extends BugChecker
     implements MethodTreeMatcher {
   private static final long serialVersionUID = 1L;
+
   /**
    * A comparator that minimally reorders {@link AnnotationType}s, such that declaration annotations
    * are placed before type annotations.

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/MockitoMockClassReference.java

@@ -71,7 +71,7 @@ public final class MockitoMockClassReference extends BugChecker
     Tree parent = state.getPath().getParentPath().getLeaf();
     switch (parent.getKind()) {
       case VARIABLE:
-        return !ASTHelpers.hasNoExplicitType((VariableTree) parent, state)
+        return !ASTHelpers.hasImplicitType((VariableTree) parent, state)
             && MoreASTHelpers.areSameType(tree, parent, state);
       case ASSIGNMENT:
         return MoreASTHelpers.areSameType(tree, parent, state);

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/NonStaticImport.java

@@ -0,0 +1,215 @@
+package tech.picnic.errorprone.bugpatterns;
+
+import static com.google.errorprone.BugPattern.LinkType.CUSTOM;
+import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
+import static com.google.errorprone.BugPattern.StandardTags.STYLE;
+import static tech.picnic.errorprone.bugpatterns.StaticImport.STATIC_IMPORT_CANDIDATE_MEMBERS;
+import static tech.picnic.errorprone.bugpatterns.util.Documentation.BUG_PATTERNS_BASE_URL;
+
+import com.google.auto.service.AutoService;
+import com.google.auto.value.AutoValue;
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.ImmutableSetMultimap;
+import com.google.common.collect.ImmutableTable;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.CompilationUnitTreeMatcher;
+import com.google.errorprone.fixes.SuggestedFix;
+import com.google.errorprone.fixes.SuggestedFixes;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.util.ASTHelpers;
+import com.sun.source.tree.CompilationUnitTree;
+import com.sun.source.tree.IdentifierTree;
+import com.sun.source.tree.ImportTree;
+import com.sun.source.tree.MemberSelectTree;
+import com.sun.source.tree.Tree;
+import com.sun.source.util.TreeScanner;
+import com.sun.tools.javac.code.Symbol;
+import org.jspecify.annotations.Nullable;
+import tech.picnic.errorprone.bugpatterns.util.SourceCode;
+
+/**
+ * A {@link BugChecker} that flags static imports of type members that should *not* be statically
+ * imported.
+ */
+// XXX: This check is closely linked to `StaticImport`. Consider merging the two.
+// XXX: Add suppression support. If qualification of one more more identifiers is suppressed, then
+// the associated static import should *not* be removed.
+// XXX: Also introduce logic that disallows statically importing `ZoneOffset.ofHours` and other
+// `ofXXX`-style methods.
+@AutoService(BugChecker.class)
+@BugPattern(
+    summary = "Member should not be statically imported",
+    link = BUG_PATTERNS_BASE_URL + "NonStaticImport",
+    linkType = CUSTOM,
+    severity = SUGGESTION,
+    tags = STYLE)
+public final class NonStaticImport extends BugChecker implements CompilationUnitTreeMatcher {
+  private static final long serialVersionUID = 1L;
+
+  /**
+   * Types whose members should not be statically imported, unless exempted by {@link
+   * StaticImport#STATIC_IMPORT_CANDIDATE_MEMBERS}.
+   *
+   * <p>Types listed here should be mutually exclusive with {@link
+   * StaticImport#STATIC_IMPORT_CANDIDATE_TYPES}.
+   */
+  @VisibleForTesting
+  static final ImmutableSet<String> NON_STATIC_IMPORT_CANDIDATE_TYPES =
+      ImmutableSet.of(
+          "com.google.common.base.Strings",
+          "com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode",
+          "java.time.Clock",
+          "java.time.ZoneOffset");
+
+  /**
+   * Type members that should never be statically imported.
+   *
+   * <p>Please note that:
+   *
+   * <ul>
+   *   <li>Types listed by {@link #NON_STATIC_IMPORT_CANDIDATE_TYPES} and members listed by {@link
+   *       #NON_STATIC_IMPORT_CANDIDATE_IDENTIFIERS} should be omitted from this collection.
+   *   <li>This collection should be mutually exclusive with {@link
+   *       StaticImport#STATIC_IMPORT_CANDIDATE_MEMBERS}.
+   * </ul>
+   */
+  // XXX: Perhaps the set of exempted `java.util.Collections` methods is too strict. For now any
+  // method name that could be considered "too vague" or could conceivably mean something else in a
+  // specific context is left out.
+  static final ImmutableSetMultimap<String, String> NON_STATIC_IMPORT_CANDIDATE_MEMBERS =
+      ImmutableSetMultimap.<String, String>builder()
+          .put("com.google.common.base.Predicates", "contains")
+          .putAll(
+              "java.util.Collections",
+              "addAll",
+              "copy",
+              "fill",
+              "list",
+              "max",
+              "min",
+              "nCopies",
+              "rotate",
+              "sort",
+              "swap")
+          .put("java.util.Locale", "ROOT")
+          .putAll("java.util.regex.Pattern", "compile", "matches", "quote")
+          .put("org.springframework.http.MediaType", "ALL")
+          .build();
+
+  /**
+   * Identifiers that should never be statically imported.
+   *
+   * <p>Please note that:
+   *
+   * <ul>
+   *   <li>Identifiers listed by {@link StaticImport#STATIC_IMPORT_CANDIDATE_MEMBERS} should be
+   *       mutually exclusive with identifiers listed here.
+   *   <li>This list should contain a superset of the identifiers flagged by {@link
+   *       com.google.errorprone.bugpatterns.BadImport}.
+   * </ul>
+   */
+  static final ImmutableSet<String> NON_STATIC_IMPORT_CANDIDATE_IDENTIFIERS =
+      ImmutableSet.of(
+          "builder",
+          "copyOf",
+          "create",
+          "empty",
+          "from",
+          "getDefaultInstance",
+          "INSTANCE",
+          "MAX",
+          "MAX_VALUE",
+          "MIN",
+          "MIN_VALUE",
+          "newBuilder",
+          "newInstance",
+          "of",
+          "ONE",
+          "parse",
+          "valueOf",
+          "ZERO");
+
+  /** Instantiates a new {@link NonStaticImport} instance. */
+  public NonStaticImport() {}
+
+  @Override
+  public Description matchCompilationUnit(CompilationUnitTree tree, VisitorState state) {
+    ImmutableTable<String, String, UndesiredStaticImport> undesiredStaticImports =
+        getUndesiredStaticImports(tree, state);
+
+    if (!undesiredStaticImports.isEmpty()) {
+      replaceUndesiredStaticImportUsages(tree, undesiredStaticImports, state);
+
+      for (UndesiredStaticImport staticImport : undesiredStaticImports.values()) {
+        state.reportMatch(
+            describeMatch(staticImport.importTree(), staticImport.fixBuilder().build()));
+      }
+    }
+
+    /* Any violations have been flagged against the offending static import statement. */
+    return Description.NO_MATCH;
+  }
+
+  private static ImmutableTable<String, String, UndesiredStaticImport> getUndesiredStaticImports(
+      CompilationUnitTree tree, VisitorState state) {
+    ImmutableTable.Builder<String, String, UndesiredStaticImport> imports =
+        ImmutableTable.builder();
+    for (ImportTree importTree : tree.getImports()) {
+      Tree qualifiedIdentifier = importTree.getQualifiedIdentifier();
+      if (importTree.isStatic() && qualifiedIdentifier instanceof MemberSelectTree) {
+        MemberSelectTree memberSelectTree = (MemberSelectTree) qualifiedIdentifier;
+        String type = SourceCode.treeToString(memberSelectTree.getExpression(), state);
+        String member = memberSelectTree.getIdentifier().toString();
+        if (shouldNotBeStaticallyImported(type, member)) {
+          imports.put(
+              type,
+              member,
+              new AutoValue_NonStaticImport_UndesiredStaticImport(
+                  importTree, SuggestedFix.builder().removeStaticImport(type + '.' + member)));
+        }
+      }
+    }
+
+    return imports.build();
+  }
+
+  private static boolean shouldNotBeStaticallyImported(String type, String member) {
+    return (NON_STATIC_IMPORT_CANDIDATE_TYPES.contains(type)
+            && !STATIC_IMPORT_CANDIDATE_MEMBERS.containsEntry(type, member))
+        || NON_STATIC_IMPORT_CANDIDATE_MEMBERS.containsEntry(type, member)
+        || NON_STATIC_IMPORT_CANDIDATE_IDENTIFIERS.contains(member);
+  }
+
+  private static void replaceUndesiredStaticImportUsages(
+      CompilationUnitTree tree,
+      ImmutableTable<String, String, UndesiredStaticImport> undesiredStaticImports,
+      VisitorState state) {
+    new TreeScanner<@Nullable Void, @Nullable Void>() {
+      @Override
+      public @Nullable Void visitIdentifier(IdentifierTree node, @Nullable Void unused) {
+        Symbol symbol = ASTHelpers.getSymbol(node);
+        if (symbol != null) {
+          UndesiredStaticImport staticImport =
+              undesiredStaticImports.get(
+                  symbol.owner.getQualifiedName().toString(), symbol.name.toString());
+          if (staticImport != null) {
+            SuggestedFix.Builder fix = staticImport.fixBuilder();
+            fix.prefixWith(node, SuggestedFixes.qualifyType(state, fix, symbol.owner) + '.');
+          }
+        }
+
+        return super.visitIdentifier(node, unused);
+      }
+    }.scan(tree, null);
+  }
+
+  @AutoValue
+  abstract static class UndesiredStaticImport {
+    abstract ImportTree importTree();
+
+    abstract SuggestedFix.Builder fixBuilder();
+  }
+}

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/ScheduledTransactionTrace.java

@@ -1,94 +0,0 @@
-package tech.picnic.errorprone.bugpatterns;
-
-import static com.google.errorprone.BugPattern.LinkType.CUSTOM;
-import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
-import static com.google.errorprone.BugPattern.StandardTags.LIKELY_ERROR;
-import static com.google.errorprone.matchers.ChildMultiMatcher.MatchType.AT_LEAST_ONE;
-import static com.google.errorprone.matchers.Matchers.annotations;
-import static com.google.errorprone.matchers.Matchers.hasAnnotation;
-import static com.google.errorprone.matchers.Matchers.isType;
-import static tech.picnic.errorprone.bugpatterns.util.Documentation.BUG_PATTERNS_BASE_URL;
-
-import com.google.auto.common.AnnotationMirrors;
-import com.google.auto.service.AutoService;
-import com.google.common.collect.ImmutableList;
-import com.google.common.collect.Iterables;
-import com.google.errorprone.BugPattern;
-import com.google.errorprone.VisitorState;
-import com.google.errorprone.bugpatterns.BugChecker;
-import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
-import com.google.errorprone.fixes.SuggestedFix;
-import com.google.errorprone.fixes.SuggestedFixes;
-import com.google.errorprone.matchers.Description;
-import com.google.errorprone.matchers.Matcher;
-import com.google.errorprone.matchers.MultiMatcher;
-import com.google.errorprone.util.ASTHelpers;
-import com.sun.source.tree.AnnotationTree;
-import com.sun.source.tree.MethodTree;
-import com.sun.source.tree.Tree;
-import tech.picnic.errorprone.bugpatterns.util.ThirdPartyLibrary;
-
-/**
- * A {@link BugChecker} that flags methods with Spring's {@code @Scheduled} annotation that lack New
- * Relic Agent's {@code @Trace(dispatcher = true)}.
- */
-@AutoService(BugChecker.class)
-@BugPattern(
-    summary = "Scheduled operation must start a new New Relic transaction",
-    link = BUG_PATTERNS_BASE_URL + "ScheduledTransactionTrace",
-    linkType = CUSTOM,
-    severity = ERROR,
-    tags = LIKELY_ERROR)
-public final class ScheduledTransactionTrace extends BugChecker implements MethodTreeMatcher {
-  private static final long serialVersionUID = 1L;
-  private static final String TRACE_ANNOTATION_FQCN = "com.newrelic.api.agent.Trace";
-  private static final Matcher<Tree> IS_SCHEDULED =
-      hasAnnotation("org.springframework.scheduling.annotation.Scheduled");
-  private static final MultiMatcher<Tree, AnnotationTree> TRACE_ANNOTATION =
-      annotations(AT_LEAST_ONE, isType(TRACE_ANNOTATION_FQCN));
-
-  /** Instantiates a new {@link ScheduledTransactionTrace} instance. */
-  public ScheduledTransactionTrace() {}
-
-  @Override
-  public Description matchMethod(MethodTree tree, VisitorState state) {
-    if (!ThirdPartyLibrary.NEW_RELIC_AGENT_API.isIntroductionAllowed(state)
-        || !IS_SCHEDULED.matches(tree, state)) {
-      return Description.NO_MATCH;
-    }
-
-    ImmutableList<AnnotationTree> traceAnnotations =
-        TRACE_ANNOTATION.multiMatchResult(tree, state).matchingNodes();
-    if (traceAnnotations.isEmpty()) {
-      /* This method completely lacks the `@Trace` annotation; add it. */
-      return describeMatch(
-          tree,
-          SuggestedFix.builder()
-              .addImport(TRACE_ANNOTATION_FQCN)
-              .prefixWith(tree, "@Trace(dispatcher = true)")
-              .build());
-    }
-
-    AnnotationTree traceAnnotation = Iterables.getOnlyElement(traceAnnotations);
-    if (isCorrectAnnotation(traceAnnotation)) {
-      return Description.NO_MATCH;
-    }
-
-    /*
-     * The `@Trace` annotation is present but does not specify `dispatcher = true`. Add or update
-     * the `dispatcher` annotation element.
-     */
-    return describeMatch(
-        traceAnnotation,
-        SuggestedFixes.updateAnnotationArgumentValues(
-                traceAnnotation, state, "dispatcher", ImmutableList.of("true"))
-            .build());
-  }
-
-  private static boolean isCorrectAnnotation(AnnotationTree traceAnnotation) {
-    return Boolean.TRUE.equals(
-        AnnotationMirrors.getAnnotationValue(
-                ASTHelpers.getAnnotationMirror(traceAnnotation), "dispatcher")
-            .getValue());
-  }
-}

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/StaticImport.java

@@ -2,8 +2,10 @@ package tech.picnic.errorprone.bugpatterns;
 
 import static com.google.errorprone.BugPattern.LinkType.CUSTOM;
 import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
-import static com.google.errorprone.BugPattern.StandardTags.SIMPLIFICATION;
+import static com.google.errorprone.BugPattern.StandardTags.STYLE;
 import static java.util.Objects.requireNonNull;
+import static tech.picnic.errorprone.bugpatterns.NonStaticImport.NON_STATIC_IMPORT_CANDIDATE_IDENTIFIERS;
+import static tech.picnic.errorprone.bugpatterns.NonStaticImport.NON_STATIC_IMPORT_CANDIDATE_MEMBERS;
 import static tech.picnic.errorprone.bugpatterns.util.Documentation.BUG_PATTERNS_BASE_URL;
 
 import com.google.auto.service.AutoService;
@@ -27,35 +29,30 @@ import com.sun.source.tree.Tree;
 import com.sun.tools.javac.code.Type;
 import java.util.Optional;
 
-/**
- * A {@link BugChecker} that flags methods and constants that can and should be statically imported.
- */
+/** A {@link BugChecker} that flags type members that can and should be statically imported. */
+// XXX: This check is closely linked to `NonStaticImport`. Consider merging the two.
 // XXX: Tricky cases:
 // - `org.springframework.http.HttpStatus` (not always an improvement, and `valueOf` must
 //    certainly be excluded)
 // - `com.google.common.collect.Tables`
-// - `ch.qos.logback.classic.Level.{DEBUG, ERROR, INFO, TRACE, WARN"}`
-// XXX: Also introduce a check that disallows static imports of certain methods. Candidates:
-// - `com.google.common.base.Strings`
-// - `java.util.Optional.empty`
-// - `java.util.Locale.ROOT`
-// - `ZoneOffset.ofHours` and other `ofXXX`-style methods.
-// - `java.time.Clock`.
-// - Several other `java.time` classes.
-// - Likely any of `*.{ZERO, ONE, MIX, MAX, MIN_VALUE, MAX_VALUE}`.
+// - `ch.qos.logback.classic.Level.{DEBUG, ERROR, INFO, TRACE, WARN}`
 @AutoService(BugChecker.class)
 @BugPattern(
     summary = "Identifier should be statically imported",
     link = BUG_PATTERNS_BASE_URL + "StaticImport",
     linkType = CUSTOM,
     severity = SUGGESTION,
-    tags = SIMPLIFICATION)
+    tags = STYLE)
 public final class StaticImport extends BugChecker implements MemberSelectTreeMatcher {
   private static final long serialVersionUID = 1L;
 
   /**
    * Types whose members should be statically imported, unless exempted by {@link
-   * #STATIC_IMPORT_EXEMPTED_MEMBERS} or {@link #STATIC_IMPORT_EXEMPTED_IDENTIFIERS}.
+   * NonStaticImport#NON_STATIC_IMPORT_CANDIDATE_MEMBERS} or {@link
+   * NonStaticImport#NON_STATIC_IMPORT_CANDIDATE_IDENTIFIERS}.
+   *
+   * <p>Types listed here should be mutually exclusive with {@link
+   * NonStaticImport#NON_STATIC_IMPORT_CANDIDATE_TYPES}.
    */
   @VisibleForTesting
   static final ImmutableSet<String> STATIC_IMPORT_CANDIDATE_TYPES =
@@ -104,8 +101,20 @@ public final class StaticImport extends BugChecker implements MemberSelectTreeMa
           "reactor.function.TupleUtils",
           "tech.picnic.errorprone.bugpatterns.util.MoreTypes");
 
-  /** Type members that should be statically imported. */
-  @VisibleForTesting
+  /**
+   * Type members that should be statically imported.
+   *
+   * <p>Please note that:
+   *
+   * <ul>
+   *   <li>Types listed by {@link #STATIC_IMPORT_CANDIDATE_TYPES} should be omitted from this
+   *       collection.
+   *   <li>This collection should be mutually exclusive with {@link
+   *       NonStaticImport#NON_STATIC_IMPORT_CANDIDATE_MEMBERS}.
+   *   <li>This collection should not list members contained in {@link
+   *       NonStaticImport#NON_STATIC_IMPORT_CANDIDATE_IDENTIFIERS}.
+   * </ul>
+   */
   static final ImmutableSetMultimap<String, String> STATIC_IMPORT_CANDIDATE_MEMBERS =
       ImmutableSetMultimap.<String, String>builder()
           .putAll(
@@ -143,54 +152,6 @@ public final class StaticImport extends BugChecker implements MemberSelectTreeMa
           .putAll("com.google.common.collect.Comparators", "emptiesFirst", "emptiesLast")
           .build();
 
-  /**
-   * Type members that should never be statically imported.
-   *
-   * <p>Identifiers listed by {@link #STATIC_IMPORT_EXEMPTED_IDENTIFIERS} should be omitted from
-   * this collection.
-   */
-  // XXX: Perhaps the set of exempted `java.util.Collections` methods is too strict. For now any
-  // method name that could be considered "too vague" or could conceivably mean something else in a
-  // specific context is left out.
-  @VisibleForTesting
-  static final ImmutableSetMultimap<String, String> STATIC_IMPORT_EXEMPTED_MEMBERS =
-      ImmutableSetMultimap.<String, String>builder()
-          .put("com.mongodb.client.model.Filters", "empty")
-          .putAll(
-              "java.util.Collections",
-              "addAll",
-              "copy",
-              "fill",
-              "list",
-              "max",
-              "min",
-              "nCopies",
-              "rotate",
-              "sort",
-              "swap")
-          .putAll("java.util.regex.Pattern", "compile", "matches", "quote")
-          .put("org.springframework.http.MediaType", "ALL")
-          .build();
-
-  /**
-   * Identifiers that should never be statically imported.
-   *
-   * <p>This should be a superset of the identifiers flagged by {@link
-   * com.google.errorprone.bugpatterns.BadImport}.
-   */
-  @VisibleForTesting
-  static final ImmutableSet<String> STATIC_IMPORT_EXEMPTED_IDENTIFIERS =
-      ImmutableSet.of(
-          "builder",
-          "create",
-          "copyOf",
-          "from",
-          "getDefaultInstance",
-          "INSTANCE",
-          "newBuilder",
-          "of",
-          "valueOf");
-
   /** Instantiates a new {@link StaticImport} instance. */
   public StaticImport() {}
 
@@ -228,13 +189,13 @@ public final class StaticImport extends BugChecker implements MemberSelectTreeMa
 
   private static boolean isCandidate(MemberSelectTree tree) {
     String identifier = tree.getIdentifier().toString();
-    if (STATIC_IMPORT_EXEMPTED_IDENTIFIERS.contains(identifier)) {
+    if (NON_STATIC_IMPORT_CANDIDATE_IDENTIFIERS.contains(identifier)) {
       return false;
     }
 
     Type type = ASTHelpers.getType(tree.getExpression());
     return type != null
-        && !STATIC_IMPORT_EXEMPTED_MEMBERS.containsEntry(type.toString(), identifier);
+        && !NON_STATIC_IMPORT_CANDIDATE_MEMBERS.containsEntry(type.toString(), identifier);
   }
 
   private static Optional<String> getCandidateSimpleName(StaticImportInfo importInfo) {

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/StringJoin.java

@@ -23,7 +23,7 @@ import com.google.errorprone.util.ASTHelpers;
 import com.sun.source.tree.ExpressionTree;
 import com.sun.source.tree.MethodInvocationTree;
 import com.sun.tools.javac.code.Type;
-import com.sun.tools.javac.util.Convert;
+import com.sun.tools.javac.util.Constants;
 import java.util.Formattable;
 import java.util.Iterator;
 import java.util.List;
@@ -150,7 +150,7 @@ public final class StringJoin extends BugChecker implements MethodInvocationTree
     SuggestedFix.Builder fix =
         SuggestedFix.builder()
             .replace(tree.getMethodSelect(), "String.join")
-            .replace(arguments.next(), String.format("\"%s\"", Convert.quote(separator)));
+            .replace(arguments.next(), Constants.format(separator));
 
     while (arguments.hasNext()) {
       ExpressionTree argument = arguments.next();

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/util/Flags.java

@@ -16,10 +16,7 @@ public final class Flags {
    *     provided, or if the flag's value is the empty string.
    */
   public static ImmutableList<String> getList(ErrorProneFlags errorProneFlags, String name) {
-    return errorProneFlags
-        .getList(name)
-        .map(ImmutableList::copyOf)
-        .filter(flags -> !flags.equals(ImmutableList.of("")))
-        .orElseGet(ImmutableList::of);
+    ImmutableList<String> list = errorProneFlags.getListOrEmpty(name);
+    return list.equals(ImmutableList.of("")) ? ImmutableList.of() : list;
   }
 }

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/util/JavaKeywords.java

@@ -17,6 +17,7 @@ public final class JavaKeywords {
    */
   private static final ImmutableSet<String> BOOLEAN_AND_NULL_LITERALS =
       ImmutableSet.of("true", "false", "null");
+
   /**
    * List of all reserved keywords in the Java language.
    *
@@ -76,6 +77,7 @@ public final class JavaKeywords {
           "void",
           "volatile",
           "while");
+
   /**
    * List of all contextual keywords in the Java language.
    *
@@ -100,6 +102,7 @@ public final class JavaKeywords {
           "var",
           "with",
           "yield");
+
   /** List of all keywords in the Java language. */
   private static final ImmutableSet<String> ALL_KEYWORDS =
       Sets.union(RESERVED_KEYWORDS, CONTEXTUAL_KEYWORDS).immutableCopy();

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/util/MethodMatcherFactory.java

@@ -18,6 +18,7 @@ import java.util.regex.Pattern;
 public final class MethodMatcherFactory {
   private static final Splitter ARGUMENT_TYPE_SPLITTER =
       Splitter.on(',').trimResults().omitEmptyStrings();
+
   // XXX: Check whether we can use a parser for "standard" Java signatures here. Maybe
   // `sun.reflect.generics.parser.SignatureParser`?
   @SuppressWarnings("java:S5998" /* In practice there will be only modest recursion. */)

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/util/MoreJUnitMatchers.java

@@ -34,6 +34,7 @@ public final class MoreJUnitMatchers {
           anyOf(
               isType("org.junit.jupiter.api.Test"),
               hasMetaAnnotation("org.junit.jupiter.api.TestTemplate")));
+
   /** Matches JUnit Jupiter setup and teardown methods. */
   public static final MultiMatcher<MethodTree, AnnotationTree> SETUP_OR_TEARDOWN_METHOD =
       annotations(
@@ -43,6 +44,7 @@ public final class MoreJUnitMatchers {
               isType("org.junit.jupiter.api.AfterEach"),
               isType("org.junit.jupiter.api.BeforeAll"),
               isType("org.junit.jupiter.api.BeforeEach")));
+
   /**
    * Matches methods that have a {@link org.junit.jupiter.params.provider.MethodSource} annotation.
    */

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/util/ThirdPartyLibrary.java

@@ -32,13 +32,6 @@ public enum ThirdPartyLibrary {
    * @see <a href="https://github.com/google/guava">Guava on GitHub</a>
    */
   GUAVA("com.google.common.collect.ImmutableList"),
-  /**
-   * New Relic's Java agent API.
-   *
-   * @see <a href="https://github.com/newrelic/newrelic-java-agent/tree/main/newrelic-api">New Relic
-   *     Java agent API on GitHub</a>
-   */
-  NEW_RELIC_AGENT_API("com.newrelic.api.agent.Agent"),
   /**
    * VMWare's Project Reactor.
    *

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/AssertJMapRules.java

@@ -3,80 +3,40 @@ package tech.picnic.errorprone.refasterrules;
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.assertj.core.api.Assertions.assertThat;
 
-import com.google.common.collect.ImmutableBiMap;
-import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
-import com.google.common.collect.ImmutableMultiset;
-import com.google.common.collect.ImmutableSet;
-import com.google.common.collect.ImmutableSortedMap;
-import com.google.common.collect.ImmutableSortedMultiset;
-import com.google.common.collect.ImmutableSortedSet;
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import com.google.errorprone.refaster.annotation.Matches;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
-import java.util.ArrayList;
 import java.util.Collection;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.LinkedHashMap;
-import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Set;
-import java.util.TreeMap;
-import java.util.TreeSet;
 import org.assertj.core.api.AbstractAssert;
 import org.assertj.core.api.AbstractBooleanAssert;
 import org.assertj.core.api.AbstractCollectionAssert;
 import org.assertj.core.api.AbstractMapAssert;
 import org.assertj.core.api.MapAssert;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
+import tech.picnic.errorprone.refaster.matchers.IsEmpty;
 
 @OnlineDocumentation
 final class AssertJMapRules {
   private AssertJMapRules() {}
 
-  // XXX: Reduce boilerplate using a `Matcher` that identifies "empty" instances.
   static final class AbstractMapAssertIsEmpty<K, V> {
     @BeforeTemplate
-    @SuppressWarnings("unchecked")
-    void before(AbstractMapAssert<?, ?, K, V> mapAssert) {
+    void before(
+        AbstractMapAssert<?, ?, K, V> mapAssert,
+        @Matches(IsEmpty.class) Map<? extends K, ? extends V> wellTypedMap,
+        @Matches(IsEmpty.class) Map<?, ?> arbitrarilyTypedMap,
+        @Matches(IsEmpty.class) Iterable<? extends K> keys) {
       Refaster.anyOf(
-          mapAssert.containsExactlyEntriesOf(
-              Refaster.anyOf(
-                  ImmutableMap.of(),
-                  ImmutableBiMap.of(),
-                  ImmutableSortedMap.of(),
-                  new HashMap<>(),
-                  new LinkedHashMap<>(),
-                  new TreeMap<>())),
-          mapAssert.hasSameSizeAs(
-              Refaster.anyOf(
-                  ImmutableMap.of(),
-                  ImmutableBiMap.of(),
-                  ImmutableSortedMap.of(),
-                  new HashMap<>(),
-                  new LinkedHashMap<>(),
-                  new TreeMap<>())),
-          mapAssert.isEqualTo(
-              Refaster.anyOf(
-                  ImmutableMap.of(),
-                  ImmutableBiMap.of(),
-                  ImmutableSortedMap.of(),
-                  new HashMap<>(),
-                  new LinkedHashMap<>(),
-                  new TreeMap<>())),
-          mapAssert.containsOnlyKeys(
-              Refaster.anyOf(
-                  ImmutableList.of(),
-                  new ArrayList<>(),
-                  ImmutableSet.of(),
-                  new HashSet<>(),
-                  new LinkedHashSet<>(),
-                  ImmutableSortedSet.of(),
-                  new TreeSet<>(),
-                  ImmutableMultiset.of(),
-                  ImmutableSortedMultiset.of())),
+          mapAssert.containsExactlyEntriesOf(wellTypedMap),
+          mapAssert.containsExactlyInAnyOrderEntriesOf(wellTypedMap),
+          mapAssert.hasSameSizeAs(arbitrarilyTypedMap),
+          mapAssert.isEqualTo(arbitrarilyTypedMap),
+          mapAssert.containsOnlyKeys(keys),
           mapAssert.containsExactly(),
           mapAssert.containsOnly(),
           mapAssert.containsOnlyKeys());
@@ -112,15 +72,9 @@ final class AssertJMapRules {
 
   static final class AbstractMapAssertIsNotEmpty<K, V> {
     @BeforeTemplate
-    AbstractMapAssert<?, ?, K, V> before(AbstractMapAssert<?, ?, K, V> mapAssert) {
-      return mapAssert.isNotEqualTo(
-          Refaster.anyOf(
-              ImmutableMap.of(),
-              ImmutableBiMap.of(),
-              ImmutableSortedMap.of(),
-              new HashMap<>(),
-              new LinkedHashMap<>(),
-              new TreeMap<>()));
+    AbstractMapAssert<?, ?, K, V> before(
+        AbstractMapAssert<?, ?, K, V> mapAssert, @Matches(IsEmpty.class) Map<?, ?> map) {
+      return mapAssert.isNotEqualTo(map);
     }
 
     @AfterTemplate
@@ -148,12 +102,14 @@ final class AssertJMapRules {
 
   static final class AbstractMapAssertContainsExactlyInAnyOrderEntriesOf<K, V> {
     @BeforeTemplate
-    AbstractMapAssert<?, ?, K, V> before(AbstractMapAssert<?, ?, K, V> mapAssert, Map<K, V> map) {
+    AbstractMapAssert<?, ?, K, V> before(
+        AbstractMapAssert<?, ?, K, V> mapAssert, Map<? extends K, ? extends V> map) {
       return mapAssert.isEqualTo(map);
     }
 
     @AfterTemplate
-    AbstractMapAssert<?, ?, K, V> after(AbstractMapAssert<?, ?, K, V> mapAssert, Map<K, V> map) {
+    AbstractMapAssert<?, ?, K, V> after(
+        AbstractMapAssert<?, ?, K, V> mapAssert, Map<? extends K, ? extends V> map) {
       return mapAssert.containsExactlyInAnyOrderEntriesOf(map);
     }
   }
@@ -187,12 +143,12 @@ final class AssertJMapRules {
 
   static final class AbstractMapAssertHasSameSizeAs<K, V> {
     @BeforeTemplate
-    AbstractMapAssert<?, ?, K, V> before(AbstractMapAssert<?, ?, K, V> mapAssert, Map<K, V> map) {
+    AbstractMapAssert<?, ?, K, V> before(AbstractMapAssert<?, ?, K, V> mapAssert, Map<?, ?> map) {
       return mapAssert.hasSize(map.size());
     }
 
     @AfterTemplate
-    AbstractMapAssert<?, ?, K, V> after(AbstractMapAssert<?, ?, K, V> mapAssert, Map<K, V> map) {
+    AbstractMapAssert<?, ?, K, V> after(AbstractMapAssert<?, ?, K, V> mapAssert, Map<?, ?> map) {
       return mapAssert.hasSameSizeAs(map);
     }
   }
@@ -225,13 +181,14 @@ final class AssertJMapRules {
 
   static final class AssertThatMapContainsOnlyKeys<K, V> {
     @BeforeTemplate
-    AbstractCollectionAssert<?, Collection<? extends K>, K, ?> before(Map<K, V> map, Set<K> keys) {
+    AbstractCollectionAssert<?, Collection<? extends K>, K, ?> before(
+        Map<K, V> map, Set<? extends K> keys) {
       return assertThat(map.keySet()).hasSameElementsAs(keys);
     }
 
     @AfterTemplate
     @UseImportPolicy(STATIC_IMPORT_ALWAYS)
-    MapAssert<K, V> after(Map<K, V> map, Set<K> keys) {
+    MapAssert<K, V> after(Map<K, V> map, Set<? extends K> keys) {
       return assertThat(map).containsOnlyKeys(keys);
     }
   }

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/AssertJRules.java

@@ -6,28 +6,23 @@ import static org.assertj.core.api.Assertions.assertThat;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMultiset;
 import com.google.common.collect.ImmutableSet;
-import com.google.common.collect.ImmutableSortedMultiset;
-import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Multiset;
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import com.google.errorprone.refaster.annotation.Matches;
 import com.google.errorprone.refaster.annotation.NotMatches;
 import com.google.errorprone.refaster.annotation.Repeated;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.HashSet;
-import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.OptionalDouble;
 import java.util.OptionalInt;
 import java.util.OptionalLong;
 import java.util.Set;
-import java.util.TreeSet;
 import java.util.function.Predicate;
 import java.util.stream.Collector;
 import java.util.stream.Stream;
@@ -47,6 +42,7 @@ import org.assertj.core.api.OptionalIntAssert;
 import org.assertj.core.api.OptionalLongAssert;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 import tech.picnic.errorprone.refaster.matchers.IsArray;
+import tech.picnic.errorprone.refaster.matchers.IsEmpty;
 
 /** Refaster rules related to AssertJ expressions and statements. */
 // XXX: Most `AbstractIntegerAssert` rules can also be applied for other primitive types. Generate
@@ -181,63 +177,16 @@ final class AssertJRules {
   static final class AssertThatObjectEnumerableIsEmpty<E> {
     @BeforeTemplate
     @SuppressWarnings("unchecked")
-    void before(ObjectEnumerableAssert<?, E> enumAssert) {
+    void before(
+        ObjectEnumerableAssert<?, E> enumAssert,
+        @Matches(IsEmpty.class) Iterable<? extends E> wellTypedIterable,
+        @Matches(IsEmpty.class) Iterable<?> arbitrarilyTypedIterable) {
       Refaster.anyOf(
-          enumAssert.containsExactlyElementsOf(
-              Refaster.anyOf(
-                  ImmutableList.of(),
-                  new ArrayList<>(),
-                  ImmutableSet.of(),
-                  new HashSet<>(),
-                  new LinkedHashSet<>(),
-                  ImmutableSortedSet.of(),
-                  new TreeSet<>(),
-                  ImmutableMultiset.of(),
-                  ImmutableSortedMultiset.of())),
-          enumAssert.containsExactlyInAnyOrderElementsOf(
-              Refaster.anyOf(
-                  ImmutableList.of(),
-                  new ArrayList<>(),
-                  ImmutableSet.of(),
-                  new HashSet<>(),
-                  new LinkedHashSet<>(),
-                  ImmutableSortedSet.of(),
-                  new TreeSet<>(),
-                  ImmutableMultiset.of(),
-                  ImmutableSortedMultiset.of())),
-          enumAssert.hasSameElementsAs(
-              Refaster.anyOf(
-                  ImmutableList.of(),
-                  new ArrayList<>(),
-                  ImmutableSet.of(),
-                  new HashSet<>(),
-                  new LinkedHashSet<>(),
-                  ImmutableSortedSet.of(),
-                  new TreeSet<>(),
-                  ImmutableMultiset.of(),
-                  ImmutableSortedMultiset.of())),
-          enumAssert.hasSameSizeAs(
-              Refaster.anyOf(
-                  ImmutableList.of(),
-                  new ArrayList<>(),
-                  ImmutableSet.of(),
-                  new HashSet<>(),
-                  new LinkedHashSet<>(),
-                  ImmutableSortedSet.of(),
-                  new TreeSet<>(),
-                  ImmutableMultiset.of(),
-                  ImmutableSortedMultiset.of())),
-          enumAssert.isSubsetOf(
-              Refaster.anyOf(
-                  ImmutableList.of(),
-                  new ArrayList<>(),
-                  ImmutableSet.of(),
-                  new HashSet<>(),
-                  new LinkedHashSet<>(),
-                  ImmutableSortedSet.of(),
-                  new TreeSet<>(),
-                  ImmutableMultiset.of(),
-                  ImmutableSortedMultiset.of())),
+          enumAssert.containsExactlyElementsOf(wellTypedIterable),
+          enumAssert.containsExactlyInAnyOrderElementsOf(wellTypedIterable),
+          enumAssert.hasSameElementsAs(wellTypedIterable),
+          enumAssert.hasSameSizeAs(arbitrarilyTypedIterable),
+          enumAssert.isSubsetOf(wellTypedIterable),
           enumAssert.containsExactly(),
           enumAssert.containsExactlyInAnyOrder(),
           enumAssert.containsOnly(),

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/AssortedRules.java

@@ -103,8 +103,7 @@ final class AssortedRules {
     }
 
     @AfterTemplate
-    @Nullable
-    T after(Iterator<T> iterator, T defaultValue) {
+    @Nullable T after(Iterator<T> iterator, T defaultValue) {
       return Iterators.getNext(iterator, defaultValue);
     }
   }

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/BigDecimalRules.java

@@ -2,6 +2,7 @@ package tech.picnic.errorprone.refasterrules;
 
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
+import com.google.errorprone.refaster.annotation.AlsoNegation;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import java.math.BigDecimal;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
@@ -66,4 +67,61 @@ final class BigDecimalRules {
       return BigDecimal.valueOf(value);
     }
   }
+
+  /** Prefer using {@link BigDecimal#signum()} over more contrived alternatives. */
+  static final class BigDecimalSignumIsZero {
+    @BeforeTemplate
+    boolean before(BigDecimal value) {
+      return Refaster.anyOf(
+          value.compareTo(BigDecimal.ZERO) == 0, BigDecimal.ZERO.compareTo(value) == 0);
+    }
+
+    @AfterTemplate
+    @AlsoNegation
+    boolean after(BigDecimal value) {
+      return value.signum() == 0;
+    }
+  }
+
+  /**
+   * Prefer a {@link BigDecimal#signum()} comparison to 1 over more contrived or less clear
+   * alternatives.
+   */
+  static final class BigDecimalSignumIsPositive {
+    @BeforeTemplate
+    boolean before(BigDecimal value) {
+      return Refaster.anyOf(
+          value.compareTo(BigDecimal.ZERO) > 0,
+          BigDecimal.ZERO.compareTo(value) < 0,
+          value.signum() > 0,
+          value.signum() >= 1);
+    }
+
+    @AfterTemplate
+    @AlsoNegation
+    boolean after(BigDecimal value) {
+      return value.signum() == 1;
+    }
+  }
+
+  /**
+   * Prefer a {@link BigDecimal#signum()} comparison to -1 over more contrived or less clear
+   * alternatives.
+   */
+  static final class BigDecimalSignumIsNegative {
+    @BeforeTemplate
+    boolean before(BigDecimal value) {
+      return Refaster.anyOf(
+          value.compareTo(BigDecimal.ZERO) < 0,
+          BigDecimal.ZERO.compareTo(value) > 0,
+          value.signum() < 0,
+          value.signum() <= -1);
+    }
+
+    @AfterTemplate
+    @AlsoNegation
+    boolean after(BigDecimal value) {
+      return value.signum() == -1;
+    }
+  }
 }

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/BugCheckerRules.java

@@ -7,6 +7,8 @@ import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import com.sun.tools.javac.util.Constants;
+import com.sun.tools.javac.util.Convert;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
 /** Refaster rules related to {@link com.google.errorprone.bugpatterns.BugChecker} classes. */
@@ -52,4 +54,17 @@ final class BugCheckerRules {
       return helper.addInputLines(path, source).expectUnchanged();
     }
   }
+
+  /** Prefer using the {@link Constants} API over more verbose alternatives. */
+  static final class ConstantsFormat {
+    @BeforeTemplate
+    String before(String value) {
+      return String.format("\"%s\"", Convert.quote(value));
+    }
+
+    @AfterTemplate
+    String after(String value) {
+      return Constants.format(value);
+    }
+  }
 }

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ClassRules.java

@@ -0,0 +1,65 @@
+package tech.picnic.errorprone.refasterrules;
+
+import com.google.errorprone.refaster.Refaster;
+import com.google.errorprone.refaster.annotation.AfterTemplate;
+import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import java.util.function.Predicate;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
+
+/** Refaster rules related to expressions dealing with classes. */
+@OnlineDocumentation
+final class ClassRules {
+  private ClassRules() {}
+
+  /** Prefer {@link Class#isInstance(Object)} over more contrived alternatives. */
+  static final class ClassIsInstance<T, S> {
+    @BeforeTemplate
+    boolean before(Class<T> clazz, S object) {
+      return clazz.isAssignableFrom(object.getClass());
+    }
+
+    @AfterTemplate
+    boolean after(Class<T> clazz, S object) {
+      return clazz.isInstance(object);
+    }
+  }
+
+  /** Prefer using the {@code instanceof} keyword over less idiomatic alternatives. */
+  static final class Instanceof<T, S> {
+    @BeforeTemplate
+    boolean before(S object) {
+      return Refaster.<T>clazz().isInstance(object);
+    }
+
+    @AfterTemplate
+    boolean after(S object) {
+      return Refaster.<T>isInstance(object);
+    }
+  }
+
+  /** Prefer {@link Class#isInstance(Object)} method references over more verbose alternatives. */
+  static final class ClassLiteralIsInstancePredicate<T, S> {
+    @BeforeTemplate
+    Predicate<S> before() {
+      return o -> Refaster.<T>isInstance(o);
+    }
+
+    @AfterTemplate
+    Predicate<S> after() {
+      return Refaster.<T>clazz()::isInstance;
+    }
+  }
+
+  /** Prefer {@link Class#isInstance(Object)} method references over more verbose alternatives. */
+  static final class ClassReferenceIsInstancePredicate<T, S> {
+    @BeforeTemplate
+    Predicate<S> before(Class<T> clazz) {
+      return o -> clazz.isInstance(o);
+    }
+
+    @AfterTemplate
+    Predicate<S> after(Class<T> clazz) {
+      return clazz::isInstance;
+    }
+  }
+}

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/CollectionRules.java

@@ -74,6 +74,19 @@ final class CollectionRules {
     }
   }
 
+  /** Prefer {@link Collection#contains(Object)} over more contrived alternatives. */
+  static final class CollectionContains<T, S> {
+    @BeforeTemplate
+    boolean before(Collection<T> collection, S value) {
+      return collection.stream().anyMatch(value::equals);
+    }
+
+    @AfterTemplate
+    boolean after(Collection<T> collection, S value) {
+      return collection.contains(value);
+    }
+  }
+
   /**
    * Don't call {@link Iterables#addAll(Collection, Iterable)} when the elements to be added are
    * already part of a {@link Collection}.

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ComparatorRules.java

@@ -7,7 +7,6 @@ import static java.util.Comparator.comparingInt;
 import static java.util.Comparator.comparingLong;
 import static java.util.Comparator.naturalOrder;
 import static java.util.Comparator.reverseOrder;
-import static java.util.function.Function.identity;
 
 import com.google.common.collect.Comparators;
 import com.google.common.collect.ImmutableList;
@@ -16,6 +15,7 @@ import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import com.google.errorprone.refaster.annotation.Matches;
 import com.google.errorprone.refaster.annotation.Repeated;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
 import java.util.Arrays;
@@ -28,6 +28,7 @@ import java.util.function.ToIntFunction;
 import java.util.function.ToLongFunction;
 import java.util.stream.Stream;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
+import tech.picnic.errorprone.refaster.matchers.IsIdentityOperation;
 
 /** Refaster rules related to expressions dealing with {@link Comparator}s. */
 @OnlineDocumentation
@@ -36,12 +37,12 @@ final class ComparatorRules {
 
   /** Prefer {@link Comparator#naturalOrder()} over more complicated constructs. */
   static final class NaturalOrder<T extends Comparable<? super T>> {
-    // XXX: Drop the `Refaster.anyOf` if/when we decide to rewrite one to the other.
     @BeforeTemplate
-    Comparator<T> before() {
+    Comparator<T> before(
+        @Matches(IsIdentityOperation.class) Function<? super T, ? extends T> keyExtractor) {
       return Refaster.anyOf(
           T::compareTo,
-          comparing(Refaster.anyOf(identity(), v -> v)),
+          comparing(keyExtractor),
           Collections.<T>reverseOrder(reverseOrder()),
           Comparator.<T>reverseOrder().reversed());
     }
@@ -72,10 +73,11 @@ final class ComparatorRules {
   }
 
   static final class CustomComparator<T> {
-    // XXX: Drop the `Refaster.anyOf` if/when we decide to rewrite one to the other.
     @BeforeTemplate
-    Comparator<T> before(Comparator<T> cmp) {
-      return comparing(Refaster.anyOf(identity(), v -> v), cmp);
+    Comparator<T> before(
+        Comparator<T> cmp,
+        @Matches(IsIdentityOperation.class) Function<? super T, ? extends T> keyExtractor) {
+      return comparing(keyExtractor, cmp);
     }
 
     @AfterTemplate
@@ -183,14 +185,15 @@ final class ComparatorRules {
   }
 
   /**
-   * Where applicable, prefer {@link Comparator#naturalOrder()} over {@link Function#identity()}, as
-   * it more clearly states intent.
+   * Where applicable, prefer {@link Comparator#naturalOrder()} over identity function-based
+   * comparisons, as the former more clearly states intent.
    */
   static final class ThenComparingNaturalOrder<T extends Comparable<? super T>> {
-    // XXX: Drop the `Refaster.anyOf` if/when we decide to rewrite one to the other.
     @BeforeTemplate
-    Comparator<T> before(Comparator<T> cmp) {
-      return cmp.thenComparing(Refaster.anyOf(identity(), v -> v));
+    Comparator<T> before(
+        Comparator<T> cmp,
+        @Matches(IsIdentityOperation.class) Function<? super T, ? extends T> keyExtractor) {
+      return cmp.thenComparing(keyExtractor);
     }
 
     @AfterTemplate

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/EqualityRules.java

@@ -1,11 +1,16 @@
 package tech.picnic.errorprone.refasterrules;
 
+import static java.util.function.Predicate.not;
+
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.AlsoNegation;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import com.google.errorprone.refaster.annotation.MayOptionallyUse;
+import com.google.errorprone.refaster.annotation.Placeholder;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.function.Predicate;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
@@ -131,4 +136,62 @@ final class EqualityRules {
       return a == b;
     }
   }
+
+  /**
+   * Don't pass a lambda expression to {@link Predicate#not(Predicate)}; instead push the negation
+   * into the lambda expression.
+   */
+  abstract static class PredicateLambda<T> {
+    @Placeholder(allowsIdentity = true)
+    abstract boolean predicate(@MayOptionallyUse T value);
+
+    @BeforeTemplate
+    Predicate<T> before() {
+      return not(v -> predicate(v));
+    }
+
+    @AfterTemplate
+    Predicate<T> after() {
+      return v -> !predicate(v);
+    }
+  }
+
+  /** Avoid contrived ways of handling {@code null} values during equality testing. */
+  static final class EqualsLhsNullable<T, S> {
+    @BeforeTemplate
+    boolean before(T value1, S value2) {
+      return Optional.ofNullable(value1).equals(Optional.of(value2));
+    }
+
+    @AfterTemplate
+    boolean after(T value1, S value2) {
+      return value2.equals(value1);
+    }
+  }
+
+  /** Avoid contrived ways of handling {@code null} values during equality testing. */
+  static final class EqualsRhsNullable<T, S> {
+    @BeforeTemplate
+    boolean before(T value1, S value2) {
+      return Optional.of(value1).equals(Optional.ofNullable(value2));
+    }
+
+    @AfterTemplate
+    boolean after(T value1, S value2) {
+      return value1.equals(value2);
+    }
+  }
+
+  /** Avoid contrived ways of handling {@code null} values during equality testing. */
+  static final class EqualsLhsAndRhsNullable<T, S> {
+    @BeforeTemplate
+    boolean before(T value1, S value2) {
+      return Optional.ofNullable(value1).equals(Optional.ofNullable(value2));
+    }
+
+    @AfterTemplate
+    boolean after(T value1, S value2) {
+      return Objects.equals(value1, value2);
+    }
+  }
 }

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/FileRules.java

@@ -0,0 +1,43 @@
+package tech.picnic.errorprone.refasterrules;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import com.google.errorprone.refaster.annotation.AfterTemplate;
+import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import java.io.IOException;
+import java.nio.charset.Charset;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
+
+/** Refaster rules related to expressions dealing with files. */
+@OnlineDocumentation
+final class FileRules {
+  private FileRules() {}
+
+  /** Prefer {@link Files#readString(Path, Charset)} over more contrived alternatives. */
+  static final class FilesReadStringWithCharset {
+    @BeforeTemplate
+    String before(Path path, Charset charset) throws IOException {
+      return new String(Files.readAllBytes(path), charset);
+    }
+
+    @AfterTemplate
+    String after(Path path, Charset charset) throws IOException {
+      return Files.readString(path, charset);
+    }
+  }
+
+  /** Prefer {@link Files#readString(Path)} over more verbose alternatives. */
+  static final class FilesReadString {
+    @BeforeTemplate
+    String before(Path path) throws IOException {
+      return Files.readString(path, UTF_8);
+    }
+
+    @AfterTemplate
+    String after(Path path) throws IOException {
+      return Files.readString(path);
+    }
+  }
+}

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ImmutableListMultimapRules.java

@@ -3,7 +3,6 @@ package tech.picnic.errorprone.refasterrules;
 import static com.google.common.collect.ImmutableListMultimap.flatteningToImmutableListMultimap;
 import static com.google.common.collect.ImmutableListMultimap.toImmutableListMultimap;
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
-import static java.util.function.Function.identity;
 
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.ImmutableMultimap;
@@ -16,6 +15,7 @@ import com.google.common.collect.Streams;
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import com.google.errorprone.refaster.annotation.Matches;
 import com.google.errorprone.refaster.annotation.MayOptionallyUse;
 import com.google.errorprone.refaster.annotation.Placeholder;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
@@ -25,6 +25,7 @@ import java.util.Map;
 import java.util.function.Function;
 import java.util.stream.Stream;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
+import tech.picnic.errorprone.refaster.matchers.IsIdentityOperation;
 
 /** Refaster rules related to expressions dealing with {@link ImmutableListMultimap}s. */
 @OnlineDocumentation
@@ -173,27 +174,29 @@ final class ImmutableListMultimapRules {
    * Prefer {@link Multimaps#index(Iterable, com.google.common.base.Function)} over the stream-based
    * alternative.
    */
-  // XXX: Drop the `Refaster.anyOf` if/when we decide to rewrite one to the other.
   static final class IndexIterableToImmutableListMultimap<K, V> {
     @BeforeTemplate
     ImmutableListMultimap<K, V> before(
-        Iterator<V> iterable, Function<? super V, ? extends K> keyFunction) {
-      return Streams.stream(iterable)
-          .collect(toImmutableListMultimap(keyFunction, Refaster.anyOf(identity(), v -> v)));
+        Iterator<V> iterable,
+        Function<? super V, ? extends K> keyFunction,
+        @Matches(IsIdentityOperation.class) Function<? super V, ? extends V> valueFunction) {
+      return Streams.stream(iterable).collect(toImmutableListMultimap(keyFunction, valueFunction));
     }
 
     @BeforeTemplate
     ImmutableListMultimap<K, V> before(
-        Iterable<V> iterable, Function<? super V, ? extends K> keyFunction) {
-      return Streams.stream(iterable)
-          .collect(toImmutableListMultimap(keyFunction, Refaster.anyOf(identity(), v -> v)));
+        Iterable<V> iterable,
+        Function<? super V, ? extends K> keyFunction,
+        @Matches(IsIdentityOperation.class) Function<? super V, ? extends V> valueFunction) {
+      return Streams.stream(iterable).collect(toImmutableListMultimap(keyFunction, valueFunction));
     }
 
     @BeforeTemplate
     ImmutableListMultimap<K, V> before(
-        Collection<V> iterable, Function<? super V, ? extends K> keyFunction) {
-      return iterable.stream()
-          .collect(toImmutableListMultimap(keyFunction, Refaster.anyOf(identity(), v -> v)));
+        Collection<V> iterable,
+        Function<? super V, ? extends K> keyFunction,
+        @Matches(IsIdentityOperation.class) Function<? super V, ? extends V> valueFunction) {
+      return iterable.stream().collect(toImmutableListMultimap(keyFunction, valueFunction));
     }
 
     @AfterTemplate

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ImmutableMapRules.java

@@ -4,7 +4,6 @@ import static com.google.common.collect.ImmutableMap.toImmutableMap;
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static java.util.Collections.emptyMap;
 import static java.util.Collections.singletonMap;
-import static java.util.function.Function.identity;
 
 import com.google.common.base.Predicate;
 import com.google.common.collect.ImmutableMap;
@@ -13,6 +12,7 @@ import com.google.common.collect.Streams;
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import com.google.errorprone.refaster.annotation.Matches;
 import com.google.errorprone.refaster.annotation.MayOptionallyUse;
 import com.google.errorprone.refaster.annotation.Placeholder;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
@@ -23,6 +23,7 @@ import java.util.Set;
 import java.util.function.Function;
 import java.util.stream.Stream;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
+import tech.picnic.errorprone.refaster.matchers.IsIdentityOperation;
 
 /** Refaster rules related to expressions dealing with {@link ImmutableMap}s. */
 @OnlineDocumentation
@@ -63,27 +64,29 @@ final class ImmutableMapRules {
    * Prefer {@link Maps#toMap(Iterable, com.google.common.base.Function)} over more contrived
    * alternatives.
    */
-  // XXX: Drop the `Refaster.anyOf` if/when we decide to rewrite one to the other.
   static final class IterableToImmutableMap<K, V> {
     @BeforeTemplate
     ImmutableMap<K, V> before(
-        Iterator<K> iterable, Function<? super K, ? extends V> valueFunction) {
-      return Streams.stream(iterable)
-          .collect(toImmutableMap(Refaster.anyOf(identity(), k -> k), valueFunction));
+        Iterator<K> iterable,
+        Function<? super K, ? extends V> valueFunction,
+        @Matches(IsIdentityOperation.class) Function<? super K, ? extends K> keyFunction) {
+      return Streams.stream(iterable).collect(toImmutableMap(keyFunction, valueFunction));
     }
 
     @BeforeTemplate
     ImmutableMap<K, V> before(
-        Iterable<K> iterable, Function<? super K, ? extends V> valueFunction) {
-      return Streams.stream(iterable)
-          .collect(toImmutableMap(Refaster.anyOf(identity(), k -> k), valueFunction));
+        Iterable<K> iterable,
+        Function<? super K, ? extends V> valueFunction,
+        @Matches(IsIdentityOperation.class) Function<? super K, ? extends K> keyFunction) {
+      return Streams.stream(iterable).collect(toImmutableMap(keyFunction, valueFunction));
     }
 
     @BeforeTemplate
     ImmutableMap<K, V> before(
-        Collection<K> iterable, Function<? super K, ? extends V> valueFunction) {
-      return iterable.stream()
-          .collect(toImmutableMap(Refaster.anyOf(identity(), k -> k), valueFunction));
+        Collection<K> iterable,
+        Function<? super K, ? extends V> valueFunction,
+        @Matches(IsIdentityOperation.class) Function<? super K, ? extends K> keyFunction) {
+      return iterable.stream().collect(toImmutableMap(keyFunction, valueFunction));
     }
 
     @BeforeTemplate
@@ -157,25 +160,29 @@ final class ImmutableMapRules {
    * Prefer {@link Maps#uniqueIndex(Iterable, com.google.common.base.Function)} over the
    * stream-based alternative.
    */
-  // XXX: Drop the `Refaster.anyOf` if/when we decide to rewrite one to the other.
   static final class IndexIterableToImmutableMap<K, V> {
     @BeforeTemplate
-    ImmutableMap<K, V> before(Iterator<V> iterable, Function<? super V, ? extends K> keyFunction) {
-      return Streams.stream(iterable)
-          .collect(toImmutableMap(keyFunction, Refaster.anyOf(identity(), v -> v)));
-    }
-
-    @BeforeTemplate
-    ImmutableMap<K, V> before(Iterable<V> iterable, Function<? super V, ? extends K> keyFunction) {
-      return Streams.stream(iterable)
-          .collect(toImmutableMap(keyFunction, Refaster.anyOf(identity(), v -> v)));
+    ImmutableMap<K, V> before(
+        Iterator<V> iterable,
+        Function<? super V, ? extends K> keyFunction,
+        @Matches(IsIdentityOperation.class) Function<? super V, ? extends V> valueFunction) {
+      return Streams.stream(iterable).collect(toImmutableMap(keyFunction, valueFunction));
     }
 
     @BeforeTemplate
     ImmutableMap<K, V> before(
-        Collection<V> iterable, Function<? super V, ? extends K> keyFunction) {
-      return iterable.stream()
-          .collect(toImmutableMap(keyFunction, Refaster.anyOf(identity(), v -> v)));
+        Iterable<V> iterable,
+        Function<? super V, ? extends K> keyFunction,
+        @Matches(IsIdentityOperation.class) Function<? super V, ? extends V> valueFunction) {
+      return Streams.stream(iterable).collect(toImmutableMap(keyFunction, valueFunction));
+    }
+
+    @BeforeTemplate
+    ImmutableMap<K, V> before(
+        Collection<V> iterable,
+        Function<? super V, ? extends K> keyFunction,
+        @Matches(IsIdentityOperation.class) Function<? super V, ? extends V> valueFunction) {
+      return iterable.stream().collect(toImmutableMap(keyFunction, valueFunction));
     }
 
     @AfterTemplate

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/JUnitToAssertJRules.java

@@ -6,6 +6,7 @@ import static org.assertj.core.api.Assertions.assertThatCode;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.assertj.core.api.Assertions.fail;
 import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
@@ -517,4 +518,82 @@ final class JUnitToAssertJRules {
       assertThat(actual).withFailMessage(supplier).isInstanceOf(clazz);
     }
   }
+
+  static final class AssertThatByteIsEqualTo {
+    @BeforeTemplate
+    void before(byte actual, byte expected) {
+      assertEquals(actual, expected);
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(byte actual, byte expected) {
+      assertThat(actual).isEqualTo(expected);
+    }
+  }
+
+  static final class AssertThatByteWithFailMessageStringIsEqualTo {
+    @BeforeTemplate
+    void before(byte actual, byte expected, String message) {
+      assertEquals(actual, expected, message);
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(byte actual, byte expected, String message) {
+      assertThat(actual).withFailMessage(message).isEqualTo(expected);
+    }
+  }
+
+  static final class AssertThatByteWithFailMessageSupplierIsEqualTo {
+    @BeforeTemplate
+    void before(byte actual, byte expected, Supplier<String> message) {
+      assertEquals(actual, expected, message);
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(byte actual, byte expected, Supplier<String> message) {
+      assertThat(actual).withFailMessage(message).isEqualTo(expected);
+    }
+  }
+
+  static final class AssertThatCharIsEqualTo {
+    @BeforeTemplate
+    void before(char actual, char expected) {
+      assertEquals(actual, expected);
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(char actual, char expected) {
+      assertThat(actual).isEqualTo(expected);
+    }
+  }
+
+  static final class AssertThatCharWithFailMessageStringIsEqualTo {
+    @BeforeTemplate
+    void before(char actual, char expected, String message) {
+      assertEquals(actual, expected, message);
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(char actual, char expected, String message) {
+      assertThat(actual).withFailMessage(message).isEqualTo(expected);
+    }
+  }
+
+  static final class AssertThatCharWithFailMessageSupplierIsEqualTo {
+    @BeforeTemplate
+    void before(char actual, char expected, Supplier<String> message) {
+      assertEquals(actual, expected, message);
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(char actual, char expected, Supplier<String> message) {
+      assertThat(actual).withFailMessage(message).isEqualTo(expected);
+    }
+  }
 }

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/MapRules.java

@@ -33,14 +33,12 @@ final class MapRules {
 
   static final class MapGetOrNull<K, V, T> {
     @BeforeTemplate
-    @Nullable
-    V before(Map<K, V> map, T key) {
+    @Nullable V before(Map<K, V> map, T key) {
       return map.getOrDefault(key, null);
     }
 
     @AfterTemplate
-    @Nullable
-    V after(Map<K, V> map, T key) {
+    @Nullable V after(Map<K, V> map, T key) {
       return map.get(key);
     }
   }

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/MockitoRules.java

@@ -5,10 +5,12 @@ import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 
+import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
 import org.mockito.Mockito;
+import org.mockito.invocation.InvocationOnMock;
 import org.mockito.verification.VerificationMode;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
@@ -50,4 +52,30 @@ final class MockitoRules {
       return verify(mock);
     }
   }
+
+  static final class InvocationOnMockGetArguments {
+    @BeforeTemplate
+    Object before(InvocationOnMock invocation, int i) {
+      return invocation.getArguments()[i];
+    }
+
+    @AfterTemplate
+    Object after(InvocationOnMock invocation, int i) {
+      return invocation.getArgument(i);
+    }
+  }
+
+  static final class InvocationOnMockGetArgumentsWithTypeParameter<T> {
+    @BeforeTemplate
+    @SuppressWarnings("unchecked")
+    T before(InvocationOnMock invocation, int i) {
+      return Refaster.anyOf(
+          invocation.getArgument(i, Refaster.<T>clazz()), (T) invocation.getArgument(i));
+    }
+
+    @AfterTemplate
+    T after(InvocationOnMock invocation, int i) {
+      return invocation.<T>getArgument(i);
+    }
+  }
 }

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/MultimapRules.java

@@ -50,8 +50,7 @@ final class MultimapRules {
    */
   static final class MultimapGet<K, V> {
     @BeforeTemplate
-    @Nullable
-    Collection<V> before(Multimap<K, V> multimap, K key) {
+    @Nullable Collection<V> before(Multimap<K, V> multimap, K key) {
       return Refaster.anyOf(multimap.asMap(), Multimaps.asMap(multimap)).get(key);
     }
 

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/OptionalRules.java

@@ -100,6 +100,20 @@ final class OptionalRules {
     }
   }
 
+  /** Prefer {@link Optional#equals(Object)} over more contrived alternatives. */
+  static final class OptionalEqualsOptional<T, S> {
+    @BeforeTemplate
+    boolean before(Optional<T> optional, S value) {
+      return Refaster.anyOf(
+          optional.filter(value::equals).isPresent(), optional.stream().anyMatch(value::equals));
+    }
+
+    @AfterTemplate
+    boolean after(Optional<T> optional, S value) {
+      return optional.equals(Optional.of(value));
+    }
+  }
+
   /**
    * Don't use the ternary operator to extract the first element of a possibly-empty {@link
    * Iterator} as an {@link Optional}.
@@ -350,13 +364,14 @@ final class OptionalRules {
     Optional<T> before(Optional<T> optional1, Optional<T> optional2) {
       // XXX: Note that rewriting the first and third variant will change the code's behavior if
       // `optional2` has side-effects.
-      // XXX: Note that rewriting the first and third variant will introduce a compilation error if
-      // `optional2` is not effectively final. Review whether a `@Matcher` can be used to avoid
-      // this.
+      // XXX: Note that rewriting the first, third and fourth variant will introduce a compilation
+      // error if `optional2` is not effectively final. Review whether a `@Matcher` can be used to
+      // avoid this.
       return Refaster.anyOf(
           optional1.map(Optional::of).orElse(optional2),
           optional1.map(Optional::of).orElseGet(() -> optional2),
-          Stream.of(optional1, optional2).flatMap(Optional::stream).findFirst());
+          Stream.of(optional1, optional2).flatMap(Optional::stream).findFirst(),
+          optional1.isPresent() ? optional1 : optional2);
     }
 
     @AfterTemplate
@@ -422,12 +437,22 @@ final class OptionalRules {
     }
   }
 
-  // XXX: Add a rule for:
-  // `optional.flatMap(x -> pred(x) ? Optional.empty() : Optional.of(x))` and variants.
-  // (Maybe canonicalize the inner expression. Maybe we rewrite already.)
+  /** Prefer {@link Optional#stream()} over more contrived alternatives. */
+  static final class OptionalStream<T> {
+    @BeforeTemplate
+    Stream<T> before(Optional<T> optional) {
+      return Refaster.anyOf(
+          optional.map(Stream::of).orElse(Stream.empty()),
+          optional.map(Stream::of).orElseGet(Stream::empty));
+    }
+
+    @AfterTemplate
+    Stream<T> after(Optional<T> optional) {
+      return optional.stream();
+    }
+  }
 
   // XXX: Add a rule for:
-  // `optional.map(Stream::of).orElse(Stream.empty())`
-  // `optional.map(Stream::of).orElseGet(Stream::empty)`
-  // -> `optional.stream()`
+  // `optional.flatMap(x -> pred(x) ? Optional.empty() : Optional.of(x))` and variants.
+  // (Maybe canonicalize the inner expression. Maybe we rewrite it already.)
 }

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/PatternRules.java

@@ -0,0 +1,46 @@
+package tech.picnic.errorprone.refasterrules;
+
+import static com.google.common.base.Predicates.containsPattern;
+
+import com.google.common.base.Predicates;
+import com.google.errorprone.refaster.annotation.AfterTemplate;
+import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import java.util.function.Predicate;
+import java.util.regex.Pattern;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
+
+/** Refaster rules related to code dealing with regular expressions. */
+@OnlineDocumentation
+final class PatternRules {
+  private PatternRules() {}
+
+  /** Prefer {@link Pattern#asPredicate()} over non-JDK alternatives. */
+  // XXX: This rule could also replace `s -> pattern.matcher(s).find()`, though the lambda
+  // expression may match functional interfaces other than `Predicate`. If we do add such a rule, we
+  // should also add a rule that replaces `s -> pattern.matcher(s).matches()` with
+  // `pattern.asMatchPredicate()`.
+  static final class PatternAsPredicate {
+    @BeforeTemplate
+    Predicate<CharSequence> before(Pattern pattern) {
+      return Predicates.contains(pattern);
+    }
+
+    @AfterTemplate
+    Predicate<String> after(Pattern pattern) {
+      return pattern.asPredicate();
+    }
+  }
+
+  /** Prefer {@link Pattern#asPredicate()} over non-JDK alternatives. */
+  static final class PatternCompileAsPredicate {
+    @BeforeTemplate
+    Predicate<CharSequence> before(String pattern) {
+      return containsPattern(pattern);
+    }
+
+    @AfterTemplate
+    Predicate<String> after(String pattern) {
+      return Pattern.compile(pattern).asPredicate();
+    }
+  }
+}

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/PrimitiveRules.java

@@ -8,7 +8,9 @@ import com.google.common.primitives.Floats;
 import com.google.common.primitives.Ints;
 import com.google.common.primitives.Longs;
 import com.google.common.primitives.Shorts;
+import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
+import com.google.errorprone.refaster.annotation.AlsoNegation;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
@@ -384,4 +386,60 @@ final class PrimitiveRules {
       return Double.isFinite(d);
     }
   }
+
+  /** Prefer an {@link Integer#signum(int)} comparison to 1 over less clear alternatives. */
+  static final class IntegerSignumIsPositive {
+    @BeforeTemplate
+    boolean before(int i) {
+      return Refaster.anyOf(Integer.signum(i) > 0, Integer.signum(i) >= 1);
+    }
+
+    @AfterTemplate
+    @AlsoNegation
+    boolean after(int i) {
+      return Integer.signum(i) == 1;
+    }
+  }
+
+  /** Prefer an {@link Integer#signum(int)} comparison to -1 over less clear alternatives. */
+  static final class IntegerSignumIsNegative {
+    @BeforeTemplate
+    boolean before(int i) {
+      return Refaster.anyOf(Integer.signum(i) < 0, Integer.signum(i) <= -1);
+    }
+
+    @AfterTemplate
+    @AlsoNegation
+    boolean after(int i) {
+      return Integer.signum(i) == -1;
+    }
+  }
+
+  /** Prefer an {@link Long#signum(long)} comparison to 1 over less clear alternatives. */
+  static final class LongSignumIsPositive {
+    @BeforeTemplate
+    boolean before(long l) {
+      return Refaster.anyOf(Long.signum(l) > 0, Long.signum(l) >= 1);
+    }
+
+    @AfterTemplate
+    @AlsoNegation
+    boolean after(long l) {
+      return Long.signum(l) == 1;
+    }
+  }
+
+  /** Prefer an {@link Long#signum(long)} comparison to -1 over less clear alternatives. */
+  static final class LongSignumIsNegative {
+    @BeforeTemplate
+    boolean before(long l) {
+      return Refaster.anyOf(Long.signum(l) < 0, Long.signum(l) <= -1);
+    }
+
+    @AfterTemplate
+    @AlsoNegation
+    boolean after(long l) {
+      return Long.signum(l) == -1;
+    }
+  }
 }

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/ReactorRules.java

@@ -12,12 +12,12 @@ import static reactor.function.TupleUtils.function;
 
 import com.google.common.collect.ImmutableCollection;
 import com.google.common.collect.ImmutableList;
-import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import com.google.errorprone.refaster.annotation.Matches;
 import com.google.errorprone.refaster.annotation.MayOptionallyUse;
 import com.google.errorprone.refaster.annotation.NotMatches;
 import com.google.errorprone.refaster.annotation.Placeholder;
@@ -26,8 +26,8 @@ import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Comparator;
-import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 import java.util.concurrent.Callable;
 import java.util.function.BiConsumer;
@@ -48,6 +48,8 @@ import reactor.util.function.Tuple2;
 import tech.picnic.errorprone.refaster.annotation.Description;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 import tech.picnic.errorprone.refaster.annotation.Severity;
+import tech.picnic.errorprone.refaster.matchers.IsEmpty;
+import tech.picnic.errorprone.refaster.matchers.IsIdentityOperation;
 import tech.picnic.errorprone.refaster.matchers.ThrowsCheckedException;
 
 /** Refaster rules related to Reactor expressions and statements. */
@@ -247,11 +249,43 @@ final class ReactorRules {
     }
   }
 
+  /** Prefer {@link Flux#zipWithIterable(Iterable)} over more contrived alternatives. */
+  static final class FluxZipWithIterable<T, S> {
+    @BeforeTemplate
+    Flux<Tuple2<T, S>> before(Flux<T> flux, Iterable<S> iterable) {
+      return Flux.zip(flux, Flux.fromIterable(iterable));
+    }
+
+    @AfterTemplate
+    Flux<Tuple2<T, S>> after(Flux<T> flux, Iterable<S> iterable) {
+      return flux.zipWithIterable(iterable);
+    }
+  }
+
+  /** Prefer {@link Flux#zipWithIterable(Iterable, BiFunction)} over more contrived alternatives. */
+  static final class FluxZipWithIterableBiFunction<T, S, R> {
+    @BeforeTemplate
+    Flux<R> before(
+        Flux<T> flux,
+        Iterable<S> iterable,
+        BiFunction<? super T, ? super S, ? extends R> function) {
+      return flux.zipWith(Flux.fromIterable(iterable), function);
+    }
+
+    @AfterTemplate
+    Flux<R> after(
+        Flux<T> flux,
+        Iterable<S> iterable,
+        BiFunction<? super T, ? super S, ? extends R> function) {
+      return flux.zipWithIterable(iterable, function);
+    }
+  }
+
   /**
    * Prefer {@link Flux#zipWithIterable(Iterable)} with a chained combinator over {@link
    * Flux#zipWithIterable(Iterable, BiFunction)}, as the former generally yields more readable code.
    */
-  static final class FluxZipWithIterable<T, S, R> {
+  static final class FluxZipWithIterableMapFunction<T, S, R> {
     @BeforeTemplate
     Flux<R> before(Flux<T> flux, Iterable<S> iterable, BiFunction<T, S, R> combinator) {
       return flux.zipWithIterable(iterable, combinator);
@@ -328,7 +362,10 @@ final class ReactorRules {
   static final class MonoThenReturn<T, S> {
     @BeforeTemplate
     Mono<S> before(Mono<T> mono, S object) {
-      return mono.then(Mono.just(object));
+      return Refaster.anyOf(
+          mono.ignoreElement().thenReturn(object),
+          mono.then().thenReturn(object),
+          mono.then(Mono.just(object)));
     }
 
     @AfterTemplate
@@ -391,6 +428,74 @@ final class ReactorRules {
     }
   }
 
+  /** Prefer {@link Flux#empty()} over more contrived alternatives. */
+  // XXX: In combination with the `IsEmpty` matcher introduced by
+  // https://github.com/PicnicSupermarket/error-prone-support/pull/744, the non-varargs overloads of
+  // most methods referenced here can be rewritten as well. Additionally, some invocations of
+  // methods such as `Flux#fromIterable`, `Flux#fromArray` and `Flux#justOrEmpty` can also be
+  // rewritten.
+  static final class FluxEmpty<T, S extends Comparable<? super S>> {
+    @BeforeTemplate
+    Flux<T> before(
+        int prefetch,
+        Function<? super Object[], ? extends T> combinator,
+        Comparator<? super T> comparator) {
+      return Refaster.anyOf(
+          Flux.concat(),
+          Flux.concatDelayError(),
+          Flux.firstWithSignal(),
+          Flux.just(),
+          Flux.merge(),
+          Flux.merge(prefetch),
+          Flux.mergeComparing(comparator),
+          Flux.mergeComparing(prefetch, comparator),
+          Flux.mergeComparingDelayError(prefetch, comparator),
+          Flux.mergeDelayError(prefetch),
+          Flux.mergePriority(comparator),
+          Flux.mergePriority(prefetch, comparator),
+          Flux.mergePriorityDelayError(prefetch, comparator),
+          Flux.mergeSequential(),
+          Flux.mergeSequential(prefetch),
+          Flux.mergeSequentialDelayError(prefetch),
+          Flux.zip(combinator),
+          Flux.zip(combinator, prefetch));
+    }
+
+    @BeforeTemplate
+    Flux<T> before(int prefetch, Function<Object[], T> combinator) {
+      return Refaster.anyOf(
+          Flux.combineLatest(combinator), Flux.combineLatest(combinator, prefetch));
+    }
+
+    @BeforeTemplate
+    Flux<S> before() {
+      return Refaster.anyOf(Flux.mergeComparing(), Flux.mergePriority());
+    }
+
+    @BeforeTemplate
+    Flux<Integer> before(int start) {
+      return Flux.range(start, 0);
+    }
+
+    @AfterTemplate
+    Flux<T> after() {
+      return Flux.empty();
+    }
+  }
+
+  /** Prefer {@link Flux#just(Object)} over more contrived alternatives. */
+  static final class FluxJust {
+    @BeforeTemplate
+    Flux<Integer> before(int start) {
+      return Flux.range(start, 1);
+    }
+
+    @AfterTemplate
+    Flux<Integer> after(int start) {
+      return Flux.just(start);
+    }
+  }
+
   /** Don't unnecessarily transform a {@link Mono} to an equivalent instance. */
   static final class MonoIdentity<T> {
     @BeforeTemplate
@@ -401,11 +506,12 @@ final class ReactorRules {
 
     @BeforeTemplate
     Mono<@Nullable Void> before2(Mono<@Nullable Void> mono) {
-      return mono.then();
+      return Refaster.anyOf(mono.ignoreElement(), mono.then());
     }
 
     // XXX: Replace this rule with an extension of the `IdentityConversion` rule, supporting
-    // `Stream#map`, `Mono#map` and `Flux#map`.
+    // `Stream#map`, `Mono#map` and `Flux#map`. Alternatively, extend the `IsIdentityOperation`
+    // matcher and use it to constrain the matched `map` argument.
     @BeforeTemplate
     Mono<ImmutableList<T>> before3(Mono<ImmutableList<T>> mono) {
       return mono.map(ImmutableList::copyOf);
@@ -446,53 +552,97 @@ final class ReactorRules {
   }
 
   /** Prefer {@link Flux#concatMap(Function)} over more contrived alternatives. */
-  static final class FluxConcatMap<T, S> {
+  static final class FluxConcatMap<T, S, P extends Publisher<? extends S>> {
     @BeforeTemplate
     @SuppressWarnings("NestedPublishers")
-    Flux<S> before(Flux<T> flux, Function<? super T, ? extends Publisher<? extends S>> function) {
+    Flux<S> before(
+        Flux<T> flux,
+        Function<? super T, ? extends P> function,
+        @Matches(IsIdentityOperation.class)
+            Function<? super P, ? extends Publisher<? extends S>> identityOperation) {
       return Refaster.anyOf(
           flux.flatMap(function, 1),
           flux.flatMapSequential(function, 1),
-          flux.map(function).concatMap(identity()));
+          flux.map(function).concatMap(identityOperation));
     }
 
     @AfterTemplate
-    Flux<S> after(Flux<T> flux, Function<? super T, ? extends Publisher<? extends S>> function) {
+    Flux<S> after(Flux<T> flux, Function<? super T, ? extends P> function) {
       return flux.concatMap(function);
     }
   }
 
   /** Prefer {@link Flux#concatMap(Function, int)} over more contrived alternatives. */
-  static final class FluxConcatMapWithPrefetch<T, S> {
+  static final class FluxConcatMapWithPrefetch<T, S, P extends Publisher<? extends S>> {
     @BeforeTemplate
     @SuppressWarnings("NestedPublishers")
     Flux<S> before(
         Flux<T> flux,
-        Function<? super T, ? extends Publisher<? extends S>> function,
-        int prefetch) {
+        Function<? super T, ? extends P> function,
+        int prefetch,
+        @Matches(IsIdentityOperation.class)
+            Function<? super P, ? extends Publisher<? extends S>> identityOperation) {
       return Refaster.anyOf(
           flux.flatMap(function, 1, prefetch),
           flux.flatMapSequential(function, 1, prefetch),
-          flux.map(function).concatMap(identity(), prefetch));
+          flux.map(function).concatMap(identityOperation, prefetch));
     }
 
     @AfterTemplate
-    Flux<S> after(
-        Flux<T> flux,
-        Function<? super T, ? extends Publisher<? extends S>> function,
-        int prefetch) {
+    Flux<S> after(Flux<T> flux, Function<? super T, ? extends P> function, int prefetch) {
       return flux.concatMap(function, prefetch);
     }
   }
 
-  /**
-   * Prefer {@link Flux#concatMapIterable(Function)} over {@link Flux#flatMapIterable(Function)}, as
-   * the former has equivalent semantics but a clearer name.
-   */
-  static final class FluxConcatMapIterable<T, S> {
+  /** Avoid contrived alternatives to {@link Mono#flatMapIterable(Function)}. */
+  static final class MonoFlatMapIterable<T, S, I extends Iterable<? extends S>> {
     @BeforeTemplate
-    Flux<S> before(Flux<T> flux, Function<? super T, ? extends Iterable<? extends S>> function) {
-      return flux.flatMapIterable(function);
+    Flux<S> before(
+        Mono<T> mono,
+        Function<? super T, I> function,
+        @Matches(IsIdentityOperation.class)
+            Function<? super I, ? extends Iterable<? extends S>> identityOperation) {
+      return Refaster.anyOf(
+          mono.map(function).flatMapIterable(identityOperation),
+          mono.flux().concatMapIterable(function));
+    }
+
+    @AfterTemplate
+    Flux<S> after(Mono<T> mono, Function<? super T, ? extends Iterable<? extends S>> function) {
+      return mono.flatMapIterable(function);
+    }
+  }
+
+  /**
+   * Prefer {@link Mono#flatMapIterable(Function)} to flatten a {@link Mono} of some {@link
+   * Iterable} over less efficient alternatives.
+   */
+  static final class MonoFlatMapIterableIdentity<T, S extends Iterable<T>> {
+    @BeforeTemplate
+    Flux<T> before(Mono<S> mono) {
+      return mono.flatMapMany(Flux::fromIterable);
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    Flux<T> after(Mono<S> mono) {
+      return mono.flatMapIterable(identity());
+    }
+  }
+
+  /**
+   * Prefer {@link Flux#concatMapIterable(Function)} over alternatives with less clear syntax or
+   * semantics.
+   */
+  static final class FluxConcatMapIterable<T, S, I extends Iterable<? extends S>> {
+    @BeforeTemplate
+    Flux<S> before(
+        Flux<T> flux,
+        Function<? super T, I> function,
+        @Matches(IsIdentityOperation.class)
+            Function<? super I, ? extends Iterable<? extends S>> identityOperation) {
+      return Refaster.anyOf(
+          flux.flatMapIterable(function), flux.map(function).concatMapIterable(identityOperation));
     }
 
     @AfterTemplate
@@ -502,14 +652,20 @@ final class ReactorRules {
   }
 
   /**
-   * Prefer {@link Flux#concatMapIterable(Function, int)} over {@link Flux#flatMapIterable(Function,
-   * int)}, as the former has equivalent semantics but a clearer name.
+   * Prefer {@link Flux#concatMapIterable(Function, int)} over alternatives with less clear syntax
+   * or semantics.
    */
-  static final class FluxConcatMapIterableWithPrefetch<T, S> {
+  static final class FluxConcatMapIterableWithPrefetch<T, S, I extends Iterable<? extends S>> {
     @BeforeTemplate
     Flux<S> before(
-        Flux<T> flux, Function<? super T, ? extends Iterable<? extends S>> function, int prefetch) {
-      return flux.flatMapIterable(function, prefetch);
+        Flux<T> flux,
+        Function<? super T, I> function,
+        int prefetch,
+        @Matches(IsIdentityOperation.class)
+            Function<? super I, ? extends Iterable<? extends S>> identityOperation) {
+      return Refaster.anyOf(
+          flux.flatMapIterable(function, prefetch),
+          flux.map(function).concatMapIterable(identityOperation, prefetch));
     }
 
     @AfterTemplate
@@ -741,7 +897,7 @@ final class ReactorRules {
   static final class MonoThen<T> {
     @BeforeTemplate
     Mono<@Nullable Void> before(Mono<T> mono) {
-      return mono.flux().then();
+      return Refaster.anyOf(mono.ignoreElement().then(), mono.flux().then());
     }
 
     @AfterTemplate
@@ -750,6 +906,128 @@ final class ReactorRules {
     }
   }
 
+  /** Avoid vacuous invocations of {@link Flux#ignoreElements()}. */
+  static final class FluxThen<T> {
+    @BeforeTemplate
+    Mono<@Nullable Void> before(Flux<T> flux) {
+      return flux.ignoreElements().then();
+    }
+
+    @BeforeTemplate
+    Mono<@Nullable Void> before2(Flux<@Nullable Void> flux) {
+      return flux.ignoreElements();
+    }
+
+    @AfterTemplate
+    Mono<@Nullable Void> after(Flux<T> flux) {
+      return flux.then();
+    }
+  }
+
+  /** Avoid vacuous invocations of {@link Mono#ignoreElement()}. */
+  static final class MonoThenEmpty<T> {
+    @BeforeTemplate
+    Mono<@Nullable Void> before(Mono<T> mono, Publisher<@Nullable Void> publisher) {
+      return mono.ignoreElement().thenEmpty(publisher);
+    }
+
+    @AfterTemplate
+    Mono<@Nullable Void> after(Mono<T> mono, Publisher<@Nullable Void> publisher) {
+      return mono.thenEmpty(publisher);
+    }
+  }
+
+  /** Avoid vacuous invocations of {@link Flux#ignoreElements()}. */
+  static final class FluxThenEmpty<T> {
+    @BeforeTemplate
+    Mono<@Nullable Void> before(Flux<T> flux, Publisher<@Nullable Void> publisher) {
+      return flux.ignoreElements().thenEmpty(publisher);
+    }
+
+    @AfterTemplate
+    Mono<@Nullable Void> after(Flux<T> flux, Publisher<@Nullable Void> publisher) {
+      return flux.thenEmpty(publisher);
+    }
+  }
+
+  /** Avoid vacuous invocations of {@link Mono#ignoreElement()}. */
+  static final class MonoThenMany<T, S> {
+    @BeforeTemplate
+    Flux<S> before(Mono<T> mono, Publisher<S> publisher) {
+      return mono.ignoreElement().thenMany(publisher);
+    }
+
+    @AfterTemplate
+    Flux<S> after(Mono<T> mono, Publisher<S> publisher) {
+      return mono.thenMany(publisher);
+    }
+  }
+
+  /**
+   * Prefer explicit invocation of {@link Mono#flux()} over implicit conversions from {@link Mono}
+   * to {@link Flux}.
+   */
+  static final class MonoThenMonoFlux<T, S> {
+    @BeforeTemplate
+    Flux<S> before(Mono<T> mono1, Mono<S> mono2) {
+      return mono1.thenMany(mono2);
+    }
+
+    @AfterTemplate
+    Flux<S> after(Mono<T> mono1, Mono<S> mono2) {
+      return mono1.then(mono2).flux();
+    }
+  }
+
+  /** Avoid vacuous invocations of {@link Flux#ignoreElements()}. */
+  static final class FluxThenMany<T, S> {
+    @BeforeTemplate
+    Flux<S> before(Flux<T> flux, Publisher<S> publisher) {
+      return flux.ignoreElements().thenMany(publisher);
+    }
+
+    @AfterTemplate
+    Flux<S> after(Flux<T> flux, Publisher<S> publisher) {
+      return flux.thenMany(publisher);
+    }
+  }
+
+  /** Avoid vacuous invocations of {@link Mono#ignoreElement()}. */
+  static final class MonoThenMono<T, S> {
+    @BeforeTemplate
+    Mono<S> before(Mono<T> mono1, Mono<S> mono2) {
+      return mono1.ignoreElement().then(mono2);
+    }
+
+    @BeforeTemplate
+    Mono<@Nullable Void> before2(Mono<T> mono1, Mono<@Nullable Void> mono2) {
+      return mono1.thenEmpty(mono2);
+    }
+
+    @AfterTemplate
+    Mono<S> after(Mono<T> mono1, Mono<S> mono2) {
+      return mono1.then(mono2);
+    }
+  }
+
+  /** Avoid vacuous invocations of {@link Flux#ignoreElements()}. */
+  static final class FluxThenMono<T, S> {
+    @BeforeTemplate
+    Mono<S> before(Flux<T> flux, Mono<S> mono) {
+      return flux.ignoreElements().then(mono);
+    }
+
+    @BeforeTemplate
+    Mono<@Nullable Void> before2(Flux<T> flux, Mono<@Nullable Void> mono) {
+      return flux.thenEmpty(mono);
+    }
+
+    @AfterTemplate
+    Mono<S> after(Flux<T> flux, Mono<S> mono) {
+      return flux.then(mono);
+    }
+  }
+
   /** Prefer {@link Mono#singleOptional()} over more contrived alternatives. */
   // XXX: Consider creating a plugin that flags/discourages `Mono<Optional<T>>` method return
   // types, just as we discourage nullable `Boolean`s and `Optional`s.
@@ -794,30 +1072,84 @@ final class ReactorRules {
     }
   }
 
-  /** Prefer {@link Mono#flatMap(Function)} over more contrived alternatives. */
-  static final class MonoFlatMap<S, T> {
+  /** Prefer {@link Mono#ofType(Class)} over more contrived alternatives. */
+  static final class MonoOfType<T, S> {
     @BeforeTemplate
-    @SuppressWarnings("NestedPublishers")
-    Mono<T> before(Mono<S> mono, Function<? super S, ? extends Mono<? extends T>> function) {
-      return mono.map(function).flatMap(identity());
+    Mono<S> before(Mono<T> mono, Class<S> clazz) {
+      return mono.filter(clazz::isInstance).cast(clazz);
     }
 
     @AfterTemplate
-    Mono<T> after(Mono<S> mono, Function<? super S, ? extends Mono<? extends T>> function) {
+    Mono<S> after(Mono<T> mono, Class<S> clazz) {
+      return mono.ofType(clazz);
+    }
+  }
+
+  /** Prefer {@link Flux#ofType(Class)} over more contrived alternatives. */
+  static final class FluxOfType<T, S> {
+    @BeforeTemplate
+    Flux<S> before(Flux<T> flux, Class<S> clazz) {
+      return flux.filter(clazz::isInstance).cast(clazz);
+    }
+
+    @AfterTemplate
+    Flux<S> after(Flux<T> flux, Class<S> clazz) {
+      return flux.ofType(clazz);
+    }
+  }
+
+  /** Prefer {@link Mono#flatMap(Function)} over more contrived alternatives. */
+  static final class MonoFlatMap<S, T, P extends Mono<? extends T>> {
+    @BeforeTemplate
+    @SuppressWarnings("NestedPublishers")
+    Mono<T> before(
+        Mono<S> mono,
+        Function<? super S, ? extends P> function,
+        @Matches(IsIdentityOperation.class)
+            Function<? super P, ? extends Mono<? extends T>> identityOperation) {
+      return mono.map(function).flatMap(identityOperation);
+    }
+
+    @AfterTemplate
+    Mono<T> after(Mono<S> mono, Function<? super S, ? extends P> function) {
       return mono.flatMap(function);
     }
   }
 
   /** Prefer {@link Mono#flatMapMany(Function)} over more contrived alternatives. */
-  static final class MonoFlatMapMany<S, T> {
+  static final class MonoFlatMapMany<S, T, P extends Publisher<? extends T>> {
     @BeforeTemplate
     @SuppressWarnings("NestedPublishers")
-    Flux<T> before(Mono<S> mono, Function<? super S, ? extends Publisher<? extends T>> function) {
-      return mono.map(function).flatMapMany(identity());
+    Flux<T> before(
+        Mono<S> mono,
+        Function<? super S, P> function,
+        @Matches(IsIdentityOperation.class)
+            Function<? super P, ? extends Publisher<? extends T>> identityOperation,
+        boolean delayUntilEnd,
+        int maxConcurrency,
+        int prefetch) {
+      return Refaster.anyOf(
+          mono.map(function).flatMapMany(identityOperation),
+          mono.flux().concatMap(function),
+          mono.flux().concatMap(function, prefetch),
+          mono.flux().concatMapDelayError(function),
+          mono.flux().concatMapDelayError(function, prefetch),
+          mono.flux().concatMapDelayError(function, delayUntilEnd, prefetch),
+          mono.flux().flatMap(function, maxConcurrency),
+          mono.flux().flatMap(function, maxConcurrency, prefetch),
+          mono.flux().flatMapDelayError(function, maxConcurrency, prefetch),
+          mono.flux().flatMapSequential(function, maxConcurrency),
+          mono.flux().flatMapSequential(function, maxConcurrency, prefetch),
+          mono.flux().flatMapSequentialDelayError(function, maxConcurrency, prefetch));
+    }
+
+    @BeforeTemplate
+    Flux<T> before(Mono<S> mono, Function<? super S, Publisher<? extends T>> function) {
+      return mono.flux().switchMap(function);
     }
 
     @AfterTemplate
-    Flux<T> after(Mono<S> mono, Function<? super S, ? extends Publisher<? extends T>> function) {
+    Flux<T> after(Mono<S> mono, Function<? super S, ? extends P> function) {
       return mono.flatMapMany(function);
     }
   }
@@ -1248,12 +1580,12 @@ final class ReactorRules {
   }
 
   /** Prefer {@link reactor.util.context.Context#empty()}} over more verbose alternatives. */
-  // XXX: Consider introducing an `IsEmpty` matcher that identifies a wide range of guaranteed-empty
-  // `Collection` and `Map` expressions.
+  // XXX: Introduce Refaster rules or a `BugChecker` that maps `(Immutable)Map.of(k, v)` to
+  // `Context.of(k, v)` and likewise for multi-pair overloads.
   static final class ContextEmpty {
     @BeforeTemplate
-    Context before() {
-      return Context.of(Refaster.anyOf(new HashMap<>(), ImmutableMap.of()));
+    Context before(@Matches(IsEmpty.class) Map<?, ?> map) {
+      return Context.of(map);
     }
 
     @AfterTemplate
@@ -1302,13 +1634,13 @@ final class ReactorRules {
   }
 
   /** Don't unnecessarily have {@link StepVerifier.Step} expect no elements. */
-  // XXX: Given an `IsEmpty` matcher that identifies a wide range of guaranteed-empty `Iterable`
-  // expressions, consider also simplifying `step.expectNextSequence(someEmptyIterable)`.
   static final class StepVerifierStepIdentity<T> {
     @BeforeTemplate
     @SuppressWarnings("unchecked")
-    StepVerifier.Step<T> before(StepVerifier.Step<T> step) {
-      return Refaster.anyOf(step.expectNext(), step.expectNextCount(0));
+    StepVerifier.Step<T> before(
+        StepVerifier.Step<T> step, @Matches(IsEmpty.class) Iterable<? extends T> iterable) {
+      return Refaster.anyOf(
+          step.expectNext(), step.expectNextCount(0), step.expectNextSequence(iterable));
     }
 
     @AfterTemplate
@@ -1381,6 +1713,7 @@ final class ReactorRules {
     Duration before(StepVerifier.LastStep step, Class<T> clazz) {
       return Refaster.anyOf(
           step.expectError(clazz).verify(),
+          step.verifyErrorMatches(clazz::isInstance),
           step.verifyErrorSatisfies(t -> assertThat(t).isInstanceOf(clazz)));
     }
 

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/StreamRules.java

@@ -3,7 +3,6 @@ package tech.picnic.errorprone.refasterrules;
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static java.util.Comparator.naturalOrder;
 import static java.util.Comparator.reverseOrder;
-import static java.util.function.Function.identity;
 import static java.util.function.Predicate.not;
 import static java.util.stream.Collectors.counting;
 import static java.util.stream.Collectors.filtering;
@@ -20,6 +19,7 @@ import static java.util.stream.Collectors.summingDouble;
 import static java.util.stream.Collectors.summingInt;
 import static java.util.stream.Collectors.summingLong;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Streams;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import com.google.errorprone.refaster.Refaster;
@@ -45,10 +45,12 @@ import java.util.function.Predicate;
 import java.util.function.ToDoubleFunction;
 import java.util.function.ToIntFunction;
 import java.util.function.ToLongFunction;
+import java.util.function.UnaryOperator;
 import java.util.stream.Collector;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
+import tech.picnic.errorprone.refaster.matchers.IsIdentityOperation;
 import tech.picnic.errorprone.refaster.matchers.IsLambdaExpressionOrMethodReference;
 import tech.picnic.errorprone.refaster.matchers.IsRefasterAsVarargs;
 
@@ -355,6 +357,8 @@ final class StreamRules {
           stream.filter(predicate).findAny().isEmpty());
     }
 
+    // XXX: Consider extending `@Matches(IsIdentityOperation.class)` such that it can replace this
+    // template's `Refaster.anyOf` usage.
     @BeforeTemplate
     boolean before2(
         Stream<T> stream,
@@ -393,6 +397,8 @@ final class StreamRules {
           !stream.noneMatch(predicate), stream.filter(predicate).findAny().isPresent());
     }
 
+    // XXX: Consider extending `@Matches(IsIdentityOperation.class)` such that it can replace this
+    // template's `Refaster.anyOf` usage.
     @BeforeTemplate
     boolean before2(
         Stream<T> stream,
@@ -413,6 +419,8 @@ final class StreamRules {
       return stream.noneMatch(Refaster.anyOf(not(predicate), predicate.negate()));
     }
 
+    // XXX: Consider extending `@Matches(IsIdentityOperation.class)` such that it can replace this
+    // template's `Refaster.anyOf` usage.
     @BeforeTemplate
     boolean before2(
         Stream<T> stream,
@@ -630,8 +638,11 @@ final class StreamRules {
 
   static final class StreamsConcat<T> {
     @BeforeTemplate
-    Stream<T> before(@Repeated Stream<T> stream) {
-      return Stream.of(Refaster.asVarargs(stream)).flatMap(Refaster.anyOf(identity(), s -> s));
+    Stream<T> before(
+        @Repeated Stream<T> stream,
+        @Matches(IsIdentityOperation.class)
+            Function<? super Stream<T>, ? extends Stream<? extends T>> mapper) {
+      return Stream.of(Refaster.asVarargs(stream)).flatMap(mapper);
     }
 
     @AfterTemplate
@@ -651,4 +662,90 @@ final class StreamRules {
       return stream.takeWhile(predicate);
     }
   }
+
+  /**
+   * Prefer {@link Stream#iterate(Object, Predicate, UnaryOperator)} over more contrived
+   * alternatives.
+   */
+  static final class StreamIterate<T> {
+    @BeforeTemplate
+    Stream<T> before(T seed, Predicate<? super T> hasNext, UnaryOperator<T> next) {
+      return Stream.iterate(seed, next).takeWhile(hasNext);
+    }
+
+    @AfterTemplate
+    Stream<T> after(T seed, Predicate<? super T> hasNext, UnaryOperator<T> next) {
+      return Stream.iterate(seed, hasNext, next);
+    }
+  }
+
+  /** Prefer {@link Stream#of(Object)} over more contrived alternatives. */
+  // XXX: Generalize this and similar rules using an Error Prone check.
+  static final class StreamOf1<T> {
+    @BeforeTemplate
+    Stream<T> before(T e1) {
+      return ImmutableList.of(e1).stream();
+    }
+
+    @AfterTemplate
+    Stream<T> after(T e1) {
+      return Stream.of(e1);
+    }
+  }
+
+  /** Prefer {@link Stream#of(Object[])} over more contrived alternatives. */
+  // XXX: Generalize this and similar rules using an Error Prone check.
+  static final class StreamOf2<T> {
+    @BeforeTemplate
+    Stream<T> before(T e1, T e2) {
+      return ImmutableList.of(e1, e2).stream();
+    }
+
+    @AfterTemplate
+    Stream<T> after(T e1, T e2) {
+      return Stream.of(e1, e2);
+    }
+  }
+
+  /** Prefer {@link Stream#of(Object[])} over more contrived alternatives. */
+  // XXX: Generalize this and similar rules using an Error Prone check.
+  static final class StreamOf3<T> {
+    @BeforeTemplate
+    Stream<T> before(T e1, T e2, T e3) {
+      return ImmutableList.of(e1, e2, e3).stream();
+    }
+
+    @AfterTemplate
+    Stream<T> after(T e1, T e2, T e3) {
+      return Stream.of(e1, e2, e3);
+    }
+  }
+
+  /** Prefer {@link Stream#of(Object[])} over more contrived alternatives. */
+  // XXX: Generalize this and similar rules using an Error Prone check.
+  static final class StreamOf4<T> {
+    @BeforeTemplate
+    Stream<T> before(T e1, T e2, T e3, T e4) {
+      return ImmutableList.of(e1, e2, e3, e4).stream();
+    }
+
+    @AfterTemplate
+    Stream<T> after(T e1, T e2, T e3, T e4) {
+      return Stream.of(e1, e2, e3, e4);
+    }
+  }
+
+  /** Prefer {@link Stream#of(Object[])} over more contrived alternatives. */
+  // XXX: Generalize this and similar rules using an Error Prone check.
+  static final class StreamOf5<T> {
+    @BeforeTemplate
+    Stream<T> before(T e1, T e2, T e3, T e4, T e5) {
+      return ImmutableList.of(e1, e2, e3, e4, e5).stream();
+    }
+
+    @AfterTemplate
+    Stream<T> after(T e1, T e2, T e3, T e4, T e5) {
+      return Stream.of(e1, e2, e3, e4, e5);
+    }
+  }
 }

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/AmbiguousJsonCreatorTest.java

@@ -1,7 +1,5 @@
 package tech.picnic.errorprone.bugpatterns;
 
-import static com.google.common.base.Predicates.containsPattern;
-
 import com.google.errorprone.BugCheckerRefactoringTestHelper;
 import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
 import com.google.errorprone.CompilationTestHelper;
@@ -12,7 +10,7 @@ final class AmbiguousJsonCreatorTest {
   void identification() {
     CompilationTestHelper.newInstance(AmbiguousJsonCreator.class, getClass())
         .expectErrorMessage(
-            "X", containsPattern("`JsonCreator.Mode` should be set for single-argument creators"))
+            "X", m -> m.contains("`JsonCreator.Mode` should be set for single-argument creators"))
         .addSourceLines(
             "Container.java",
             "import com.fasterxml.jackson.annotation.JsonCreator;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/FluxImplicitBlockTest.java

@@ -1,14 +1,12 @@
 package tech.picnic.errorprone.bugpatterns;
 
-import static com.google.common.base.Predicates.and;
-import static com.google.common.base.Predicates.containsPattern;
-import static com.google.common.base.Predicates.not;
 import static com.google.errorprone.BugCheckerRefactoringTestHelper.FixChoosers.SECOND;
 import static com.google.errorprone.BugCheckerRefactoringTestHelper.FixChoosers.THIRD;
 
 import com.google.errorprone.BugCheckerRefactoringTestHelper;
 import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
 import com.google.errorprone.CompilationTestHelper;
+import java.util.stream.Stream;
 import org.junit.jupiter.api.Test;
 import org.reactivestreams.Publisher;
 import reactor.core.CorePublisher;
@@ -20,10 +18,7 @@ final class FluxImplicitBlockTest {
     CompilationTestHelper.newInstance(FluxImplicitBlock.class, getClass())
         .expectErrorMessage(
             "X",
-            and(
-                containsPattern("SuppressWarnings"),
-                containsPattern("toImmutableList"),
-                containsPattern("toList")))
+            m -> Stream.of("SuppressWarnings", "toImmutableList", "toList").allMatch(m::contains))
         .addSourceLines(
             "A.java",
             "import com.google.common.collect.ImmutableList;",
@@ -63,7 +58,7 @@ final class FluxImplicitBlockTest {
   void identificationWithoutGuavaOnClasspath() {
     CompilationTestHelper.newInstance(FluxImplicitBlock.class, getClass())
         .withClasspath(CorePublisher.class, Flux.class, Publisher.class)
-        .expectErrorMessage("X", not(containsPattern("toImmutableList")))
+        .expectErrorMessage("X", m -> !m.contains("toImmutableList"))
         .addSourceLines(
             "A.java",
             "import reactor.core.publisher.Flux;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/JUnitNullaryParameterizedTestDeclarationTest.java

@@ -0,0 +1,155 @@
+package tech.picnic.errorprone.bugpatterns;
+
+import com.google.errorprone.BugCheckerRefactoringTestHelper;
+import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.jupiter.api.Test;
+
+final class JUnitNullaryParameterizedTestDeclarationTest {
+  @Test
+  void identification() {
+    CompilationTestHelper.newInstance(JUnitNullaryParameterizedTestDeclaration.class, getClass())
+        .addSourceLines(
+            "A.java",
+            "import org.junit.jupiter.api.Test;",
+            "import org.junit.jupiter.params.ParameterizedTest;",
+            "import org.junit.jupiter.params.provider.ValueSource;",
+            "",
+            "class A {",
+            "  void nonTest() {}",
+            "",
+            "  @Test",
+            "  void nonParameterizedTest() {}",
+            "",
+            "  @ParameterizedTest",
+            "  @ValueSource(ints = {0, 1})",
+            "  void goodParameterizedTest(int someInt) {}",
+            "",
+            "  @ParameterizedTest",
+            "  @ValueSource(ints = {0, 1})",
+            "  // BUG: Diagnostic contains:",
+            "  void nullaryParameterizedTest() {}",
+            "}")
+        .doTest();
+  }
+
+  @Test
+  void replacement() {
+    BugCheckerRefactoringTestHelper.newInstance(
+            JUnitNullaryParameterizedTestDeclaration.class, getClass())
+        .addInputLines(
+            "A.java",
+            "import org.junit.jupiter.params.ParameterizedTest;",
+            "import org.junit.jupiter.params.provider.ArgumentsProvider;",
+            "import org.junit.jupiter.params.provider.ArgumentsSource;",
+            "import org.junit.jupiter.params.provider.ArgumentsSources;",
+            "import org.junit.jupiter.params.provider.MethodSource;",
+            "import org.junit.jupiter.params.provider.ValueSource;",
+            "",
+            "class A {",
+            "  @ParameterizedTest",
+            "  void withoutArgumentSource() {}",
+            "",
+            "  @ParameterizedTest",
+            "  @ArgumentsSource(ArgumentsProvider.class)",
+            "  void withCustomArgumentSource() {}",
+            "",
+            "  @ParameterizedTest",
+            "  @ArgumentsSources({",
+            "    @ArgumentsSource(ArgumentsProvider.class),",
+            "    @ArgumentsSource(ArgumentsProvider.class)",
+            "  })",
+            "  void withCustomerArgumentSources() {}",
+            "",
+            "  /** Foo. */",
+            "  @ParameterizedTest",
+            "  @ValueSource(ints = {0, 1})",
+            "  void withValueSourceAndJavadoc() {}",
+            "",
+            "  @ParameterizedTest",
+            "  @MethodSource(\"nonexistentMethod\")",
+            "  @SuppressWarnings(\"foo\")",
+            "  void withMethodSourceAndUnrelatedAnnotation() {}",
+            "",
+            "  @org.junit.jupiter.params.ParameterizedTest",
+            "  @ArgumentsSource(ArgumentsProvider.class)",
+            "  @ValueSource(ints = {0, 1})",
+            "  @MethodSource(\"nonexistentMethod\")",
+            "  void withMultipleArgumentSourcesAndFullyQualifiedImport() {}",
+            "",
+            "  class NestedWithTestAnnotationFirst {",
+            "    @ParameterizedTest",
+            "    @ValueSource(ints = {0, 1})",
+            "    void withValueSource() {}",
+            "  }",
+            "",
+            "  class NestedWithTestAnnotationSecond {",
+            "    @ValueSource(ints = {0, 1})",
+            "    @ParameterizedTest",
+            "    void withValueSource() {}",
+            "  }",
+            "}")
+        .addOutputLines(
+            "A.java",
+            "import org.junit.jupiter.api.Test;",
+            "import org.junit.jupiter.params.ParameterizedTest;",
+            "import org.junit.jupiter.params.provider.ArgumentsProvider;",
+            "import org.junit.jupiter.params.provider.ArgumentsSource;",
+            "import org.junit.jupiter.params.provider.ArgumentsSources;",
+            "import org.junit.jupiter.params.provider.MethodSource;",
+            "import org.junit.jupiter.params.provider.ValueSource;",
+            "",
+            "class A {",
+            "  @Test",
+            "  void withoutArgumentSource() {}",
+            "",
+            "  @Test",
+            "  void withCustomArgumentSource() {}",
+            "",
+            "  @Test",
+            "  void withCustomerArgumentSources() {}",
+            "",
+            "  /** Foo. */",
+            "  @Test",
+            "  void withValueSourceAndJavadoc() {}",
+            "",
+            "  @Test",
+            "  @SuppressWarnings(\"foo\")",
+            "  void withMethodSourceAndUnrelatedAnnotation() {}",
+            "",
+            "  @Test",
+            "  void withMultipleArgumentSourcesAndFullyQualifiedImport() {}",
+            "",
+            "  class NestedWithTestAnnotationFirst {",
+            "    @Test",
+            "    void withValueSource() {}",
+            "  }",
+            "",
+            "  class NestedWithTestAnnotationSecond {",
+            "    @Test",
+            "    void withValueSource() {}",
+            "  }",
+            "}")
+        .addInputLines(
+            "B.java",
+            "import org.junit.jupiter.params.ParameterizedTest;",
+            "",
+            "class B {",
+            "  @ParameterizedTest",
+            "  void scopeInWhichIdentifierTestIsAlreadyDeclared() {}",
+            "",
+            "  class Test {}",
+            "}")
+        .addOutputLines(
+            "B.java",
+            "import org.junit.jupiter.params.ParameterizedTest;",
+            "",
+            "class B {",
+            "  @org.junit.jupiter.api.Test",
+            "  void scopeInWhichIdentifierTestIsAlreadyDeclared() {}",
+            "",
+            "  class Test {}",
+            "}")
+        .doTest(TestMode.TEXT_MATCH);
+  }
+}

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/NonStaticImportTest.java

@@ -0,0 +1,196 @@
+package tech.picnic.errorprone.bugpatterns;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.google.errorprone.BugCheckerRefactoringTestHelper;
+import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.jupiter.api.Test;
+
+final class NonStaticImportTest {
+  @Test
+  void candidateTypesDoNotClash() {
+    assertThat(NonStaticImport.NON_STATIC_IMPORT_CANDIDATE_TYPES)
+        .doesNotContainAnyElementsOf(StaticImport.STATIC_IMPORT_CANDIDATE_TYPES);
+  }
+
+  @Test
+  void candidateMembersAreNotRedundant() {
+    assertThat(NonStaticImport.NON_STATIC_IMPORT_CANDIDATE_MEMBERS.keySet())
+        .doesNotContainAnyElementsOf(NonStaticImport.NON_STATIC_IMPORT_CANDIDATE_TYPES);
+
+    assertThat(NonStaticImport.NON_STATIC_IMPORT_CANDIDATE_MEMBERS.values())
+        .doesNotContainAnyElementsOf(NonStaticImport.NON_STATIC_IMPORT_CANDIDATE_IDENTIFIERS);
+  }
+
+  @Test
+  void candidateMembersDoNotClash() {
+    assertThat(NonStaticImport.NON_STATIC_IMPORT_CANDIDATE_MEMBERS.entries())
+        .doesNotContainAnyElementsOf(StaticImport.STATIC_IMPORT_CANDIDATE_MEMBERS.entries());
+  }
+
+  @Test
+  void candidateIdentifiersDoNotClash() {
+    assertThat(NonStaticImport.NON_STATIC_IMPORT_CANDIDATE_IDENTIFIERS)
+        .doesNotContainAnyElementsOf(StaticImport.STATIC_IMPORT_CANDIDATE_MEMBERS.values());
+  }
+
+  @Test
+  void identification() {
+    CompilationTestHelper.newInstance(NonStaticImport.class, getClass())
+        .addSourceLines(
+            "pkg/A.java",
+            "package pkg;",
+            "",
+            "// BUG: Diagnostic contains:",
+            "import static com.google.common.base.Strings.nullToEmpty;",
+            "// BUG: Diagnostic contains:",
+            "import static com.google.common.collect.ImmutableList.copyOf;",
+            "// BUG: Diagnostic contains:",
+            "import static java.lang.Integer.MAX_VALUE;",
+            "// BUG: Diagnostic contains:",
+            "import static java.lang.Integer.MIN_VALUE;",
+            "// BUG: Diagnostic contains:",
+            "import static java.time.Clock.systemUTC;",
+            "// BUG: Diagnostic contains:",
+            "import static java.time.Instant.MIN;",
+            "// BUG: Diagnostic contains:",
+            "import static java.time.ZoneOffset.SHORT_IDS;",
+            "import static java.time.ZoneOffset.UTC;",
+            "// BUG: Diagnostic contains:",
+            "import static java.util.Collections.min;",
+            "import static java.util.Locale.ENGLISH;",
+            "// BUG: Diagnostic contains:",
+            "import static java.util.Locale.ROOT;",
+            "// BUG: Diagnostic contains:",
+            "import static java.util.Optional.empty;",
+            "import static pkg.A.WithMethodThatIsSelectivelyFlagged.list;",
+            "",
+            "import com.google.common.collect.ImmutableList;",
+            "import com.google.common.collect.ImmutableSet;",
+            "import java.time.Instant;",
+            "import java.time.ZoneOffset;",
+            "import java.util.Locale;",
+            "import java.util.Map;",
+            "import pkg.A.Wrapper.ZERO;",
+            "",
+            "class A {",
+            "  private Integer MIN_VALUE = 12;",
+            "",
+            "  void m() {",
+            "    nullToEmpty(null);",
+            "    copyOf(ImmutableList.of());",
+            "    int max = MAX_VALUE;",
+            "    int min = MIN_VALUE;",
+            "    systemUTC();",
+            "    Instant minInstant = MIN;",
+            "    Map<String, String> shortIds = SHORT_IDS;",
+            "    ZoneOffset utc = UTC;",
+            "    min(ImmutableSet.of());",
+            "    Locale english = ENGLISH;",
+            "    Locale root = ROOT;",
+            "    empty();",
+            "",
+            "    list();",
+            "    new ZERO();",
+            "  }",
+            "",
+            "  static final class WithMethodThatIsSelectivelyFlagged {",
+            "    static ImmutableList<String> list() {",
+            "      return ImmutableList.of();",
+            "    }",
+            "  }",
+            "",
+            "  static final class Wrapper {",
+            "    static final class ZERO {}",
+            "  }",
+            "}")
+        .doTest();
+  }
+
+  @Test
+  void replacement() {
+    BugCheckerRefactoringTestHelper.newInstance(NonStaticImport.class, getClass())
+        .addInputLines(
+            "A.java",
+            "import static com.google.common.collect.ImmutableList.copyOf;",
+            "import static com.google.common.collect.ImmutableSet.of;",
+            "import static java.time.Clock.systemUTC;",
+            "import static java.time.Instant.MAX;",
+            "import static java.time.Instant.MIN;",
+            "import static java.util.Collections.min;",
+            "import static java.util.Locale.ROOT;",
+            "import static java.util.Optional.empty;",
+            "",
+            "import com.google.common.collect.ImmutableList;",
+            "import com.google.common.collect.ImmutableSet;",
+            "import java.time.Clock;",
+            "import java.time.Instant;",
+            "import java.util.Locale;",
+            "import java.util.Optional;",
+            "",
+            "class A {",
+            "  void m() {",
+            "    systemUTC();",
+            "    Clock.systemUTC();",
+            "",
+            "    Optional<Integer> o1 = empty();",
+            "    Optional<Integer> o2 = Optional.empty();",
+            "",
+            "    Object l1 = copyOf(ImmutableList.of());",
+            "    Object l2 = ImmutableList.copyOf(ImmutableList.of());",
+            "",
+            "    Locale lo1 = ROOT;",
+            "    Locale lo2 = Locale.ROOT;",
+            "",
+            "    Instant i1 = MIN;",
+            "    Instant i2 = MAX;",
+            "",
+            "    ImmutableSet.of(min(of()));",
+            "  }",
+            "",
+            "  private static final class WithCustomConstant {",
+            "    private static final Instant MIN = Instant.EPOCH;",
+            "    private static final Instant OTHER = MIN;",
+            "    private static final Instant OTHER_MAX = MAX;",
+            "  }",
+            "}")
+        .addOutputLines(
+            "A.java",
+            "import com.google.common.collect.ImmutableList;",
+            "import com.google.common.collect.ImmutableSet;",
+            "import java.time.Clock;",
+            "import java.time.Instant;",
+            "import java.util.Collections;",
+            "import java.util.Locale;",
+            "import java.util.Optional;",
+            "",
+            "class A {",
+            "  void m() {",
+            "    Clock.systemUTC();",
+            "    Clock.systemUTC();",
+            "",
+            "    Optional<Integer> o1 = Optional.empty();",
+            "    Optional<Integer> o2 = Optional.empty();",
+            "",
+            "    Object l1 = ImmutableList.copyOf(ImmutableList.of());",
+            "    Object l2 = ImmutableList.copyOf(ImmutableList.of());",
+            "",
+            "    Locale lo1 = Locale.ROOT;",
+            "    Locale lo2 = Locale.ROOT;",
+            "",
+            "    Instant i1 = Instant.MIN;",
+            "    Instant i2 = Instant.MAX;",
+            "",
+            "    ImmutableSet.of(Collections.min(ImmutableSet.of()));",
+            "  }",
+            "",
+            "  private static final class WithCustomConstant {",
+            "    private static final Instant MIN = Instant.EPOCH;",
+            "    private static final Instant OTHER = MIN;",
+            "    private static final Instant OTHER_MAX = Instant.MAX;",
+            "  }",
+            "}")
+        .doTest(TestMode.TEXT_MATCH);
+  }
+}

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/ScheduledTransactionTraceTest.java

@@ -1,105 +0,0 @@
-package tech.picnic.errorprone.bugpatterns;
-
-import com.google.errorprone.BugCheckerRefactoringTestHelper;
-import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
-import com.google.errorprone.CompilationTestHelper;
-import org.junit.jupiter.api.Test;
-import org.springframework.scheduling.annotation.Scheduled;
-
-final class ScheduledTransactionTraceTest {
-  @Test
-  void identification() {
-    CompilationTestHelper.newInstance(ScheduledTransactionTrace.class, getClass())
-        .addSourceLines(
-            "A.java",
-            "import com.newrelic.api.agent.Trace;",
-            "import org.springframework.scheduling.annotation.Scheduled;",
-            "",
-            "class A {",
-            "  void notScheduled() {}",
-            "",
-            "  @Scheduled(fixedDelay = 1)",
-            "  // BUG: Diagnostic contains:",
-            "  void scheduledButNotTraced() {}",
-            "",
-            "  @Scheduled(fixedDelay = 1)",
-            "  // BUG: Diagnostic contains:",
-            "  @Trace",
-            "  void scheduledButImproperlyTraced1() {}",
-            "",
-            "  @Scheduled(fixedDelay = 1)",
-            "  // BUG: Diagnostic contains:",
-            "  @Trace(dispatcher = false)",
-            "  void scheduledButImproperlyTraced2() {}",
-            "",
-            "  @Scheduled(fixedDelay = 1)",
-            "  @Trace(dispatcher = true)",
-            "  void scheduledAndProperlyTraced() {}",
-            "}")
-        .doTest();
-  }
-
-  @Test
-  void identificationWithoutNewRelicAgentApiOnClasspath() {
-    CompilationTestHelper.newInstance(ScheduledTransactionTrace.class, getClass())
-        .withClasspath(Scheduled.class)
-        .addSourceLines(
-            "A.java",
-            "import org.springframework.scheduling.annotation.Scheduled;",
-            "",
-            "class A {",
-            "  @Scheduled(fixedDelay = 1)",
-            "  void scheduledButNotTraced() {}",
-            "}")
-        .doTest();
-  }
-
-  @Test
-  void replacement() {
-    BugCheckerRefactoringTestHelper.newInstance(ScheduledTransactionTrace.class, getClass())
-        .addInputLines(
-            "A.java",
-            "import com.newrelic.api.agent.Trace;",
-            "import org.springframework.scheduling.annotation.Scheduled;",
-            "",
-            "class A {",
-            "  @Scheduled(fixedDelay = 1)",
-            "  void scheduledButNotTraced() {}",
-            "",
-            "  @Scheduled(fixedDelay = 1)",
-            "  @Trace",
-            "  void scheduledButImproperlyTraced1() {}",
-            "",
-            "  @Scheduled(fixedDelay = 1)",
-            "  @Trace(dispatcher = false)",
-            "  void scheduledButImproperlyTraced2() {}",
-            "",
-            "  @Scheduled(fixedDelay = 1)",
-            "  @Trace(leaf = true)",
-            "  void scheduledButImproperlyTraced3() {}",
-            "}")
-        .addOutputLines(
-            "A.java",
-            "import com.newrelic.api.agent.Trace;",
-            "import org.springframework.scheduling.annotation.Scheduled;",
-            "",
-            "class A {",
-            "  @Trace(dispatcher = true)",
-            "  @Scheduled(fixedDelay = 1)",
-            "  void scheduledButNotTraced() {}",
-            "",
-            "  @Scheduled(fixedDelay = 1)",
-            "  @Trace(dispatcher = true)",
-            "  void scheduledButImproperlyTraced1() {}",
-            "",
-            "  @Scheduled(fixedDelay = 1)",
-            "  @Trace(dispatcher = true)",
-            "  void scheduledButImproperlyTraced2() {}",
-            "",
-            "  @Scheduled(fixedDelay = 1)",
-            "  @Trace(dispatcher = true, leaf = true)",
-            "  void scheduledButImproperlyTraced3() {}",
-            "}")
-        .doTest(TestMode.TEXT_MATCH);
-  }
-}

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/StaticImportTest.java

@@ -9,21 +9,24 @@ import org.junit.jupiter.api.Test;
 
 final class StaticImportTest {
   @Test
-  void candidateMethodsAreNotRedundant() {
+  void candidateTypesDoNotClash() {
+    assertThat(StaticImport.STATIC_IMPORT_CANDIDATE_TYPES)
+        .doesNotContainAnyElementsOf(NonStaticImport.NON_STATIC_IMPORT_CANDIDATE_TYPES);
+  }
+
+  @Test
+  void candidateMembersAreNotRedundant() {
     assertThat(StaticImport.STATIC_IMPORT_CANDIDATE_MEMBERS.keySet())
         .doesNotContainAnyElementsOf(StaticImport.STATIC_IMPORT_CANDIDATE_TYPES);
   }
 
   @Test
-  void exemptedMembersAreNotVacuous() {
-    assertThat(StaticImport.STATIC_IMPORT_EXEMPTED_MEMBERS.keySet())
-        .isSubsetOf(StaticImport.STATIC_IMPORT_CANDIDATE_TYPES);
-  }
+  void candidateMembersDoNotClash() {
+    assertThat(StaticImport.STATIC_IMPORT_CANDIDATE_MEMBERS.entries())
+        .doesNotContainAnyElementsOf(NonStaticImport.NON_STATIC_IMPORT_CANDIDATE_MEMBERS.entries());
 
-  @Test
-  void exemptedMembersAreNotRedundant() {
-    assertThat(StaticImport.STATIC_IMPORT_EXEMPTED_MEMBERS.values())
-        .doesNotContainAnyElementsOf(StaticImport.STATIC_IMPORT_EXEMPTED_IDENTIFIERS);
+    assertThat(StaticImport.STATIC_IMPORT_CANDIDATE_MEMBERS.values())
+        .doesNotContainAnyElementsOf(NonStaticImport.NON_STATIC_IMPORT_CANDIDATE_IDENTIFIERS);
   }
 
   @Test

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/StringJoinTest.java

@@ -1,7 +1,5 @@
 package tech.picnic.errorprone.bugpatterns;
 
-import static com.google.common.base.Predicates.containsPattern;
-
 import com.google.errorprone.BugCheckerRefactoringTestHelper;
 import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
 import com.google.errorprone.CompilationTestHelper;
@@ -12,8 +10,8 @@ final class StringJoinTest {
   void identification() {
     CompilationTestHelper.newInstance(StringJoin.class, getClass())
         .expectErrorMessage(
-            "valueOf", containsPattern("Prefer `String#valueOf` over `String#format`"))
-        .expectErrorMessage("join", containsPattern("Prefer `String#join` over `String#format`"))
+            "valueOf", m -> m.contains("Prefer `String#valueOf` over `String#format`"))
+        .expectErrorMessage("join", m -> m.contains("Prefer `String#join` over `String#format`"))
         .addSourceLines(
             "A.java",
             "import java.util.Formattable;",

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/util/ThirdPartyLibraryTest.java

@@ -23,7 +23,7 @@ final class ThirdPartyLibraryTest {
     CompilationTestHelper.newInstance(TestChecker.class, getClass())
         .addSourceLines(
             "A.java",
-            "// BUG: Diagnostic contains: ASSERTJ: true, GUAVA: true, NEW_RELIC_AGENT_API: true, REACTOR: true",
+            "// BUG: Diagnostic contains: ASSERTJ: true, GUAVA: true, REACTOR: true",
             "class A {}")
         .doTest();
   }
@@ -34,16 +34,14 @@ final class ThirdPartyLibraryTest {
         .addSourceLines(
             "A.java",
             "import com.google.common.collect.ImmutableList;",
-            "import com.newrelic.api.agent.Agent;",
             "import org.assertj.core.api.Assertions;",
             "import reactor.core.publisher.Flux;",
             "",
-            "// BUG: Diagnostic contains: ASSERTJ: true, GUAVA: true, NEW_RELIC_AGENT_API: true, REACTOR: true",
+            "// BUG: Diagnostic contains: ASSERTJ: true, GUAVA: true, REACTOR: true",
             "class A {",
             "  void m(Class<?> clazz) {",
             "    m(Assertions.class);",
             "    m(ImmutableList.class);",
-            "    m(Agent.class);",
             "    m(Flux.class);",
             "  }",
             "}")
@@ -56,7 +54,7 @@ final class ThirdPartyLibraryTest {
         .withClasspath(ImmutableList.class, Flux.class)
         .addSourceLines(
             "A.java",
-            "// BUG: Diagnostic contains: ASSERTJ: false, GUAVA: true, NEW_RELIC_AGENT_API: false, REACTOR: true",
+            "// BUG: Diagnostic contains: ASSERTJ: false, GUAVA: true, REACTOR: true",
             "class A {}")
         .doTest();
   }
@@ -67,7 +65,7 @@ final class ThirdPartyLibraryTest {
         .withClasspath()
         .addSourceLines(
             "A.java",
-            "// BUG: Diagnostic contains: ASSERTJ: false, GUAVA: false, NEW_RELIC_AGENT_API: false, REACTOR:",
+            "// BUG: Diagnostic contains: ASSERTJ: false, GUAVA: false, REACTOR:",
             "// false",
             "class A {}")
         .doTest();
@@ -82,8 +80,8 @@ final class ThirdPartyLibraryTest {
         .addSourceLines(
             "A.java",
             String.format(
-                "// BUG: Diagnostic contains: ASSERTJ: %s, GUAVA: true, NEW_RELIC_AGENT_API: %s, REACTOR: true",
-                ignoreClassPath, ignoreClassPath),
+                "// BUG: Diagnostic contains: ASSERTJ: %s, GUAVA: true, REACTOR: true",
+                ignoreClassPath),
             "class A {}")
         .doTest();
   }

error-prone-contrib/src/test/java/tech/picnic/errorprone/refasterrules/RefasterRulesTest.java

@@ -36,10 +36,12 @@ final class RefasterRulesTest {
           AssortedRules.class,
           BigDecimalRules.class,
           BugCheckerRules.class,
+          ClassRules.class,
           CollectionRules.class,
           ComparatorRules.class,
           DoubleStreamRules.class,
           EqualityRules.class,
+          FileRules.class,
           ImmutableListRules.class,
           ImmutableListMultimapRules.class,
           ImmutableMapRules.class,
@@ -59,6 +61,7 @@ final class RefasterRulesTest {
           MultimapRules.class,
           NullRules.class,
           OptionalRules.class,
+          PatternRules.class,
           PreconditionsRules.class,
           PrimitiveRules.class,
           ReactorRules.class,

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/AssertJMapRulesTestInput.java

@@ -41,34 +41,19 @@ final class AssertJMapRulesTest implements RefasterRuleCollectionTestCase {
 
   void testAbstractMapAssertIsEmpty() {
     assertThat(ImmutableMap.of(1, 0)).containsExactlyEntriesOf(ImmutableMap.of());
-    assertThat(ImmutableMap.of(2, 0)).containsExactlyEntriesOf(ImmutableBiMap.of());
-    assertThat(ImmutableMap.of(3, 0)).containsExactlyEntriesOf(ImmutableSortedMap.of());
-    assertThat(ImmutableMap.of(4, 0)).containsExactlyEntriesOf(new HashMap<>());
-    assertThat(ImmutableMap.of(5, 0)).containsExactlyEntriesOf(new LinkedHashMap<>());
-    assertThat(ImmutableMap.of(6, 0)).containsExactlyEntriesOf(new TreeMap<>());
-    assertThat(ImmutableMap.of(7, 0)).hasSameSizeAs(ImmutableMap.of());
-    assertThat(ImmutableMap.of(8, 0)).hasSameSizeAs(ImmutableBiMap.of());
-    assertThat(ImmutableMap.of(9, 0)).hasSameSizeAs(ImmutableSortedMap.of());
-    assertThat(ImmutableMap.of(10, 0)).hasSameSizeAs(new HashMap<>());
-    assertThat(ImmutableMap.of(11, 0)).hasSameSizeAs(new LinkedHashMap<>());
-    assertThat(ImmutableMap.of(12, 0)).hasSameSizeAs(new TreeMap<>());
-    assertThat(ImmutableMap.of(13, 0)).isEqualTo(ImmutableMap.of());
-    assertThat(ImmutableMap.of(14, 0)).isEqualTo(ImmutableBiMap.of());
-    assertThat(ImmutableMap.of(15, 0)).isEqualTo(ImmutableSortedMap.of());
-    assertThat(ImmutableMap.of(16, 0)).isEqualTo(new HashMap<>());
-    assertThat(ImmutableMap.of(17, 0)).isEqualTo(new LinkedHashMap<>());
-    assertThat(ImmutableMap.of(18, 0)).isEqualTo(new TreeMap<>());
-    assertThat(ImmutableMap.of(19, 0)).containsOnlyKeys(ImmutableList.of());
-    assertThat(ImmutableMap.of(20, 0)).containsOnlyKeys(new ArrayList<>());
-    assertThat(ImmutableMap.of(21, 0)).containsOnlyKeys(ImmutableSet.of());
-    assertThat(ImmutableMap.of(22, 0)).containsOnlyKeys(new HashSet<>());
-    assertThat(ImmutableMap.of(23, 0)).containsOnlyKeys(ImmutableSortedSet.of());
-    assertThat(ImmutableMap.of(24, 0)).containsOnlyKeys(new TreeSet<>());
-    assertThat(ImmutableMap.of(25, 0)).containsOnlyKeys(ImmutableMultiset.of());
-    assertThat(ImmutableMap.of(26, 0)).containsOnlyKeys(ImmutableSortedMultiset.of());
-    assertThat(ImmutableMap.of(27, 0)).containsExactly();
-    assertThat(ImmutableMap.of(28, 0)).containsOnly();
-    assertThat(ImmutableMap.of(29, 0)).containsOnlyKeys();
+    assertThat(ImmutableMap.of(2, 0)).containsExactlyEntriesOf(ImmutableMap.of(1, 2));
+    assertThat(ImmutableMap.of(3, 0)).containsExactlyInAnyOrderEntriesOf(ImmutableMap.of());
+    assertThat(ImmutableMap.of(4, 0))
+        .containsExactlyInAnyOrderEntriesOf(ImmutableMap.of(1, 2, 3, 4));
+    assertThat(ImmutableMap.of(5, 0)).hasSameSizeAs(ImmutableMap.of());
+    assertThat(ImmutableMap.of(6, 0)).hasSameSizeAs(ImmutableMap.of(1, 2));
+    assertThat(ImmutableMap.of(7, 0)).isEqualTo(ImmutableMap.of());
+    assertThat(ImmutableMap.of(8, 0)).isEqualTo(ImmutableMap.of("foo", "bar"));
+    assertThat(ImmutableMap.of(9, 0)).containsOnlyKeys(ImmutableList.of());
+    assertThat(ImmutableMap.of(10, 0)).containsOnlyKeys(ImmutableList.of(1));
+    assertThat(ImmutableMap.of(11, 0)).containsExactly();
+    assertThat(ImmutableMap.of(12, 0)).containsOnly();
+    assertThat(ImmutableMap.of(13, 0)).containsOnlyKeys();
   }
 
   void testAssertThatMapIsEmpty() {
@@ -84,11 +69,7 @@ final class AssertJMapRulesTest implements RefasterRuleCollectionTestCase {
   ImmutableSet<MapAssert<Integer, Integer>> testAbstractMapAssertIsNotEmpty() {
     return ImmutableSet.of(
         assertThat(ImmutableMap.of(1, 0)).isNotEqualTo(ImmutableMap.of()),
-        assertThat(ImmutableMap.of(2, 0)).isNotEqualTo(ImmutableBiMap.of()),
-        assertThat(ImmutableMap.of(3, 0)).isNotEqualTo(ImmutableSortedMap.of()),
-        assertThat(ImmutableMap.of(4, 0)).isNotEqualTo(new HashMap<>()),
-        assertThat(ImmutableMap.of(5, 0)).isNotEqualTo(new LinkedHashMap<>()),
-        assertThat(ImmutableMap.of(6, 0)).isNotEqualTo(new TreeMap<>()));
+        assertThat(ImmutableMap.of(2, 0)).isNotEqualTo(ImmutableMap.of("foo", "bar")));
   }
 
   ImmutableSet<AbstractAssert<?, ?>> testAssertThatMapIsNotEmpty() {

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/AssertJMapRulesTestOutput.java

@@ -41,34 +41,19 @@ final class AssertJMapRulesTest implements RefasterRuleCollectionTestCase {
 
   void testAbstractMapAssertIsEmpty() {
     assertThat(ImmutableMap.of(1, 0)).isEmpty();
-    assertThat(ImmutableMap.of(2, 0)).isEmpty();
+    assertThat(ImmutableMap.of(2, 0)).containsExactlyEntriesOf(ImmutableMap.of(1, 2));
     assertThat(ImmutableMap.of(3, 0)).isEmpty();
-    assertThat(ImmutableMap.of(4, 0)).isEmpty();
+    assertThat(ImmutableMap.of(4, 0))
+        .containsExactlyInAnyOrderEntriesOf(ImmutableMap.of(1, 2, 3, 4));
     assertThat(ImmutableMap.of(5, 0)).isEmpty();
-    assertThat(ImmutableMap.of(6, 0)).isEmpty();
+    assertThat(ImmutableMap.of(6, 0)).hasSameSizeAs(ImmutableMap.of(1, 2));
     assertThat(ImmutableMap.of(7, 0)).isEmpty();
-    assertThat(ImmutableMap.of(8, 0)).isEmpty();
+    assertThat(ImmutableMap.of(8, 0)).isEqualTo(ImmutableMap.of("foo", "bar"));
     assertThat(ImmutableMap.of(9, 0)).isEmpty();
-    assertThat(ImmutableMap.of(10, 0)).isEmpty();
+    assertThat(ImmutableMap.of(10, 0)).containsOnlyKeys(ImmutableList.of(1));
     assertThat(ImmutableMap.of(11, 0)).isEmpty();
     assertThat(ImmutableMap.of(12, 0)).isEmpty();
     assertThat(ImmutableMap.of(13, 0)).isEmpty();
-    assertThat(ImmutableMap.of(14, 0)).isEmpty();
-    assertThat(ImmutableMap.of(15, 0)).isEmpty();
-    assertThat(ImmutableMap.of(16, 0)).isEmpty();
-    assertThat(ImmutableMap.of(17, 0)).isEmpty();
-    assertThat(ImmutableMap.of(18, 0)).isEmpty();
-    assertThat(ImmutableMap.of(19, 0)).isEmpty();
-    assertThat(ImmutableMap.of(20, 0)).isEmpty();
-    assertThat(ImmutableMap.of(21, 0)).isEmpty();
-    assertThat(ImmutableMap.of(22, 0)).isEmpty();
-    assertThat(ImmutableMap.of(23, 0)).isEmpty();
-    assertThat(ImmutableMap.of(24, 0)).isEmpty();
-    assertThat(ImmutableMap.of(25, 0)).isEmpty();
-    assertThat(ImmutableMap.of(26, 0)).isEmpty();
-    assertThat(ImmutableMap.of(27, 0)).isEmpty();
-    assertThat(ImmutableMap.of(28, 0)).isEmpty();
-    assertThat(ImmutableMap.of(29, 0)).isEmpty();
   }
 
   void testAssertThatMapIsEmpty() {
@@ -84,11 +69,7 @@ final class AssertJMapRulesTest implements RefasterRuleCollectionTestCase {
   ImmutableSet<MapAssert<Integer, Integer>> testAbstractMapAssertIsNotEmpty() {
     return ImmutableSet.of(
         assertThat(ImmutableMap.of(1, 0)).isNotEmpty(),
-        assertThat(ImmutableMap.of(2, 0)).isNotEmpty(),
-        assertThat(ImmutableMap.of(3, 0)).isNotEmpty(),
-        assertThat(ImmutableMap.of(4, 0)).isNotEmpty(),
-        assertThat(ImmutableMap.of(5, 0)).isNotEmpty(),
-        assertThat(ImmutableMap.of(6, 0)).isNotEmpty());
+        assertThat(ImmutableMap.of(2, 0)).isNotEqualTo(ImmutableMap.of("foo", "bar")));
   }
 
   ImmutableSet<AbstractAssert<?, ?>> testAssertThatMapIsNotEmpty() {

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/BigDecimalRulesTestInput.java

@@ -20,4 +20,36 @@ final class BigDecimalRulesTest implements RefasterRuleCollectionTestCase {
   ImmutableSet<BigDecimal> testBigDecimalValueOf() {
     return ImmutableSet.of(new BigDecimal(2), new BigDecimal(2L), new BigDecimal(2.0));
   }
+
+  ImmutableSet<Boolean> testBigDecimalSignumIsZero() {
+    return ImmutableSet.of(
+        BigDecimal.valueOf(1).compareTo(BigDecimal.ZERO) == 0,
+        BigDecimal.ZERO.compareTo(BigDecimal.valueOf(2)) == 0,
+        BigDecimal.valueOf(3).compareTo(BigDecimal.ZERO) != 0,
+        BigDecimal.ZERO.compareTo(BigDecimal.valueOf(4)) != 0);
+  }
+
+  ImmutableSet<Boolean> testBigDecimalSignumIsPositive() {
+    return ImmutableSet.of(
+        BigDecimal.valueOf(1).compareTo(BigDecimal.ZERO) > 0,
+        BigDecimal.ZERO.compareTo(BigDecimal.valueOf(2)) < 0,
+        BigDecimal.valueOf(3).signum() > 0,
+        BigDecimal.valueOf(4).signum() >= 1,
+        BigDecimal.valueOf(5).compareTo(BigDecimal.ZERO) <= 0,
+        BigDecimal.ZERO.compareTo(BigDecimal.valueOf(6)) >= 0,
+        BigDecimal.valueOf(7).signum() <= 0,
+        BigDecimal.valueOf(8).signum() < 1);
+  }
+
+  ImmutableSet<Boolean> testBigDecimalSignumIsNegative() {
+    return ImmutableSet.of(
+        BigDecimal.valueOf(1).compareTo(BigDecimal.ZERO) < 0,
+        BigDecimal.ZERO.compareTo(BigDecimal.valueOf(2)) > 0,
+        BigDecimal.valueOf(3).signum() < 0,
+        BigDecimal.valueOf(4).signum() <= -1,
+        BigDecimal.valueOf(5).compareTo(BigDecimal.ZERO) >= 0,
+        BigDecimal.ZERO.compareTo(BigDecimal.valueOf(6)) <= 0,
+        BigDecimal.valueOf(7).signum() >= 0,
+        BigDecimal.valueOf(8).signum() > -1);
+  }
 }

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/BigDecimalRulesTestOutput.java

@@ -20,4 +20,36 @@ final class BigDecimalRulesTest implements RefasterRuleCollectionTestCase {
   ImmutableSet<BigDecimal> testBigDecimalValueOf() {
     return ImmutableSet.of(BigDecimal.valueOf(2), BigDecimal.valueOf(2L), BigDecimal.valueOf(2.0));
   }
+
+  ImmutableSet<Boolean> testBigDecimalSignumIsZero() {
+    return ImmutableSet.of(
+        BigDecimal.valueOf(1).signum() == 0,
+        BigDecimal.valueOf(2).signum() == 0,
+        BigDecimal.valueOf(3).signum() != 0,
+        BigDecimal.valueOf(4).signum() != 0);
+  }
+
+  ImmutableSet<Boolean> testBigDecimalSignumIsPositive() {
+    return ImmutableSet.of(
+        BigDecimal.valueOf(1).signum() == 1,
+        BigDecimal.valueOf(2).signum() == 1,
+        BigDecimal.valueOf(3).signum() == 1,
+        BigDecimal.valueOf(4).signum() == 1,
+        BigDecimal.valueOf(5).signum() != 1,
+        BigDecimal.valueOf(6).signum() != 1,
+        BigDecimal.valueOf(7).signum() != 1,
+        BigDecimal.valueOf(8).signum() != 1);
+  }
+
+  ImmutableSet<Boolean> testBigDecimalSignumIsNegative() {
+    return ImmutableSet.of(
+        BigDecimal.valueOf(1).signum() == -1,
+        BigDecimal.valueOf(2).signum() == -1,
+        BigDecimal.valueOf(3).signum() == -1,
+        BigDecimal.valueOf(4).signum() == -1,
+        BigDecimal.valueOf(5).signum() != -1,
+        BigDecimal.valueOf(6).signum() != -1,
+        BigDecimal.valueOf(7).signum() != -1,
+        BigDecimal.valueOf(8).signum() != -1);
+  }
 }

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/BugCheckerRulesTestInput.java

@@ -4,12 +4,13 @@ import com.google.common.collect.ImmutableSet;
 import com.google.errorprone.BugCheckerRefactoringTestHelper;
 import com.google.errorprone.BugCheckerRefactoringTestHelper.FixChoosers;
 import com.google.errorprone.bugpatterns.BugChecker;
+import com.sun.tools.javac.util.Convert;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
 final class BugCheckerRulesTest implements RefasterRuleCollectionTestCase {
   @Override
   public ImmutableSet<Object> elidedTypesAndStaticImports() {
-    return ImmutableSet.of(FixChoosers.class);
+    return ImmutableSet.of(Convert.class, FixChoosers.class);
   }
 
   ImmutableSet<BugCheckerRefactoringTestHelper> testBugCheckerRefactoringTestHelperIdentity() {
@@ -26,4 +27,8 @@ final class BugCheckerRulesTest implements RefasterRuleCollectionTestCase {
         .addInputLines("A.java", "class A {}")
         .addOutputLines("A.java", "class A {}");
   }
+
+  String testConstantsFormat() {
+    return String.format("\"%s\"", Convert.quote("foo"));
+  }
 }

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/BugCheckerRulesTestOutput.java

@@ -4,12 +4,14 @@ import com.google.common.collect.ImmutableSet;
 import com.google.errorprone.BugCheckerRefactoringTestHelper;
 import com.google.errorprone.BugCheckerRefactoringTestHelper.FixChoosers;
 import com.google.errorprone.bugpatterns.BugChecker;
+import com.sun.tools.javac.util.Constants;
+import com.sun.tools.javac.util.Convert;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
 final class BugCheckerRulesTest implements RefasterRuleCollectionTestCase {
   @Override
   public ImmutableSet<Object> elidedTypesAndStaticImports() {
-    return ImmutableSet.of(FixChoosers.class);
+    return ImmutableSet.of(Convert.class, FixChoosers.class);
   }
 
   ImmutableSet<BugCheckerRefactoringTestHelper> testBugCheckerRefactoringTestHelperIdentity() {
@@ -24,4 +26,8 @@ final class BugCheckerRulesTest implements RefasterRuleCollectionTestCase {
         .addInputLines("A.java", "class A {}")
         .expectUnchanged();
   }
+
+  String testConstantsFormat() {
+    return Constants.format("foo");
+  }
 }

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ClassRulesTestInput.java

@@ -0,0 +1,26 @@
+package tech.picnic.errorprone.refasterrules;
+
+import com.google.common.collect.ImmutableSet;
+import java.io.IOException;
+import java.util.function.Predicate;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class ClassRulesTest implements RefasterRuleCollectionTestCase {
+  boolean testClassIsInstance() throws IOException {
+    return CharSequence.class.isAssignableFrom("foo".getClass());
+  }
+
+  ImmutableSet<Boolean> testInstanceof() throws IOException {
+    Class<?> clazz = CharSequence.class;
+    return ImmutableSet.of(CharSequence.class.isInstance("foo"), clazz.isInstance("bar"));
+  }
+
+  Predicate<String> testClassLiteralIsInstancePredicate() throws IOException {
+    return s -> s instanceof CharSequence;
+  }
+
+  Predicate<String> testClassReferenceIsInstancePredicate() throws IOException {
+    Class<?> clazz = CharSequence.class;
+    return s -> clazz.isInstance(s);
+  }
+}

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ClassRulesTestOutput.java

@@ -0,0 +1,26 @@
+package tech.picnic.errorprone.refasterrules;
+
+import com.google.common.collect.ImmutableSet;
+import java.io.IOException;
+import java.util.function.Predicate;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class ClassRulesTest implements RefasterRuleCollectionTestCase {
+  boolean testClassIsInstance() throws IOException {
+    return CharSequence.class.isInstance("foo");
+  }
+
+  ImmutableSet<Boolean> testInstanceof() throws IOException {
+    Class<?> clazz = CharSequence.class;
+    return ImmutableSet.of("foo" instanceof CharSequence, clazz.isInstance("bar"));
+  }
+
+  Predicate<String> testClassLiteralIsInstancePredicate() throws IOException {
+    return CharSequence.class::isInstance;
+  }
+
+  Predicate<String> testClassReferenceIsInstancePredicate() throws IOException {
+    Class<?> clazz = CharSequence.class;
+    return clazz::isInstance;
+  }
+}

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/CollectionRulesTestInput.java

@@ -36,6 +36,10 @@ final class CollectionRulesTest implements RefasterRuleCollectionTestCase {
     return ImmutableSet.of(Iterables.size(ImmutableSet.of(1)), ImmutableSet.of(2).asList().size());
   }
 
+  boolean testCollectionContains() {
+    return ImmutableSet.of("foo").stream().anyMatch("bar"::equals);
+  }
+
   boolean testCollectionAddAllToCollectionExpression() {
     return Iterables.addAll(new ArrayList<>(), ImmutableSet.of("foo"));
   }

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/CollectionRulesTestOutput.java

@@ -36,6 +36,10 @@ final class CollectionRulesTest implements RefasterRuleCollectionTestCase {
     return ImmutableSet.of(ImmutableSet.of(1).size(), ImmutableSet.of(2).size());
   }
 
+  boolean testCollectionContains() {
+    return ImmutableSet.of("foo").contains("bar");
+  }
+
   boolean testCollectionAddAllToCollectionExpression() {
     return new ArrayList<>().addAll(ImmutableSet.of("foo"));
   }

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ComparatorRulesTestInput.java

@@ -31,6 +31,7 @@ final class ComparatorRulesTest implements RefasterRuleCollectionTestCase {
         String::compareTo,
         Comparator.comparing(identity()),
         Comparator.comparing(s -> s),
+        Comparator.comparing(s -> 0),
         Collections.<String>reverseOrder(reverseOrder()),
         Comparator.<String>reverseOrder().reversed());
   }
@@ -45,7 +46,8 @@ final class ComparatorRulesTest implements RefasterRuleCollectionTestCase {
   ImmutableSet<Comparator<String>> testCustomComparator() {
     return ImmutableSet.of(
         Comparator.comparing(identity(), Comparator.comparingInt(String::length)),
-        Comparator.comparing(s -> s, Comparator.comparingInt(String::length)));
+        Comparator.comparing(s -> s, Comparator.comparingInt(String::length)),
+        Comparator.comparing(s -> "foo", Comparator.comparingInt(String::length)));
   }
 
   Comparator<String> testThenComparing() {
@@ -86,7 +88,8 @@ final class ComparatorRulesTest implements RefasterRuleCollectionTestCase {
   ImmutableSet<Comparator<String>> testThenComparingNaturalOrder() {
     return ImmutableSet.of(
         Comparator.<String>naturalOrder().thenComparing(identity()),
-        Comparator.<String>naturalOrder().thenComparing(s -> s));
+        Comparator.<String>naturalOrder().thenComparing(s -> s),
+        Comparator.<String>naturalOrder().thenComparing(s -> 0));
   }
 
   ImmutableSet<Integer> testCompareTo() {

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/ComparatorRulesTestOutput.java

@@ -28,7 +28,12 @@ final class ComparatorRulesTest implements RefasterRuleCollectionTestCase {
 
   ImmutableSet<Comparator<String>> testNaturalOrder() {
     return ImmutableSet.of(
-        naturalOrder(), naturalOrder(), naturalOrder(), naturalOrder(), naturalOrder());
+        naturalOrder(),
+        naturalOrder(),
+        naturalOrder(),
+        Comparator.comparing(s -> 0),
+        naturalOrder(),
+        naturalOrder());
   }
 
   ImmutableSet<Comparator<String>> testReverseOrder() {
@@ -38,7 +43,9 @@ final class ComparatorRulesTest implements RefasterRuleCollectionTestCase {
 
   ImmutableSet<Comparator<String>> testCustomComparator() {
     return ImmutableSet.of(
-        Comparator.comparingInt(String::length), Comparator.comparingInt(String::length));
+        Comparator.comparingInt(String::length),
+        Comparator.comparingInt(String::length),
+        Comparator.comparing(s -> "foo", Comparator.comparingInt(String::length)));
   }
 
   Comparator<String> testThenComparing() {
@@ -73,7 +80,8 @@ final class ComparatorRulesTest implements RefasterRuleCollectionTestCase {
   ImmutableSet<Comparator<String>> testThenComparingNaturalOrder() {
     return ImmutableSet.of(
         Comparator.<String>naturalOrder().thenComparing(naturalOrder()),
-        Comparator.<String>naturalOrder().thenComparing(naturalOrder()));
+        Comparator.<String>naturalOrder().thenComparing(naturalOrder()),
+        Comparator.<String>naturalOrder().thenComparing(s -> 0));
   }
 
   ImmutableSet<Integer> testCompareTo() {

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/EqualityRulesTestInput.java

@@ -1,16 +1,20 @@
 package tech.picnic.errorprone.refasterrules;
 
+import static java.util.function.Predicate.not;
+
 import com.google.common.collect.BoundType;
 import com.google.common.collect.ImmutableSet;
 import java.math.RoundingMode;
 import java.util.Objects;
+import java.util.Optional;
+import java.util.function.Predicate;
 import java.util.stream.Stream;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
 final class EqualityRulesTest implements RefasterRuleCollectionTestCase {
   @Override
   public ImmutableSet<Object> elidedTypesAndStaticImports() {
-    return ImmutableSet.of(Objects.class);
+    return ImmutableSet.of(Objects.class, Optional.class, not(null));
   }
 
   ImmutableSet<Boolean> testPrimitiveOrReferenceEquality() {
@@ -60,4 +64,20 @@ final class EqualityRulesTest implements RefasterRuleCollectionTestCase {
         !(3.0 != 4.0),
         !(BoundType.OPEN != BoundType.CLOSED));
   }
+
+  Predicate<String> testPredicateLambda() {
+    return not(v -> v.isEmpty());
+  }
+
+  boolean testEqualsLhsNullable() {
+    return Optional.ofNullable("foo").equals(Optional.of("bar"));
+  }
+
+  boolean testEqualsRhsNullable() {
+    return Optional.of("foo").equals(Optional.ofNullable("bar"));
+  }
+
+  boolean testEqualsLhsAndRhsNullable() {
+    return Optional.ofNullable("foo").equals(Optional.ofNullable("bar"));
+  }
 }

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/EqualityRulesTestOutput.java

@@ -1,16 +1,20 @@
 package tech.picnic.errorprone.refasterrules;
 
+import static java.util.function.Predicate.not;
+
 import com.google.common.collect.BoundType;
 import com.google.common.collect.ImmutableSet;
 import java.math.RoundingMode;
 import java.util.Objects;
+import java.util.Optional;
+import java.util.function.Predicate;
 import java.util.stream.Stream;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
 final class EqualityRulesTest implements RefasterRuleCollectionTestCase {
   @Override
   public ImmutableSet<Object> elidedTypesAndStaticImports() {
-    return ImmutableSet.of(Objects.class);
+    return ImmutableSet.of(Objects.class, Optional.class, not(null));
   }
 
   ImmutableSet<Boolean> testPrimitiveOrReferenceEquality() {
@@ -60,4 +64,20 @@ final class EqualityRulesTest implements RefasterRuleCollectionTestCase {
         3.0 == 4.0,
         BoundType.OPEN == BoundType.CLOSED);
   }
+
+  Predicate<String> testPredicateLambda() {
+    return v -> !v.isEmpty();
+  }
+
+  boolean testEqualsLhsNullable() {
+    return "bar".equals("foo");
+  }
+
+  boolean testEqualsRhsNullable() {
+    return "foo".equals("bar");
+  }
+
+  boolean testEqualsLhsAndRhsNullable() {
+    return Objects.equals("foo", "bar");
+  }
 }

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/FileRulesTestInput.java

@@ -0,0 +1,17 @@
+package tech.picnic.errorprone.refasterrules;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class FileRulesTest implements RefasterRuleCollectionTestCase {
+  String testFilesReadStringWithCharset() throws IOException {
+    return new String(Files.readAllBytes(Paths.get("foo")), StandardCharsets.ISO_8859_1);
+  }
+
+  String testFilesReadString() throws IOException {
+    return Files.readString(Paths.get("foo"), StandardCharsets.UTF_8);
+  }
+}

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/FileRulesTestOutput.java

@@ -0,0 +1,17 @@
+package tech.picnic.errorprone.refasterrules;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class FileRulesTest implements RefasterRuleCollectionTestCase {
+  String testFilesReadStringWithCharset() throws IOException {
+    return Files.readString(Paths.get("foo"), StandardCharsets.ISO_8859_1);
+  }
+
+  String testFilesReadString() throws IOException {
+    return Files.readString(Paths.get("foo"));
+  }
+}