[maven-release-plugin] prepare release v0.5.0

See:
- https://checkstyle.sourceforge.io/releasenotes.html
- https://github.com/checkstyle/checkstyle/releases/tag/checkstyle-10.4
- https://github.com/checkstyle/checkstyle/compare/checkstyle-10.3.4...checkstyle-10.4

.github/release.yml

@@ -3,7 +3,7 @@ changelog:
     labels:
       - "ignore-changelog"
   categories:
-    - title: ":rocket: New Error Prone checks and Refaster templates"
+    - title: ":rocket: New Error Prone checks and Refaster rules"
       labels:
         - "new feature"
     - title: ":sparkles: Improvements"

.github/workflows/build.yaml

@@ -2,15 +2,32 @@ name: Build and verify
 on:
   pull_request:
   push:
-    branches: [$default-branch]
+    branches: [ master ]
 permissions:
   contents: read
 jobs:
   build:
-    runs-on: ubuntu-22.04
     strategy:
       matrix:
-        jdk: [ 11.0.16, 17.0.4 ]
+        os: [ ubuntu-22.04 ]
+        jdk: [ 11.0.16, 17.0.4, 19 ]
+        distribution: [ temurin ]
+        experimental: [ false ]
+        include:
+          - os: macos-12
+            jdk: 17.0.4
+            distribution: temurin
+            experimental: false
+          - os: windows-2022
+            jdk: 17.0.4
+            distribution: temurin
+            experimental: false
+          - os: ubuntu-22.04
+            jdk: 20-ea
+            distribution: zulu
+            experimental: true
+    runs-on: ${{ matrix.os }}
+    continue-on-error: ${{ matrix.experimental }}
     steps:
         # We run the build twice for each supported JDK: once against the
         # original Error Prone release, using only Error Prone checks available
@@ -18,12 +35,12 @@ 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@v3.0.2
+        uses: actions/checkout@v3.1.0
       - name: Set up JDK
-        uses: actions/setup-java@v3.5.1
+        uses: actions/setup-java@v3.6.0
         with:
           java-version: ${{ matrix.jdk }}
-          distribution: temurin
+          distribution: ${{ matrix.distribution }}
           cache: maven
       - name: Display build environment details
         run: mvn --version

.github/workflows/deploy-website.yaml

@@ -2,39 +2,43 @@ name: Update `error-prone.picnic.tech` website content
 on:
   pull_request:
   push:
-    branches: [$default-branch]
-permissions:
-  contents: read
-  id-token: write
-  pages: write
+    branches: [ master, website ]
 concurrency:
-  group: pages
-  cancel-in-progress: true
+  group: ${{ github.workflow }}-${{ github.ref }}
 jobs:
   build:
+    permissions:
+      contents: read
     runs-on: ubuntu-22.04
     steps:
       - name: Check out code
-        uses: actions/checkout@v3.0.2
+        uses: actions/checkout@v3.1.0
+      - uses: ruby/setup-ruby@v1.120.0
+        with:
+          working-directory: ./website
+          bundler-cache: true
       - name: Configure Github Pages
-        uses: actions/configure-pages@v2.1.1
+        uses: actions/configure-pages@v2.1.2
       - name: Generate documentation
         run: ./generate-docs.sh
       - name: Build website with Jekyll
-        uses: actions/jekyll-build-pages@v1.0.5
-        with:
-          source: website/
-          destination: ./_site
+        working-directory: ./website
+        run: bundle exec jekyll build
       - name: Validate HTML output
-        uses: anishathalye/proof-html@v1.4.1
-        with:
-          directory: ./_site
-          check_external_hash: false
+        working-directory: ./website
+        # XXX: Drop `--disable_external true` once we fully adopted the
+        # "Refaster rules" terminology on our website and in the code.
+        run: bundle exec htmlproofer --disable_external true --check-external-hash false ./_site
       - name: Upload website as artifact
         uses: actions/upload-pages-artifact@v1.0.4
+        with:
+          path: ./website/_site
   deploy:
-    if: github.ref == format('refs/heads/{0}', github.event.repository.default_branch)
+    if: github.ref == 'refs/heads/website'
     needs: build
+    permissions:
+      id-token: write
+      pages: write
     runs-on: ubuntu-22.04
     environment:
       name: github-pages
@@ -42,4 +46,4 @@ jobs:
     steps:
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@v1.2.1
+        uses: actions/deploy-pages@v1.2.2

README.md

@@ -15,6 +15,10 @@ 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].
+
 [![Maven Central][maven-central-badge]][maven-central-search]
 [![GitHub Actions][github-actions-build-badge]][github-actions-build-master]
 [![License][license-badge]][license]
@@ -59,7 +63,7 @@ it:
                                <artifactId>error-prone-contrib</artifactId>
                                <version>${error-prone-support.version}</version>
                            </path>
-                           <!-- Error Prone Support's Refaster templates. -->
+                           <!-- Error Prone Support's Refaster rules. -->
                            <path>
                                <groupId>tech.picnic.error-prone-support</groupId>
                                <artifactId>refaster-runner</artifactId>
@@ -115,16 +119,13 @@ code with Maven should yield two compiler warnings:
 ```sh
 $ mvn clean install
 ...
-[INFO] -------------------------------------------------------------
-[WARNING] COMPILATION WARNING :
-[INFO] -------------------------------------------------------------
-[WARNING] Example.java:[9,34] [tech.picnic.errorprone.refastertemplates.BigDecimalTemplates.BigDecimalZero]
+[INFO] Example.java:[9,34] [Refaster Rule] BigDecimalRules.BigDecimalZero: Refactoring opportunity
+    (see https://error-prone.picnic.tech/refasterrules/BigDecimalRules#BigDecimalZero)
   Did you mean 'return BigDecimal.ZERO;'?
+...
 [WARNING] Example.java:[13,35] [IdentityConversion] This method invocation appears redundant; remove it or suppress this warning and add a comment explaining its purpose
     (see https://error-prone.picnic.tech/bugpatterns/IdentityConversion)
   Did you mean 'return set;' or '@SuppressWarnings("IdentityConversion") public ImmutableSet<Integer> getSet() {'?
-[INFO] 2 warnings
-[INFO] -------------------------------------------------------------
 ...
 ```
 
@@ -132,12 +133,12 @@ Two things are kicking in here:
 
 1. An Error Prone [`BugChecker`][error-prone-bugchecker] that flags unnecessary
    [identity conversions][bug-checks-identity-conversion].
-2. A [Refaster][refaster] template capable of
-   [rewriting][refaster-templates-bigdecimal] expressions of the form
+2. A [Refaster][refaster] rule capable of
+   [rewriting][refaster-rules-bigdecimal] expressions of the form
    `BigDecimal.valueOf(0)` and `new BigDecimal(0)` to `BigDecimal.ZERO`.
 
 Be sure to check out all [bug checks][bug-checks] and [refaster
-templates][refaster-templates].
+rules][refaster-rules].
 
 ## 👷 Developing Error Prone Support
 
@@ -218,9 +219,10 @@ guidelines][contributing].
 [maven-central-search]: https://search.maven.org/artifact/tech.picnic.error-prone-support/error-prone-support
 [maven]: https://maven.apache.org
 [picnic-blog]: https://blog.picnic.nl
+[picnic-blog-ep-post]: https://blog.picnic.nl/picnic-loves-error-prone-producing-high-quality-and-consistent-java-code-b8a566be6886
 [pitest]: https://pitest.org
 [pitest-maven]: https://pitest.org/quickstart/maven
 [pr-badge]: https://img.shields.io/badge/PRs-welcome-brightgreen.svg
 [refaster]: https://errorprone.info/docs/refaster
-[refaster-templates-bigdecimal]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/error-prone-contrib/src/main/java/tech/picnic/errorprone/refastertemplates/BigDecimalTemplates.java
-[refaster-templates]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/error-prone-contrib/src/main/java/tech/picnic/errorprone/refastertemplates/
+[refaster-rules-bigdecimal]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/BigDecimalRules.java
+[refaster-rules]: https://github.com/PicnicSupermarket/error-prone-support/blob/master/error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/

error-prone-contrib/README.md

@@ -267,7 +267,7 @@ Refaster's expressiveness:
   motivating example, see the two subtly different loop definitions in
   `CollectionRemoveAllFromCollectionExpression`.
 - Figure out why Refaster sometimes doesn't match the correct generic overload.
-  See the `AssertThatIterableHasOneComparableElementEqualTo` template for an
+  See the `AssertThatIterableHasOneComparableElementEqualTo` rule for an
   example.
 
 [autorefactor]: https://autorefactor.org

error-prone-contrib/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.3.1-SNAPSHOT</version>
+        <version>0.5.0</version>
     </parent>
 
     <artifactId>error-prone-contrib</artifactId>
@@ -64,11 +64,6 @@
             <artifactId>auto-service-annotations</artifactId>
             <scope>provided</scope>
         </dependency>
-        <dependency>
-            <groupId>com.google.code.findbugs</groupId>
-            <artifactId>jsr305</artifactId>
-            <scope>provided</scope>
-        </dependency>
         <dependency>
             <groupId>com.google.googlejavaformat</groupId>
             <artifactId>google-java-format</artifactId>
@@ -98,6 +93,11 @@
             <artifactId>reactor-adapter</artifactId>
             <scope>provided</scope>
         </dependency>
+        <dependency>
+            <groupId>io.projectreactor.addons</groupId>
+            <artifactId>reactor-extra</artifactId>
+            <scope>provided</scope>
+        </dependency>
         <dependency>
             <groupId>io.reactivex.rxjava2</groupId>
             <artifactId>rxjava</artifactId>
@@ -173,6 +173,11 @@
             <artifactId>slf4j-api</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-context</artifactId>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.springframework</groupId>
             <artifactId>spring-test</artifactId>

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

@@ -36,6 +36,9 @@ public final class AmbiguousJsonCreator extends BugChecker implements Annotation
   private static final Matcher<AnnotationTree> IS_JSON_CREATOR_ANNOTATION =
       isType("com.fasterxml.jackson.annotation.JsonCreator");
 
+  /** Instantiates a new {@link AmbiguousJsonCreator} instance. */
+  public AmbiguousJsonCreator() {}
+
   @Override
   public Description matchAnnotation(AnnotationTree tree, VisitorState state) {
     if (!IS_JSON_CREATOR_ANNOTATION.matches(tree, state)) {

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

@@ -24,7 +24,7 @@ import com.sun.source.tree.MethodInvocationTree;
 /**
  * A {@link BugChecker} that flags AssertJ {@code isEqualTo(null)} checks for simplification.
  *
- * <p>This bug checker cannot be replaced with a simple Refaster template, as the Refaster approach
+ * <p>This bug checker cannot be replaced with a simple Refaster rule, as the Refaster approach
  * would require that all overloads of {@link org.assertj.core.api.Assert#isEqualTo(Object)} (such
  * as {@link org.assertj.core.api.AbstractStringAssert#isEqualTo(String)}) are explicitly
  * enumerated. This bug checker generically matches all such current and future overloads.
@@ -44,6 +44,9 @@ public final class AssertJIsNull extends BugChecker implements MethodInvocationT
           argumentCount(1),
           argument(0, nullLiteral()));
 
+  /** Instantiates a new {@link AssertJIsNull} instance. */
+  public AssertJIsNull() {}
+
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
     if (!ASSERT_IS_EQUAL_TO_NULL.matches(tree, state)) {

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

@@ -38,6 +38,9 @@ public final class AutowiredConstructor extends BugChecker implements ClassTreeM
   private static final MultiMatcher<Tree, AnnotationTree> AUTOWIRED_ANNOTATION =
       annotations(AT_LEAST_ONE, isType("org.springframework.beans.factory.annotation.Autowired"));
 
+  /** Instantiates a new {@link AutowiredConstructor} instance. */
+  public AutowiredConstructor() {}
+
   @Override
   public Description matchClass(ClassTree tree, VisitorState state) {
     List<MethodTree> constructors = ASTHelpers.getConstructors(tree);

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

@@ -46,6 +46,9 @@ public final class CanonicalAnnotationSyntax extends BugChecker implements Annot
               CanonicalAnnotationSyntax::dropRedundantValueAttribute,
               CanonicalAnnotationSyntax::dropRedundantCurlies);
 
+  /** Instantiates a new {@link CanonicalAnnotationSyntax} instance. */
+  public CanonicalAnnotationSyntax() {}
+
   @Override
   public Description matchAnnotation(AnnotationTree tree, VisitorState state) {
     return FIX_FACTORIES.stream()

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

@@ -18,6 +18,7 @@ import com.google.errorprone.matchers.Matcher;
 import com.sun.source.tree.ExpressionTree;
 import com.sun.source.tree.MethodInvocationTree;
 import java.util.stream.Collector;
+import tech.picnic.errorprone.bugpatterns.util.ThirdPartyLibrary;
 
 /**
  * A {@link BugChecker} that flags {@link Collector Collectors} that don't clearly express
@@ -45,9 +46,13 @@ public final class CollectorMutability extends BugChecker implements MethodInvoc
   private static final Matcher<ExpressionTree> SET_COLLECTOR =
       staticMethod().anyClass().named("toSet");
 
+  /** Instantiates a new {@link CollectorMutability} instance. */
+  public CollectorMutability() {}
+
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
-    if (!COLLECTOR_METHOD.matches(tree, state)) {
+    if (!ThirdPartyLibrary.GUAVA.isIntroductionAllowed(state)
+        || !COLLECTOR_METHOD.matches(tree, state)) {
       return Description.NO_MATCH;
     }
 

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

@@ -38,6 +38,9 @@ public final class EmptyMethod extends BugChecker implements MethodTreeMatcher {
           AT_LEAST_ONE,
           anyOf(isType("java.lang.Override"), isType("org.aspectj.lang.annotation.Pointcut")));
 
+  /** Instantiates a new {@link EmptyMethod} instance. */
+  public EmptyMethod() {}
+
   @Override
   public Description matchMethod(MethodTree tree, VisitorState state) {
     if (tree.getBody() == null

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

@@ -72,6 +72,9 @@ public final class ErrorProneTestHelperSourceFormat extends BugChecker
           .onDescendantOf("com.google.errorprone.BugCheckerRefactoringTestHelper.ExpectOutput")
           .named("addOutputLines");
 
+  /** Instantiates a new {@link ErrorProneTestHelperSourceFormat} instance. */
+  public ErrorProneTestHelperSourceFormat() {}
+
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
     boolean isOutputSource = OUTPUT_SOURCE_ACCEPTING_METHOD.matches(tree, state);

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

@@ -46,6 +46,9 @@ public final class ExplicitEnumOrdering extends BugChecker implements MethodInvo
   private static final Matcher<ExpressionTree> EXPLICIT_ORDERING =
       staticMethod().onClass(Ordering.class.getName()).named("explicit");
 
+  /** Instantiates a new {@link ExplicitEnumOrdering} instance. */
+  public ExplicitEnumOrdering() {}
+
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
     if (!EXPLICIT_ORDERING.matches(tree, state)) {
@@ -86,6 +89,6 @@ public final class ExplicitEnumOrdering extends BugChecker implements MethodInvo
   private static Stream<String> getMissingEnumValues(Type enumType, Set<String> values) {
     Symbol.TypeSymbol typeSymbol = enumType.asElement();
     return Sets.difference(ASTHelpers.enumValues(typeSymbol), values).stream()
-        .map(v -> String.format("%s.%s", typeSymbol.getSimpleName(), v));
+        .map(v -> String.join(".", typeSymbol.getSimpleName(), v));
   }
 }

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

@@ -5,6 +5,10 @@ import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
 import static com.google.errorprone.BugPattern.StandardTags.LIKELY_ERROR;
 import static com.google.errorprone.matchers.method.MethodMatchers.instanceMethod;
 import static tech.picnic.errorprone.bugpatterns.util.Documentation.BUG_PATTERNS_BASE_URL;
+import static tech.picnic.errorprone.bugpatterns.util.MoreTypes.generic;
+import static tech.picnic.errorprone.bugpatterns.util.MoreTypes.subOf;
+import static tech.picnic.errorprone.bugpatterns.util.MoreTypes.type;
+import static tech.picnic.errorprone.bugpatterns.util.MoreTypes.unbound;
 
 import com.google.auto.service.AutoService;
 import com.google.common.collect.Iterables;
@@ -17,11 +21,14 @@ 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.suppliers.Supplier;
+import com.google.errorprone.suppliers.Suppliers;
+import com.google.errorprone.util.ASTHelpers;
 import com.sun.source.tree.ExpressionTree;
 import com.sun.source.tree.MemberReferenceTree;
 import com.sun.source.tree.MethodInvocationTree;
+import com.sun.tools.javac.code.Type;
 import java.util.function.Function;
-import java.util.function.Supplier;
 import reactor.core.publisher.Flux;
 
 /**
@@ -33,11 +40,12 @@ import reactor.core.publisher.Flux;
  * former interleaves values as they are emitted, yielding nondeterministic results. In most cases
  * {@link Flux#concatMap(Function)} should be preferred, as it produces consistent results and
  * avoids potentially saturating the thread pool on which subscription happens. If {@code
- * concatMap}'s single-subscription semantics are undesirable one should invoke a {@code flatMap} or
- * {@code flatMapSequential} overload with an explicit concurrency level.
+ * concatMap}'s sequential-subscription semantics are undesirable one should invoke a {@code
+ * flatMap} or {@code flatMapSequential} overload with an explicit concurrency level.
  *
- * <p>NB: The rarely-used overload {@link Flux#flatMap(Function, Function, Supplier)} is not flagged
- * by this check because there is no clear alternative to point to.
+ * <p>NB: The rarely-used overload {@link Flux#flatMap(Function, Function,
+ * java.util.function.Supplier)} is not flagged by this check because there is no clear alternative
+ * to point to.
  */
 @AutoService(BugChecker.class)
 @BugPattern(
@@ -52,11 +60,19 @@ public final class FluxFlatMapUsage extends BugChecker
     implements MethodInvocationTreeMatcher, MemberReferenceTreeMatcher {
   private static final long serialVersionUID = 1L;
   private static final String MAX_CONCURRENCY_ARG_NAME = "MAX_CONCURRENCY";
+  private static final Supplier<Type> FLUX =
+      Suppliers.typeFromString("reactor.core.publisher.Flux");
   private static final Matcher<ExpressionTree> FLUX_FLATMAP =
       instanceMethod()
-          .onDescendantOf("reactor.core.publisher.Flux")
+          .onDescendantOf(FLUX)
           .namedAnyOf("flatMap", "flatMapSequential")
           .withParameters(Function.class.getName());
+  private static final Supplier<Type> FLUX_OF_PUBLISHERS =
+      VisitorState.memoize(
+          generic(FLUX, subOf(generic(type("org.reactivestreams.Publisher"), unbound()))));
+
+  /** Instantiates a new {@link FluxFlatMapUsage} instance. */
+  public FluxFlatMapUsage() {}
 
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
@@ -64,14 +80,27 @@ public final class FluxFlatMapUsage extends BugChecker
       return Description.NO_MATCH;
     }
 
-    return buildDescription(tree)
-        .addFix(SuggestedFixes.renameMethodInvocation(tree, "concatMap", state))
-        .addFix(
-            SuggestedFix.builder()
-                .postfixWith(
-                    Iterables.getOnlyElement(tree.getArguments()), ", " + MAX_CONCURRENCY_ARG_NAME)
-                .build())
-        .build();
+    SuggestedFix serializationFix = SuggestedFixes.renameMethodInvocation(tree, "concatMap", state);
+    SuggestedFix concurrencyCapFix =
+        SuggestedFix.builder()
+            .postfixWith(
+                Iterables.getOnlyElement(tree.getArguments()), ", " + MAX_CONCURRENCY_ARG_NAME)
+            .build();
+
+    Description.Builder description = buildDescription(tree);
+
+    if (state.getTypes().isSubtype(ASTHelpers.getType(tree), FLUX_OF_PUBLISHERS.get(state))) {
+      /*
+       * Nested publishers may need to be subscribed to eagerly in order to avoid a deadlock, e.g.
+       * if they are produced by `Flux#groupBy`. In this case we suggest specifying an explicit
+       * concurrently bound, in favour of sequential subscriptions using `Flux#concatMap`.
+       */
+      description.addFix(concurrencyCapFix).addFix(serializationFix);
+    } else {
+      description.addFix(serializationFix).addFix(concurrencyCapFix);
+    }
+
+    return description.build();
   }
 
   @Override

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

@@ -32,7 +32,7 @@ import com.sun.source.util.SimpleTreeVisitor;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
-import javax.annotation.Nullable;
+import org.jspecify.nullness.Nullable;
 import tech.picnic.errorprone.bugpatterns.util.SourceCode;
 
 /**
@@ -48,7 +48,7 @@ import tech.picnic.errorprone.bugpatterns.util.SourceCode;
 // `Formattable#toString` invocation with a `Formattable#formatTo` invocation. But likely that
 // should be considered a bug fix, too.
 // XXX: Introduce a separate check that adds/removes the `Locale` parameter to `String.format`
-// invocations, as necessary.
+// invocations, as necessary. See also a comment in the `StringJoin` check.
 @AutoService(BugChecker.class)
 @BugPattern(
     summary = "Defer string concatenation to the invoked method",
@@ -129,6 +129,9 @@ public final class FormatStringConcatenation extends BugChecker
           .onDescendantOf("org.slf4j.Logger")
           .namedAnyOf("debug", "error", "info", "trace", "warn");
 
+  /** Instantiates a new {@link FormatStringConcatenation} instance. */
+  public FormatStringConcatenation() {}
+
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
     if (hasNonConstantStringConcatenationArgument(tree, 0, state)) {
@@ -204,7 +207,7 @@ public final class FormatStringConcatenation extends BugChecker
   }
 
   private static class ReplacementArgumentsConstructor
-      extends SimpleTreeVisitor<Void, VisitorState> {
+      extends SimpleTreeVisitor<@Nullable Void, VisitorState> {
     private final StringBuilder formatString = new StringBuilder();
     private final List<Tree> formatArguments = new ArrayList<>();
     private final String formatSpecifier;
@@ -213,9 +216,8 @@ public final class FormatStringConcatenation extends BugChecker
       this.formatSpecifier = formatSpecifier;
     }
 
-    @Nullable
     @Override
-    public Void visitBinary(BinaryTree tree, VisitorState state) {
+    public @Nullable Void visitBinary(BinaryTree tree, VisitorState state) {
       if (tree.getKind() == Kind.PLUS && isStringTyped(tree, state)) {
         tree.getLeftOperand().accept(this, state);
         tree.getRightOperand().accept(this, state);
@@ -226,15 +228,13 @@ public final class FormatStringConcatenation extends BugChecker
       return null;
     }
 
-    @Nullable
     @Override
-    public Void visitParenthesized(ParenthesizedTree tree, VisitorState state) {
+    public @Nullable Void visitParenthesized(ParenthesizedTree tree, VisitorState state) {
       return tree.getExpression().accept(this, state);
     }
 
-    @Nullable
     @Override
-    protected Void defaultAction(Tree tree, VisitorState state) {
+    protected @Nullable Void defaultAction(Tree tree, VisitorState state) {
       appendExpression(tree);
       return null;
     }

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

@@ -72,6 +72,9 @@ public final class IdentityConversion extends BugChecker implements MethodInvoca
               .namedAnyOf("concat", "firstWithSignal", "from", "merge"),
           staticMethod().onClass("reactor.core.publisher.Mono").namedAnyOf("from", "fromDirect"));
 
+  /** Instantiates a new {@link IdentityConversion} instance. */
+  public IdentityConversion() {}
+
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
     List<? extends ExpressionTree> arguments = tree.getArguments();

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

@@ -67,6 +67,9 @@ public final class ImmutablesSortedSetComparator extends BugChecker implements M
                   hasAnnotation("org.immutables.value.Value.NaturalOrder"),
                   hasAnnotation("org.immutables.value.Value.ReverseOrder"))));
 
+  /** Instantiates a new {@link ImmutablesSortedSetComparator} instance. */
+  public ImmutablesSortedSetComparator() {}
+
   @Override
   public Description matchMethod(MethodTree tree, VisitorState state) {
     if (!METHOD_LACKS_ANNOTATION.matches(tree, state)) {

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

@@ -79,6 +79,9 @@ public final class JUnitMethodDeclaration extends BugChecker implements MethodTr
               isType("org.junit.jupiter.api.BeforeAll"),
               isType("org.junit.jupiter.api.BeforeEach")));
 
+  /** Instantiates a new {@link JUnitMethodDeclaration} instance. */
+  public JUnitMethodDeclaration() {}
+
   @Override
   public Description matchMethod(MethodTree tree, VisitorState state) {
     if (HAS_UNMODIFIABLE_SIGNATURE.matches(tree, state)) {

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

@@ -1,5 +1,6 @@
 package tech.picnic.errorprone.bugpatterns;
 
+import static com.google.common.collect.ImmutableList.toImmutableList;
 import static com.google.errorprone.BugPattern.LinkType.CUSTOM;
 import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
 import static com.google.errorprone.BugPattern.StandardTags.STYLE;
@@ -9,6 +10,7 @@ import static java.util.stream.Collectors.joining;
 import static tech.picnic.errorprone.bugpatterns.util.Documentation.BUG_PATTERNS_BASE_URL;
 
 import com.google.auto.service.AutoService;
+import com.google.common.base.Splitter;
 import com.google.common.collect.Comparators;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
@@ -38,7 +40,7 @@ import java.util.List;
 import java.util.Optional;
 import java.util.Set;
 import java.util.stream.Stream;
-import javax.annotation.Nullable;
+import org.jspecify.nullness.Nullable;
 import tech.picnic.errorprone.bugpatterns.util.AnnotationAttributeMatcher;
 import tech.picnic.errorprone.bugpatterns.util.SourceCode;
 
@@ -71,10 +73,16 @@ 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
+   * properly sorted by key, then value.
+   */
+  private static final Splitter STRING_ARGUMENT_SPLITTER = Splitter.on('=');
 
   private final AnnotationAttributeMatcher matcher;
 
-  /** Instantiates the default {@link LexicographicalAnnotationAttributeListing}. */
+  /** Instantiates a default {@link LexicographicalAnnotationAttributeListing} instance. */
   public LexicographicalAnnotationAttributeListing() {
     this(ErrorProneFlags.empty());
   }
@@ -126,7 +134,7 @@ public final class LexicographicalAnnotationAttributeListing extends BugChecker
     }
 
     List<? extends ExpressionTree> actualOrdering = array.getInitializers();
-    ImmutableList<? extends ExpressionTree> desiredOrdering = doSort(actualOrdering, state);
+    ImmutableList<? extends ExpressionTree> desiredOrdering = doSort(actualOrdering);
     if (actualOrdering.equals(desiredOrdering)) {
       /* In the (presumably) common case the elements are already sorted. */
       return Optional.empty();
@@ -156,12 +164,12 @@ public final class LexicographicalAnnotationAttributeListing extends BugChecker
   }
 
   private static ImmutableList<? extends ExpressionTree> doSort(
-      Iterable<? extends ExpressionTree> elements, VisitorState state) {
+      Iterable<? extends ExpressionTree> elements) {
     // XXX: Perhaps we should use `Collator` with `.setStrength(Collator.PRIMARY)` and
     // `getCollationKey`. Not clear whether that's worth the hassle at this point.
     return ImmutableList.sortedCopyOf(
         comparing(
-            e -> getStructure(e, state),
+            LexicographicalAnnotationAttributeListing::getStructure,
             Comparators.lexicographical(
                 Comparators.lexicographical(
                     String.CASE_INSENSITIVE_ORDER.thenComparing(naturalOrder())))),
@@ -173,38 +181,31 @@ public final class LexicographicalAnnotationAttributeListing extends BugChecker
    * performed. This approach disregards e.g. irrelevant whitespace. It also allows special
    * structure within string literals to be respected.
    */
-  private static ImmutableList<ImmutableList<String>> getStructure(
-      ExpressionTree array, VisitorState state) {
+  private static ImmutableList<ImmutableList<String>> getStructure(ExpressionTree array) {
     ImmutableList.Builder<ImmutableList<String>> nodes = ImmutableList.builder();
 
-    new TreeScanner<Void, Void>() {
-      @Nullable
+    new TreeScanner<@Nullable Void, @Nullable Void>() {
       @Override
-      public Void visitIdentifier(IdentifierTree node, @Nullable Void ctx) {
-        nodes.add(tokenize(node));
-        return super.visitIdentifier(node, ctx);
+      public @Nullable Void visitIdentifier(IdentifierTree node, @Nullable Void unused) {
+        nodes.add(ImmutableList.of(node.getName().toString()));
+        return super.visitIdentifier(node, unused);
       }
 
-      @Nullable
       @Override
-      public Void visitLiteral(LiteralTree node, @Nullable Void ctx) {
-        nodes.add(tokenize(node));
-        return super.visitLiteral(node, ctx);
+      public @Nullable Void visitLiteral(LiteralTree node, @Nullable Void unused) {
+        Object value = ASTHelpers.constValue(node);
+        nodes.add(
+            value instanceof String
+                ? STRING_ARGUMENT_SPLITTER.splitToStream((String) value).collect(toImmutableList())
+                : ImmutableList.of(String.valueOf(value)));
+
+        return super.visitLiteral(node, unused);
       }
 
-      @Nullable
       @Override
-      public Void visitPrimitiveType(PrimitiveTypeTree node, @Nullable Void ctx) {
-        nodes.add(tokenize(node));
-        return super.visitPrimitiveType(node, ctx);
-      }
-
-      private ImmutableList<String> tokenize(Tree node) {
-        /*
-         * Tokens are split on `=` so that e.g. inline Spring property declarations are properly
-         * sorted by key, then value.
-         */
-        return ImmutableList.copyOf(SourceCode.treeToString(node, state).split("=", -1));
+      public @Nullable Void visitPrimitiveType(PrimitiveTypeTree node, @Nullable Void unused) {
+        nodes.add(ImmutableList.of(node.getPrimitiveTypeKind().toString()));
+        return super.visitPrimitiveType(node, unused);
       }
     }.scan(array, null);
 

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

@@ -4,10 +4,13 @@ import static com.google.common.collect.ImmutableList.toImmutableList;
 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 com.sun.tools.javac.code.TypeAnnotations.AnnotationType.DECLARATION;
+import static com.sun.tools.javac.code.TypeAnnotations.AnnotationType.TYPE;
 import static java.util.Comparator.comparing;
 import static tech.picnic.errorprone.bugpatterns.util.Documentation.BUG_PATTERNS_BASE_URL;
 
 import com.google.auto.service.AutoService;
+import com.google.common.base.VerifyException;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Streams;
 import com.google.errorprone.BugPattern;
@@ -17,10 +20,14 @@ import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
 import com.google.errorprone.fixes.Fix;
 import com.google.errorprone.fixes.SuggestedFix;
 import com.google.errorprone.matchers.Description;
+import com.google.errorprone.util.ASTHelpers;
 import com.sun.source.tree.AnnotationTree;
 import com.sun.source.tree.MethodTree;
+import com.sun.tools.javac.code.Symbol;
+import com.sun.tools.javac.code.TypeAnnotations.AnnotationType;
+import java.util.Comparator;
 import java.util.List;
-import java.util.Optional;
+import org.jspecify.nullness.Nullable;
 import tech.picnic.errorprone.bugpatterns.util.SourceCode;
 
 /**
@@ -39,6 +46,12 @@ import tech.picnic.errorprone.bugpatterns.util.SourceCode;
 public final class LexicographicalAnnotationListing extends BugChecker
     implements MethodTreeMatcher {
   private static final long serialVersionUID = 1L;
+  private static final Comparator<@Nullable AnnotationType> BY_ANNOTATION_TYPE =
+      (a, b) ->
+          (a == null || a == DECLARATION) && b == TYPE ? -1 : a == TYPE && b == DECLARATION ? 1 : 0;
+
+  /** Instantiates a new {@link LexicographicalAnnotationListing} instance. */
+  public LexicographicalAnnotationListing() {}
 
   @Override
   public Description matchMethod(MethodTree tree, VisitorState state) {
@@ -47,26 +60,29 @@ public final class LexicographicalAnnotationListing extends BugChecker
       return Description.NO_MATCH;
     }
 
-    ImmutableList<? extends AnnotationTree> sortedAnnotations = sort(originalOrdering, state);
+    ImmutableList<? extends AnnotationTree> sortedAnnotations =
+        sort(originalOrdering, ASTHelpers.getSymbol(tree), state);
     if (originalOrdering.equals(sortedAnnotations)) {
       return Description.NO_MATCH;
     }
 
-    Optional<Fix> fix = tryFixOrdering(originalOrdering, sortedAnnotations, state);
-
-    Description.Builder description = buildDescription(originalOrdering.get(0));
-    fix.ifPresent(description::addFix);
-    return description.build();
+    return describeMatch(
+        originalOrdering.get(0), fixOrdering(originalOrdering, sortedAnnotations, state));
   }
 
   private static ImmutableList<? extends AnnotationTree> sort(
-      List<? extends AnnotationTree> annotations, VisitorState state) {
+      List<? extends AnnotationTree> annotations, Symbol symbol, VisitorState state) {
     return annotations.stream()
-        .sorted(comparing(annotation -> SourceCode.treeToString(annotation, state)))
+        .sorted(
+            comparing(
+                    (AnnotationTree annotation) ->
+                        ASTHelpers.getAnnotationType(annotation, symbol, state),
+                    BY_ANNOTATION_TYPE)
+                .thenComparing(annotation -> SourceCode.treeToString(annotation, state)))
         .collect(toImmutableList());
   }
 
-  private static Optional<Fix> tryFixOrdering(
+  private static Fix fixOrdering(
       List<? extends AnnotationTree> originalAnnotations,
       ImmutableList<? extends AnnotationTree> sortedAnnotations,
       VisitorState state) {
@@ -77,6 +93,7 @@ public final class LexicographicalAnnotationListing extends BugChecker
                 SuggestedFix.builder()
                     .replace(original, SourceCode.treeToString(replacement, state)))
         .reduce(SuggestedFix.Builder::merge)
-        .map(SuggestedFix.Builder::build);
+        .map(SuggestedFix.Builder::build)
+        .orElseThrow(() -> new VerifyException("No annotations were provided"));
   }
 }

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

@@ -60,6 +60,9 @@ import javax.lang.model.element.Name;
 public final class MethodReferenceUsage extends BugChecker implements LambdaExpressionTreeMatcher {
   private static final long serialVersionUID = 1L;
 
+  /** Instantiates a new {@link MethodReferenceUsage} instance. */
+  public MethodReferenceUsage() {}
+
   @Override
   public Description matchLambdaExpression(LambdaExpressionTree tree, VisitorState state) {
     /*
@@ -122,7 +125,7 @@ public final class MethodReferenceUsage extends BugChecker implements LambdaExpr
           return Optional.empty();
         }
         Symbol sym = ASTHelpers.getSymbol(methodSelect);
-        if (!sym.isStatic()) {
+        if (!ASTHelpers.isStatic(sym)) {
           return constructFix(lambdaExpr, "this", methodSelect);
         }
         return constructFix(lambdaExpr, sym.owner, methodSelect);
@@ -192,7 +195,7 @@ public final class MethodReferenceUsage extends BugChecker implements LambdaExpr
     Name sName = target.getSimpleName();
     Optional<SuggestedFix.Builder> fix = constructFix(lambdaExpr, sName, methodName);
 
-    if (!"java.lang".equals(target.packge().toString())) {
+    if (!"java.lang".equals(ASTHelpers.enclosingPackage(target).toString())) {
       Name fqName = target.getQualifiedName();
       if (!sName.equals(fqName)) {
         return fix.map(b -> b.addImport(fqName.toString()));

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

@@ -25,7 +25,7 @@ import com.sun.source.tree.Tree;
 /** A {@link BugChecker} that flags likely missing Refaster annotations. */
 @AutoService(BugChecker.class)
 @BugPattern(
-    summary = "The Refaster template contains a method without any Refaster annotations",
+    summary = "The Refaster rule contains a method without any Refaster annotations",
     link = BUG_PATTERNS_BASE_URL + "MissingRefasterAnnotation",
     linkType = CUSTOM,
     severity = WARNING,
@@ -40,6 +40,9 @@ public final class MissingRefasterAnnotation extends BugChecker implements Class
               isType("com.google.errorprone.refaster.annotation.BeforeTemplate"),
               isType("com.google.errorprone.refaster.annotation.AfterTemplate")));
 
+  /** Instantiates a new {@link MissingRefasterAnnotation} instance. */
+  public MissingRefasterAnnotation() {}
+
   @Override
   public Description matchClass(ClassTree tree, VisitorState state) {
     long methodTypes =

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

@@ -36,6 +36,9 @@ public final class MockitoStubbing extends BugChecker implements MethodInvocatio
   private static final Matcher<ExpressionTree> MOCKITO_EQ_METHOD =
       staticMethod().onClass("org.mockito.ArgumentMatchers").named("eq");
 
+  /** Instantiates a new {@link MockitoStubbing} instance. */
+  public MockitoStubbing() {}
+
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
     List<? extends ExpressionTree> arguments = tree.getArguments();

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

@@ -4,9 +4,11 @@ import static com.google.errorprone.BugPattern.LinkType.CUSTOM;
 import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
 import static com.google.errorprone.BugPattern.StandardTags.FRAGILE_CODE;
 import static tech.picnic.errorprone.bugpatterns.util.Documentation.BUG_PATTERNS_BASE_URL;
+import static tech.picnic.errorprone.bugpatterns.util.MoreTypes.generic;
+import static tech.picnic.errorprone.bugpatterns.util.MoreTypes.raw;
+import static tech.picnic.errorprone.bugpatterns.util.MoreTypes.subOf;
 
 import com.google.auto.service.AutoService;
-import com.google.common.collect.Iterables;
 import com.google.errorprone.BugPattern;
 import com.google.errorprone.VisitorState;
 import com.google.errorprone.bugpatterns.BugChecker;
@@ -16,9 +18,7 @@ import com.google.errorprone.suppliers.Supplier;
 import com.google.errorprone.suppliers.Suppliers;
 import com.google.errorprone.util.ASTHelpers;
 import com.sun.source.tree.MethodInvocationTree;
-import com.sun.source.tree.Tree;
 import com.sun.tools.javac.code.Type;
-import com.sun.tools.javac.util.List;
 import java.util.Optional;
 
 /** A {@link BugChecker} that flags nesting of {@link Optional Optionals}. */
@@ -33,21 +33,16 @@ import java.util.Optional;
 public final class NestedOptionals extends BugChecker implements MethodInvocationTreeMatcher {
   private static final long serialVersionUID = 1L;
   private static final Supplier<Type> OPTIONAL = Suppliers.typeFromClass(Optional.class);
+  private static final Supplier<Type> OPTIONAL_OF_OPTIONAL =
+      VisitorState.memoize(generic(OPTIONAL, subOf(raw(OPTIONAL))));
+
+  /** Instantiates a new {@link NestedOptionals} instance. */
+  public NestedOptionals() {}
 
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
-    return isOptionalOfOptional(tree, state) ? describeMatch(tree) : Description.NO_MATCH;
-  }
-
-  private static boolean isOptionalOfOptional(Tree tree, VisitorState state) {
-    Type optionalType = OPTIONAL.get(state);
-    Type type = ASTHelpers.getType(tree);
-    if (!ASTHelpers.isSubtype(type, optionalType, state)) {
-      return false;
-    }
-
-    List<Type> typeArguments = type.getTypeArguments();
-    return !typeArguments.isEmpty()
-        && ASTHelpers.isSubtype(Iterables.getOnlyElement(typeArguments), optionalType, state);
+    return state.getTypes().isSubtype(ASTHelpers.getType(tree), OPTIONAL_OF_OPTIONAL.get(state))
+        ? describeMatch(tree)
+        : Description.NO_MATCH;
   }
 }

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

@@ -76,6 +76,9 @@ public final class NonEmptyMono extends BugChecker implements MethodInvocationTr
               .onDescendantOf("reactor.core.publisher.Mono")
               .namedAnyOf("defaultIfEmpty", "hasElement", "single"));
 
+  /** Instantiates a new {@link NonEmptyMono} instance. */
+  public NonEmptyMono() {}
+
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
     if (!MONO_SIZE_CHECK.matches(tree, state)) {

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

@@ -70,6 +70,9 @@ public final class PrimitiveComparison extends BugChecker implements MethodInvoc
               .named("thenComparing")
               .withParameters(Function.class.getName()));
 
+  /** Instantiates a new {@link PrimitiveComparison} instance. */
+  public PrimitiveComparison() {}
+
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
     boolean isStatic = STATIC_COMPARISON_METHOD.matches(tree, state);

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

@@ -141,7 +141,7 @@ public final class RedundantStringConversion extends BugChecker
 
   private final Matcher<MethodInvocationTree> conversionMethodMatcher;
 
-  /** Instantiates the default {@link RedundantStringConversion}. */
+  /** Instantiates a default {@link RedundantStringConversion} instance. */
   public RedundantStringConversion() {
     this(ErrorProneFlags.empty());
   }

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

@@ -22,8 +22,8 @@ import tech.picnic.errorprone.bugpatterns.util.SourceCode;
 /**
  * A {@link BugChecker} that flags unnecessary {@link Refaster#anyOf(Object[])} usages.
  *
- * <p>Note that this logic can't be implemented as a Refaster template, as the {@link Refaster}
- * class is treated specially.
+ * <p>Note that this logic can't be implemented as a Refaster rule, as the {@link Refaster} class is
+ * treated specially.
  */
 @AutoService(BugChecker.class)
 @BugPattern(
@@ -37,6 +37,9 @@ public final class RefasterAnyOfUsage extends BugChecker implements MethodInvoca
   private static final Matcher<ExpressionTree> REFASTER_ANY_OF =
       staticMethod().onClass(Refaster.class.getName()).named("anyOf");
 
+  /** Instantiates a new {@link RefasterAnyOfUsage} instance. */
+  public RefasterAnyOfUsage() {}
+
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
     if (REFASTER_ANY_OF.matches(tree, state)) {

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

@@ -29,17 +29,17 @@ import java.util.Set;
 import javax.lang.model.element.Modifier;
 
 /**
- * A {@link BugChecker} which suggests a canonical set of modifiers for Refaster class and method
+ * A {@link BugChecker} that suggests a canonical set of modifiers for Refaster class and method
  * definitions.
  */
 @AutoService(BugChecker.class)
 @BugPattern(
     summary = "Refaster class and method definitions should specify a canonical set of modifiers",
-    link = BUG_PATTERNS_BASE_URL + "RefasterTemplateModifiers",
+    link = BUG_PATTERNS_BASE_URL + "RefasterRuleModifiers",
     linkType = CUSTOM,
     severity = SUGGESTION,
     tags = STYLE)
-public final class RefasterTemplateModifiers extends BugChecker
+public final class RefasterRuleModifiers extends BugChecker
     implements ClassTreeMatcher, MethodTreeMatcher {
   private static final long serialVersionUID = 1L;
   private static final Matcher<Tree> BEFORE_TEMPLATE_METHOD = hasAnnotation(BeforeTemplate.class);
@@ -48,6 +48,9 @@ public final class RefasterTemplateModifiers extends BugChecker
   private static final Matcher<Tree> REFASTER_METHOD =
       anyOf(BEFORE_TEMPLATE_METHOD, AFTER_TEMPLATE_METHOD, PLACEHOLDER_METHOD);
 
+  /** Instantiates a new {@link RefasterRuleModifiers} instance. */
+  public RefasterRuleModifiers() {}
+
   @Override
   public Description matchClass(ClassTree tree, VisitorState state) {
     if (!hasMatchingMember(tree, BEFORE_TEMPLATE_METHOD, state)) {
@@ -85,8 +88,8 @@ public final class RefasterTemplateModifiers extends BugChecker
 
     if (!hasMatchingMember(tree, PLACEHOLDER_METHOD, state)) {
       /*
-       * Templates without a `@Placeholder` method should be `final`. Note that Refaster enforces
-       * that `@Placeholder` methods are `abstract`, so templates _with_ such a method will
+       * Rules without a `@Placeholder` method should be `final`. Note that Refaster enforces
+       * that `@Placeholder` methods are `abstract`, so rules _with_ such a method will
        * naturally be `abstract` and non-`final`.
        */
       modifiersToAdd.add(Modifier.FINAL);

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

@@ -83,6 +83,9 @@ public final class RequestMappingAnnotation extends BugChecker implements Method
                   isSameType("org.springframework.web.util.UriBuilder"),
                   isSameType("org.springframework.web.util.UriComponentsBuilder"))));
 
+  /** Instantiates a new {@link RequestMappingAnnotation} instance. */
+  public RequestMappingAnnotation() {}
+
   @Override
   public Description matchMethod(MethodTree tree, VisitorState state) {
     // XXX: Auto-add `@RequestParam` where applicable.

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

@@ -37,6 +37,9 @@ public final class RequestParamType extends BugChecker implements VariableTreeMa
           annotations(AT_LEAST_ONE, isType("org.springframework.web.bind.annotation.RequestParam")),
           anyOf(isSubtypeOf(ImmutableCollection.class), isSubtypeOf(ImmutableMap.class)));
 
+  /** Instantiates a new {@link RequestParamType} instance. */
+  public RequestParamType() {}
+
   @Override
   public Description matchVariable(VariableTree tree, VisitorState state) {
     return HAS_UNSUPPORTED_REQUEST_PARAM.matches(tree, state)

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

@@ -26,6 +26,7 @@ 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
@@ -46,9 +47,13 @@ public final class ScheduledTransactionTrace extends BugChecker implements Metho
   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 (!IS_SCHEDULED.matches(tree, state)) {
+    if (!ThirdPartyLibrary.NEW_RELIC_AGENT_API.isIntroductionAllowed(state)
+        || !IS_SCHEDULED.matches(tree, state)) {
       return Description.NO_MATCH;
     }
 

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/Slf4jLogStatement.java

@@ -29,6 +29,7 @@ import tech.picnic.errorprone.bugpatterns.util.SourceCode;
 // XXX: The special-casing of Throwable applies only to SLF4J 1.6.0+; see
 // https://www.slf4j.org/faq.html#paramException. That should be documented.
 // XXX: Also simplify `LOG.error(String.format("Something %s", arg), throwable)`.
+// XXX: Also simplify `LOG.error(String.join("sep", arg1, arg2), throwable)`? Perhaps too obscure.
 // XXX: Write a similar checker for Spring RestTemplates, String.format and friends, Guava
 // preconditions, ...
 @AutoService(BugChecker.class)
@@ -47,6 +48,9 @@ public final class Slf4jLogStatement extends BugChecker implements MethodInvocat
           .onDescendantOf("org.slf4j.Logger")
           .namedAnyOf("trace", "debug", "info", "warn", "error");
 
+  /** Instantiates a new {@link Slf4jLogStatement} instance. */
+  public Slf4jLogStatement() {}
+
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
     if (!SLF4J_LOGGER_INVOCATION.matches(tree, state)) {

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

@@ -57,6 +57,9 @@ public final class SpringMvcAnnotation extends BugChecker implements AnnotationT
           .put("PUT", "PutMapping")
           .build();
 
+  /** Instantiates a new {@link SpringMvcAnnotation} instance. */
+  public SpringMvcAnnotation() {}
+
   @Override
   public Description matchAnnotation(AnnotationTree tree, VisitorState state) {
     // XXX: We could remove the `@RequestMapping` import if not other usages remain.

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

@@ -101,7 +101,8 @@ public final class StaticImport extends BugChecker implements MemberSelectTreeMa
           "org.springframework.http.HttpMethod",
           "org.springframework.http.MediaType",
           "org.testng.Assert",
-          "reactor.function.TupleUtils");
+          "reactor.function.TupleUtils",
+          "tech.picnic.errorprone.bugpatterns.util.MoreTypes");
 
   /** Type members that should be statically imported. */
   @VisibleForTesting
@@ -190,6 +191,9 @@ public final class StaticImport extends BugChecker implements MemberSelectTreeMa
           "of",
           "valueOf");
 
+  /** Instantiates a new {@link StaticImport} instance. */
+  public StaticImport() {}
+
   @Override
   public Description matchMemberSelect(MemberSelectTree tree, VisitorState state) {
     if (!isCandidateContext(state) || !isCandidate(tree)) {

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

@@ -0,0 +1,185 @@
+package tech.picnic.errorprone.bugpatterns;
+
+import static com.google.errorprone.BugPattern.LinkType.NONE;
+import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
+import static com.google.errorprone.BugPattern.StandardTags.SIMPLIFICATION;
+import static com.google.errorprone.matchers.method.MethodMatchers.staticMethod;
+
+import com.google.auto.service.AutoService;
+import com.google.common.base.Splitter;
+import com.google.common.collect.ImmutableSet;
+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.MethodInvocationTreeMatcher;
+import com.google.errorprone.fixes.SuggestedFix;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.google.errorprone.suppliers.Supplier;
+import com.google.errorprone.suppliers.Suppliers;
+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 java.util.Formattable;
+import java.util.Iterator;
+import java.util.List;
+import org.jspecify.nullness.Nullable;
+import tech.picnic.errorprone.bugpatterns.util.SourceCode;
+
+/**
+ * A {@link BugChecker} that flags {@link String#format(String, Object...)} invocations which can be
+ * replaced with a {@link String#join(CharSequence, CharSequence...)} or even a {@link
+ * String#valueOf} invocation.
+ */
+// XXX: What about `v1 + "sep" + v2` and similar expressions? Do we want to rewrite those to
+// `String.join`, or should some `String.join` invocations be rewritten to use the `+` operator?
+// (The latter suggestion would conflict with the `FormatStringConcatenation` check.)
+@AutoService(BugChecker.class)
+@BugPattern(
+    summary = "Prefer `String#join` over `String#format`",
+    linkType = NONE,
+    severity = SUGGESTION,
+    tags = SIMPLIFICATION)
+public final class StringJoin extends BugChecker implements MethodInvocationTreeMatcher {
+  private static final long serialVersionUID = 1L;
+  private static final Splitter FORMAT_SPECIFIER_SPLITTER = Splitter.on("%s");
+  private static final Matcher<ExpressionTree> STRING_FORMAT_INVOCATION =
+      staticMethod().onClass(String.class.getName()).named("format");
+  private static final Supplier<Type> CHAR_SEQUENCE_TYPE =
+      Suppliers.typeFromClass(CharSequence.class);
+  private static final Supplier<Type> FORMATTABLE_TYPE = Suppliers.typeFromClass(Formattable.class);
+
+  /** Instantiates a new {@link StringJoin} instance. */
+  public StringJoin() {}
+
+  @Override
+  public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+    if (!STRING_FORMAT_INVOCATION.matches(tree, state)) {
+      return Description.NO_MATCH;
+    }
+
+    // XXX: This check assumes that if the first argument to `String#format` is a `Locale`, that
+    // this argument is not vacuous, and that as a result the expression cannot be simplified using
+    // `#valueOf` or `#join`. Implement a separate check that identifies and drops redundant
+    // `Locale` arguments. See also a related comment in `FormatStringConcatenation`.
+    String formatString = ASTHelpers.constValue(tree.getArguments().get(0), String.class);
+    if (formatString == null) {
+      return Description.NO_MATCH;
+    }
+
+    List<String> separators = FORMAT_SPECIFIER_SPLITTER.splitToList(formatString);
+    if (separators.size() < 2) {
+      /* The format string does not contain `%s` format specifiers. */
+      return Description.NO_MATCH;
+    }
+
+    if (separators.size() != tree.getArguments().size()) {
+      /* The number of arguments does not match the number of `%s` format specifiers. */
+      return Description.NO_MATCH;
+    }
+
+    int lastIndex = separators.size() - 1;
+    if (!separators.get(0).isEmpty() || !separators.get(lastIndex).isEmpty()) {
+      /* The format string contains leading or trailing characters. */
+      return Description.NO_MATCH;
+    }
+
+    ImmutableSet<String> innerSeparators = ImmutableSet.copyOf(separators.subList(1, lastIndex));
+    if (innerSeparators.size() > 1) {
+      /* The `%s` format specifiers are not uniformly separated. */
+      return Description.NO_MATCH;
+    }
+
+    if (innerSeparators.isEmpty()) {
+      /*
+       * This `String#format` invocation performs a straightforward string conversion; use
+       * `String#valueOf` instead.
+       */
+      return trySuggestExplicitStringConversion(tree, state);
+    }
+
+    String separator = Iterables.getOnlyElement(innerSeparators);
+    if (separator.indexOf('%') >= 0) {
+      /* The `%s` format specifiers are separated by another format specifier. */
+      // XXX: Strictly speaking we could support `%%` by mapping it to a literal `%`, but that
+      // doesn't seem worth the trouble.
+      return Description.NO_MATCH;
+    }
+
+    return trySuggestExplicitJoin(tree, separator, state);
+  }
+
+  /**
+   * If guaranteed to be behavior preserving, suggests replacing {@code String.format("%s", arg)}
+   * with {@code String.valueOf(arg)}.
+   *
+   * <p>If {@code arg} is already a string then the resultant conversion is vacuous. The {@link
+   * IdentityConversion} check will subsequently drop it.
+   */
+  private Description trySuggestExplicitStringConversion(
+      MethodInvocationTree tree, VisitorState state) {
+    ExpressionTree argument = tree.getArguments().get(1);
+    if (isSubtype(ASTHelpers.getType(argument), FORMATTABLE_TYPE, state)) {
+      /*
+       * `Formattable` arguments are handled specially; `String#valueOf` is not a suitable
+       * alternative.
+       */
+      return Description.NO_MATCH;
+    }
+
+    return buildDescription(tree)
+        .setMessage("Prefer `String#valueOf` over `String#format`")
+        .addFix(SuggestedFix.replace(tree, withStringConversionExpression(argument, state)))
+        .build();
+  }
+
+  /**
+   * Unless the given {@code String.format} expression includes {@link Formattable} arguments,
+   * suggests replacing it with a {@code String.join} expression using the specified argument
+   * separator.
+   */
+  private Description trySuggestExplicitJoin(
+      MethodInvocationTree tree, String separator, VisitorState state) {
+    Iterator<? extends ExpressionTree> arguments = tree.getArguments().iterator();
+
+    SuggestedFix.Builder fix =
+        SuggestedFix.builder()
+            .replace(tree.getMethodSelect(), "String.join")
+            .replace(arguments.next(), String.format("\"%s\"", Convert.quote(separator)));
+
+    while (arguments.hasNext()) {
+      ExpressionTree argument = arguments.next();
+      Type argumentType = ASTHelpers.getType(argument);
+      if (isSubtype(argumentType, FORMATTABLE_TYPE, state)) {
+        /*
+         * `Formattable` arguments are handled specially; `String#join` is not a suitable
+         * alternative.
+         */
+        return Description.NO_MATCH;
+      }
+
+      if (!isSubtype(argumentType, CHAR_SEQUENCE_TYPE, state)) {
+        /*
+         * The argument was previously implicitly converted to a string; now this must happen
+         * explicitly.
+         */
+        fix.replace(argument, withStringConversionExpression(argument, state));
+      }
+    }
+
+    return describeMatch(tree, fix.build());
+  }
+
+  private static boolean isSubtype(
+      @Nullable Type subType, Supplier<Type> superType, VisitorState state) {
+    return ASTHelpers.isSubtype(subType, superType.get(state), state);
+  }
+
+  private static String withStringConversionExpression(
+      ExpressionTree argument, VisitorState state) {
+    return String.format("String.valueOf(%s)", SourceCode.treeToString(argument, state));
+  }
+}

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

@@ -26,6 +26,9 @@ import java.time.Instant;
 import java.time.LocalDate;
 import java.time.LocalDateTime;
 import java.time.LocalTime;
+import java.time.OffsetDateTime;
+import java.time.OffsetTime;
+import java.time.ZonedDateTime;
 
 /** A {@link BugChecker} that flags illegal time-zone related operations. */
 @AutoService(BugChecker.class)
@@ -58,10 +61,16 @@ public final class TimeZoneUsage extends BugChecker implements MethodInvocationT
               .onClassAny(
                   LocalDate.class.getName(),
                   LocalDateTime.class.getName(),
-                  LocalTime.class.getName())
+                  LocalTime.class.getName(),
+                  OffsetDateTime.class.getName(),
+                  OffsetTime.class.getName(),
+                  ZonedDateTime.class.getName())
               .named("now"),
           staticMethod().onClassAny(Instant.class.getName()).named("now").withNoParameters());
 
+  /** Instantiates a new {@link TimeZoneUsage} instance. */
+  public TimeZoneUsage() {}
+
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
     return BANNED_TIME_METHOD.matches(tree, state)

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

@@ -1,4 +1,4 @@
 /** Picnic Error Prone Contrib checks. */
 @com.google.errorprone.annotations.CheckReturnValue
-@javax.annotation.ParametersAreNonnullByDefault
+@org.jspecify.nullness.NullMarked
 package tech.picnic.errorprone.bugpatterns;

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

@@ -21,6 +21,9 @@ public final class MethodMatcherFactory {
   private static final Pattern METHOD_SIGNATURE =
       Pattern.compile("([^\\s#(,)]+)#([^\\s#(,)]+)\\(((?:[^\\s#(,)]+(?:,[^\\s#(,)]+)*)?)\\)");
 
+  /** Instantiates a new {@link MethodMatcherFactory} instance. */
+  public MethodMatcherFactory() {}
+
   /**
    * Creates a {@link Matcher} of methods with any of the given signatures.
    *

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

@@ -0,0 +1,132 @@
+package tech.picnic.errorprone.bugpatterns.util;
+
+import static java.util.stream.Collectors.toCollection;
+
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.suppliers.Supplier;
+import com.google.errorprone.suppliers.Suppliers;
+import com.sun.tools.javac.code.BoundKind;
+import com.sun.tools.javac.code.Type;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.function.BiFunction;
+
+/**
+ * A set of helper methods which together define a DSL for defining {@link Type types}.
+ *
+ * <p>These methods are meant to be statically imported. Example usage:
+ *
+ * <pre>{@code
+ * Supplier<Type> type =
+ *     VisitorState.memoize(
+ *         generic(
+ *             type("reactor.core.publisher.Flux"),
+ *             subOf(generic(type("org.reactivestreams.Publisher"), unbound()))));
+ * }</pre>
+ *
+ * This statement produces a memoized supplier of the type {@code Flux<? extends Publisher<?>>}.
+ */
+public final class MoreTypes {
+  private MoreTypes() {}
+
+  /**
+   * Creates a supplier of the type with the given fully qualified name.
+   *
+   * <p>This method should only be used when building more complex types in combination with other
+   * {@link MoreTypes} methods. In other cases prefer directly calling {@link
+   * Suppliers#typeFromString(String)}.
+   *
+   * @param typeName The type of interest.
+   * @return A supplier which returns the described type if available in the given state, and {@code
+   *     null} otherwise.
+   */
+  public static Supplier<Type> type(String typeName) {
+    return Suppliers.typeFromString(typeName);
+  }
+
+  /**
+   * Creates a supplier of the described generic type.
+   *
+   * @param type The base type of interest.
+   * @param typeArgs The desired type arguments.
+   * @return A supplier which returns the described type if available in the given state, and {@code
+   *     null} otherwise.
+   */
+  // XXX: The given `type` should be a generic type, so perhaps `withParams` would be a better
+  // method name. But the DSL wouldn't look as nice that way.
+  @SafeVarargs
+  @SuppressWarnings("varargs")
+  public static Supplier<Type> generic(Supplier<Type> type, Supplier<Type>... typeArgs) {
+    return propagateNull(
+        type,
+        (state, baseType) -> {
+          List<Type> params =
+              Arrays.stream(typeArgs).map(s -> s.get(state)).collect(toCollection(ArrayList::new));
+          if (params.stream().anyMatch(Objects::isNull)) {
+            return null;
+          }
+
+          return state.getType(baseType, /* isArray= */ false, params);
+        });
+  }
+
+  /**
+   * Creates a raw (erased, non-generic) variant of the given type.
+   *
+   * @param type The base type of interest.
+   * @return A supplier which returns the described type if available in the given state, and {@code
+   *     null} otherwise.
+   */
+  public static Supplier<Type> raw(Supplier<Type> type) {
+    return propagateNull(type, (state, baseType) -> baseType.tsym.erasure(state.getTypes()));
+  }
+
+  /**
+   * Creates a {@code ? super T} wildcard type, with {@code T} bound to the given type.
+   *
+   * @param type The base type of interest.
+   * @return A supplier which returns the described type if available in the given state, and {@code
+   *     null} otherwise.
+   */
+  public static Supplier<Type> superOf(Supplier<Type> type) {
+    return propagateNull(
+        type,
+        (state, baseType) ->
+            new Type.WildcardType(baseType, BoundKind.SUPER, state.getSymtab().boundClass));
+  }
+
+  /**
+   * Creates a {@code ? extends T} wildcard type, with {@code T} bound to the given type.
+   *
+   * @param type The base type of interest.
+   * @return A supplier which returns the described type if available in the given state, and {@code
+   *     null} otherwise.
+   */
+  public static Supplier<Type> subOf(Supplier<Type> type) {
+    return propagateNull(
+        type,
+        (state, baseType) ->
+            new Type.WildcardType(
+                type.get(state), BoundKind.EXTENDS, state.getSymtab().boundClass));
+  }
+
+  /**
+   * Creates an unbound wildcard type ({@code ?}).
+   *
+   * @return A supplier which returns the described type.
+   */
+  public static Supplier<Type> unbound() {
+    return state ->
+        new Type.WildcardType(
+            state.getSymtab().objectType, BoundKind.UNBOUND, state.getSymtab().boundClass);
+  }
+
+  private static Supplier<Type> propagateNull(
+      Supplier<Type> type, BiFunction<VisitorState, Type, Type> transformer) {
+    return state ->
+        Optional.ofNullable(type.get(state)).map(t -> transformer.apply(state, t)).orElse(null);
+  }
+}

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

@@ -0,0 +1,105 @@
+package tech.picnic.errorprone.bugpatterns.util;
+
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.suppliers.Supplier;
+import com.sun.tools.javac.code.ClassFinder;
+import com.sun.tools.javac.code.Symbol.CompletionFailure;
+import com.sun.tools.javac.util.Name;
+
+/**
+ * Utility class that helps decide whether it is appropriate to introduce references to (well-known)
+ * third-party libraries.
+ *
+ * <p>This class should be used by {@link BugChecker}s that may otherwise suggest the introduction
+ * of code that depends on possibly-not-present third-party libraries.
+ */
+// XXX: Consider giving users more fine-grained control. This would be beneficial in cases where a
+// dependency is on the classpath, but new usages are undesirable.
+public enum ThirdPartyLibrary {
+  /**
+   * AssertJ.
+   *
+   * @see <a href="https://assertj.github.io/doc">AssertJ documentation</a>
+   */
+  ASSERTJ("org.assertj.core.api.Assertions"),
+  /**
+   * Google's Guava.
+   *
+   * @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.
+   *
+   * @see <a href="https://projectreactor.io">Home page</a>
+   */
+  REACTOR("reactor.core.publisher.Flux");
+
+  private static final String IGNORE_CLASSPATH_COMPAT_FLAG =
+      "ErrorProneSupport:IgnoreClasspathCompat";
+
+  @SuppressWarnings("ImmutableEnumChecker" /* Supplier is deterministic. */)
+  private final Supplier<Boolean> canUse;
+
+  /**
+   * Instantiates a {@link ThirdPartyLibrary} enum value.
+   *
+   * @param witnessFqcn The fully-qualified class name of a type that is expected to be on the
+   *     classpath iff the associated third-party library is on the classpath.
+   */
+  ThirdPartyLibrary(String witnessFqcn) {
+    this.canUse = VisitorState.memoize(state -> canIntroduceUsage(witnessFqcn, state));
+  }
+
+  /**
+   * Tells whether it is okay to introduce a dependency on this well-known third party library in
+   * the given context.
+   *
+   * @param state The context under consideration.
+   * @return {@code true} iff it is okay to assume or create a dependency on this library.
+   */
+  public boolean isIntroductionAllowed(VisitorState state) {
+    return canUse.get(state);
+  }
+
+  private static boolean canIntroduceUsage(String className, VisitorState state) {
+    return shouldIgnoreClasspath(state) || isKnownClass(className, state);
+  }
+
+  /**
+   * Attempts to determine whether a class with the given FQCN is on the classpath.
+   *
+   * <p>The {@link VisitorState}'s symbol table is consulted first. If the type has not yet been
+   * loaded, then an attempt is made to do so.
+   */
+  private static boolean isKnownClass(String className, VisitorState state) {
+    return state.getTypeFromString(className) != null || canLoadClass(className, state);
+  }
+
+  private static boolean canLoadClass(String className, VisitorState state) {
+    ClassFinder classFinder = ClassFinder.instance(state.context);
+    Name binaryName = state.binaryNameFromClassname(className);
+    try {
+      classFinder.loadClass(state.getSymtab().unnamedModule, binaryName);
+      return true;
+    } catch (CompletionFailure e) {
+      return false;
+    }
+  }
+
+  private static boolean shouldIgnoreClasspath(VisitorState state) {
+    return state
+        .errorProneOptions()
+        .getFlags()
+        .getBoolean(IGNORE_CLASSPATH_COMPAT_FLAG)
+        .orElse(Boolean.FALSE);
+  }
+}

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

@@ -1,4 +1,4 @@
 /** Auxiliary utilities for use by Error Prone checks. */
 @com.google.errorprone.annotations.CheckReturnValue
-@javax.annotation.ParametersAreNonnullByDefault
+@org.jspecify.nullness.NullMarked
 package tech.picnic.errorprone.bugpatterns.util;

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static org.assertj.core.data.Offset.offset;
 import static org.assertj.core.data.Percentage.withPercentage;
@@ -9,19 +9,21 @@ import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import java.math.BigDecimal;
 import org.assertj.core.api.AbstractBigDecimalAssert;
 import org.assertj.core.api.BigDecimalAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
 /**
- * Refaster templates related to AssertJ assertions over {@link BigDecimal}s.
+ * Refaster rules related to AssertJ assertions over {@link BigDecimal}s.
  *
- * <p>Note that, contrary to collections of Refaster templates for other {@link
- * org.assertj.core.api.NumberAssert} subtypes, these templates do not rewrite to/from {@link
+ * <p>Note that, contrary to collections of Refaster rules for other {@link
+ * org.assertj.core.api.NumberAssert} subtypes, these rules do not rewrite to/from {@link
  * BigDecimalAssert#isEqualTo(Object)} and {@link BigDecimalAssert#isNotEqualTo(Object)}. This is
  * because {@link BigDecimal#equals(Object)} considers not only the numeric value of compared
  * instances, but also their scale. As a result various seemingly straightforward transformations
  * would actually subtly change the assertion's semantics.
  */
-final class AssertJBigDecimalTemplates {
-  private AssertJBigDecimalTemplates() {}
+@OnlineDocumentation
+final class AssertJBigDecimalRules {
+  private AssertJBigDecimalRules() {}
 
   static final class AbstractBigDecimalAssertIsEqualByComparingTo {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static org.assertj.core.data.Offset.offset;
 import static org.assertj.core.data.Percentage.withPercentage;
@@ -8,11 +8,13 @@ import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import java.math.BigInteger;
 import org.assertj.core.api.AbstractBigIntegerAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
 // XXX: If we add a rule that drops unnecessary `L` suffixes from literal longs, then the `0L`/`1L`
 // cases below can go.
-final class AssertJBigIntegerTemplates {
-  private AssertJBigIntegerTemplates() {}
+@OnlineDocumentation
+final class AssertJBigIntegerRules {
+  private AssertJBigIntegerRules() {}
 
   static final class AbstractBigIntegerAssertIsEqualTo {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -8,9 +8,11 @@ import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
 import org.assertj.core.api.AbstractBooleanAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJBooleanTemplates {
-  private AssertJBooleanTemplates() {}
+@OnlineDocumentation
+final class AssertJBooleanRules {
+  private AssertJBooleanRules() {}
 
   static final class AbstractBooleanAssertIsEqualTo {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static org.assertj.core.data.Offset.offset;
 import static org.assertj.core.data.Percentage.withPercentage;
@@ -7,9 +7,11 @@ import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import org.assertj.core.api.AbstractByteAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJByteTemplates {
-  private AssertJByteTemplates() {}
+@OnlineDocumentation
+final class AssertJByteRules {
+  private AssertJByteRules() {}
 
   static final class AbstractByteAssertIsEqualTo {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -8,9 +8,11 @@ import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
 import org.assertj.core.api.AbstractAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJCharSequenceTemplates {
-  private AssertJCharSequenceTemplates() {}
+@OnlineDocumentation
+final class AssertJCharSequenceRules {
+  private AssertJCharSequenceRules() {}
 
   static final class AssertThatCharSequenceIsEmpty {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -8,9 +8,11 @@ import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
 import org.assertj.core.api.AbstractComparableAssert;
 import org.assertj.core.api.AbstractIntegerAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJComparableTemplates {
-  private AssertJComparableTemplates() {}
+@OnlineDocumentation
+final class AssertJComparableRules {
+  private AssertJComparableRules() {}
 
   static final class AssertThatIsEqualByComparingTo<T extends Comparable<? super T>> {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static org.assertj.core.data.Offset.offset;
 import static org.assertj.core.data.Percentage.withPercentage;
@@ -8,9 +8,11 @@ import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import org.assertj.core.api.AbstractDoubleAssert;
 import org.assertj.core.data.Offset;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJDoubleTemplates {
-  private AssertJDoubleTemplates() {}
+@OnlineDocumentation
+final class AssertJDoubleRules {
+  private AssertJDoubleRules() {}
 
   static final class AbstractDoubleAssertIsCloseToWithOffset {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import com.google.common.collect.Iterables;
 import com.google.errorprone.refaster.Refaster;
@@ -6,9 +6,11 @@ import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import java.util.Collection;
 import org.assertj.core.api.EnumerableAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJEnumerableTemplates {
-  private AssertJEnumerableTemplates() {}
+@OnlineDocumentation
+final class AssertJEnumerableRules {
+  private AssertJEnumerableRules() {}
 
   static final class EnumerableAssertIsEmpty<E> {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static org.assertj.core.data.Offset.offset;
 import static org.assertj.core.data.Percentage.withPercentage;
@@ -8,9 +8,11 @@ import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import org.assertj.core.api.AbstractFloatAssert;
 import org.assertj.core.data.Offset;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJFloatTemplates {
-  private AssertJFloatTemplates() {}
+@OnlineDocumentation
+final class AssertJFloatRules {
+  private AssertJFloatRules() {}
 
   static final class AbstractFloatAssertIsCloseToWithOffset {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static org.assertj.core.data.Offset.offset;
 import static org.assertj.core.data.Percentage.withPercentage;
@@ -7,9 +7,11 @@ import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import org.assertj.core.api.AbstractIntegerAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJIntegerTemplates {
-  private AssertJIntegerTemplates() {}
+@OnlineDocumentation
+final class AssertJIntegerRules {
+  private AssertJIntegerRules() {}
 
   static final class AbstractIntegerAssertIsEqualTo {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static org.assertj.core.data.Offset.offset;
 import static org.assertj.core.data.Percentage.withPercentage;
@@ -7,9 +7,11 @@ import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import org.assertj.core.api.AbstractLongAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJLongTemplates {
-  private AssertJLongTemplates() {}
+@OnlineDocumentation
+final class AssertJLongRules {
+  private AssertJLongRules() {}
 
   static final class AbstractLongAssertIsEqualTo {
     @BeforeTemplate

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

@@ -1,13 +1,15 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import com.google.common.collect.ImmutableMap;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import java.util.Map;
 import org.assertj.core.api.AbstractMapAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJMapTemplates {
-  private AssertJMapTemplates() {}
+@OnlineDocumentation
+final class AssertJMapRules {
+  private AssertJMapRules() {}
 
   static final class AbstractMapAssertContainsExactlyInAnyOrderEntriesOf<K, V> {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -19,10 +19,12 @@ import org.assertj.core.api.AbstractIntegerAssert;
 import org.assertj.core.api.AbstractLongAssert;
 import org.assertj.core.api.AbstractShortAssert;
 import org.assertj.core.api.NumberAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 import tech.picnic.errorprone.refaster.matchers.IsCharacter;
 
-final class AssertJNumberTemplates {
-  private AssertJNumberTemplates() {}
+@OnlineDocumentation
+final class AssertJNumberRules {
+  private AssertJNumberRules() {}
 
   static final class NumberAssertIsPositive {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -10,9 +10,11 @@ import com.google.errorprone.refaster.annotation.UseImportPolicy;
 import org.assertj.core.api.AbstractBooleanAssert;
 import org.assertj.core.api.AbstractStringAssert;
 import org.assertj.core.api.ObjectAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJObjectTemplates {
-  private AssertJObjectTemplates() {}
+@OnlineDocumentation
+final class AssertJObjectRules {
+  private AssertJObjectRules() {}
 
   static final class AssertThatIsInstanceOf<S, T> {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -14,9 +14,11 @@ import org.assertj.core.api.AbstractObjectAssert;
 import org.assertj.core.api.AbstractOptionalAssert;
 import org.assertj.core.api.ObjectAssert;
 import org.assertj.core.api.OptionalAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJOptionalTemplates {
-  private AssertJOptionalTemplates() {}
+@OnlineDocumentation
+final class AssertJOptionalRules {
+  private AssertJOptionalRules() {}
 
   static final class AssertThatOptional<T> {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -9,9 +9,11 @@ import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
 import org.assertj.core.api.AbstractBooleanAssert;
 import org.assertj.core.api.AbstractDoubleAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJPrimitiveTemplates {
-  private AssertJPrimitiveTemplates() {}
+@OnlineDocumentation
+final class AssertJPrimitiveRules {
+  private AssertJPrimitiveRules() {}
 
   static final class AssertThatIsEqualTo {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -53,9 +53,10 @@ import org.assertj.core.api.ObjectEnumerableAssert;
 import org.assertj.core.api.OptionalDoubleAssert;
 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;
 
-/** Refaster templates related to AssertJ expressions and statements. */
+/** Refaster rules related to AssertJ expressions and statements. */
 // XXX: Most `AbstractIntegerAssert` rules can also be applied for other primitive types. Generate
 // these in separate files.
 // XXX: Also do for BigInteger/BigDecimal?
@@ -63,7 +64,7 @@ import tech.picnic.errorprone.refaster.matchers.IsArray;
 // ^ And variants.
 // XXX: Consider splitting this class into multiple classes.
 // XXX: Some of these rules may not apply given the updated TestNG rewrite rules. Review.
-// XXX: For the templates that "unwrap" explicitly enumerated collections, also introduce variants
+// XXX: For the rules that "unwrap" explicitly enumerated collections, also introduce variants
 // with explicitly enumerated sorted collections. (Requires that the type bound is Comparable.)
 // XXX: Handle `.isEqualTo(explicitlyEnumeratedCollection)`. Can be considered equivalent to
 // `.containsOnly(elements)`. (This does mean the auto-generated code needs to be more advanced.
@@ -101,7 +102,7 @@ import tech.picnic.errorprone.refaster.matchers.IsArray;
 // (etc.)
 // XXX: Look into using Assertions#contentOf(URL url, Charset charset) instead of our own test
 // method.
-// XXX: Write Optional templates also for `OptionalInt` and variants.
+// XXX: Write `Optional` rules also for `OptionalInt` and variants.
 // XXX: Write plugin to flag `assertThat(compileTimeConstant)` occurrences. Also other likely
 // candidates, such as `assertThat(ImmutableSet(foo, bar)).XXX`
 // XXX: Write generic plugin to replace explicit array parameters with varargs (`new int[] {1, 2}`
@@ -118,10 +119,11 @@ import tech.picnic.errorprone.refaster.matchers.IsArray;
 // XXX: `assertThat(ImmutableList.sortedCopyOf(cmp, values)).somethingExactOrder` -> just compare
 // "in any order".
 // XXX: Turns out a lot of this is also covered by https://github.com/palantir/assertj-automation.
-// See how we can combine these things. Do note that (at present) their Refaster templates don't
+// See how we can combine these things. Do note that (at present) their Refaster rules don't
 // show up as Error Prone checks. So we'd have to build an integration for that.
-final class AssertJTemplates {
-  private AssertJTemplates() {}
+@OnlineDocumentation
+final class AssertJRules {
+  private AssertJRules() {}
 
   //
   // OptionalDouble
@@ -491,7 +493,7 @@ final class AssertJTemplates {
   }
 
   // XXX: This overload is here because `assertThat` has an overload for `Comparable` types.
-  // Unfortunately this still doesn't convince Refaster to match this template in the context of
+  // Unfortunately this still doesn't convince Refaster to match this rule in the context of
   // Comparable types. Figure out why! Note that this also affects the `AssertThatOptional` rule.
   static final class AssertThatIterableHasOneComparableElementEqualTo<
       S extends Comparable<? super S>, T extends S> {

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static org.assertj.core.data.Offset.offset;
 import static org.assertj.core.data.Percentage.withPercentage;
@@ -7,9 +7,11 @@ import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import org.assertj.core.api.AbstractShortAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJShortTemplates {
-  private AssertJShortTemplates() {}
+@OnlineDocumentation
+final class AssertJShortRules {
+  private AssertJShortRules() {}
 
   static final class AbstractShortAssertIsEqualTo {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -8,9 +8,11 @@ import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
 import org.assertj.core.api.AbstractAssert;
 import org.assertj.core.api.AbstractStringAssert;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-final class AssertJStringTemplates {
-  private AssertJStringTemplates() {}
+@OnlineDocumentation
+final class AssertJStringRules {
+  private AssertJStringRules() {}
 
   static final class AbstractStringAssertStringIsEmpty {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
@@ -16,18 +16,20 @@ import java.io.IOException;
 import org.assertj.core.api.AbstractObjectAssert;
 import org.assertj.core.api.AbstractThrowableAssert;
 import org.assertj.core.api.ThrowableAssert.ThrowingCallable;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
 /**
- * Refaster templates related to AssertJ assertions over expressions that may throw a {@link
- * Throwable} subtype.
+ * Refaster rules related to AssertJ assertions over expressions that may throw a {@link Throwable}
+ * subtype.
  *
  * <p>For reasons of consistency we prefer {@link
  * org.assertj.core.api.Assertions#assertThatThrownBy} over static methods for specific exception
  * types. Note that only the most common assertion expressions are rewritten here; covering all
  * cases would require the implementation of an Error Prone check instead.
  */
-final class AssertJThrowingCallableTemplates {
-  private AssertJThrowingCallableTemplates() {}
+@OnlineDocumentation
+final class AssertJThrowingCallableRules {
+  private AssertJThrowingCallableRules() {}
 
   static final class AssertThatThrownByIllegalArgumentException {
     @BeforeTemplate
@@ -429,8 +431,8 @@ final class AssertJThrowingCallableTemplates {
     }
   }
 
-  // XXX: Drop this template in favour of a generic Error Prone check that flags
-  // `String.format(...)` arguments to a wide range of format methods.
+  // XXX: Drop this rule in favour of a generic Error Prone check that flags `String.format(...)`
+  // arguments to a wide range of format methods.
   static final class AbstractThrowableAssertHasMessage {
     @BeforeTemplate
     AbstractThrowableAssert<?, ? extends Throwable> before(
@@ -449,8 +451,8 @@ final class AssertJThrowingCallableTemplates {
     }
   }
 
-  // XXX: Drop this template in favour of a generic Error Prone check that flags
-  // `String.format(...)` arguments to a wide range of format methods.
+  // XXX: Drop this rule in favour of a generic Error Prone check that flags `String.format(...)`
+  // arguments to a wide range of format methods.
   static final class AbstractThrowableAssertWithFailMessage {
     @BeforeTemplate
     AbstractThrowableAssert<?, ? extends Throwable> before(

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.common.base.Preconditions.checkElementIndex;
 import static com.google.common.collect.ImmutableSet.toImmutableSet;
@@ -27,14 +27,16 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 import java.util.stream.Stream;
-import javax.annotation.Nullable;
+import org.jspecify.nullness.Nullable;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
 /**
- * Assorted Refaster templates that do not (yet) belong in one of the other classes with more
- * topical Refaster templates.
+ * Assorted Refaster rules that do not (yet) belong in one of the other classes with more topical
+ * Refaster rules.
  */
-final class AssortedTemplates {
-  private AssortedTemplates() {}
+@OnlineDocumentation
+final class AssortedRules {
+  private AssortedRules() {}
 
   /** Prefer {@link Objects#checkIndex(int, int)} over the Guava alternative. */
   static final class CheckIndex {
@@ -44,11 +46,33 @@ final class AssortedTemplates {
     }
 
     @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
     int after(int index, int size) {
       return checkIndex(index, size);
     }
   }
 
+  /**
+   * Prefer {@link Objects#checkIndex(int, int)} over less descriptive or more verbose alternatives.
+   *
+   * <p>If a custom error message is desired, consider using Guava's {@link
+   * com.google.common.base.Preconditions#checkElementIndex(int, int, String)}.
+   */
+  static final class CheckIndexConditional {
+    @BeforeTemplate
+    void before(int index, int size) {
+      if (index < 0 || index >= size) {
+        throw new IndexOutOfBoundsException();
+      }
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(int index, int size) {
+      checkIndex(index, size);
+    }
+  }
+
   // XXX: We could add a rule for `new EnumMap(Map<K, ? extends V> m)`, but that constructor does
   // not allow an empty non-EnumMap to be provided.
   static final class CreateEnumMap<K extends Enum<K>, V> {
@@ -65,14 +89,12 @@ final class AssortedTemplates {
 
   static final class MapGetOrNull<K, V, L> {
     @BeforeTemplate
-    @Nullable
-    V before(Map<K, V> map, L key) {
+    @Nullable V before(Map<K, V> map, L key) {
       return map.getOrDefault(key, null);
     }
 
     @AfterTemplate
-    @Nullable
-    V after(Map<K, V> map, L key) {
+    @Nullable V after(Map<K, V> map, L key) {
       return map.get(key);
     }
   }
@@ -110,14 +132,13 @@ final class AssortedTemplates {
     }
 
     @AfterTemplate
-    @Nullable
-    T after(Iterator<T> iterator, T defaultValue) {
+    @Nullable T after(Iterator<T> iterator, T defaultValue) {
       return Iterators.getNext(iterator, defaultValue);
     }
   }
 
   /** Don't unnecessarily repeat boolean expressions. */
-  // XXX: This template captures only the simplest case. `@AlsoNegation` doesn't help. Consider
+  // XXX: This rule captures only the simplest case. `@AlsoNegation` doesn't help. Consider
   // contributing a Refaster patch, which handles the negation in the `@BeforeTemplate` more
   // intelligently.
   static final class LogicalImplication {
@@ -172,8 +193,8 @@ final class AssortedTemplates {
    * Collections#disjoint(Collection, Collection)}.
    */
   // XXX: Other copy operations could be elided too, but these are most common after application of
-  // the `DisjointSets` template defined above. If we ever introduce a generic "makes a copy"
-  // stand-in, use it here.
+  // the `DisjointSets` rule defined above. If we ever introduce a generic "makes a copy" stand-in,
+  // use it here.
   static final class DisjointCollections<T> {
     @BeforeTemplate
     boolean before(Collection<T> collection1, Collection<T> collection2) {

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

@@ -1,13 +1,15 @@
-package tech.picnic.errorprone.refastertemplates;
+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.math.BigDecimal;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link BigDecimal}s. */
-final class BigDecimalTemplates {
-  private BigDecimalTemplates() {}
+/** Refaster rules related to expressions dealing with {@link BigDecimal}s. */
+@OnlineDocumentation
+final class BigDecimalRules {
+  private BigDecimalRules() {}
 
   /** Prefer using the constant {@link BigDecimal#ZERO} when possible. */
   static final class BigDecimalZero {

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import com.google.common.collect.ImmutableCollection;
 import com.google.common.collect.ImmutableList;
@@ -19,12 +19,14 @@ import java.util.Set;
 import java.util.SortedSet;
 import java.util.function.IntFunction;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with (arbitrary) collections. */
+/** Refaster rules related to expressions dealing with (arbitrary) collections. */
 // XXX: There are other Guava `Iterables` methods that should not be called if the input is known to
 // be a `Collection`. Add those here.
-final class CollectionTemplates {
-  private CollectionTemplates() {}
+@OnlineDocumentation
+final class CollectionRules {
+  private CollectionRules() {}
 
   /**
    * Prefer {@link Collection#isEmpty()} over alternatives that consult the collection's size or are

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static java.util.Comparator.comparing;
@@ -24,10 +24,12 @@ import java.util.function.Function;
 import java.util.function.ToDoubleFunction;
 import java.util.function.ToIntFunction;
 import java.util.function.ToLongFunction;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link Comparator}s. */
-final class ComparatorTemplates {
-  private ComparatorTemplates() {}
+/** Refaster rules related to expressions dealing with {@link Comparator}s. */
+@OnlineDocumentation
+final class ComparatorRules {
+  private ComparatorRules() {}
 
   /** Prefer {@link Comparator#naturalOrder()} over more complicated constructs. */
   static final class NaturalOrder<T extends Comparable<? super T>> {

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import com.google.common.collect.Streams;
 import com.google.errorprone.refaster.Refaster;
@@ -12,10 +12,12 @@ import java.util.function.DoublePredicate;
 import java.util.function.DoubleUnaryOperator;
 import java.util.stream.DoubleStream;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link DoubleStream}s. */
-final class DoubleStreamTemplates {
-  private DoubleStreamTemplates() {}
+/** Refaster rules related to expressions dealing with {@link DoubleStream}s. */
+@OnlineDocumentation
+final class DoubleStreamRules {
+  private DoubleStreamRules() {}
 
   /** Don't unnecessarily call {@link Streams#concat(DoubleStream...)}. */
   static final class ConcatOneDoubleStream {

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
@@ -6,10 +6,12 @@ import com.google.errorprone.refaster.annotation.AlsoNegation;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import java.util.Objects;
 import java.util.function.Predicate;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with (in)equalities. */
-final class EqualityTemplates {
-  private EqualityTemplates() {}
+/** Refaster rules related to expressions dealing with (in)equalities. */
+@OnlineDocumentation
+final class EqualityRules {
+  private EqualityRules() {}
 
   /** Prefer reference-based quality for enums. */
   // Primitive value comparisons are not listed, because Error Prone flags those out of the box.

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.common.collect.ImmutableListMultimap.flatteningToImmutableListMultimap;
 import static com.google.common.collect.ImmutableListMultimap.toImmutableListMultimap;
@@ -24,10 +24,12 @@ import java.util.Iterator;
 import java.util.Map;
 import java.util.function.Function;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link ImmutableListMultimap}s. */
-final class ImmutableListMultimapTemplates {
-  private ImmutableListMultimapTemplates() {}
+/** Refaster rules related to expressions dealing with {@link ImmutableListMultimap}s. */
+@OnlineDocumentation
+final class ImmutableListMultimapRules {
+  private ImmutableListMultimapRules() {}
 
   /**
    * Prefer {@link ImmutableListMultimap#builder()} over the associated constructor on constructions
@@ -70,7 +72,7 @@ final class ImmutableListMultimapTemplates {
    * alternatives.
    */
   // XXX: One can define variants for more than one key-value pair, but at some point the builder
-  // actually produces nicer code. So it's not clear we should add Refaster templates for those
+  // actually produces nicer code. So it's not clear we should add Refaster rules for those
   // variants.
   static final class PairToImmutableListMultimap<K, V> {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.common.collect.ImmutableList.toImmutableList;
 import static com.google.common.collect.ImmutableSet.toImmutableSet;
@@ -20,10 +20,12 @@ import java.util.Comparator;
 import java.util.Iterator;
 import java.util.List;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link ImmutableList}s. */
-final class ImmutableListTemplates {
-  private ImmutableListTemplates() {}
+/** Refaster rules related to expressions dealing with {@link ImmutableList}s. */
+@OnlineDocumentation
+final class ImmutableListRules {
+  private ImmutableListRules() {}
 
   /** Prefer {@link ImmutableList#builder()} over the associated constructor. */
   // XXX: This drops generic type information, sometimes leading to non-compilable code. See
@@ -154,7 +156,7 @@ final class ImmutableListTemplates {
    * communicate the immutability of the resulting list at the type level.
    */
   // XXX: The `Stream` variant may be too contrived to warrant inclusion. Review its usage if/when
-  // this and similar Refaster templates are replaced with an Error Prone check.
+  // this and similar Refaster rules are replaced with an Error Prone check.
   static final class ImmutableListOf<T> {
     @BeforeTemplate
     List<T> before() {

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.common.collect.ImmutableMap.toImmutableMap;
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
@@ -21,10 +21,12 @@ import java.util.Map;
 import java.util.Set;
 import java.util.function.Function;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link ImmutableMap}s. */
-final class ImmutableMapTemplates {
-  private ImmutableMapTemplates() {}
+/** Refaster rules related to expressions dealing with {@link ImmutableMap}s. */
+@OnlineDocumentation
+final class ImmutableMapRules {
+  private ImmutableMapRules() {}
 
   /** Prefer {@link ImmutableMap#builder()} over the associated constructor. */
   // XXX: This drops generic type information, sometimes leading to non-compilable code. See
@@ -313,7 +315,7 @@ final class ImmutableMapTemplates {
     }
   }
 
-  // XXX: Add a template for this:
+  // XXX: Add a rule for this:
   // Maps.transformValues(streamOfEntries.collect(groupBy(fun)), ImmutableMap::copyOf)
   // ->
   // streamOfEntries.collect(groupBy(fun, toImmutableMap(Map.Entry::getKey, Map.Entry::getValue)))

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.common.collect.ImmutableMultiset.toImmutableMultiset;
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
@@ -13,10 +13,12 @@ import java.util.Arrays;
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link ImmutableMultiset}s. */
-final class ImmutableMultisetTemplates {
-  private ImmutableMultisetTemplates() {}
+/** Refaster rules related to expressions dealing with {@link ImmutableMultiset}s. */
+@OnlineDocumentation
+final class ImmutableMultisetRules {
+  private ImmutableMultisetRules() {}
 
   /** Prefer {@link ImmutableMultiset#builder()} over the associated constructor. */
   // XXX: This drops generic type information, sometimes leading to non-compilable code. See

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.common.collect.ImmutableSetMultimap.flatteningToImmutableSetMultimap;
 import static com.google.common.collect.ImmutableSetMultimap.toImmutableSetMultimap;
@@ -21,10 +21,12 @@ import java.util.Collection;
 import java.util.Map;
 import java.util.function.Function;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link ImmutableSetMultimap}s. */
-final class ImmutableSetMultimapTemplates {
-  private ImmutableSetMultimapTemplates() {}
+/** Refaster rules related to expressions dealing with {@link ImmutableSetMultimap}s. */
+@OnlineDocumentation
+final class ImmutableSetMultimapRules {
+  private ImmutableSetMultimapRules() {}
 
   /** Prefer {@link ImmutableSetMultimap#builder()} over the associated constructor. */
   // XXX: This drops generic type information, sometimes leading to non-compilable code. See
@@ -56,7 +58,7 @@ final class ImmutableSetMultimapTemplates {
 
   /** Prefer {@link ImmutableSetMultimap#of(Object, Object)} over more contrived alternatives. */
   // XXX: One can define variants for more than one key-value pair, but at some point the builder
-  // actually produces nicer code. So it's not clear we should add Refaster templates for those
+  // actually produces nicer code. So it's not clear we should add Refaster rules for those
   // variants.
   static final class PairToImmutableSetMultimap<K, V> {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.common.collect.ImmutableSet.toImmutableSet;
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
@@ -17,10 +17,12 @@ import java.util.Collection;
 import java.util.Iterator;
 import java.util.Set;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link ImmutableSet}s. */
-final class ImmutableSetTemplates {
-  private ImmutableSetTemplates() {}
+/** Refaster rules related to expressions dealing with {@link ImmutableSet}s. */
+@OnlineDocumentation
+final class ImmutableSetRules {
+  private ImmutableSetRules() {}
 
   /** Prefer {@link ImmutableSet#builder()} over the associated constructor. */
   // XXX: This drops generic type information, sometimes leading to non-compilable code. See
@@ -104,7 +106,7 @@ final class ImmutableSetTemplates {
    * communicate the immutability of the resulting set at the type level.
    */
   // XXX: The `Stream` variant may be too contrived to warrant inclusion. Review its usage if/when
-  // this and similar Refaster templates are replaced with an Error Prone check.
+  // this and similar Refaster rules are replaced with an Error Prone check.
   static final class ImmutableSetOf<T> {
     @BeforeTemplate
     Set<T> before() {

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.common.collect.ImmutableSortedMap.toImmutableSortedMap;
 import static java.util.Comparator.naturalOrder;
@@ -13,10 +13,12 @@ import java.util.Collection;
 import java.util.Comparator;
 import java.util.Map;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link ImmutableSortedMap}s. */
-final class ImmutableSortedMapTemplates {
-  private ImmutableSortedMapTemplates() {}
+/** Refaster rules related to expressions dealing with {@link ImmutableSortedMap}s. */
+@OnlineDocumentation
+final class ImmutableSortedMapRules {
+  private ImmutableSortedMapRules() {}
 
   /** Prefer {@link ImmutableSortedMap#orderedBy(Comparator)} over the associated constructor. */
   static final class ImmutableSortedMapBuilder<K, V> {
@@ -82,7 +84,7 @@ final class ImmutableSortedMapTemplates {
 
   /** Prefer {@link ImmutableSortedMap#of(Object, Object)} over more contrived alternatives. */
   // XXX: One can define variants for more than one key-value pair, but at some point the builder
-  // actually produces nicer code. So it's not clear we should add Refaster templates for those
+  // actually produces nicer code. So it's not clear we should add Refaster rules for those
   // variants.
   // XXX: We could also rewrite builders with non-natural orders, but that would affect
   // `ImmutableSortedMap#comparator()`.

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.common.collect.ImmutableSortedMultiset.toImmutableSortedMultiset;
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
@@ -15,10 +15,12 @@ import java.util.Collection;
 import java.util.Comparator;
 import java.util.Iterator;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link ImmutableSortedMultiset}s. */
-final class ImmutableSortedMultisetTemplates {
-  private ImmutableSortedMultisetTemplates() {}
+/** Refaster rules related to expressions dealing with {@link ImmutableSortedMultiset}s. */
+@OnlineDocumentation
+final class ImmutableSortedMultisetRules {
+  private ImmutableSortedMultisetRules() {}
 
   /**
    * Prefer {@link ImmutableSortedMultiset#orderedBy(Comparator)} over the associated constructor.

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.common.collect.ImmutableSortedSet.toImmutableSortedSet;
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
@@ -15,10 +15,12 @@ import java.util.Collection;
 import java.util.Comparator;
 import java.util.Iterator;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link ImmutableSortedSet}s. */
-final class ImmutableSortedSetTemplates {
-  private ImmutableSortedSetTemplates() {}
+/** Refaster rules related to expressions dealing with {@link ImmutableSortedSet}s. */
+@OnlineDocumentation
+final class ImmutableSortedSetRules {
+  private ImmutableSortedSetRules() {}
 
   /** Prefer {@link ImmutableSortedSet#orderedBy(Comparator)} over the associated constructor. */
   static final class ImmutableSortedSetBuilder<T> {

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import com.google.common.collect.Streams;
 import com.google.errorprone.refaster.Refaster;
@@ -12,10 +12,12 @@ import java.util.function.IntPredicate;
 import java.util.function.IntUnaryOperator;
 import java.util.stream.IntStream;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link IntStream}s. */
-final class IntStreamTemplates {
-  private IntStreamTemplates() {}
+/** Refaster rules related to expressions dealing with {@link IntStream}s. */
+@OnlineDocumentation
+final class IntStreamRules {
+  private IntStreamRules() {}
 
   /** Prefer {@link IntStream#range(int, int)} over the more contrived alternative. */
   static final class IntStreamClosedOpenRange {

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.junit.jupiter.params.provider.Arguments.arguments;
@@ -8,10 +8,12 @@ import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import com.google.errorprone.refaster.annotation.Repeated;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
 import org.junit.jupiter.params.provider.Arguments;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to JUnit expressions and statements. */
-final class JUnitTemplates {
-  private JUnitTemplates() {}
+/** Refaster rules related to JUnit expressions and statements. */
+@OnlineDocumentation
+final class JUnitRules {
+  private JUnitRules() {}
 
   /** Prefer statically imported {@link Arguments#arguments} over {@link Arguments#of} calls. */
   static final class ArgumentsEnumeration<T> {

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import com.google.common.collect.Streams;
 import com.google.errorprone.refaster.Refaster;
@@ -12,10 +12,12 @@ import java.util.function.LongPredicate;
 import java.util.function.LongUnaryOperator;
 import java.util.stream.LongStream;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link LongStream}s. */
-final class LongStreamTemplates {
-  private LongStreamTemplates() {}
+/** Refaster rules related to expressions dealing with {@link LongStream}s. */
+@OnlineDocumentation
+final class LongStreamRules {
+  private LongStreamRules() {}
 
   /** Prefer {@link LongStream#range(long, long)} over the more contrived alternative. */
   static final class LongStreamClosedOpenRange {

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static java.util.Comparator.comparing;
@@ -14,10 +14,12 @@ import com.google.errorprone.refaster.annotation.UseImportPolicy;
 import java.util.AbstractMap;
 import java.util.Comparator;
 import java.util.Map;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link Map.Entry} instances. */
-final class MapEntryTemplates {
-  private MapEntryTemplates() {}
+/** Refaster rules related to expressions dealing with {@link Map.Entry} instances. */
+@OnlineDocumentation
+final class MapEntryRules {
+  private MapEntryRules() {}
 
   /**
    * Prefer {@link Map#entry(Object, Object)} over alternative ways to create an immutable map

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.mockito.Mockito.never;
@@ -10,10 +10,12 @@ import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
 import org.mockito.Mockito;
 import org.mockito.verification.VerificationMode;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to Mockito expressions and statements. */
-final class MockitoTemplates {
-  private MockitoTemplates() {}
+/** Refaster rules related to Mockito expressions and statements. */
+@OnlineDocumentation
+final class MockitoRules {
+  private MockitoRules() {}
 
   /**
    * Prefer {@link Mockito#never()}} over explicitly specifying that the associated invocation must

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import com.google.common.collect.Multimap;
 import com.google.common.collect.Multimaps;
@@ -7,11 +7,13 @@ import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import java.util.Collection;
 import java.util.Set;
-import javax.annotation.Nullable;
+import org.jspecify.nullness.Nullable;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link Multimap}s. */
-final class MultimapTemplates {
-  private MultimapTemplates() {}
+/** Refaster rules related to expressions dealing with {@link Multimap}s. */
+@OnlineDocumentation
+final class MultimapRules {
+  private MultimapRules() {}
 
   /** Prefer {@link Multimap#keySet()} over more contrived alternatives. */
   static final class MultimapKeySet<K, V> {
@@ -48,8 +50,7 @@ final class MultimapTemplates {
    */
   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/NullRules.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static java.util.Objects.requireNonNullElse;
@@ -9,11 +9,13 @@ import com.google.errorprone.refaster.annotation.BeforeTemplate;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
 import java.util.Objects;
 import java.util.function.Predicate;
-import javax.annotation.Nullable;
+import org.jspecify.nullness.Nullable;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with (possibly) null values. */
-final class NullTemplates {
-  private NullTemplates() {}
+/** Refaster rules related to expressions dealing with (possibly) null values. */
+@OnlineDocumentation
+final class NullRules {
+  private NullRules() {}
 
   /** Prefer the {@code ==} operator over {@link Objects#isNull(Object)}. */
   static final class IsNull {

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 
@@ -16,11 +16,13 @@ import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
 import java.util.stream.Stream;
-import javax.annotation.Nullable;
+import org.jspecify.nullness.Nullable;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link Optional}s. */
-final class OptionalTemplates {
-  private OptionalTemplates() {}
+/** Refaster rules related to expressions dealing with {@link Optional}s. */
+@OnlineDocumentation
+final class OptionalRules {
+  private OptionalRules() {}
 
   static final class OptionalOfNullable<T> {
     // XXX: Refaster should be smart enough to also rewrite occurrences in which there are
@@ -78,8 +80,8 @@ final class OptionalTemplates {
   }
 
   /** Prefer {@link Optional#orElseThrow()} over the less explicit {@link Optional#get()}. */
-  // XXX: This template is analogous to `OptionalOrElseThrow` above. Arguably this is its
-  // generalization. If/when Refaster is extended to understand this, delete the template above.
+  // XXX: This rule is analogous to `OptionalOrElseThrow` above. Arguably this is its
+  // generalization. If/when Refaster is extended to understand this, delete the rule above.
   static final class OptionalOrElseThrowMethodReference<T> {
     @BeforeTemplate
     Function<Optional<T>, T> before() {

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

@@ -0,0 +1,176 @@
+package tech.picnic.errorprone.refasterrules;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkElementIndex;
+import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.base.Preconditions.checkPositionIndex;
+import static com.google.common.base.Preconditions.checkState;
+import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
+
+import com.google.common.base.Preconditions;
+import com.google.errorprone.refaster.annotation.AfterTemplate;
+import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import com.google.errorprone.refaster.annotation.UseImportPolicy;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
+
+/** Refaster templates related to statements dealing with {@link Preconditions}. */
+@OnlineDocumentation
+final class PreconditionsRules {
+  private PreconditionsRules() {}
+
+  /** Prefer {@link Preconditions#checkArgument(boolean)} over more verbose alternatives. */
+  static final class CheckArgument {
+    @BeforeTemplate
+    void before(boolean condition) {
+      if (condition) {
+        throw new IllegalArgumentException();
+      }
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(boolean condition) {
+      checkArgument(!condition);
+    }
+  }
+
+  /** Prefer {@link Preconditions#checkArgument(boolean, Object)} over more verbose alternatives. */
+  static final class CheckArgumentWithMessage {
+    @BeforeTemplate
+    void before(boolean condition, String message) {
+      if (condition) {
+        throw new IllegalArgumentException(message);
+      }
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(boolean condition, String message) {
+      checkArgument(!condition, message);
+    }
+  }
+
+  /**
+   * Prefer {@link Preconditions#checkElementIndex(int, int, String)} over less descriptive or more
+   * verbose alternatives.
+   *
+   * <p>Note that the two-argument {@link Preconditions#checkElementIndex(int, int)} is better
+   * replaced with {@link java.util.Objects#checkIndex(int, int)}.
+   */
+  static final class CheckElementIndexWithMessage {
+    @BeforeTemplate
+    void before(int index, int size, String message) {
+      if (index < 0 || index >= size) {
+        throw new IndexOutOfBoundsException(message);
+      }
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(int index, int size, String message) {
+      checkElementIndex(index, size, message);
+    }
+  }
+
+  /** Prefer {@link Preconditions#checkNotNull(Object)} over more verbose alternatives. */
+  static final class CheckNotNull<T> {
+    @BeforeTemplate
+    void before(T object) {
+      if (object == null) {
+        throw new NullPointerException();
+      }
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(T object) {
+      checkNotNull(object);
+    }
+  }
+
+  /** Prefer {@link Preconditions#checkNotNull(Object, Object)} over more verbose alternatives. */
+  static final class CheckNotNullWithMessage<T> {
+    @BeforeTemplate
+    void before(T object, String message) {
+      if (object == null) {
+        throw new NullPointerException(message);
+      }
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(T object, String message) {
+      checkNotNull(object, message);
+    }
+  }
+
+  /**
+   * Prefer {@link Preconditions#checkPositionIndex(int, int)} over less descriptive or more verbose
+   * alternatives.
+   */
+  static final class CheckPositionIndex {
+    @BeforeTemplate
+    void before(int index, int size) {
+      if (index < 0 || index > size) {
+        throw new IndexOutOfBoundsException();
+      }
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(int index, int size) {
+      checkPositionIndex(index, size);
+    }
+  }
+
+  /**
+   * Prefer {@link Preconditions#checkPositionIndex(int, int, String)} over less descriptive or more
+   * verbose alternatives.
+   */
+  static final class CheckPositionIndexWithMessage {
+    @BeforeTemplate
+    void before(int index, int size, String message) {
+      if (index < 0 || index > size) {
+        throw new IndexOutOfBoundsException(message);
+      }
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(int index, int size, String message) {
+      checkPositionIndex(index, size, message);
+    }
+  }
+
+  /** Prefer {@link Preconditions#checkState(boolean)} over more verbose alternatives. */
+  static final class CheckState {
+    @BeforeTemplate
+    void before(boolean condition) {
+      if (condition) {
+        throw new IllegalStateException();
+      }
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(boolean condition) {
+      checkState(!condition);
+    }
+  }
+
+  /** Prefer {@link Preconditions#checkState(boolean, Object)} over more verbose alternatives. */
+  static final class CheckStateWithMessage {
+    @BeforeTemplate
+    void before(boolean condition, String message) {
+      if (condition) {
+        throw new IllegalStateException(message);
+      }
+    }
+
+    @AfterTemplate
+    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
+    void after(boolean condition, String message) {
+      checkState(!condition, message);
+    }
+  }
+}

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

@@ -1,12 +1,14 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import com.google.common.primitives.Ints;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with primitives. */
-final class PrimitiveTemplates {
-  private PrimitiveTemplates() {}
+/** Refaster rules related to expressions dealing with primitives. */
+@OnlineDocumentation
+final class PrimitiveRules {
+  private PrimitiveRules() {}
 
   /** Avoid contrived ways of expressing the "less than" relationship. */
   static final class LessThan {

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/RxJava2AdapterRules.java

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
@@ -13,10 +13,12 @@ import org.jspecify.nullness.Nullable;
 import reactor.adapter.rxjava.RxJava2Adapter;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link RxJava2Adapter}. */
-final class RxJava2AdapterTemplates {
-  private RxJava2AdapterTemplates() {}
+/** Refaster rules related to expressions dealing with {@link RxJava2Adapter}. */
+@OnlineDocumentation
+final class RxJava2AdapterRules {
+  private RxJava2AdapterRules() {}
 
   /** Use the fluent API style when using {@link RxJava2Adapter#completableToMono}. */
   static final class CompletableToMono {

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static java.util.Comparator.naturalOrder;
@@ -22,10 +22,12 @@ import java.util.function.Predicate;
 import java.util.stream.Collector;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link Stream}s. */
-final class StreamTemplates {
-  private StreamTemplates() {}
+/** Refaster rules related to expressions dealing with {@link Stream}s. */
+@OnlineDocumentation
+final class StreamRules {
+  private StreamRules() {}
 
   /**
    * Prefer {@link Collectors#joining()} over {@link Collectors#joining(CharSequence)} with an empty

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static java.util.stream.Collectors.joining;
@@ -16,12 +16,14 @@ import java.util.Collection;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.function.Function;
-import javax.annotation.Nullable;
+import org.jspecify.nullness.Nullable;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with {@link String}s. */
+/** Refaster rules related to expressions dealing with {@link String}s. */
 // XXX: Should we prefer `s -> !s.isEmpty()` or `not(String::isEmpty)`?
-final class StringTemplates {
-  private StringTemplates() {}
+@OnlineDocumentation
+final class StringRules {
+  private StringRules() {}
 
   /** Prefer {@link String#isEmpty()} over alternatives that consult the string's length. */
   static final class StringIsEmpty {
@@ -128,8 +130,8 @@ final class StringTemplates {
    * Prefer direct delegation to {@link String#valueOf(Object)} over the indirection introduced by
    * {@link Objects#toString(Object)}.
    */
-  // XXX: This template is analogous to `StringValueOf` above. Arguably this is its generalization.
-  // If/when Refaster is extended to understand this, delete the template above.
+  // XXX: This rule is analogous to `StringValueOf` above. Arguably this is its generalization.
+  // If/when Refaster is extended to understand this, delete the rule above.
   static final class StringValueOfMethodReference {
     @BeforeTemplate
     Function<Object, String> before() {

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
 import static org.assertj.core.api.Assertions.assertThat;
@@ -30,7 +30,7 @@ import org.testng.Assert;
 import org.testng.Assert.ThrowingRunnable;
 
 /**
- * Refaster templates that replace TestNG assertions with equivalent AssertJ assertions.
+ * Refaster rules that replace TestNG assertions with equivalent AssertJ assertions.
  *
  * <p>Some of the classes below have TestNG {@code @BeforeTemplate}s that reference wildcard type
  * bounds ({@code <?>}), while the associated AssertJ {@code @AfterTemplate}s reference stricter
@@ -69,11 +69,11 @@ import org.testng.Assert.ThrowingRunnable;
  *       </ul>
  * </ul>
  */
-// XXX: As-is these templates do not result in a complete migration:
+// XXX: As-is these rules do not result in a complete migration:
 // - Expressions containing comments are skipped due to a limitation of Refaster.
 // - Assertions inside lambda expressions are also skipped. Unclear why.
-final class TestNGToAssertJTemplates {
-  private TestNGToAssertJTemplates() {}
+final class TestNGToAssertJRules {
+  private TestNGToAssertJRules() {}
 
   static final class Fail {
     @BeforeTemplate

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static java.time.ZoneOffset.UTC;
 
@@ -21,10 +21,12 @@ import java.time.chrono.ChronoLocalDateTime;
 import java.time.chrono.ChronoZonedDateTime;
 import java.time.temporal.ChronoUnit;
 import java.time.temporal.TemporalUnit;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
-/** Refaster templates related to expressions dealing with time. */
-final class TimeTemplates {
-  private TimeTemplates() {}
+/** Refaster rules related to expressions dealing with time. */
+@OnlineDocumentation
+final class TimeRules {
+  private TimeRules() {}
 
   /**
    * Prefer {@link Clock#instant()} over {@link Instant#now(Clock)}, as it is more concise and more

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

@@ -1,4 +1,4 @@
-package tech.picnic.errorprone.refastertemplates;
+package tech.picnic.errorprone.refasterrules;
 
 import static org.springframework.http.HttpMethod.GET;
 import static org.springframework.http.HttpMethod.HEAD;
@@ -20,13 +20,15 @@ import org.springframework.web.reactive.function.client.WebClient.RequestBodySpe
 import org.springframework.web.reactive.function.client.WebClient.RequestBodyUriSpec;
 import org.springframework.web.reactive.function.client.WebClient.RequestHeadersSpec;
 import org.springframework.web.reactive.function.client.WebClient.RequestHeadersUriSpec;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
 /**
- * Refaster templates related to expressions dealing with {@link
+ * Refaster rules related to expressions dealing with {@link
  * org.springframework.web.reactive.function.client.WebClient} and related types.
  */
-final class WebClientTemplates {
-  private WebClientTemplates() {}
+@OnlineDocumentation
+final class WebClientRules {
+  private WebClientRules() {}
 
   /** Prefer {@link RequestBodySpec#bodyValue(Object)} over more contrived alternatives. */
   static final class BodyValue<T> {

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

@@ -0,0 +1,4 @@
+/** Picnic Refaster rules. */
+@com.google.errorprone.annotations.CheckReturnValue
+@org.jspecify.nullness.NullMarked
+package tech.picnic.errorprone.refasterrules;

error-prone-contrib/src/main/java/tech/picnic/errorprone/refastertemplates/ReactorTemplates.java

@@ -1,443 +0,0 @@
-package tech.picnic.errorprone.refastertemplates;
-
-import static com.google.common.collect.MoreCollectors.toOptional;
-import static com.google.errorprone.refaster.ImportPolicy.STATIC_IMPORT_ALWAYS;
-import static org.assertj.core.api.Assertions.assertThat;
-
-import com.google.common.collect.MoreCollectors;
-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.MayOptionallyUse;
-import com.google.errorprone.refaster.annotation.NotMatches;
-import com.google.errorprone.refaster.annotation.Placeholder;
-import com.google.errorprone.refaster.annotation.UseImportPolicy;
-import java.time.Duration;
-import java.util.Optional;
-import java.util.concurrent.Callable;
-import java.util.function.Consumer;
-import java.util.function.Function;
-import java.util.function.Predicate;
-import java.util.function.Supplier;
-import org.reactivestreams.Publisher;
-import reactor.core.publisher.Flux;
-import reactor.core.publisher.Mono;
-import reactor.test.StepVerifier;
-import reactor.test.publisher.PublisherProbe;
-import tech.picnic.errorprone.refaster.matchers.ThrowsCheckedException;
-
-/** Refaster templates related to Reactor expressions and statements. */
-final class ReactorTemplates {
-  private ReactorTemplates() {}
-
-  /**
-   * Prefer {@link Mono#fromSupplier(Supplier)} over {@link Mono#fromCallable(Callable)} where
-   * feasible.
-   */
-  static final class MonoFromSupplier<T> {
-    @BeforeTemplate
-    Mono<T> before(@NotMatches(ThrowsCheckedException.class) Callable<? extends T> supplier) {
-      return Mono.fromCallable(supplier);
-    }
-
-    @AfterTemplate
-    Mono<T> after(Supplier<? extends T> supplier) {
-      return Mono.fromSupplier(supplier);
-    }
-  }
-
-  /** Prefer {@link Mono#justOrEmpty(Optional)} over more verbose alternatives. */
-  // XXX: If `optional` is a constant and effectively-final expression then the `Mono.defer` can be
-  // dropped. Should look into Refaster support for identifying this.
-  static final class MonoFromOptional<T> {
-    @BeforeTemplate
-    @SuppressWarnings(
-        "MonoFromSupplier" /* `optional` may match a checked exception-throwing expression. */)
-    Mono<T> before(Optional<T> optional) {
-      return Refaster.anyOf(
-          Mono.fromCallable(() -> optional.orElse(null)),
-          Mono.fromSupplier(() -> optional.orElse(null)));
-    }
-
-    @AfterTemplate
-    Mono<T> after(Optional<T> optional) {
-      return Mono.defer(() -> Mono.justOrEmpty(optional));
-    }
-  }
-
-  /** Don't unnecessarily defer {@link Mono#error(Throwable)}. */
-  static final class MonoDeferredError<T> {
-    @BeforeTemplate
-    Mono<T> before(Throwable throwable) {
-      return Mono.defer(() -> Mono.error(throwable));
-    }
-
-    @AfterTemplate
-    Mono<T> after(Throwable throwable) {
-      return Mono.error(() -> throwable);
-    }
-  }
-
-  /** Don't unnecessarily defer {@link Flux#error(Throwable)}. */
-  static final class FluxDeferredError<T> {
-    @BeforeTemplate
-    Flux<T> before(Throwable throwable) {
-      return Flux.defer(() -> Flux.error(throwable));
-    }
-
-    @AfterTemplate
-    Flux<T> after(Throwable throwable) {
-      return Flux.error(() -> throwable);
-    }
-  }
-
-  /**
-   * Don't unnecessarily pass {@link Mono#error(Supplier)} a method reference or lambda expression.
-   */
-  // XXX: Drop this rule once the more general rule `AssortedTemplates#SupplierAsSupplier` works
-  // reliably.
-  static final class MonoErrorSupplier<T, E extends Throwable> {
-    @BeforeTemplate
-    Mono<T> before(Supplier<E> supplier) {
-      return Mono.error(() -> supplier.get());
-    }
-
-    @AfterTemplate
-    Mono<T> after(Supplier<E> supplier) {
-      return Mono.error(supplier);
-    }
-  }
-
-  /**
-   * Don't unnecessarily pass {@link Flux#error(Supplier)} a method reference or lambda expression.
-   */
-  // XXX: Drop this rule once the more general rule `AssortedTemplates#SupplierAsSupplier` works
-  // reliably.
-  static final class FluxErrorSupplier<T, E extends Throwable> {
-    @BeforeTemplate
-    Flux<T> before(Supplier<E> supplier) {
-      return Flux.error(() -> supplier.get());
-    }
-
-    @AfterTemplate
-    Flux<T> after(Supplier<E> supplier) {
-      return Flux.error(supplier);
-    }
-  }
-
-  /** Prefer {@link Mono#thenReturn(Object)} over more verbose alternatives. */
-  static final class MonoThenReturn<T, S> {
-    @BeforeTemplate
-    Mono<S> before(Mono<T> mono, S object) {
-      return mono.then(Mono.just(object));
-    }
-
-    @AfterTemplate
-    Mono<S> after(Mono<T> mono, S object) {
-      return mono.thenReturn(object);
-    }
-  }
-
-  /** Don't unnecessarily pass an empty publisher to {@link Mono#switchIfEmpty(Mono)}. */
-  static final class MonoSwitchIfEmptyOfEmptyPublisher<T> {
-    @BeforeTemplate
-    Mono<T> before(Mono<T> mono) {
-      return mono.switchIfEmpty(Mono.empty());
-    }
-
-    @AfterTemplate
-    Mono<T> after(Mono<T> mono) {
-      return mono;
-    }
-  }
-
-  /** Don't unnecessarily pass an empty publisher to {@link Flux#switchIfEmpty(Publisher)}. */
-  static final class FluxSwitchIfEmptyOfEmptyPublisher<T> {
-    @BeforeTemplate
-    Flux<T> before(Flux<T> flux) {
-      return flux.switchIfEmpty(Refaster.anyOf(Mono.empty(), Flux.empty()));
-    }
-
-    @AfterTemplate
-    Flux<T> after(Flux<T> flux) {
-      return flux;
-    }
-  }
-
-  /** Prefer {@link Flux#concatMap(Function)} over more contrived alternatives. */
-  static final class FluxConcatMap<T, S> {
-    @BeforeTemplate
-    Flux<S> before(Flux<T> flux, Function<? super T, ? extends Publisher<? extends S>> function) {
-      return Refaster.anyOf(flux.flatMap(function, 1), flux.flatMapSequential(function, 1));
-    }
-
-    @AfterTemplate
-    Flux<S> after(Flux<T> flux, Function<? super T, ? extends Publisher<? extends S>> function) {
-      return flux.concatMap(function);
-    }
-  }
-
-  /**
-   * 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> {
-    @BeforeTemplate
-    Flux<S> before(Flux<T> flux, Function<? super T, ? extends Iterable<? extends S>> function) {
-      return flux.flatMapIterable(function);
-    }
-
-    @AfterTemplate
-    Flux<S> after(Flux<T> flux, Function<? super T, ? extends Iterable<? extends S>> function) {
-      return flux.concatMapIterable(function);
-    }
-  }
-
-  /**
-   * Don't use {@link Mono#flatMapMany(Function)} to implicitly convert a {@link Mono} to a {@link
-   * Flux}.
-   */
-  abstract static class MonoFlatMapToFlux<T, S> {
-    @Placeholder(allowsIdentity = true)
-    abstract Mono<S> valueTransformation(@MayOptionallyUse T value);
-
-    @BeforeTemplate
-    Flux<S> before(Mono<T> mono) {
-      return mono.flatMapMany(v -> valueTransformation(v));
-    }
-
-    @AfterTemplate
-    Flux<S> after(Mono<T> mono) {
-      return mono.flatMap(v -> valueTransformation(v)).flux();
-    }
-  }
-
-  /** Prefer {@link Mono#flux()}} over more contrived alternatives. */
-  static final class MonoFlux<T> {
-    @BeforeTemplate
-    Flux<T> before(Mono<T> mono) {
-      return Flux.concat(mono);
-    }
-
-    @AfterTemplate
-    Flux<T> after(Mono<T> mono) {
-      return mono.flux();
-    }
-  }
-
-  /**
-   * Prefer a collection using {@link MoreCollectors#toOptional()} 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.
-  static final class MonoCollectToOptional<T> {
-    @BeforeTemplate
-    Mono<Optional<T>> before(Mono<T> mono) {
-      return Refaster.anyOf(
-          mono.map(Optional::of).defaultIfEmpty(Optional.empty()),
-          mono.map(Optional::of).switchIfEmpty(Mono.just(Optional.empty())));
-    }
-
-    @AfterTemplate
-    @UseImportPolicy(STATIC_IMPORT_ALWAYS)
-    Mono<Optional<T>> after(Mono<T> mono) {
-      return mono.flux().collect(toOptional());
-    }
-  }
-
-  /** Prefer {@link Mono#cast(Class)} over {@link Mono#map(Function)} with a cast. */
-  static final class MonoCast<T, S> {
-    @BeforeTemplate
-    Mono<S> before(Mono<T> mono) {
-      return mono.map(Refaster.<S>clazz()::cast);
-    }
-
-    @AfterTemplate
-    Mono<S> after(Mono<T> mono) {
-      return mono.cast(Refaster.<S>clazz());
-    }
-  }
-
-  /** Prefer {@link Flux#cast(Class)} over {@link Flux#map(Function)} with a cast. */
-  static final class FluxCast<T, S> {
-    @BeforeTemplate
-    Flux<S> before(Flux<T> flux) {
-      return flux.map(Refaster.<S>clazz()::cast);
-    }
-
-    @AfterTemplate
-    Flux<S> after(Flux<T> flux) {
-      return flux.cast(Refaster.<S>clazz());
-    }
-  }
-
-  /** Prefer {@link PublisherProbe#empty()}} over more verbose alternatives. */
-  static final class PublisherProbeEmpty<T> {
-    @BeforeTemplate
-    PublisherProbe<T> before() {
-      return Refaster.anyOf(PublisherProbe.of(Mono.empty()), PublisherProbe.of(Flux.empty()));
-    }
-
-    @AfterTemplate
-    PublisherProbe<T> after() {
-      return PublisherProbe.empty();
-    }
-  }
-
-  /** Prefer {@link Mono#as(Function)} when creating a {@link StepVerifier}. */
-  static final class StepVerifierFromMono<T> {
-    @BeforeTemplate
-    StepVerifier.FirstStep<? extends T> before(Mono<T> mono) {
-      return StepVerifier.create(mono);
-    }
-
-    @AfterTemplate
-    StepVerifier.FirstStep<? extends T> after(Mono<T> mono) {
-      return mono.as(StepVerifier::create);
-    }
-  }
-
-  /** Prefer {@link Flux#as(Function)} when creating a {@link StepVerifier}. */
-  static final class StepVerifierFromFlux<T> {
-    @BeforeTemplate
-    StepVerifier.FirstStep<? extends T> before(Flux<T> flux) {
-      return StepVerifier.create(flux);
-    }
-
-    @AfterTemplate
-    StepVerifier.FirstStep<? extends T> after(Flux<T> flux) {
-      return flux.as(StepVerifier::create);
-    }
-  }
-
-  /** Don't unnecessarily call {@link StepVerifier.Step#expectNext(Object[])}. */
-  static final class StepVerifierStepExpectNextEmpty<T> {
-    @BeforeTemplate
-    @SuppressWarnings("unchecked")
-    StepVerifier.Step<T> before(StepVerifier.Step<T> step) {
-      return step.expectNext();
-    }
-
-    @AfterTemplate
-    StepVerifier.Step<T> after(StepVerifier.Step<T> step) {
-      return step;
-    }
-  }
-
-  /** Prefer {@link StepVerifier.Step#expectNext(Object)} over more verbose alternatives. */
-  static final class StepVerifierStepExpectNext<T> {
-    @BeforeTemplate
-    StepVerifier.Step<T> before(StepVerifier.Step<T> step, T object) {
-      return Refaster.anyOf(
-          step.expectNextMatches(e -> e.equals(object)), step.expectNextMatches(object::equals));
-    }
-
-    @AfterTemplate
-    StepVerifier.Step<T> after(StepVerifier.Step<T> step, T object) {
-      return step.expectNext(object);
-    }
-  }
-
-  /** Prefer {@link StepVerifier.LastStep#verifyComplete()} over more verbose alternatives. */
-  static final class StepVerifierLastStepVerifyComplete {
-    @BeforeTemplate
-    Duration before(StepVerifier.LastStep step) {
-      return step.expectComplete().verify();
-    }
-
-    @AfterTemplate
-    Duration after(StepVerifier.LastStep step) {
-      return step.verifyComplete();
-    }
-  }
-
-  /** Prefer {@link StepVerifier.LastStep#verifyError()} over more verbose alternatives. */
-  static final class StepVerifierLastStepVerifyError {
-    @BeforeTemplate
-    Duration before(StepVerifier.LastStep step) {
-      return step.expectError().verify();
-    }
-
-    @AfterTemplate
-    Duration after(StepVerifier.LastStep step) {
-      return step.verifyError();
-    }
-  }
-
-  /** Prefer {@link StepVerifier.LastStep#verifyError(Class)} over more verbose alternatives. */
-  static final class StepVerifierLastStepVerifyErrorClass<T extends Throwable> {
-    @BeforeTemplate
-    Duration before(StepVerifier.LastStep step, Class<T> clazz) {
-      return Refaster.anyOf(
-          step.expectError(clazz).verify(),
-          step.verifyErrorSatisfies(t -> assertThat(t).isInstanceOf(clazz)));
-    }
-
-    @AfterTemplate
-    Duration after(StepVerifier.LastStep step, Class<T> clazz) {
-      return step.verifyError(clazz);
-    }
-  }
-
-  /**
-   * Prefer {@link StepVerifier.LastStep#verifyErrorMatches(Predicate)} over more verbose
-   * alternatives.
-   */
-  static final class StepVerifierLastStepVerifyErrorMatches {
-    @BeforeTemplate
-    Duration before(StepVerifier.LastStep step, Predicate<Throwable> predicate) {
-      return step.expectErrorMatches(predicate).verify();
-    }
-
-    @AfterTemplate
-    Duration after(StepVerifier.LastStep step, Predicate<Throwable> predicate) {
-      return step.verifyErrorMatches(predicate);
-    }
-  }
-
-  /**
-   * Prefer {@link StepVerifier.LastStep#verifyErrorSatisfies(Consumer)} over more verbose
-   * alternatives.
-   */
-  static final class StepVerifierLastStepVerifyErrorSatisfies {
-    @BeforeTemplate
-    Duration before(StepVerifier.LastStep step, Consumer<Throwable> consumer) {
-      return step.expectErrorSatisfies(consumer).verify();
-    }
-
-    @AfterTemplate
-    Duration after(StepVerifier.LastStep step, Consumer<Throwable> consumer) {
-      return step.verifyErrorSatisfies(consumer);
-    }
-  }
-
-  /**
-   * Prefer {@link StepVerifier.LastStep#verifyErrorMessage(String)} over more verbose alternatives.
-   */
-  static final class StepVerifierLastStepVerifyErrorMessage {
-    @BeforeTemplate
-    Duration before(StepVerifier.LastStep step, String message) {
-      return step.expectErrorMessage(message).verify();
-    }
-
-    @AfterTemplate
-    Duration after(StepVerifier.LastStep step, String message) {
-      return step.verifyErrorMessage(message);
-    }
-  }
-
-  /**
-   * Prefer {@link StepVerifier.LastStep#verifyTimeout(Duration)} over more verbose alternatives.
-   */
-  static final class StepVerifierLastStepVerifyTimeout {
-    @BeforeTemplate
-    Duration before(StepVerifier.LastStep step, Duration duration) {
-      return step.expectTimeout(duration).verify();
-    }
-
-    @AfterTemplate
-    Duration after(StepVerifier.LastStep step, Duration duration) {
-      return step.verifyTimeout(duration);
-    }
-  }
-}

error-prone-contrib/src/main/java/tech/picnic/errorprone/refastertemplates/package-info.java

@@ -1,4 +0,0 @@
-/** Picnic Refaster templates. */
-@com.google.errorprone.annotations.CheckReturnValue
-@javax.annotation.ParametersAreNonnullByDefault
-package tech.picnic.errorprone.refastertemplates;

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

@@ -65,6 +65,23 @@ final class CollectorMutabilityTest {
         .doTest();
   }
 
+  @Test
+  void identificationWithoutGuavaOnClasspath() {
+    compilationTestHelper
+        .withClasspath()
+        .addSourceLines(
+            "A.java",
+            "import java.util.stream.Collectors;",
+            "import java.util.stream.Stream;",
+            "",
+            "class A {",
+            "  void m() {",
+            "    Stream.empty().collect(Collectors.toList());",
+            "  }",
+            "}")
+        .doTest();
+  }
+
   @Test
   void replacementFirstSuggestedFix() {
     refactoringTestHelper

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

@@ -4,6 +4,7 @@ import static com.google.errorprone.BugCheckerRefactoringTestHelper.newInstance;
 
 import com.google.errorprone.BugCheckerRefactoringTestHelper;
 import com.google.errorprone.BugCheckerRefactoringTestHelper.FixChoosers;
+import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
 import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
@@ -33,6 +34,14 @@ final class FluxFlatMapUsageTest {
             "    Flux.just(1).flatMapSequential(Flux::just);",
             "    // BUG: Diagnostic contains:",
             "    Flux.just(1).<String>flatMapSequential(i -> Flux.just(String.valueOf(i)));",
+            "    // BUG: Diagnostic contains:",
+            "    Flux.just(1, 2).groupBy(i -> i).flatMap(Flux::just);",
+            "    // BUG: Diagnostic contains:",
+            "    Flux.just(1, 2).groupBy(i -> i).<String>flatMap(i -> Flux.just(String.valueOf(i)));",
+            "    // BUG: Diagnostic contains:",
+            "    Flux.just(1, 2).groupBy(i -> i).flatMapSequential(Flux::just);",
+            "    // BUG: Diagnostic contains:",
+            "    Flux.just(1, 2).groupBy(i -> i).<String>flatMapSequential(i -> Flux.just(String.valueOf(i)));",
             "",
             "    Mono.just(1).flatMap(Mono::just);",
             "    Flux.just(1).concatMap(Flux::just);",
@@ -71,9 +80,13 @@ final class FluxFlatMapUsageTest {
             "import reactor.core.publisher.Flux;",
             "",
             "class A {",
+            "  private static final int MAX_CONCURRENCY = 8;",
+            "",
             "  void m() {",
             "    Flux.just(1).flatMap(Flux::just);",
             "    Flux.just(1).flatMapSequential(Flux::just);",
+            "    Flux.just(1, 2).groupBy(i -> i).flatMap(Flux::just);",
+            "    Flux.just(1, 2).groupBy(i -> i).flatMapSequential(Flux::just);",
             "  }",
             "}")
         .addOutputLines(
@@ -81,12 +94,16 @@ final class FluxFlatMapUsageTest {
             "import reactor.core.publisher.Flux;",
             "",
             "class A {",
+            "  private static final int MAX_CONCURRENCY = 8;",
+            "",
             "  void m() {",
             "    Flux.just(1).concatMap(Flux::just);",
             "    Flux.just(1).concatMap(Flux::just);",
+            "    Flux.just(1, 2).groupBy(i -> i).flatMap(Flux::just, MAX_CONCURRENCY);",
+            "    Flux.just(1, 2).groupBy(i -> i).flatMapSequential(Flux::just, MAX_CONCURRENCY);",
             "  }",
             "}")
-        .doTest();
+        .doTest(TestMode.TEXT_MATCH);
   }
 
   @Test
@@ -103,6 +120,8 @@ final class FluxFlatMapUsageTest {
             "  void m() {",
             "    Flux.just(1).flatMap(Flux::just);",
             "    Flux.just(1).flatMapSequential(Flux::just);",
+            "    Flux.just(1, 2).groupBy(i -> i).flatMap(Flux::just);",
+            "    Flux.just(1, 2).groupBy(i -> i).flatMapSequential(Flux::just);",
             "  }",
             "}")
         .addOutputLines(
@@ -115,8 +134,10 @@ final class FluxFlatMapUsageTest {
             "  void m() {",
             "    Flux.just(1).flatMap(Flux::just, MAX_CONCURRENCY);",
             "    Flux.just(1).flatMapSequential(Flux::just, MAX_CONCURRENCY);",
+            "    Flux.just(1, 2).groupBy(i -> i).concatMap(Flux::just);",
+            "    Flux.just(1, 2).groupBy(i -> i).concatMap(Flux::just);",
             "  }",
             "}")
-        .doTest();
+        .doTest(TestMode.TEXT_MATCH);
   }
 }