Merge branch 'master' into website

This new `Extractor` implementation collects Refaster example input and 
output code from rule collection tests.

This change also introduces explicit compilation steps for the test
code. As a side-effect this produces faster feedback in case of invalid
input or output code.

.github/workflows/build.yml

@@ -10,7 +10,7 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-22.04 ]
-        jdk: [ 17.0.10, 21.0.2 ]
+        jdk: [ 17.0.10, 21.0.2, 22.0.2 ]
         distribution: [ temurin ]
         experimental: [ false ]
         include:
@@ -46,7 +46,7 @@ jobs:
         with:
           java-version: ${{ matrix.jdk }}
           java-distribution: ${{ matrix.distribution }}
-          maven-version: 3.9.6
+          maven-version: 3.9.9
       - name: Display build environment details
         run: mvn --version
       - name: Build project against vanilla Error Prone, compile Javadoc

.github/workflows/codeql.yml

@@ -38,7 +38,7 @@ jobs:
         with:
           java-version: 17.0.10
           java-distribution: temurin
-          maven-version: 3.9.6
+          maven-version: 3.9.9
       - name: Initialize CodeQL
         uses: github/codeql-action/init@c7f9125735019aa87cfc361530512d50ea439c71 # v3.25.1
         with:

.github/workflows/deploy-website.yml

@@ -38,26 +38,29 @@ jobs:
             www.bestpractices.dev:443
             www.youtube.com:443
             youtrack.jetbrains.com:443
-      - name: Check out code
-        uses: actions/checkout@a5ac7e51b41094c92402da3b24376905380afc29 # v4.1.6
+      - name: Check out code and set up JDK and Maven
+        uses: s4u/setup-maven-action@489441643219d2b93ee2a127b2402eb640a1b947 # v1.13.0
         with:
-          persist-credentials: false
+          java-version: 17.0.10
+          java-distribution: temurin
+          maven-version: 3.9.6
       - uses: ruby/setup-ruby@6bd3d993c602f6b675728ebaecb2b569ff86e99b # v1.174.0
         with:
           working-directory: ./website
           bundler-cache: true
       - name: Configure Github Pages
         uses: actions/configure-pages@983d7736d9b0ae728b81ab479565c72886d7745b # v5.0.0
+      - name: Compile project and extract data
+        run: mvn -T1C clean install -DskipTests -Dverification.skip
       - name: Generate documentation
-        run: ./generate-docs.sh
+        run: mvn exec:java@generate-docs -pl documentation-support
       - name: Build website with Jekyll
         working-directory: ./website
         run: bundle exec jekyll build
       - name: Validate HTML output
         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
+        # XXX: StackOverflow returns a 403 when run on GHA.
+        run: bundle exec htmlproofer --no-check-external-hash --swap-url 'https\://error-prone.picnic.tech:' --ignore-urls '/^https:\/\/stackoverflow.com\/.*/' ./_site
       - name: Upload website as artifact
         uses: actions/upload-pages-artifact@56afc609e74202658d3ffba0e8f6dda462b719fa # v3.0.1
         with:

.github/workflows/openssf-scorecard.yml

@@ -30,11 +30,9 @@ jobs:
             api.osv.dev:443
             api.scorecard.dev:443
             api.securityscorecards.dev:443
-            fulcio.sigstore.dev:443
             github.com:443
             oss-fuzz-build-logs.storage.googleapis.com:443
-            rekor.sigstore.dev:443
-            tuf-repo-cdn.sigstore.dev:443
+            *.sigstore.dev:443
             www.bestpractices.dev:443
       - name: Check out code
         uses: actions/checkout@a5ac7e51b41094c92402da3b24376905380afc29 # v4.1.6

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

@@ -27,7 +27,7 @@ jobs:
           checkout-fetch-depth: 2
           java-version: 17.0.10
           java-distribution: temurin
-          maven-version: 3.9.6
+          maven-version: 3.9.9
       - name: Run Pitest
         # By running with features `+GIT(from[HEAD~1]), +gitci`, Pitest only
         # analyzes lines changed in the associated pull request, as GitHub

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

@@ -35,7 +35,7 @@ jobs:
         with:
           java-version: 17.0.10
           java-distribution: temurin
-          maven-version: 3.9.6
+          maven-version: 3.9.9
       - name: Download Pitest analysis artifact
         uses: dawidd6/action-download-artifact@09f2f74827fd3a8607589e5ad7f9398816f540fe # v3.1.4
         with:

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

@@ -38,7 +38,7 @@ jobs:
           checkout-ref: "refs/pull/${{ github.event.issue.number }}/head"
           java-version: 17.0.10
           java-distribution: temurin
-          maven-version: 3.9.6
+          maven-version: 3.9.9
       - name: Install project to local Maven repository
         run: mvn -T1C install -DskipTests -Dverification.skip
       - name: Run integration test

.github/workflows/sonarcloud.yml

@@ -24,14 +24,15 @@ jobs:
           disable-sudo: true
           egress-policy: block
           allowed-endpoints: >
+            analysis-sensorcache-eu-central-1-prod.s3.amazonaws.com:443
             api.adoptium.net:443
-            api.sonarcloud.io:443
+            api.nuget.org:443
             ea6ne4j2sb.execute-api.eu-central-1.amazonaws.com:443
             github.com:443
             objects.githubusercontent.com:443
             repo.maven.apache.org:443
             sc-cleancode-sensorcache-eu-central-1-prod.s3.amazonaws.com:443
-            scanner.sonarcloud.io:443
+            *.sonarcloud.io:443
             sonarcloud.io:443
       - name: Check out code and set up JDK and Maven
         uses: s4u/setup-maven-action@489441643219d2b93ee2a127b2402eb640a1b947 # v1.13.0
@@ -39,7 +40,7 @@ jobs:
           checkout-fetch-depth: 0
           java-version: 17.0.10
           java-distribution: temurin
-          maven-version: 3.9.6
+          maven-version: 3.9.9
       - name: Create missing `test` directory
         # XXX: Drop this step in favour of actually having a test.
         run: mkdir refaster-compiler/src/test

documentation-support/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.17.0</version>
+        <version>0.18.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>documentation-support</artifactId>
@@ -33,14 +33,31 @@
             <artifactId>error_prone_test_helpers</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>error-prone-utils</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>refaster-test-support</artifactId>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-annotations</artifactId>
         </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-core</artifactId>
+        </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
         </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.dataformat</groupId>
+            <artifactId>jackson-dataformat-yaml</artifactId>
+        </dependency>
         <dependency>
             <groupId>com.fasterxml.jackson.datatype</groupId>
             <artifactId>jackson-datatype-guava</artifactId>
@@ -67,6 +84,10 @@
             <groupId>com.google.guava</groupId>
             <artifactId>guava</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.github.java-diff-utils</groupId>
+            <artifactId>java-diff-utils</artifactId>
+        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>
@@ -95,4 +116,29 @@
             <scope>test</scope>
         </dependency>
     </dependencies>
+
+    <build>
+        <pluginManagement>
+            <plugins>
+                <plugin>
+                    <groupId>org.codehaus.mojo</groupId>
+                    <artifactId>exec-maven-plugin</artifactId>
+                    <executions>
+                        <execution>
+                            <id>generate-docs</id>
+                            <goals>
+                                <goal>java</goal>
+                            </goals>
+                            <configuration>
+                                <mainClass>tech.picnic.errorprone.documentation.JekyllCollectionGenerator</mainClass>
+                                <arguments>
+                                    <argument>${maven.multiModuleProjectDirectory}</argument>
+                                </arguments>
+                            </configuration>
+                        </execution>
+                    </executions>
+                </plugin>
+            </plugins>
+        </pluginManagement>
+    </build>
 </project>

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

@@ -27,7 +27,7 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
 import org.jspecify.annotations.Nullable;
-import tech.picnic.errorprone.documentation.BugPatternTestExtractor.TestCases;
+import tech.picnic.errorprone.documentation.BugPatternTestExtractor.BugPatternTestCases;
 
 /**
  * An {@link Extractor} that describes how to extract data from classes that test a {@code
@@ -40,7 +40,7 @@ import tech.picnic.errorprone.documentation.BugPatternTestExtractor.TestCases;
 @Immutable
 @AutoService(Extractor.class)
 @SuppressWarnings("rawtypes" /* See https://github.com/google/auto/issues/870. */)
-public final class BugPatternTestExtractor implements Extractor<TestCases> {
+public final class BugPatternTestExtractor implements Extractor<BugPatternTestCases> {
   /** Instantiates a new {@link BugPatternTestExtractor} instance. */
   public BugPatternTestExtractor() {}
 
@@ -50,7 +50,7 @@ public final class BugPatternTestExtractor implements Extractor<TestCases> {
   }
 
   @Override
-  public Optional<TestCases> tryExtract(ClassTree tree, VisitorState state) {
+  public Optional<BugPatternTestCases> tryExtract(ClassTree tree, VisitorState state) {
     BugPatternTestCollector collector = new BugPatternTestCollector();
 
     collector.scan(tree, state);
@@ -59,7 +59,7 @@ public final class BugPatternTestExtractor implements Extractor<TestCases> {
         .filter(not(ImmutableList::isEmpty))
         .map(
             tests ->
-                new AutoValue_BugPatternTestExtractor_TestCases(
+                new AutoValue_BugPatternTestExtractor_BugPatternTestCases(
                     state.getPath().getCompilationUnit().getSourceFile().toUri(),
                     ASTHelpers.getSymbol(tree).className(),
                     tests));
@@ -95,10 +95,10 @@ public final class BugPatternTestExtractor implements Extractor<TestCases> {
             .onDescendantOf("com.google.errorprone.BugCheckerRefactoringTestHelper.ExpectOutput")
             .namedAnyOf("addOutputLines", "expectUnchanged");
 
-    private final List<TestCase> collectedTestCases = new ArrayList<>();
+    private final List<BugPatternTestCase> collectedBugPatternTestCases = new ArrayList<>();
 
-    private ImmutableList<TestCase> getCollectedTests() {
-      return ImmutableList.copyOf(collectedTestCases);
+    private ImmutableList<BugPatternTestCase> getCollectedTests() {
+      return ImmutableList.copyOf(collectedBugPatternTestCases);
     }
 
     @Override
@@ -110,14 +110,14 @@ public final class BugPatternTestExtractor implements Extractor<TestCases> {
                 classUnderTest -> {
                   List<TestEntry> entries = new ArrayList<>();
                   if (isReplacementTest) {
-                    extractReplacementTestCases(node, entries, state);
+                    extractReplacementBugPatternTestCases(node, entries, state);
                   } else {
-                    extractIdentificationTestCases(node, entries, state);
+                    extractIdentificationBugPatternTestCases(node, entries, state);
                   }
 
                   if (!entries.isEmpty()) {
-                    collectedTestCases.add(
-                        new AutoValue_BugPatternTestExtractor_TestCase(
+                    collectedBugPatternTestCases.add(
+                        new AutoValue_BugPatternTestExtractor_BugPatternTestCase(
                             classUnderTest, ImmutableList.copyOf(entries).reverse()));
                   }
                 });
@@ -140,7 +140,7 @@ public final class BugPatternTestExtractor implements Extractor<TestCases> {
           : Optional.empty();
     }
 
-    private static void extractIdentificationTestCases(
+    private static void extractIdentificationBugPatternTestCases(
         MethodInvocationTree tree, List<TestEntry> sink, VisitorState state) {
       if (IDENTIFICATION_SOURCE_LINES.matches(tree, state)) {
         String path = ASTHelpers.constValue(tree.getArguments().get(0), String.class);
@@ -155,11 +155,11 @@ public final class BugPatternTestExtractor implements Extractor<TestCases> {
 
       ExpressionTree receiver = ASTHelpers.getReceiver(tree);
       if (receiver instanceof MethodInvocationTree methodInvocation) {
-        extractIdentificationTestCases(methodInvocation, sink, state);
+        extractIdentificationBugPatternTestCases(methodInvocation, sink, state);
       }
     }
 
-    private static void extractReplacementTestCases(
+    private static void extractReplacementBugPatternTestCases(
         MethodInvocationTree tree, List<TestEntry> sink, VisitorState state) {
       if (REPLACEMENT_OUTPUT_SOURCE_LINES.matches(tree, state)) {
         /*
@@ -185,7 +185,7 @@ public final class BugPatternTestExtractor implements Extractor<TestCases> {
 
       ExpressionTree receiver = ASTHelpers.getReceiver(tree);
       if (receiver instanceof MethodInvocationTree methodInvocation) {
-        extractReplacementTestCases(methodInvocation, sink, state);
+        extractReplacementBugPatternTestCases(methodInvocation, sink, state);
       }
     }
 
@@ -208,24 +208,26 @@ public final class BugPatternTestExtractor implements Extractor<TestCases> {
   }
 
   @AutoValue
-  @JsonDeserialize(as = AutoValue_BugPatternTestExtractor_TestCases.class)
-  abstract static class TestCases {
-    static TestCases create(URI source, String testClass, ImmutableList<TestCase> testCases) {
-      return new AutoValue_BugPatternTestExtractor_TestCases(source, testClass, testCases);
+  @JsonDeserialize(as = AutoValue_BugPatternTestExtractor_BugPatternTestCases.class)
+  abstract static class BugPatternTestCases {
+    static BugPatternTestCases create(
+        URI source, String testClass, ImmutableList<BugPatternTestCase> testCases) {
+      return new AutoValue_BugPatternTestExtractor_BugPatternTestCases(
+          source, testClass, testCases);
     }
 
     abstract URI source();
 
     abstract String testClass();
 
-    abstract ImmutableList<TestCase> testCases();
+    abstract ImmutableList<BugPatternTestCase> testCases();
   }
 
   @AutoValue
-  @JsonDeserialize(as = AutoValue_BugPatternTestExtractor_TestCase.class)
-  abstract static class TestCase {
-    static TestCase create(String classUnderTest, ImmutableList<TestEntry> entries) {
-      return new AutoValue_BugPatternTestExtractor_TestCase(classUnderTest, entries);
+  @JsonDeserialize(as = AutoValue_BugPatternTestExtractor_BugPatternTestCase.class)
+  abstract static class BugPatternTestCase {
+    static BugPatternTestCase create(String classUnderTest, ImmutableList<TestEntry> entries) {
+      return new AutoValue_BugPatternTestExtractor_BugPatternTestCase(classUnderTest, entries);
     }
 
     abstract String classUnderTest();

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

@@ -14,7 +14,6 @@ import java.io.IOException;
 import java.net.URI;
 import java.nio.file.Files;
 import java.nio.file.Path;
-import java.nio.file.Paths;
 import java.util.ServiceLoader;
 import javax.tools.JavaFileObject;
 
@@ -87,6 +86,6 @@ final class DocumentationGeneratorTaskListener implements TaskListener {
   }
 
   private static String getSimpleClassName(URI path) {
-    return Paths.get(path).getFileName().toString().replace(".java", "");
+    return Path.of(path).getFileName().toString().replace(".java", "");
   }
 }

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

@@ -0,0 +1,332 @@
+package tech.picnic.errorprone.documentation;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.collect.ImmutableList.toImmutableList;
+import static com.google.common.collect.ImmutableListMultimap.flatteningToImmutableListMultimap;
+import static com.google.common.collect.ImmutableMap.toImmutableMap;
+import static com.google.common.collect.ImmutableTable.toImmutableTable;
+import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static java.util.Objects.requireNonNull;
+import static java.util.stream.Collectors.joining;
+
+import com.fasterxml.jackson.annotation.JsonAutoDetect.Visibility;
+import com.fasterxml.jackson.annotation.PropertyAccessor;
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.dataformat.yaml.YAMLGenerator;
+import com.fasterxml.jackson.dataformat.yaml.YAMLMapper;
+import com.github.difflib.DiffUtils;
+import com.github.difflib.UnifiedDiffUtils;
+import com.github.difflib.patch.Patch;
+import com.google.auto.value.AutoValue;
+import com.google.common.base.Function;
+import com.google.common.base.Splitter;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableListMultimap;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableTable;
+import com.google.common.collect.Sets;
+import com.google.errorprone.BugPattern.SeverityLevel;
+import java.io.BufferedWriter;
+import java.io.IOException;
+import java.nio.file.FileSystems;
+import java.nio.file.FileVisitResult;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.PathMatcher;
+import java.nio.file.SimpleFileVisitor;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.util.ArrayList;
+import java.util.List;
+import org.jspecify.annotations.Nullable;
+import tech.picnic.errorprone.documentation.BugPatternExtractor.BugPatternDocumentation;
+import tech.picnic.errorprone.documentation.BugPatternTestExtractor.BugPatternTestCase;
+import tech.picnic.errorprone.documentation.BugPatternTestExtractor.BugPatternTestCases;
+import tech.picnic.errorprone.documentation.BugPatternTestExtractor.IdentificationTestEntry;
+import tech.picnic.errorprone.documentation.BugPatternTestExtractor.ReplacementTestEntry;
+import tech.picnic.errorprone.documentation.BugPatternTestExtractor.TestEntry;
+import tech.picnic.errorprone.documentation.RefasterRuleCollectionTestExtractor.RefasterTestCase;
+import tech.picnic.errorprone.documentation.RefasterRuleCollectionTestExtractor.RefasterTestCases;
+
+/**
+ * A command line utility that produces configuration files for the Jekyll-based Error Prone Support
+ * website.
+ */
+// XXX: Expand the class documentation.
+// XXX: Rename this class. Then also update the reference in `website/.gitignore`.
+// XXX: Now that we have bug checkers in multiple Maven modules, we should
+// likely document the source of each check on the website, perhaps even
+// grouping them by module.
+public final class JekyllCollectionGenerator {
+  // XXX: Find a bette name. Also, externalize this.
+  private static final PathMatcher PATH_MATCHER =
+      FileSystems.getDefault().getPathMatcher("glob:**/target/docs/*.json");
+
+  // XXX: Review class setup.
+  private JekyllCollectionGenerator() {}
+
+  /**
+   * Runs the application.
+   *
+   * @param args Arguments to the application; must specify the path to the Error Prone Support
+   *     project root, and nothing else.
+   * @throws IOException If any file could not be read or written.
+   */
+  public static void main(String[] args) throws IOException {
+    checkArgument(args.length == 1, "Precisely one project root path must be provided");
+    Path projectRoot = Path.of(args[0]).toAbsolutePath();
+
+    generateIndex(projectRoot);
+    PageGenerator.apply(projectRoot);
+  }
+
+  private static void generateIndex(Path projectRoot) throws IOException {
+    try (BufferedWriter writer =
+        Files.newBufferedWriter(projectRoot.resolve("website").resolve("index.md"), UTF_8)) {
+      writer.write("---");
+      writer.newLine();
+      writer.write("layout: default");
+      writer.newLine();
+      writer.write("title: Home");
+      writer.newLine();
+      writer.write("nav_order: 1");
+      writer.newLine();
+      writer.write("---");
+      writer.newLine();
+      writer.write(
+          Files.readString(projectRoot.resolve("README.md")).replace("=\"website/", "=\""));
+    }
+  }
+
+  // XXX: Review this class should be split in two: one for bug patterns and one for Refaster rules.
+  private static final class PageGenerator extends SimpleFileVisitor<Path> {
+    private static final Splitter LINE_SPLITTER = Splitter.on(System.lineSeparator());
+    private static final YAMLMapper YAML_MAPPER =
+        YAMLMapper.builder()
+            .visibility(PropertyAccessor.FIELD, Visibility.ANY)
+            .disable(JsonGenerator.Feature.AUTO_CLOSE_TARGET)
+            .enable(YAMLGenerator.Feature.MINIMIZE_QUOTES)
+            .enable(YAMLGenerator.Feature.USE_PLATFORM_LINE_BREAKS)
+            .build();
+
+    private final List<BugPatternDocumentation> bugPatterns = new ArrayList<>();
+    private final List<BugPatternTestCases> bugPatternTests = new ArrayList<>();
+    private final List<RefasterTestCases> refasterRuleCollectionTests = new ArrayList<>();
+
+    static void apply(Path projectRoot) throws IOException {
+      PageGenerator pageGenerator = new PageGenerator();
+      Files.walkFileTree(projectRoot, pageGenerator);
+      pageGenerator.writePages(projectRoot);
+    }
+
+    @Override
+    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
+      if (!PATH_MATCHER.matches(file)) {
+        return FileVisitResult.CONTINUE;
+      }
+
+      // XXX: If we use a consistent ID separator, then this can become a switch statement. Now we
+      // depend on evaluation order.
+      // XXX: Alternatively, use polymorphism and let Jackson figure it out.
+      // XXX: If we stick with an ID-based approach, then deduplicate the ID references here and in
+      // the `Extractor` implementations.
+      String fileName = file.getFileName().toString();
+      if (fileName.startsWith("bugpattern-test")) {
+        bugPatternTests.add(Json.read(file, BugPatternTestCases.class));
+      } else if (fileName.startsWith("bugpattern")) {
+        bugPatterns.add(Json.read(file, BugPatternDocumentation.class));
+      } else if (fileName.startsWith("refaster-rule-collection-test")) {
+        refasterRuleCollectionTests.add(Json.read(file, RefasterTestCases.class));
+      } else {
+        // XXX: Handle differently?
+        throw new IllegalStateException("Unexpected file: " + fileName);
+      }
+
+      return FileVisitResult.CONTINUE;
+    }
+
+    private void writePages(Path projectRoot) throws IOException {
+      Path website = projectRoot.resolve("website");
+      writePages(
+          website.resolve("_bugpatterns"),
+          getJekyllBugPatternDescriptions(projectRoot),
+          JekyllBugPatternDescription::name);
+      writePages(
+          website.resolve("_refasterrules"),
+          getJekyllRefasterRuleCollectionDescription(),
+          JekyllRefasterRuleCollectionDescription::name);
+    }
+
+    private static <T> void writePages(
+        Path directory, ImmutableList<T> documents, Function<T, String> nameExtractor)
+        throws IOException {
+      for (T document : documents) {
+        Files.createDirectories(directory);
+        try (BufferedWriter writer =
+            Files.newBufferedWriter(
+                directory.resolve(nameExtractor.apply(document) + ".md"), UTF_8)) {
+          YAML_MAPPER.writeValue(writer, document);
+          writer.write("---");
+          writer.newLine();
+        }
+      }
+    }
+
+    private ImmutableList<JekyllBugPatternDescription> getJekyllBugPatternDescriptions(
+        Path projectRoot) {
+      ImmutableListMultimap<String, TestEntry> bugPatternTestCases =
+          bugPatternTests.stream()
+              .flatMap(testCases -> testCases.testCases().stream())
+              .collect(
+                  flatteningToImmutableListMultimap(
+                      BugPatternTestCase::classUnderTest, t -> t.entries().stream()));
+
+      return bugPatterns.stream()
+          .map(
+              b ->
+                  new AutoValue_JekyllCollectionGenerator_JekyllBugPatternDescription(
+                      b.name(),
+                      b.name(),
+                      b.summary(),
+                      b.severityLevel(),
+                      b.tags(),
+                      // XXX: Derive `Path` from filesytem.
+                      Path.of(b.source()).relativize(projectRoot).toString(),
+                      bugPatternTestCases.get(b.fullyQualifiedName()).stream()
+                          .filter(t -> t.type() == TestEntry.TestType.IDENTIFICATION)
+                          .map(t -> ((IdentificationTestEntry) t).code())
+                          .collect(toImmutableList()),
+                      bugPatternTestCases.get(b.fullyQualifiedName()).stream()
+                          .filter(t -> t.type() == TestEntry.TestType.REPLACEMENT)
+                          .map(t -> generateDiff((ReplacementTestEntry) t))
+                          .collect(toImmutableList())))
+          .collect(toImmutableList());
+    }
+
+    private ImmutableList<JekyllRefasterRuleCollectionDescription>
+        getJekyllRefasterRuleCollectionDescription() {
+      ImmutableTable<String, Boolean, List<RefasterTestCase>> refasterTests =
+          refasterRuleCollectionTests.stream()
+              .collect(
+                  toImmutableTable(
+                      RefasterTestCases::ruleCollection,
+                      RefasterTestCases::isInput,
+                      RefasterTestCases::testCases));
+
+      return refasterTests.rowMap().entrySet().stream()
+          .map(
+              c ->
+                  new AutoValue_JekyllCollectionGenerator_JekyllRefasterRuleCollectionDescription(
+                      c.getKey(),
+                      c.getKey(),
+                      // XXX: Derive severity from input.
+                      SUGGESTION,
+                      // XXX: Derive tags from input (or drop this feature).
+                      ImmutableList.of("Simplification"),
+                      // XXX: Derive source location from input.
+                      String.format(
+                          "error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/%s.java",
+                          c.getKey()),
+                      getRules(c.getValue().get(true), c.getValue().get(false))))
+          .collect(toImmutableList());
+    }
+
+    private static ImmutableList<JekyllRefasterRuleCollectionDescription.Rule> getRules(
+        @Nullable List<RefasterTestCase> inputTests, @Nullable List<RefasterTestCase> outputTests) {
+      ImmutableMap<String, String> inputs = indexRefasterTestData(inputTests);
+      ImmutableMap<String, String> outputs = indexRefasterTestData(outputTests);
+
+      return Sets.intersection(inputs.keySet(), outputs.keySet()).stream()
+          .map(
+              name ->
+                  new AutoValue_JekyllCollectionGenerator_JekyllRefasterRuleCollectionDescription_Rule(
+                      name,
+                      // XXX: Derive severity from input.
+                      SUGGESTION,
+                      // XXX: Derive tags from input (or drop this feature).
+                      ImmutableList.of("Simplification"),
+                      generateDiff(
+                          requireNonNull(inputs.get(name), "Input"),
+                          requireNonNull(outputs.get(name), "Output"))))
+          .collect(toImmutableList());
+    }
+
+    private static ImmutableMap<String, String> indexRefasterTestData(
+        @Nullable List<RefasterTestCase> data) {
+      return data == null
+          ? ImmutableMap.of()
+          : data.stream()
+              .collect(toImmutableMap(RefasterTestCase::name, RefasterTestCase::content));
+    }
+
+    private static String generateDiff(ReplacementTestEntry testEntry) {
+      return generateDiff(testEntry.input(), testEntry.output());
+    }
+
+    private static String generateDiff(String before, String after) {
+      // XXX: Extract splitter.
+      List<String> originalLines = LINE_SPLITTER.splitToList(before);
+      List<String> replacementLines = LINE_SPLITTER.splitToList(after);
+
+      Patch<String> diff = DiffUtils.diff(originalLines, replacementLines);
+
+      return UnifiedDiffUtils.generateUnifiedDiff(
+              "", "", originalLines, diff, Integer.MAX_VALUE / 2)
+          .stream()
+          .skip(3)
+          .collect(joining(System.lineSeparator()));
+    }
+  }
+
+  @AutoValue
+  abstract static class JekyllBugPatternDescription {
+    // XXX: Make this a derived property?
+    abstract String title();
+
+    abstract String name();
+
+    abstract String summary();
+
+    abstract SeverityLevel severity();
+
+    abstract ImmutableList<String> tags();
+
+    // XXX: The documentation could link to the original test code. Perhaps even with the correct
+    // line numbers.
+    abstract String source();
+
+    // XXX: The `identification` and `replacement` fields have odd names.
+    abstract ImmutableList<String> identification();
+
+    abstract ImmutableList<String> replacement();
+  }
+
+  @AutoValue
+  abstract static class JekyllRefasterRuleCollectionDescription {
+    // XXX: Make this a derived property?
+    abstract String title();
+
+    abstract String name();
+
+    abstract SeverityLevel severity();
+
+    abstract ImmutableList<String> tags();
+
+    // XXX: The documentation could link to the original test code. Perhaps even with the correct
+    // line numbers. If we do this, we should do the same for individual rules.
+    abstract String source();
+
+    abstract ImmutableList<Rule> rules();
+
+    @AutoValue
+    abstract static class Rule {
+      abstract String name();
+
+      abstract SeverityLevel severity();
+
+      abstract ImmutableList<String> tags();
+
+      abstract String diff();
+    }
+  }
+}

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

@@ -0,0 +1,176 @@
+package tech.picnic.errorprone.documentation;
+
+import static com.google.common.collect.ImmutableList.toImmutableList;
+import static com.google.errorprone.matchers.Matchers.isSubtypeOf;
+import static java.util.stream.Collectors.joining;
+
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import com.google.auto.service.AutoService;
+import com.google.auto.value.AutoValue;
+import com.google.common.base.Splitter;
+import com.google.common.base.Supplier;
+import com.google.common.base.VerifyException;
+import com.google.common.collect.ImmutableList;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.annotations.FormatMethod;
+import com.google.errorprone.annotations.Immutable;
+import com.google.errorprone.matchers.Matcher;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.tree.MethodTree;
+import java.net.URI;
+import java.util.Optional;
+import java.util.regex.Pattern;
+import tech.picnic.errorprone.documentation.RefasterRuleCollectionTestExtractor.RefasterTestCases;
+import tech.picnic.errorprone.utils.SourceCode;
+
+/**
+ * An {@link Extractor} that describes how to extract data from Refaster rule input and output test
+ * classes.
+ */
+// XXX: Drop this extractor if/when the Refaster test framework is reimplemented such that tests can
+// be located alongside rules, rather than in two additional resource files as currently required by
+// `RefasterRuleCollection`.
+@Immutable
+@AutoService(Extractor.class)
+@SuppressWarnings("rawtypes" /* See https://github.com/google/auto/issues/870. */)
+public final class RefasterRuleCollectionTestExtractor implements Extractor<RefasterTestCases> {
+  private static final Matcher<ClassTree> IS_REFASTER_RULE_COLLECTION_TEST_CASE =
+      isSubtypeOf("tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase");
+  private static final Pattern TEST_CLASS_NAME_PATTERN = Pattern.compile("(.*)Test");
+  private static final Pattern TEST_CLASS_FILE_NAME_PATTERN =
+      Pattern.compile(".*(Input|Output)\\.java");
+  private static final Pattern TEST_METHOD_NAME_PATTERN = Pattern.compile("test(.*)");
+  private static final String LINE_SEPARATOR = "\n";
+  private static final Splitter LINE_SPLITTER = Splitter.on(LINE_SEPARATOR);
+
+  /** Instantiates a new {@link RefasterRuleCollectionTestExtractor} instance. */
+  public RefasterRuleCollectionTestExtractor() {}
+
+  @Override
+  public String identifier() {
+    return "refaster-rule-collection-test";
+  }
+
+  @Override
+  public Optional<RefasterTestCases> tryExtract(ClassTree tree, VisitorState state) {
+    if (!IS_REFASTER_RULE_COLLECTION_TEST_CASE.matches(tree, state)) {
+      return Optional.empty();
+    }
+
+    URI sourceFile = state.getPath().getCompilationUnit().getSourceFile().toUri();
+    return Optional.of(
+        RefasterTestCases.create(
+            sourceFile,
+            getRuleCollectionName(tree),
+            isInputFile(sourceFile),
+            getRefasterTestCases(tree, state)));
+  }
+
+  private static String getRuleCollectionName(ClassTree tree) {
+    String className = tree.getSimpleName().toString();
+
+    // XXX: Instead of throwing an error here, it'd be nicer to have a bug checker validate key
+    // aspects of `RefasterRuleCollectionTestCase` subtypes.
+    return tryExtractPatternGroup(className, TEST_CLASS_NAME_PATTERN)
+        .orElseThrow(
+            violation(
+                "Refaster rule collection test class name '%s' does not match '%s'",
+                className, TEST_CLASS_NAME_PATTERN));
+  }
+
+  private static boolean isInputFile(URI sourceFile) {
+    String path = sourceFile.getPath();
+
+    // XXX: Instead of throwing an error here, it'd be nicer to have a bug checker validate key
+    // aspects of `RefasterRuleCollectionTestCase` subtypes.
+    return "Input"
+        .equals(
+            tryExtractPatternGroup(path, TEST_CLASS_FILE_NAME_PATTERN)
+                .orElseThrow(
+                    violation(
+                        "Refaster rule collection test file name '%s' does not match '%s'",
+                        path, TEST_CLASS_FILE_NAME_PATTERN)));
+  }
+
+  private static ImmutableList<RefasterTestCase> getRefasterTestCases(
+      ClassTree tree, VisitorState state) {
+    return tree.getMembers().stream()
+        .filter(MethodTree.class::isInstance)
+        .map(MethodTree.class::cast)
+        .flatMap(m -> tryExtractRefasterTestCase(m, state).stream())
+        .collect(toImmutableList());
+  }
+
+  private static Optional<RefasterTestCase> tryExtractRefasterTestCase(
+      MethodTree method, VisitorState state) {
+    return tryExtractPatternGroup(method.getName().toString(), TEST_METHOD_NAME_PATTERN)
+        .map(name -> RefasterTestCase.create(name, getFormattedSource(method, state)));
+  }
+
+  /**
+   * Returns the source code for the specified method.
+   *
+   * @implNote This operation attempts to trim leading whitespace, such that the start and end of
+   *     the method declaration are aligned. The implemented heuristic assumes that the code is
+   *     formatted using Google Java Format.
+   */
+  // XXX: Leading Javadoc and other comments are currently not extracted. Consider fixing this.
+  private static String getFormattedSource(MethodTree method, VisitorState state) {
+    String source = SourceCode.treeToString(method, state);
+    int finalNewline = source.lastIndexOf(LINE_SEPARATOR);
+    if (finalNewline < 0) {
+      return source;
+    }
+
+    int indentation = Math.max(0, source.lastIndexOf(' ') - finalNewline);
+    String prefixToStrip = " ".repeat(indentation);
+
+    return LINE_SPLITTER
+        .splitToStream(source)
+        .map(line -> line.startsWith(prefixToStrip) ? line.substring(indentation) : line)
+        .collect(joining(LINE_SEPARATOR));
+  }
+
+  private static Optional<String> tryExtractPatternGroup(String input, Pattern pattern) {
+    java.util.regex.Matcher matcher = pattern.matcher(input);
+    return matcher.matches() ? Optional.of(matcher.group(1)) : Optional.empty();
+  }
+
+  @FormatMethod
+  private static Supplier<VerifyException> violation(String format, Object... args) {
+    return () -> new VerifyException(String.format(format, args));
+  }
+
+  @AutoValue
+  @JsonDeserialize(as = AutoValue_RefasterRuleCollectionTestExtractor_RefasterTestCases.class)
+  abstract static class RefasterTestCases {
+    static RefasterTestCases create(
+        URI source,
+        String ruleCollection,
+        boolean isInput,
+        ImmutableList<RefasterTestCase> testCases) {
+      return new AutoValue_RefasterRuleCollectionTestExtractor_RefasterTestCases(
+          source, ruleCollection, isInput, testCases);
+    }
+
+    abstract URI source();
+
+    abstract String ruleCollection();
+
+    abstract boolean isInput();
+
+    abstract ImmutableList<RefasterTestCase> testCases();
+  }
+
+  @AutoValue
+  @JsonDeserialize(as = AutoValue_RefasterRuleCollectionTestExtractor_RefasterTestCase.class)
+  abstract static class RefasterTestCase {
+    static RefasterTestCase create(String name, String content) {
+      return new AutoValue_RefasterRuleCollectionTestExtractor_RefasterTestCase(name, content);
+    }
+
+    abstract String name();
+
+    abstract String content();
+  }
+}

documentation-support/src/main/java/tech/picnic/errorprone/documentation/models/RefasterTemplateCollectionData.java

@@ -0,0 +1,27 @@
+package tech.picnic.errorprone.documentation.models;
+
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableList;
+
+/**
+ * Object containing all data related to a Refaster template collection. This is solely used for
+ * serialization.
+ */
+// XXX: This class is not yet used.
+@AutoValue
+@JsonDeserialize(as = AutoValue_RefasterTemplateCollectionData.class)
+abstract class RefasterTemplateCollectionData {
+  static RefasterTemplateCollectionData create(
+      String name, String description, String link, ImmutableList<RefasterTemplateData> templates) {
+    return new AutoValue_RefasterTemplateCollectionData(name, description, link, templates);
+  }
+
+  abstract String name();
+
+  abstract String description();
+
+  abstract String link();
+
+  abstract ImmutableList<RefasterTemplateData> templates();
+}

documentation-support/src/main/java/tech/picnic/errorprone/documentation/models/RefasterTemplateData.java

@@ -0,0 +1,23 @@
+package tech.picnic.errorprone.documentation.models;
+
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import com.google.auto.value.AutoValue;
+import com.google.errorprone.BugPattern.SeverityLevel;
+
+// XXX: This class is not yet used.
+@AutoValue
+@JsonDeserialize(as = AutoValue_RefasterTemplateData.class)
+abstract class RefasterTemplateData {
+  static RefasterTemplateData create(
+      String name, String description, String link, SeverityLevel severityLevel) {
+    return new AutoValue_RefasterTemplateData(name, description, link, severityLevel);
+  }
+
+  abstract String name();
+
+  abstract String description();
+
+  abstract String link();
+
+  abstract SeverityLevel severityLevel();
+}

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

@@ -7,10 +7,10 @@ import java.net.URI;
 import java.nio.file.Path;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
+import tech.picnic.errorprone.documentation.BugPatternTestExtractor.BugPatternTestCase;
+import tech.picnic.errorprone.documentation.BugPatternTestExtractor.BugPatternTestCases;
 import tech.picnic.errorprone.documentation.BugPatternTestExtractor.IdentificationTestEntry;
 import tech.picnic.errorprone.documentation.BugPatternTestExtractor.ReplacementTestEntry;
-import tech.picnic.errorprone.documentation.BugPatternTestExtractor.TestCase;
-import tech.picnic.errorprone.documentation.BugPatternTestExtractor.TestCases;
 
 final class BugPatternTestExtractorTest {
   @Test
@@ -269,11 +269,11 @@ final class BugPatternTestExtractorTest {
     verifyGeneratedFileContent(
         outputDirectory,
         "SingleFileCompilationTestHelperTest",
-        TestCases.create(
+        BugPatternTestCases.create(
             URI.create("file:///SingleFileCompilationTestHelperTest.java"),
             "SingleFileCompilationTestHelperTest",
             ImmutableList.of(
-                TestCase.create(
+                BugPatternTestCase.create(
                     "SingleFileCompilationTestHelperTest.TestChecker",
                     ImmutableList.of(
                         IdentificationTestEntry.create(
@@ -302,11 +302,11 @@ final class BugPatternTestExtractorTest {
     verifyGeneratedFileContent(
         outputDirectory,
         "SingleFileCompilationTestHelperWithSetArgsTest",
-        TestCases.create(
+        BugPatternTestCases.create(
             URI.create("file:///SingleFileCompilationTestHelperWithSetArgsTest.java"),
             "SingleFileCompilationTestHelperWithSetArgsTest",
             ImmutableList.of(
-                TestCase.create(
+                BugPatternTestCase.create(
                     "SingleFileCompilationTestHelperWithSetArgsTest.TestChecker",
                     ImmutableList.of(
                         IdentificationTestEntry.create(
@@ -335,11 +335,11 @@ final class BugPatternTestExtractorTest {
     verifyGeneratedFileContent(
         outputDirectory,
         "MultiFileCompilationTestHelperTest",
-        TestCases.create(
+        BugPatternTestCases.create(
             URI.create("file:///MultiFileCompilationTestHelperTest.java"),
             "MultiFileCompilationTestHelperTest",
             ImmutableList.of(
-                TestCase.create(
+                BugPatternTestCase.create(
                     "MultiFileCompilationTestHelperTest.TestChecker",
                     ImmutableList.of(
                         IdentificationTestEntry.create(
@@ -370,11 +370,11 @@ final class BugPatternTestExtractorTest {
     verifyGeneratedFileContent(
         outputDirectory,
         "SingleFileBugCheckerRefactoringTestHelperTest",
-        TestCases.create(
+        BugPatternTestCases.create(
             URI.create("file:///SingleFileBugCheckerRefactoringTestHelperTest.java"),
             "SingleFileBugCheckerRefactoringTestHelperTest",
             ImmutableList.of(
-                TestCase.create(
+                BugPatternTestCase.create(
                     "SingleFileBugCheckerRefactoringTestHelperTest.TestChecker",
                     ImmutableList.of(
                         ReplacementTestEntry.create(
@@ -408,12 +408,12 @@ final class BugPatternTestExtractorTest {
     verifyGeneratedFileContent(
         outputDirectory,
         "SingleFileBugCheckerRefactoringTestHelperWithSetArgsFixChooserAndCustomTestModeTest",
-        TestCases.create(
+        BugPatternTestCases.create(
             URI.create(
                 "file:///SingleFileBugCheckerRefactoringTestHelperWithSetArgsFixChooserAndCustomTestModeTest.java"),
             "SingleFileBugCheckerRefactoringTestHelperWithSetArgsFixChooserAndCustomTestModeTest",
             ImmutableList.of(
-                TestCase.create(
+                BugPatternTestCase.create(
                     "SingleFileBugCheckerRefactoringTestHelperWithSetArgsFixChooserAndCustomTestModeTest.TestChecker",
                     ImmutableList.of(
                         ReplacementTestEntry.create(
@@ -444,11 +444,11 @@ final class BugPatternTestExtractorTest {
     verifyGeneratedFileContent(
         outputDirectory,
         "MultiFileBugCheckerRefactoringTestHelperTest",
-        TestCases.create(
+        BugPatternTestCases.create(
             URI.create("file:///MultiFileBugCheckerRefactoringTestHelperTest.java"),
             "MultiFileBugCheckerRefactoringTestHelperTest",
             ImmutableList.of(
-                TestCase.create(
+                BugPatternTestCase.create(
                     "MultiFileBugCheckerRefactoringTestHelperTest.TestChecker",
                     ImmutableList.of(
                         ReplacementTestEntry.create(
@@ -484,16 +484,16 @@ final class BugPatternTestExtractorTest {
     verifyGeneratedFileContent(
         outputDirectory,
         "CompilationAndBugCheckerRefactoringTestHelpersTest",
-        TestCases.create(
+        BugPatternTestCases.create(
             URI.create("file:///CompilationAndBugCheckerRefactoringTestHelpersTest.java"),
             "CompilationAndBugCheckerRefactoringTestHelpersTest",
             ImmutableList.of(
-                TestCase.create(
+                BugPatternTestCase.create(
                     "CompilationAndBugCheckerRefactoringTestHelpersTest.TestChecker",
                     ImmutableList.of(
                         IdentificationTestEntry.create(
                             "A.java", "// BUG: Diagnostic contains:\nclass A {}\n"))),
-                TestCase.create(
+                BugPatternTestCase.create(
                     "CompilationAndBugCheckerRefactoringTestHelpersTest.TestChecker",
                     ImmutableList.of(
                         ReplacementTestEntry.create(
@@ -532,17 +532,17 @@ final class BugPatternTestExtractorTest {
     verifyGeneratedFileContent(
         outputDirectory,
         "CompilationAndBugCheckerRefactoringTestHelpersWithCustomCheckerPackageAndNamesTest",
-        TestCases.create(
+        BugPatternTestCases.create(
             URI.create(
                 "file:///CompilationAndBugCheckerRefactoringTestHelpersWithCustomCheckerPackageAndNamesTest.java"),
             "pkg.CompilationAndBugCheckerRefactoringTestHelpersWithCustomCheckerPackageAndNamesTest",
             ImmutableList.of(
-                TestCase.create(
+                BugPatternTestCase.create(
                     "pkg.CompilationAndBugCheckerRefactoringTestHelpersWithCustomCheckerPackageAndNamesTest.CustomTestChecker",
                     ImmutableList.of(
                         IdentificationTestEntry.create(
                             "A.java", "// BUG: Diagnostic contains:\nclass A {}\n"))),
-                TestCase.create(
+                BugPatternTestCase.create(
                     "pkg.CompilationAndBugCheckerRefactoringTestHelpersWithCustomCheckerPackageAndNamesTest.CustomTestChecker2",
                     ImmutableList.of(
                         ReplacementTestEntry.create(
@@ -550,9 +550,9 @@ final class BugPatternTestExtractorTest {
   }
 
   private static void verifyGeneratedFileContent(
-      Path outputDirectory, String testClass, TestCases expected) {
+      Path outputDirectory, String testClass, BugPatternTestCases expected) {
     assertThat(outputDirectory.resolve(String.format("bugpattern-test-%s.json", testClass)))
         .exists()
-        .returns(expected, path -> Json.read(path, TestCases.class));
+        .returns(expected, path -> Json.read(path, BugPatternTestCases.class));
   }
 }

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

@@ -0,0 +1,13 @@
+package tech.picnic.errorprone.documentation;
+
+import java.io.IOException;
+import org.junit.jupiter.api.Test;
+
+// XXX: Implement tests.
+final class JekyllCollectionGeneratorTest {
+  @Test
+  void foo() throws IOException {
+    JekyllCollectionGenerator.main(
+        new String[] {"/home/sschroevers/workspace/picnic/error-prone-support"});
+  }
+}

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

@@ -0,0 +1,166 @@
+package tech.picnic.errorprone.documentation;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import com.google.common.base.VerifyException;
+import com.google.common.collect.ImmutableList;
+import java.net.URI;
+import java.nio.file.Path;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import tech.picnic.errorprone.documentation.RefasterRuleCollectionTestExtractor.RefasterTestCase;
+import tech.picnic.errorprone.documentation.RefasterRuleCollectionTestExtractor.RefasterTestCases;
+
+final class RefasterRuleCollectionTestExtractorTest {
+  @Test
+  void noRefasterRuleTest(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory, "NoRefasterRuleTest.java", "public final class NoRefasterRuleTest {}");
+
+    assertThat(outputDirectory.toAbsolutePath()).isEmptyDirectory();
+  }
+
+  @Test
+  void invalidTestClassName(@TempDir Path outputDirectory) {
+    assertThatThrownBy(
+            () ->
+                Compilation.compileWithDocumentationGenerator(
+                    outputDirectory,
+                    "InvalidTestClassNameInput.java",
+                    "import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;",
+                    "",
+                    "final class InvalidTestClassName implements RefasterRuleCollectionTestCase {}"))
+        .cause()
+        .isInstanceOf(VerifyException.class)
+        .hasMessage(
+            "Refaster rule collection test class name 'InvalidTestClassName' does not match '(.*)Test'");
+  }
+
+  @Test
+  void invalidFileName(@TempDir Path outputDirectory) {
+    assertThatThrownBy(
+            () ->
+                Compilation.compileWithDocumentationGenerator(
+                    outputDirectory,
+                    "InvalidFileNameTest.java",
+                    "import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;",
+                    "",
+                    "final class InvalidFileNameTest implements RefasterRuleCollectionTestCase {}"))
+        .cause()
+        .isInstanceOf(VerifyException.class)
+        .hasMessage(
+            "Refaster rule collection test file name '/InvalidFileNameTest.java' does not match '.*(Input|Output)\\.java'");
+  }
+
+  @Test
+  void emptyRefasterRuleCollectionTestInput(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "EmptyRefasterRuleCollectionTestInput.java",
+        "import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;",
+        "",
+        "final class EmptyRefasterRuleCollectionTest implements RefasterRuleCollectionTestCase {}");
+
+    verifyGeneratedFileContent(
+        outputDirectory,
+        "EmptyRefasterRuleCollectionTestInput",
+        RefasterTestCases.create(
+            URI.create("file:///EmptyRefasterRuleCollectionTestInput.java"),
+            "EmptyRefasterRuleCollection",
+            /* isInput= */ true,
+            ImmutableList.of()));
+  }
+
+  @Test
+  void singletonRefasterRuleCollectionTestOutput(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "SingletonRefasterRuleCollectionTestOutput.java",
+        "import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;",
+        "",
+        "final class SingletonRefasterRuleCollectionTest implements RefasterRuleCollectionTestCase {",
+        "  int testMyRule() {",
+        "    return 42;",
+        "  }",
+        "}");
+
+    verifyGeneratedFileContent(
+        outputDirectory,
+        "SingletonRefasterRuleCollectionTestOutput",
+        RefasterTestCases.create(
+            URI.create("file:///SingletonRefasterRuleCollectionTestOutput.java"),
+            "SingletonRefasterRuleCollection",
+            /* isInput= */ false,
+            ImmutableList.of(
+                RefasterTestCase.create(
+                    "MyRule",
+                    """
+                    int testMyRule() {
+                      return 42;
+                    }"""))));
+  }
+
+  @Test
+  void complexRefasterRuleCollectionTestOutput(@TempDir Path outputDirectory) {
+    Compilation.compileWithDocumentationGenerator(
+        outputDirectory,
+        "pkg/ComplexRefasterRuleCollectionTestInput.java",
+        "package pkg;",
+        "",
+        "import com.google.common.collect.ImmutableSet;",
+        "import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;",
+        "",
+        "final class ComplexRefasterRuleCollectionTest implements RefasterRuleCollectionTestCase {",
+        "  private static final String IGNORED_CONSTANT = \"constant\";",
+        "",
+        "  @Override",
+        "  public ImmutableSet<Object> elidedTypesAndStaticImports() {",
+        "    return ImmutableSet.of();",
+        "  }",
+        "",
+        "  /** Javadoc. */",
+        "  String testFirstRule() {",
+        "    return \"Don't panic\";",
+        "  }",
+        "",
+        "  // Comment.",
+        "  String testSecondRule() {",
+        "    return \"Carry a towel\";",
+        "  }",
+        "",
+        "  void testEmptyRule() {}",
+        "}");
+
+    verifyGeneratedFileContent(
+        outputDirectory,
+        "ComplexRefasterRuleCollectionTestInput",
+        RefasterTestCases.create(
+            URI.create("file:///pkg/ComplexRefasterRuleCollectionTestInput.java"),
+            "ComplexRefasterRuleCollection",
+            /* isInput= */ true,
+            ImmutableList.of(
+                RefasterTestCase.create(
+                    "FirstRule",
+                    """
+                    String testFirstRule() {
+                      return "Don't panic";
+                    }"""),
+                RefasterTestCase.create(
+                    "SecondRule",
+                    """
+                    String testSecondRule() {
+                      return "Carry a towel";
+                    }"""),
+                RefasterTestCase.create("EmptyRule", "void testEmptyRule() {}"))));
+  }
+
+  private static void verifyGeneratedFileContent(
+      Path outputDirectory, String testIdentifier, RefasterTestCases expected) {
+    assertThat(
+            outputDirectory.resolve(
+                String.format("refaster-rule-collection-test-%s.json", testIdentifier)))
+        .exists()
+        .returns(expected, path -> Json.read(path, RefasterTestCases.class));
+  }
+}

error-prone-contrib/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.17.0</version>
+        <version>0.18.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>error-prone-contrib</artifactId>
@@ -67,6 +67,11 @@
             <artifactId>jackson-annotations</artifactId>
             <scope>provided</scope>
         </dependency>
+        <dependency>
+            <groupId>com.github.ben-manes.caffeine</groupId>
+            <artifactId>caffeine</artifactId>
+            <scope>provided</scope>
+        </dependency>
         <dependency>
             <groupId>com.google.auto.service</groupId>
             <artifactId>auto-service-annotations</artifactId>
@@ -287,6 +292,55 @@
                             <arg>-Xplugin:DocumentationGenerator -XoutputDirectory=${project.build.directory}/docs</arg>
                         </compilerArgs>
                     </configuration>
+                    <executions>
+                        <!-- The Refaster input/output test classes used by
+                        `RefasterRuleCollection` are modelled as classpath
+                        resources, and thus not subject to the default test
+                        compilation step. These two custom compilation steps
+                        serve two purposes:
+                        - To provide early feedback in case of syntax errors.
+                        - To enable the `DocumentationGenerator` compiler
+                        plugin to extract documentation metadata from them.
+                        Note that the input and output files must be compiled
+                        separately and to distinct output directories, as they
+                        define the same set of class names. -->
+                        <!-- XXX: Drop these executions if/when the Refaster
+                        test framework is reimplemented such that tests can be
+                        located alongside rules, rather than in two additional
+                        resource files. -->
+                        <execution>
+                            <id>compile-refaster-test-input</id>
+                            <goals>
+                                <goal>testCompile</goal>
+                            </goals>
+                            <phase>process-test-resources</phase>
+                            <configuration>
+                                <compileSourceRoots>
+                                    <compileSourceRoot>${project.basedir}/src/test/resources</compileSourceRoot>
+                                </compileSourceRoots>
+                                <testIncludes>
+                                    <testInclude>**/*Input.java</testInclude>
+                                </testIncludes>
+                                <outputDirectory>${project.build.directory}/refaster-test-input</outputDirectory>
+                            </configuration>
+                        </execution>
+                        <execution>
+                            <id>compile-refaster-test-output</id>
+                            <goals>
+                                <goal>testCompile</goal>
+                            </goals>
+                            <phase>process-test-resources</phase>
+                            <configuration>
+                                <compileSourceRoots>
+                                    <compileSourceRoot>${project.basedir}/src/test/resources</compileSourceRoot>
+                                </compileSourceRoots>
+                                <testIncludes>
+                                    <testInclude>**/*Output.java</testInclude>
+                                </testIncludes>
+                                <outputDirectory>${project.build.directory}/refaster-test-output</outputDirectory>
+                            </configuration>
+                        </execution>
+                    </executions>
                 </plugin>
             </plugins>
         </pluginManagement>

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

@@ -51,6 +51,7 @@ import tech.picnic.errorprone.utils.SourceCode;
 // is effectively the identity operation.
 // XXX: Also flag nullary instance method invocations that represent an identity conversion, such as
 // `Boolean#booleanValue()`, `Byte#byteValue()` and friends.
+// XXX: Also flag redundant round-trip conversions such as `path.toFile().toPath()`.
 @AutoService(BugChecker.class)
 @BugPattern(
     summary = "Avoid or clarify identity conversions",

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

@@ -18,14 +18,12 @@ import com.google.errorprone.fixes.SuggestedFixes;
 import com.google.errorprone.matchers.Description;
 import com.google.errorprone.matchers.Matcher;
 import com.google.errorprone.refaster.Refaster;
-import com.google.errorprone.util.ASTHelpers;
 import com.sun.source.tree.ExpressionTree;
-import com.sun.source.tree.IdentifierTree;
-import com.sun.source.tree.LiteralTree;
 import com.sun.source.tree.MemberSelectTree;
 import com.sun.source.tree.MethodInvocationTree;
 import java.util.Optional;
 import java.util.function.Supplier;
+import tech.picnic.errorprone.refaster.matchers.RequiresComputation;
 import tech.picnic.errorprone.utils.SourceCode;
 
 /**
@@ -36,12 +34,12 @@ import tech.picnic.errorprone.utils.SourceCode;
  * it does, the suggested fix changes the program's semantics. Such fragile code must instead be
  * refactored such that the side-effectful code does not appear accidental.
  */
-// XXX: Consider also implementing the inverse, in which `.orElseGet(() -> someConstant)` is
-// flagged.
-// XXX: Once the `MethodReferenceUsageCheck` becomes generally usable, consider leaving the method
-// reference cleanup to that check, and express the remainder of the logic in this class using a
-// Refaster template, i.c.w. a `@Matches` constraint that implements the `requiresComputation`
-// logic.
+// XXX: This rule may introduce a compilation error: the `value` expression may reference a
+// non-effectively final variable, which is not allowed in the replacement lambda expression.
+// Review whether a `@Matcher` can be used to avoid this.
+// XXX: Once the `MethodReferenceUsageCheck` bug checker becomes generally usable, consider leaving
+// the method reference cleanup to that check, and express the remainder of the logic in this class
+// using a Refaster template, i.c.w. a `@NotMatches(RequiresComputation.class)` constraint.
 @AutoService(BugChecker.class)
 @BugPattern(
     summary =
@@ -51,16 +49,17 @@ import tech.picnic.errorprone.utils.SourceCode;
     linkType = NONE,
     severity = WARNING,
     tags = PERFORMANCE)
-public final class OptionalOrElse extends BugChecker implements MethodInvocationTreeMatcher {
+public final class OptionalOrElseGet extends BugChecker implements MethodInvocationTreeMatcher {
   private static final long serialVersionUID = 1L;
+  private static final Matcher<ExpressionTree> REQUIRES_COMPUTATION = new RequiresComputation();
   private static final Matcher<ExpressionTree> OPTIONAL_OR_ELSE_METHOD =
       instanceMethod().onExactClass(Optional.class.getCanonicalName()).namedAnyOf("orElse");
   // XXX: Also exclude invocations of `@Placeholder`-annotated methods.
   private static final Matcher<ExpressionTree> REFASTER_METHOD =
       staticMethod().onClass(Refaster.class.getCanonicalName());
 
-  /** Instantiates a new {@link OptionalOrElse} instance. */
-  public OptionalOrElse() {}
+  /** Instantiates a new {@link OptionalOrElseGet} instance. */
+  public OptionalOrElseGet() {}
 
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
@@ -69,7 +68,8 @@ public final class OptionalOrElse extends BugChecker implements MethodInvocation
     }
 
     ExpressionTree argument = Iterables.getOnlyElement(tree.getArguments());
-    if (!requiresComputation(argument) || REFASTER_METHOD.matches(argument, state)) {
+    if (!REQUIRES_COMPUTATION.matches(argument, state)
+        || REFASTER_METHOD.matches(argument, state)) {
       return Description.NO_MATCH;
     }
 
@@ -91,18 +91,6 @@ public final class OptionalOrElse extends BugChecker implements MethodInvocation
     return describeMatch(tree, fix);
   }
 
-  /**
-   * Tells whether the given expression contains anything other than a literal or a (possibly
-   * dereferenced) variable or constant.
-   */
-  private static boolean requiresComputation(ExpressionTree tree) {
-    return !(tree instanceof IdentifierTree
-        || tree instanceof LiteralTree
-        || (tree instanceof MemberSelectTree memberSelect
-            && !requiresComputation(memberSelect.getExpression()))
-        || ASTHelpers.constValue(tree) != null);
-  }
-
   /** Returns the nullary method reference matching the given expression, if any. */
   private static Optional<String> tryMethodReferenceConversion(
       ExpressionTree tree, VisitorState state) {
@@ -118,7 +106,7 @@ public final class OptionalOrElse extends BugChecker implements MethodInvocation
       return Optional.empty();
     }
 
-    if (requiresComputation(memberSelect.getExpression())) {
+    if (REQUIRES_COMPUTATION.matches(memberSelect.getExpression(), state)) {
       return Optional.empty();
     }
 

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

@@ -3,6 +3,7 @@ package tech.picnic.errorprone.refasterrules;
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import java.util.function.Function;
 import java.util.function.Predicate;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
@@ -37,7 +38,12 @@ final class ClassRules {
     }
   }
 
-  /** Prefer {@link Class#isInstance(Object)} method references over more verbose alternatives. */
+  /**
+   * Prefer {@link Class#isInstance(Object)} method references over lambda expressions that require
+   * naming a variable.
+   */
+  // XXX: Once the `ClassReferenceIsInstancePredicate` rule is dropped, rename this rule to just
+  // `ClassIsInstancePredicate`.
   static final class ClassLiteralIsInstancePredicate<T, S> {
     @BeforeTemplate
     Predicate<S> before() {
@@ -50,7 +56,11 @@ final class ClassRules {
     }
   }
 
-  /** Prefer {@link Class#isInstance(Object)} method references over more verbose alternatives. */
+  /**
+   * Prefer {@link Class#isInstance(Object)} method references over lambda expressions that require
+   * naming a variable.
+   */
+  // XXX: Drop this rule once the `MethodReferenceUsage` rule is enabled by default.
   static final class ClassReferenceIsInstancePredicate<T, S> {
     @BeforeTemplate
     Predicate<S> before(Class<T> clazz) {
@@ -62,4 +72,39 @@ final class ClassRules {
       return clazz::isInstance;
     }
   }
+
+  /**
+   * Prefer {@link Class#cast(Object)} method references over lambda expressions that require naming
+   * a variable.
+   */
+  // XXX: Once the `ClassReferenceCast` rule is dropped, rename this rule to just `ClassCast`.
+  static final class ClassLiteralCast<T, S> {
+    @BeforeTemplate
+    @SuppressWarnings("unchecked")
+    Function<T, S> before() {
+      return t -> (S) t;
+    }
+
+    @AfterTemplate
+    Function<T, S> after() {
+      return Refaster.<S>clazz()::cast;
+    }
+  }
+
+  /**
+   * Prefer {@link Class#cast(Object)} method references over lambda expressions that require naming
+   * a variable.
+   */
+  // XXX: Drop this rule once the `MethodReferenceUsage` rule is enabled by default.
+  static final class ClassReferenceCast<T, S> {
+    @BeforeTemplate
+    Function<T, S> before(Class<? extends S> clazz) {
+      return o -> clazz.cast(o);
+    }
+
+    @AfterTemplate
+    Function<T, S> after(Class<? extends S> clazz) {
+      return clazz::cast;
+    }
+  }
 }

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

@@ -8,7 +8,9 @@ import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.AlsoNegation;
 import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import com.google.errorprone.refaster.annotation.NotMatches;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.List;
@@ -21,6 +23,7 @@ import java.util.function.Consumer;
 import java.util.function.IntFunction;
 import java.util.stream.Stream;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
+import tech.picnic.errorprone.refaster.matchers.IsRefasterAsVarargs;
 
 /** 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
@@ -184,6 +187,24 @@ final class CollectionRules {
     }
   }
 
+  /** Don't unnecessarily call {@link Stream#distinct()} on an already-unique stream of elements. */
+  // XXX: This rule assumes that the `Set` relies on `Object#equals`, rather than a custom
+  // equivalence relation.
+  // XXX: Expressions that drop or reorder elements from the stream, such as `.filter`, `.skip` and
+  // `sorted`, can similarly be simplified. Covering all cases is better done using an Error Prone
+  // check.
+  static final class SetStream<T> {
+    @BeforeTemplate
+    Stream<?> before(Set<T> set) {
+      return set.stream().distinct();
+    }
+
+    @AfterTemplate
+    Stream<?> after(Set<T> set) {
+      return set.stream();
+    }
+  }
+
   /** Prefer {@link ArrayList#ArrayList(Collection)} over the Guava alternative. */
   @SuppressWarnings(
       "NonApiType" /* Matching against `List` would unnecessarily constrain the rule. */)
@@ -276,6 +297,23 @@ final class CollectionRules {
     }
   }
 
+  /** Prefer {@link Arrays#asList(Object[])} over more contrived alternatives. */
+  // XXX: Consider moving this rule to `ImmutableListRules` and having it suggest
+  // `ImmutableList#copyOf`. That would retain immutability, at the cost of no longer handling
+  // `null`s.
+  static final class ArraysAsList<T> {
+    // XXX: This expression produces an unmodifiable list, while the alternative doesn't.
+    @BeforeTemplate
+    List<T> before(@NotMatches(IsRefasterAsVarargs.class) T[] array) {
+      return Arrays.stream(array).toList();
+    }
+
+    @AfterTemplate
+    List<T> after(T[] array) {
+      return Arrays.asList(array);
+    }
+  }
+
   /** Prefer calling {@link Collection#toArray()} over more contrived alternatives. */
   static final class CollectionToArray<T> {
     @BeforeTemplate

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

@@ -24,8 +24,10 @@ import com.google.errorprone.refaster.annotation.Placeholder;
 import com.google.errorprone.refaster.annotation.Repeated;
 import com.google.errorprone.refaster.annotation.UseImportPolicy;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
+import java.util.List;
 import java.util.Optional;
 import java.util.function.BinaryOperator;
 import java.util.function.Function;
@@ -243,18 +245,77 @@ final class ComparatorRules {
     }
   }
 
+  /** Prefer {@link Collections#sort(List)} over more verbose alternatives. */
+  static final class CollectionsSort<T extends Comparable<? super T>> {
+    @BeforeTemplate
+    void before(List<T> collection) {
+      Collections.sort(collection, naturalOrder());
+    }
+
+    @AfterTemplate
+    void after(List<T> collection) {
+      Collections.sort(collection);
+    }
+  }
+
+  /** Prefer {@link Collections#min(Collection)} over more verbose alternatives. */
+  static final class CollectionsMin<T extends Comparable<? super T>> {
+    @BeforeTemplate
+    T before(Collection<T> collection) {
+      return Refaster.anyOf(
+          Collections.min(collection, naturalOrder()), Collections.max(collection, reverseOrder()));
+    }
+
+    @AfterTemplate
+    T after(Collection<T> collection) {
+      return Collections.min(collection);
+    }
+  }
+
   /**
    * Avoid unnecessary creation of a {@link Stream} to determine the minimum of a known collection
    * of values.
    */
-  static final class MinOfVarargs<T> {
+  static final class MinOfArray<S, T extends S> {
     @BeforeTemplate
-    T before(@Repeated T value, Comparator<T> cmp) {
+    T before(T[] array, Comparator<S> cmp) {
+      return Arrays.stream(array).min(cmp).orElseThrow();
+    }
+
+    @AfterTemplate
+    T after(T[] array, Comparator<S> cmp) {
+      return Collections.min(Arrays.asList(array), cmp);
+    }
+  }
+
+  /**
+   * Avoid unnecessary creation of a {@link Stream} to determine the minimum of a known collection
+   * of values.
+   */
+  static final class CollectionsMinWithComparator<S, T extends S> {
+    @BeforeTemplate
+    T before(Collection<T> collection, Comparator<S> cmp) {
+      return collection.stream().min(cmp).orElseThrow();
+    }
+
+    @AfterTemplate
+    T after(Collection<T> collection, Comparator<S> cmp) {
+      return Collections.min(collection, cmp);
+    }
+  }
+
+  /**
+   * Avoid unnecessary creation of a {@link Stream} to determine the minimum of a known collection
+   * of values.
+   */
+  static final class MinOfVarargs<S, T extends S> {
+    @BeforeTemplate
+    T before(@Repeated T value, Comparator<S> cmp) {
       return Stream.of(Refaster.asVarargs(value)).min(cmp).orElseThrow();
     }
 
     @AfterTemplate
-    T after(@Repeated T value, Comparator<T> cmp) {
+    T after(@Repeated T value, Comparator<S> cmp) {
       return Collections.min(Arrays.asList(value), cmp);
     }
   }
@@ -310,18 +371,64 @@ final class ComparatorRules {
     }
   }
 
+  /** Prefer {@link Collections#max(Collection)} over more verbose alternatives. */
+  static final class CollectionsMax<T extends Comparable<? super T>> {
+    @BeforeTemplate
+    T before(Collection<T> collection) {
+      return Refaster.anyOf(
+          Collections.max(collection, naturalOrder()), Collections.min(collection, reverseOrder()));
+    }
+
+    @AfterTemplate
+    T after(Collection<T> collection) {
+      return Collections.max(collection);
+    }
+  }
+
   /**
    * Avoid unnecessary creation of a {@link Stream} to determine the maximum of a known collection
    * of values.
    */
-  static final class MaxOfVarargs<T> {
+  static final class MaxOfArray<S, T extends S> {
     @BeforeTemplate
-    T before(@Repeated T value, Comparator<T> cmp) {
+    T before(T[] array, Comparator<S> cmp) {
+      return Arrays.stream(array).max(cmp).orElseThrow();
+    }
+
+    @AfterTemplate
+    T after(T[] array, Comparator<S> cmp) {
+      return Collections.max(Arrays.asList(array), cmp);
+    }
+  }
+
+  /**
+   * Avoid unnecessary creation of a {@link Stream} to determine the maximum of a known collection
+   * of values.
+   */
+  static final class CollectionsMaxWithComparator<S, T extends S> {
+    @BeforeTemplate
+    T before(Collection<T> collection, Comparator<S> cmp) {
+      return collection.stream().max(cmp).orElseThrow();
+    }
+
+    @AfterTemplate
+    T after(Collection<T> collection, Comparator<S> cmp) {
+      return Collections.max(collection, cmp);
+    }
+  }
+
+  /**
+   * Avoid unnecessary creation of a {@link Stream} to determine the maximum of a known collection
+   * of values.
+   */
+  static final class MaxOfVarargs<S, T extends S> {
+    @BeforeTemplate
+    T before(@Repeated T value, Comparator<S> cmp) {
       return Stream.of(Refaster.asVarargs(value)).max(cmp).orElseThrow();
     }
 
     @AfterTemplate
-    T after(@Repeated T value, Comparator<T> cmp) {
+    T after(@Repeated T value, Comparator<S> cmp) {
       return Collections.max(Arrays.asList(value), cmp);
     }
   }

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

@@ -2,12 +2,18 @@ package tech.picnic.errorprone.refasterrules;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
 
+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.Repeated;
+import java.io.File;
 import java.io.IOException;
+import java.net.URI;
 import java.nio.charset.Charset;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.nio.file.attribute.FileAttribute;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 
 /** Refaster rules related to expressions dealing with files. */
@@ -15,6 +21,49 @@ import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
 final class FileRules {
   private FileRules() {}
 
+  /** Prefer the more idiomatic {@link Path#of(URI)} over {@link Paths#get(URI)}. */
+  static final class PathOfUri {
+    @BeforeTemplate
+    Path before(URI uri) {
+      return Paths.get(uri);
+    }
+
+    @AfterTemplate
+    Path after(URI uri) {
+      return Path.of(uri);
+    }
+  }
+
+  /**
+   * Prefer the more idiomatic {@link Path#of(String, String...)} over {@link Paths#get(String,
+   * String...)}.
+   */
+  static final class PathOfString {
+    @BeforeTemplate
+    Path before(String first, @Repeated String more) {
+      return Paths.get(first, more);
+    }
+
+    @AfterTemplate
+    Path after(String first, @Repeated String more) {
+      return Path.of(first, more);
+    }
+  }
+
+  /** Avoid redundant conversions from {@link Path} to {@link File}. */
+  // XXX: Review whether a rule such as this one is better handled by the `IdentityConversion` rule.
+  static final class PathInstance {
+    @BeforeTemplate
+    Path before(Path path) {
+      return path.toFile().toPath();
+    }
+
+    @AfterTemplate
+    Path after(Path path) {
+      return path;
+    }
+  }
+
   /** Prefer {@link Files#readString(Path, Charset)} over more contrived alternatives. */
   static final class FilesReadStringWithCharset {
     @BeforeTemplate
@@ -40,4 +89,44 @@ final class FileRules {
       return Files.readString(path);
     }
   }
+
+  /**
+   * Prefer {@link Files#createTempFile(String, String, FileAttribute[])} over alternatives that
+   * create files with more liberal permissions.
+   */
+  static final class FilesCreateTempFileToFile {
+    @BeforeTemplate
+    @SuppressWarnings({
+      "FilesCreateTempFileInCustomDirectoryToFile" /* This is a more specific template. */,
+      "java:S5443" /* This violation will be rewritten. */,
+      "key-to-resolve-AnnotationUseStyle-and-TrailingComment-check-conflict"
+    })
+    File before(String prefix, String suffix) throws IOException {
+      return Refaster.anyOf(
+          File.createTempFile(prefix, suffix), File.createTempFile(prefix, suffix, null));
+    }
+
+    @AfterTemplate
+    @SuppressWarnings(
+        "java:S5443" /* On POSIX systems the file will only have user read-write permissions. */)
+    File after(String prefix, String suffix) throws IOException {
+      return Files.createTempFile(prefix, suffix).toFile();
+    }
+  }
+
+  /**
+   * Prefer {@link Files#createTempFile(Path, String, String, FileAttribute[])} over alternatives
+   * that create files with more liberal permissions.
+   */
+  static final class FilesCreateTempFileInCustomDirectoryToFile {
+    @BeforeTemplate
+    File before(File directory, String prefix, String suffix) throws IOException {
+      return File.createTempFile(prefix, suffix, directory);
+    }
+
+    @AfterTemplate
+    File after(File directory, String prefix, String suffix) throws IOException {
+      return Files.createTempFile(directory.toPath(), prefix, suffix).toFile();
+    }
+  }
 }

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

@@ -20,7 +20,7 @@ import java.util.function.Supplier;
 import java.util.stream.Stream;
 import org.jspecify.annotations.Nullable;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
-import tech.picnic.errorprone.refaster.matchers.IsLikelyTrivialComputation;
+import tech.picnic.errorprone.refaster.matchers.RequiresComputation;
 
 /** Refaster rules related to expressions dealing with {@link Optional}s. */
 @OnlineDocumentation
@@ -255,24 +255,21 @@ final class OptionalRules {
   }
 
   /**
-   * Prefer {@link Optional#orElseGet(Supplier)} over {@link Optional#orElse(Object)} if the
-   * fallback value is not the result of a trivial computation.
+   * Prefer {@link Optional#orElse(Object)} over {@link Optional#orElseGet(Supplier)} if the
+   * fallback value does not require non-trivial computation.
    */
-  // XXX: This rule may introduce a compilation error: the `value` expression may reference a
-  // non-effectively final variable, which is not allowed in the replacement lambda expression.
-  // Review whether a `@Matcher` can be used to avoid this.
-  // XXX: Once `MethodReferenceUsage` is "production ready", replace
-  // `@NotMatches(IsLikelyTrivialComputation.class)` with `@Matches(RequiresComputation.class)` (and
-  // reimplement the matcher accordingly).
-  static final class OptionalOrElseGet<T> {
+  // XXX: This rule is the counterpart to the `OptionalOrElseGet` bug checker. Once the
+  // `MethodReferenceUsage` bug checker is "production ready", that bug checker may similarly be
+  // replaced with a Refaster rule.
+  static final class OptionalOrElse<T> {
     @BeforeTemplate
-    T before(Optional<T> optional, @NotMatches(IsLikelyTrivialComputation.class) T value) {
-      return optional.orElse(value);
+    T before(Optional<T> optional, @NotMatches(RequiresComputation.class) T value) {
+      return optional.orElseGet(() -> value);
     }
 
     @AfterTemplate
     T after(Optional<T> optional, T value) {
-      return optional.orElseGet(() -> value);
+      return optional.orElse(value);
     }
   }
 
@@ -373,7 +370,12 @@ final class OptionalRules {
   /** Prefer {@link Optional#or(Supplier)} over more verbose alternatives. */
   static final class OptionalOrOtherOptional<T> {
     @BeforeTemplate
-    @SuppressWarnings("NestedOptionals")
+    @SuppressWarnings({
+      "LexicographicalAnnotationAttributeListing" /* `key-*` entry must remain last. */,
+      "NestedOptionals" /* This violation will be rewritten. */,
+      "OptionalOrElse" /* Parameters represent expressions that may require computation. */,
+      "key-to-resolve-AnnotationUseStyle-and-TrailingComment-check-conflict"
+    })
     Optional<T> before(Optional<T> optional1, Optional<T> optional2) {
       // XXX: Note that rewriting the first and third variant will change the code's behavior if
       // `optional2` has side-effects.

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

@@ -8,6 +8,8 @@ import com.google.common.primitives.Floats;
 import com.google.common.primitives.Ints;
 import com.google.common.primitives.Longs;
 import com.google.common.primitives.Shorts;
+import com.google.common.primitives.UnsignedInts;
+import com.google.common.primitives.UnsignedLongs;
 import com.google.errorprone.refaster.Refaster;
 import com.google.errorprone.refaster.annotation.AfterTemplate;
 import com.google.errorprone.refaster.annotation.AlsoNegation;
@@ -76,6 +78,8 @@ final class PrimitiveRules {
   }
 
   /** Prefer {@link Math#toIntExact(long)} over the Guava alternative. */
+  // XXX: This rule changes the exception possibly thrown from `IllegalArgumentException` to
+  // `ArithmeticException`.
   static final class LongToIntExact {
     @BeforeTemplate
     int before(long l) {
@@ -192,72 +196,8 @@ final class PrimitiveRules {
     }
   }
 
-  /** Prefer {@link Boolean#compare(boolean, boolean)} over the Guava alternative. */
-  static final class BooleanCompare {
-    @BeforeTemplate
-    int before(boolean a, boolean b) {
-      return Booleans.compare(a, b);
-    }
-
-    @AfterTemplate
-    int after(boolean a, boolean b) {
-      return Boolean.compare(a, b);
-    }
-  }
-
-  /** Prefer {@link Character#compare(char, char)} over the Guava alternative. */
-  static final class CharacterCompare {
-    @BeforeTemplate
-    int before(char a, char b) {
-      return Chars.compare(a, b);
-    }
-
-    @AfterTemplate
-    int after(char a, char b) {
-      return Character.compare(a, b);
-    }
-  }
-
-  /** Prefer {@link Short#compare(short, short)} over the Guava alternative. */
-  static final class ShortCompare {
-    @BeforeTemplate
-    int before(short a, short b) {
-      return Shorts.compare(a, b);
-    }
-
-    @AfterTemplate
-    int after(short a, short b) {
-      return Short.compare(a, b);
-    }
-  }
-
-  /** Prefer {@link Integer#compare(int, int)} over the Guava alternative. */
-  static final class IntegerCompare {
-    @BeforeTemplate
-    int before(int a, int b) {
-      return Ints.compare(a, b);
-    }
-
-    @AfterTemplate
-    int after(int a, int b) {
-      return Integer.compare(a, b);
-    }
-  }
-
-  /** Prefer {@link Long#compare(long, long)} over the Guava alternative. */
-  static final class LongCompare {
-    @BeforeTemplate
-    int before(long a, long b) {
-      return Longs.compare(a, b);
-    }
-
-    @AfterTemplate
-    int after(long a, long b) {
-      return Long.compare(a, b);
-    }
-  }
-
   /** Prefer {@link Float#compare(float, float)} over the Guava alternative. */
+  // XXX: Drop this rule once https://github.com/google/guava/pull/7371 is released.
   static final class FloatCompare {
     @BeforeTemplate
     int before(float a, float b) {
@@ -271,6 +211,7 @@ final class PrimitiveRules {
   }
 
   /** Prefer {@link Double#compare(double, double)} over the Guava alternative. */
+  // XXX: Drop this rule once https://github.com/google/guava/pull/7371 is released.
   static final class DoubleCompare {
     @BeforeTemplate
     int before(double a, double b) {
@@ -442,4 +383,205 @@ final class PrimitiveRules {
       return Long.signum(l) == -1;
     }
   }
+
+  /** Prefer JDK's {@link Integer#compareUnsigned(int, int)} over third-party alternatives. */
+  static final class IntegerCompareUnsigned {
+    @BeforeTemplate
+    int before(int x, int y) {
+      return UnsignedInts.compare(x, y);
+    }
+
+    @AfterTemplate
+    int after(int x, int y) {
+      return Integer.compareUnsigned(x, y);
+    }
+  }
+
+  /** Prefer JDK's {@link Long#compareUnsigned(long, long)} over third-party alternatives. */
+  static final class LongCompareUnsigned {
+    @BeforeTemplate
+    long before(long x, long y) {
+      return UnsignedLongs.compare(x, y);
+    }
+
+    @AfterTemplate
+    long after(long x, long y) {
+      return Long.compareUnsigned(x, y);
+    }
+  }
+
+  /** Prefer JDK's {@link Integer#divideUnsigned(int, int)} over third-party alternatives. */
+  static final class IntegerDivideUnsigned {
+    @BeforeTemplate
+    int before(int x, int y) {
+      return UnsignedInts.divide(x, y);
+    }
+
+    @AfterTemplate
+    int after(int x, int y) {
+      return Integer.divideUnsigned(x, y);
+    }
+  }
+
+  /** Prefer JDK's {@link Long#divideUnsigned(long, long)} over third-party alternatives. */
+  static final class LongDivideUnsigned {
+    @BeforeTemplate
+    long before(long x, long y) {
+      return UnsignedLongs.divide(x, y);
+    }
+
+    @AfterTemplate
+    long after(long x, long y) {
+      return Long.divideUnsigned(x, y);
+    }
+  }
+
+  /** Prefer JDK's {@link Integer#remainderUnsigned(int, int)} over third-party alternatives. */
+  static final class IntegerRemainderUnsigned {
+    @BeforeTemplate
+    int before(int x, int y) {
+      return UnsignedInts.remainder(x, y);
+    }
+
+    @AfterTemplate
+    int after(int x, int y) {
+      return Integer.remainderUnsigned(x, y);
+    }
+  }
+
+  /** Prefer JDK's {@link Long#remainderUnsigned(long, long)} over third-party alternatives. */
+  static final class LongRemainderUnsigned {
+    @BeforeTemplate
+    long before(long x, long y) {
+      return UnsignedLongs.remainder(x, y);
+    }
+
+    @AfterTemplate
+    long after(long x, long y) {
+      return Long.remainderUnsigned(x, y);
+    }
+  }
+
+  /**
+   * Prefer JDK's {@link Integer#parseUnsignedInt(String)} over third-party or more verbose
+   * alternatives.
+   */
+  static final class IntegerParseUnsignedInt {
+    @BeforeTemplate
+    int before(String string) {
+      return Refaster.anyOf(
+          UnsignedInts.parseUnsignedInt(string), Integer.parseUnsignedInt(string, 10));
+    }
+
+    @AfterTemplate
+    int after(String string) {
+      return Integer.parseUnsignedInt(string);
+    }
+  }
+
+  /**
+   * Prefer JDK's {@link Long#parseUnsignedLong(String)} over third-party or more verbose
+   * alternatives.
+   */
+  static final class LongParseUnsignedLong {
+    @BeforeTemplate
+    long before(String string) {
+      return Refaster.anyOf(
+          UnsignedLongs.parseUnsignedLong(string), Long.parseUnsignedLong(string, 10));
+    }
+
+    @AfterTemplate
+    long after(String string) {
+      return Long.parseUnsignedLong(string);
+    }
+  }
+
+  /** Prefer JDK's {@link Integer#parseUnsignedInt(String, int)} over third-party alternatives. */
+  static final class IntegerParseUnsignedIntWithRadix {
+    @BeforeTemplate
+    int before(String string, int radix) {
+      return UnsignedInts.parseUnsignedInt(string, radix);
+    }
+
+    @AfterTemplate
+    int after(String string, int radix) {
+      return Integer.parseUnsignedInt(string, radix);
+    }
+  }
+
+  /** Prefer JDK's {@link Long#parseUnsignedLong(String, int)} over third-party alternatives. */
+  static final class LongParseUnsignedLongWithRadix {
+    @BeforeTemplate
+    long before(String string, int radix) {
+      return UnsignedLongs.parseUnsignedLong(string, radix);
+    }
+
+    @AfterTemplate
+    long after(String string, int radix) {
+      return Long.parseUnsignedLong(string, radix);
+    }
+  }
+
+  /**
+   * Prefer JDK's {@link Integer#toUnsignedString(int)} over third-party or more verbose
+   * alternatives.
+   */
+  static final class IntegerToUnsignedString {
+    @BeforeTemplate
+    String before(int i) {
+      return Refaster.anyOf(UnsignedInts.toString(i), Integer.toUnsignedString(i, 10));
+    }
+
+    @AfterTemplate
+    String after(int i) {
+      return Integer.toUnsignedString(i);
+    }
+  }
+
+  /**
+   * Prefer JDK's {@link Long#toUnsignedString(long)} over third-party or more verbose alternatives.
+   */
+  static final class LongToUnsignedString {
+    @BeforeTemplate
+    String before(long i) {
+      return Refaster.anyOf(UnsignedLongs.toString(i), Long.toUnsignedString(i, 10));
+    }
+
+    @AfterTemplate
+    String after(long i) {
+      return Long.toUnsignedString(i);
+    }
+  }
+
+  /**
+   * Prefer JDK's {@link Integer#toUnsignedString(int,int)} over third-party or more verbose
+   * alternatives.
+   */
+  static final class IntegerToUnsignedStringWithRadix {
+    @BeforeTemplate
+    String before(int i, int radix) {
+      return UnsignedInts.toString(i, radix);
+    }
+
+    @AfterTemplate
+    String after(int i, int radix) {
+      return Integer.toUnsignedString(i, radix);
+    }
+  }
+
+  /**
+   * Prefer JDK's {@link Long#toUnsignedString(long,int)} over third-party or more verbose
+   * alternatives.
+   */
+  static final class LongToUnsignedStringWithRadix {
+    @BeforeTemplate
+    String before(long i, int radix) {
+      return UnsignedLongs.toString(i, radix);
+    }
+
+    @AfterTemplate
+    String after(long i, int radix) {
+      return Long.toUnsignedString(i, radix);
+    }
+  }
 }

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

@@ -13,6 +13,7 @@ import static java.util.stream.Collectors.toCollection;
 import static org.assertj.core.api.Assertions.assertThat;
 import static reactor.function.TupleUtils.function;
 
+import com.github.benmanes.caffeine.cache.AsyncLoadingCache;
 import com.google.common.collect.ImmutableCollection;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
@@ -41,6 +42,7 @@ import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
 import java.util.stream.Collector;
+import java.util.stream.Stream;
 import org.jspecify.annotations.Nullable;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
@@ -1204,10 +1206,17 @@ final class ReactorRules {
   }
 
   /** Prefer {@link Flux#fromIterable(Iterable)} over less efficient alternatives. */
+  // XXX: Once the `FluxFromStreamSupplier` rule is constrained using
+  // `@NotMatches(IsIdentityOperation.class)`, this rule should also cover
+  // `Flux.fromStream(collection.stream())`.
   static final class FluxFromIterable<T> {
+    // XXX: Once the `MethodReferenceUsage` check is generally enabled, drop the second
+    // `Refaster.anyOf` variant.
     @BeforeTemplate
     Flux<T> before(Collection<T> collection) {
-      return Flux.fromStream(collection.stream());
+      return Flux.fromStream(
+          Refaster.<Supplier<Stream<? extends T>>>anyOf(
+              collection::stream, () -> collection.stream()));
     }
 
     @AfterTemplate
@@ -1913,7 +1922,7 @@ final class ReactorRules {
 
   /**
    * Prefer {@link Mono#fromFuture(Supplier)} over {@link Mono#fromFuture(CompletableFuture)}, as
-   * the former may defer initiation of the asynchornous computation until subscription.
+   * the former may defer initiation of the asynchronous computation until subscription.
    */
   static final class MonoFromFutureSupplier<T> {
     // XXX: Constrain the `future` parameter using `@NotMatches(IsIdentityOperation.class)` once
@@ -1932,7 +1941,7 @@ final class ReactorRules {
   /**
    * Prefer {@link Mono#fromFuture(Supplier, boolean)} over {@link
    * Mono#fromFuture(CompletableFuture, boolean)}, as the former may defer initiation of the
-   * asynchornous computation until subscription.
+   * asynchronous computation until subscription.
    */
   static final class MonoFromFutureSupplierBoolean<T> {
     // XXX: Constrain the `future` parameter using `@NotMatches(IsIdentityOperation.class)` once
@@ -1947,4 +1956,39 @@ final class ReactorRules {
       return Mono.fromFuture(() -> future, suppressCancel);
     }
   }
+
+  /**
+   * Don't propagate {@link Mono} cancellations to an upstream cache value computation, as
+   * completion of such computations may benefit concurrent or subsequent cache usages.
+   */
+  static final class MonoFromFutureAsyncLoadingCacheGet<K, V> {
+    @BeforeTemplate
+    Mono<V> before(AsyncLoadingCache<K, V> cache, K key) {
+      return Mono.fromFuture(() -> cache.get(key));
+    }
+
+    @AfterTemplate
+    Mono<V> after(AsyncLoadingCache<K, V> cache, K key) {
+      return Mono.fromFuture(() -> cache.get(key), /* suppressCancel= */ true);
+    }
+  }
+
+  /**
+   * Prefer {@link Flux#fromStream(Supplier)} over {@link Flux#fromStream(Stream)}, as the former
+   * yields a {@link Flux} that is more likely to behave as expected when subscribed to more than
+   * once.
+   */
+  static final class FluxFromStreamSupplier<T> {
+    // XXX: Constrain the `stream` parameter using `@NotMatches(IsIdentityOperation.class)` once
+    // `IsIdentityOperation` no longer matches nullary method invocations.
+    @BeforeTemplate
+    Flux<T> before(Stream<T> stream) {
+      return Flux.fromStream(stream);
+    }
+
+    @AfterTemplate
+    Flux<T> after(Stream<T> stream) {
+      return Flux.fromStream(() -> stream);
+    }
+  }
 }

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

@@ -5,14 +5,15 @@ import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
 import com.google.errorprone.CompilationTestHelper;
 import org.junit.jupiter.api.Test;
 
-final class OptionalOrElseTest {
+final class OptionalOrElseGetTest {
   @Test
   void identification() {
-    CompilationTestHelper.newInstance(OptionalOrElse.class, getClass())
+    CompilationTestHelper.newInstance(OptionalOrElseGet.class, getClass())
         .addSourceLines(
             "A.java",
             "import com.google.errorprone.refaster.Refaster;",
             "import java.util.Optional;",
+            "import java.util.function.Supplier;",
             "",
             "class A {",
             "  private final Optional<Object> optional = Optional.empty();",
@@ -27,6 +28,7 @@ final class OptionalOrElseTest {
             "    optional.orElse(string);",
             "    optional.orElse(this.string);",
             "    optional.orElse(Refaster.anyOf(\"constant\", \"another\"));",
+            "    Optional.<Supplier<String>>empty().orElse(() -> \"constant\");",
             "",
             "    // BUG: Diagnostic contains:",
             "    Optional.empty().orElse(string + \"constant\");",
@@ -67,7 +69,7 @@ final class OptionalOrElseTest {
 
   @Test
   void replacement() {
-    BugCheckerRefactoringTestHelper.newInstance(OptionalOrElse.class, getClass())
+    BugCheckerRefactoringTestHelper.newInstance(OptionalOrElseGet.class, getClass())
         .addInputLines(
             "A.java",
             "import java.util.Optional;",

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

@@ -1,26 +1,34 @@
 package tech.picnic.errorprone.refasterrules;
 
 import com.google.common.collect.ImmutableSet;
-import java.io.IOException;
+import java.util.function.Function;
 import java.util.function.Predicate;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
 final class ClassRulesTest implements RefasterRuleCollectionTestCase {
-  boolean testClassIsInstance() throws IOException {
+  boolean testClassIsInstance() {
     return CharSequence.class.isAssignableFrom("foo".getClass());
   }
 
-  ImmutableSet<Boolean> testInstanceof() throws IOException {
+  ImmutableSet<Boolean> testInstanceof() {
     Class<?> clazz = CharSequence.class;
     return ImmutableSet.of(CharSequence.class.isInstance("foo"), clazz.isInstance("bar"));
   }
 
-  Predicate<String> testClassLiteralIsInstancePredicate() throws IOException {
+  Predicate<String> testClassLiteralIsInstancePredicate() {
     return s -> s instanceof CharSequence;
   }
 
-  Predicate<String> testClassReferenceIsInstancePredicate() throws IOException {
+  Predicate<String> testClassReferenceIsInstancePredicate() {
     Class<?> clazz = CharSequence.class;
     return s -> clazz.isInstance(s);
   }
+
+  Function<Number, Integer> testClassLiteralCast() {
+    return i -> (Integer) i;
+  }
+
+  Function<Number, Integer> testClassReferenceCast() {
+    return i -> Integer.class.cast(i);
+  }
 }

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

@@ -1,26 +1,34 @@
 package tech.picnic.errorprone.refasterrules;
 
 import com.google.common.collect.ImmutableSet;
-import java.io.IOException;
+import java.util.function.Function;
 import java.util.function.Predicate;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
 final class ClassRulesTest implements RefasterRuleCollectionTestCase {
-  boolean testClassIsInstance() throws IOException {
+  boolean testClassIsInstance() {
     return CharSequence.class.isInstance("foo");
   }
 
-  ImmutableSet<Boolean> testInstanceof() throws IOException {
+  ImmutableSet<Boolean> testInstanceof() {
     Class<?> clazz = CharSequence.class;
     return ImmutableSet.of("foo" instanceof CharSequence, clazz.isInstance("bar"));
   }
 
-  Predicate<String> testClassLiteralIsInstancePredicate() throws IOException {
+  Predicate<String> testClassLiteralIsInstancePredicate() {
     return CharSequence.class::isInstance;
   }
 
-  Predicate<String> testClassReferenceIsInstancePredicate() throws IOException {
+  Predicate<String> testClassReferenceIsInstancePredicate() {
     Class<?> clazz = CharSequence.class;
     return clazz::isInstance;
   }
+
+  Function<Number, Integer> testClassLiteralCast() {
+    return Integer.class::cast;
+  }
+
+  Function<Number, Integer> testClassReferenceCast() {
+    return Integer.class::cast;
+  }
 }

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

@@ -6,9 +6,11 @@ import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.LinkedList;
+import java.util.List;
 import java.util.Optional;
 import java.util.TreeSet;
 import java.util.stream.Stream;
@@ -70,6 +72,10 @@ final class CollectionRulesTest implements RefasterRuleCollectionTestCase {
     }
   }
 
+  Stream<Integer> testSetStream() {
+    return ImmutableSet.of(1).stream().distinct();
+  }
+
   ArrayList<String> testNewArrayListFromCollection() {
     return Lists.newArrayList(ImmutableList.of("foo"));
   }
@@ -94,6 +100,10 @@ final class CollectionRulesTest implements RefasterRuleCollectionTestCase {
     return ImmutableSet.of(1).asList().toString();
   }
 
+  List<String> testArraysAsList() {
+    return Arrays.stream(new String[0]).toList();
+  }
+
   ImmutableSet<Object[]> testCollectionToArray() {
     return ImmutableSet.of(
         ImmutableSet.of(1).toArray(new Object[1]),

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

@@ -6,9 +6,11 @@ import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.LinkedList;
+import java.util.List;
 import java.util.Optional;
 import java.util.TreeSet;
 import java.util.stream.Stream;
@@ -62,6 +64,10 @@ final class CollectionRulesTest implements RefasterRuleCollectionTestCase {
     new HashSet<Number>().removeAll(ImmutableSet.of(2));
   }
 
+  Stream<Integer> testSetStream() {
+    return ImmutableSet.of(1).stream();
+  }
+
   ArrayList<String> testNewArrayListFromCollection() {
     return new ArrayList<>(ImmutableList.of("foo"));
   }
@@ -86,6 +92,10 @@ final class CollectionRulesTest implements RefasterRuleCollectionTestCase {
     return ImmutableSet.of(1).toString();
   }
 
+  List<String> testArraysAsList() {
+    return Arrays.asList(new String[0]);
+  }
+
   ImmutableSet<Object[]> testCollectionToArray() {
     return ImmutableSet.of(
         ImmutableSet.of(1).toArray(), ImmutableSet.of(2).toArray(), ImmutableSet.of(3).toArray());

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

@@ -107,6 +107,24 @@ final class ComparatorRulesTest implements RefasterRuleCollectionTestCase {
         Comparator.<String>reverseOrder().compare("baz", "qux"));
   }
 
+  void testCollectionsSort() {
+    Collections.sort(ImmutableList.of("foo", "bar"), naturalOrder());
+  }
+
+  ImmutableSet<String> testCollectionsMin() {
+    return ImmutableSet.of(
+        Collections.min(ImmutableList.of("foo"), naturalOrder()),
+        Collections.max(ImmutableList.of("bar"), reverseOrder()));
+  }
+
+  String testMinOfArray() {
+    return Arrays.stream(new String[0]).min(naturalOrder()).orElseThrow();
+  }
+
+  String testCollectionsMinWithComparator() {
+    return ImmutableSet.of("foo", "bar").stream().min(naturalOrder()).orElseThrow();
+  }
+
   int testMinOfVarargs() {
     return Stream.of(1, 2).min(naturalOrder()).orElseThrow();
   }
@@ -135,6 +153,20 @@ final class ComparatorRulesTest implements RefasterRuleCollectionTestCase {
         Collections.min(ImmutableSet.of("a", "b"), (a, b) -> 1));
   }
 
+  ImmutableSet<String> testCollectionsMax() {
+    return ImmutableSet.of(
+        Collections.max(ImmutableList.of("foo"), naturalOrder()),
+        Collections.min(ImmutableList.of("bar"), reverseOrder()));
+  }
+
+  String testMaxOfArray() {
+    return Arrays.stream(new String[0]).max(naturalOrder()).orElseThrow();
+  }
+
+  String testCollectionsMaxWithComparator() {
+    return ImmutableSet.of("foo", "bar").stream().max(naturalOrder()).orElseThrow();
+  }
+
   int testMaxOfVarargs() {
     return Stream.of(1, 2).max(naturalOrder()).orElseThrow();
   }

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

@@ -98,6 +98,23 @@ final class ComparatorRulesTest implements RefasterRuleCollectionTestCase {
     return ImmutableSet.of("foo".compareTo("bar"), "qux".compareTo("baz"));
   }
 
+  void testCollectionsSort() {
+    Collections.sort(ImmutableList.of("foo", "bar"));
+  }
+
+  ImmutableSet<String> testCollectionsMin() {
+    return ImmutableSet.of(
+        Collections.min(ImmutableList.of("foo")), Collections.min(ImmutableList.of("bar")));
+  }
+
+  String testMinOfArray() {
+    return Collections.min(Arrays.asList(new String[0]), naturalOrder());
+  }
+
+  String testCollectionsMinWithComparator() {
+    return Collections.min(ImmutableSet.of("foo", "bar"), naturalOrder());
+  }
+
   int testMinOfVarargs() {
     return Collections.min(Arrays.asList(1, 2), naturalOrder());
   }
@@ -126,6 +143,19 @@ final class ComparatorRulesTest implements RefasterRuleCollectionTestCase {
         Comparators.min("a", "b", (a, b) -> 1));
   }
 
+  ImmutableSet<String> testCollectionsMax() {
+    return ImmutableSet.of(
+        Collections.max(ImmutableList.of("foo")), Collections.max(ImmutableList.of("bar")));
+  }
+
+  String testMaxOfArray() {
+    return Collections.max(Arrays.asList(new String[0]), naturalOrder());
+  }
+
+  String testCollectionsMaxWithComparator() {
+    return Collections.max(ImmutableSet.of("foo", "bar"), naturalOrder());
+  }
+
   int testMaxOfVarargs() {
     return Collections.max(Arrays.asList(1, 2), naturalOrder());
   }

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

@@ -1,12 +1,28 @@
 package tech.picnic.errorprone.refasterrules;
 
+import com.google.common.collect.ImmutableSet;
+import java.io.File;
 import java.io.IOException;
+import java.net.URI;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
+import java.nio.file.Path;
 import java.nio.file.Paths;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
 final class FileRulesTest implements RefasterRuleCollectionTestCase {
+  Path testPathOfUri() {
+    return Paths.get(URI.create("foo"));
+  }
+
+  ImmutableSet<Path> testPathOfString() {
+    return ImmutableSet.of(Paths.get("foo"), Paths.get("bar", "baz", "qux"));
+  }
+
+  Path testPathInstance() {
+    return Path.of("foo").toFile().toPath();
+  }
+
   String testFilesReadStringWithCharset() throws IOException {
     return new String(Files.readAllBytes(Paths.get("foo")), StandardCharsets.ISO_8859_1);
   }
@@ -14,4 +30,13 @@ final class FileRulesTest implements RefasterRuleCollectionTestCase {
   String testFilesReadString() throws IOException {
     return Files.readString(Paths.get("foo"), StandardCharsets.UTF_8);
   }
+
+  ImmutableSet<File> testFilesCreateTempFileToFile() throws IOException {
+    return ImmutableSet.of(
+        File.createTempFile("foo", "bar"), File.createTempFile("baz", "qux", null));
+  }
+
+  File testFilesCreateTempFileInCustomDirectoryToFile() throws IOException {
+    return File.createTempFile("foo", "bar", new File("baz"));
+  }
 }

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

@@ -1,12 +1,28 @@
 package tech.picnic.errorprone.refasterrules;
 
+import com.google.common.collect.ImmutableSet;
+import java.io.File;
 import java.io.IOException;
+import java.net.URI;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
+import java.nio.file.Path;
 import java.nio.file.Paths;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
 final class FileRulesTest implements RefasterRuleCollectionTestCase {
+  Path testPathOfUri() {
+    return Path.of(URI.create("foo"));
+  }
+
+  ImmutableSet<Path> testPathOfString() {
+    return ImmutableSet.of(Path.of("foo"), Path.of("bar", "baz", "qux"));
+  }
+
+  Path testPathInstance() {
+    return Path.of("foo");
+  }
+
   String testFilesReadStringWithCharset() throws IOException {
     return Files.readString(Paths.get("foo"), StandardCharsets.ISO_8859_1);
   }
@@ -14,4 +30,13 @@ final class FileRulesTest implements RefasterRuleCollectionTestCase {
   String testFilesReadString() throws IOException {
     return Files.readString(Paths.get("foo"));
   }
+
+  ImmutableSet<File> testFilesCreateTempFileToFile() throws IOException {
+    return ImmutableSet.of(
+        Files.createTempFile("foo", "bar").toFile(), Files.createTempFile("baz", "qux").toFile());
+  }
+
+  File testFilesCreateTempFileInCustomDirectoryToFile() throws IOException {
+    return Files.createTempFile(new File("baz").toPath(), "foo", "bar").toFile();
+  }
 }

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

@@ -26,6 +26,7 @@ final class ImmutableMultisetRulesTest implements RefasterRuleCollectionTestCase
         Stream.<Integer>empty().collect(toImmutableMultiset()));
   }
 
+  @SuppressWarnings("unchecked")
   ImmutableMultiset<ImmutableMultiset<Integer>> testIterableToImmutableMultiset() {
     return ImmutableMultiset.of(
         ImmutableList.of(1).stream().collect(toImmutableMultiset()),

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

@@ -24,6 +24,7 @@ final class ImmutableMultisetRulesTest implements RefasterRuleCollectionTestCase
     return ImmutableMultiset.of(ImmutableMultiset.of(), ImmutableMultiset.of());
   }
 
+  @SuppressWarnings("unchecked")
   ImmutableMultiset<ImmutableMultiset<Integer>> testIterableToImmutableMultiset() {
     return ImmutableMultiset.of(
         ImmutableMultiset.copyOf(ImmutableList.of(1)),

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

@@ -37,6 +37,7 @@ final class ImmutableSortedMultisetRulesTest implements RefasterRuleCollectionTe
         Stream.<Integer>empty().collect(toImmutableSortedMultiset(naturalOrder())));
   }
 
+  @SuppressWarnings("unchecked")
   ImmutableMultiset<ImmutableSortedMultiset<Integer>> testIterableToImmutableSortedMultiset() {
     return ImmutableMultiset.of(
         ImmutableSortedMultiset.copyOf(naturalOrder(), ImmutableList.of(1)),

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

@@ -35,6 +35,7 @@ final class ImmutableSortedMultisetRulesTest implements RefasterRuleCollectionTe
     return ImmutableMultiset.of(ImmutableSortedMultiset.of(), ImmutableSortedMultiset.of());
   }
 
+  @SuppressWarnings("unchecked")
   ImmutableMultiset<ImmutableSortedMultiset<Integer>> testIterableToImmutableSortedMultiset() {
     return ImmutableMultiset.of(
         ImmutableSortedMultiset.copyOf(ImmutableList.of(1)),

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

@@ -83,11 +83,9 @@ final class OptionalRulesTest implements RefasterRuleCollectionTestCase {
     return Optional.of("foo").orElseGet(() -> Optional.of("bar").orElseThrow());
   }
 
-  ImmutableSet<String> testOptionalOrElseGet() {
+  ImmutableSet<String> testOptionalOrElse() {
     return ImmutableSet.of(
-        Optional.of("foo").orElse("bar"),
-        Optional.of("baz").orElse(toString()),
-        Optional.of("qux").orElse(String.valueOf(true)));
+        Optional.of("foo").orElseGet(() -> "bar"), Optional.of("baz").orElseGet(() -> toString()));
   }
 
   ImmutableSet<Object> testStreamFlatMapOptional() {

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

@@ -80,11 +80,9 @@ final class OptionalRulesTest implements RefasterRuleCollectionTestCase {
     return Optional.of("foo").or(() -> Optional.of("bar")).orElseThrow();
   }
 
-  ImmutableSet<String> testOptionalOrElseGet() {
+  ImmutableSet<String> testOptionalOrElse() {
     return ImmutableSet.of(
-        Optional.of("foo").orElse("bar"),
-        Optional.of("baz").orElse(toString()),
-        Optional.of("qux").orElseGet(() -> String.valueOf(true)));
+        Optional.of("foo").orElse("bar"), Optional.of("baz").orElseGet(() -> toString()));
   }
 
   ImmutableSet<Object> testStreamFlatMapOptional() {

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

@@ -9,6 +9,8 @@ import com.google.common.primitives.Floats;
 import com.google.common.primitives.Ints;
 import com.google.common.primitives.Longs;
 import com.google.common.primitives.Shorts;
+import com.google.common.primitives.UnsignedInts;
+import com.google.common.primitives.UnsignedLongs;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
 final class PrimitiveRulesTest implements RefasterRuleCollectionTestCase {
@@ -22,7 +24,9 @@ final class PrimitiveRulesTest implements RefasterRuleCollectionTestCase {
         Floats.class,
         Ints.class,
         Longs.class,
-        Shorts.class);
+        Shorts.class,
+        UnsignedInts.class,
+        UnsignedLongs.class);
   }
 
   ImmutableSet<Boolean> testLessThan() {
@@ -105,26 +109,6 @@ final class PrimitiveRulesTest implements RefasterRuleCollectionTestCase {
     return Doubles.hashCode(1);
   }
 
-  int testBooleanCompare() {
-    return Booleans.compare(false, true);
-  }
-
-  int testCharacterCompare() {
-    return Chars.compare('a', 'b');
-  }
-
-  int testShortCompare() {
-    return Shorts.compare((short) 1, (short) 2);
-  }
-
-  int testIntegerCompare() {
-    return Ints.compare(1, 2);
-  }
-
-  int testLongCompare() {
-    return Longs.compare(1, 2);
-  }
-
   int testFloatCompare() {
     return Floats.compare(1, 2);
   }
@@ -190,4 +174,60 @@ final class PrimitiveRulesTest implements RefasterRuleCollectionTestCase {
     return ImmutableSet.of(
         Long.signum(1L) < 0, Long.signum(2L) <= -1, Long.signum(3L) >= 0, Long.signum(4L) > -1);
   }
+
+  int testIntegerCompareUnsigned() {
+    return UnsignedInts.compare(1, 2);
+  }
+
+  long testLongCompareUnsigned() {
+    return UnsignedLongs.compare(1, 2);
+  }
+
+  int testIntegerDivideUnsigned() {
+    return UnsignedInts.divide(1, 2);
+  }
+
+  long testLongDivideUnsigned() {
+    return UnsignedLongs.divide(1, 2);
+  }
+
+  int testIntegerRemainderUnsigned() {
+    return UnsignedInts.remainder(1, 2);
+  }
+
+  long testLongRemainderUnsigned() {
+    return UnsignedLongs.remainder(1, 2);
+  }
+
+  ImmutableSet<Integer> testIntegerParseUnsignedInt() {
+    return ImmutableSet.of(UnsignedInts.parseUnsignedInt("1"), Integer.parseUnsignedInt("2", 10));
+  }
+
+  ImmutableSet<Long> testLongParseUnsignedLong() {
+    return ImmutableSet.of(UnsignedLongs.parseUnsignedLong("1"), Long.parseUnsignedLong("2", 10));
+  }
+
+  int testIntegerParseUnsignedIntWithRadix() {
+    return UnsignedInts.parseUnsignedInt("1", 2);
+  }
+
+  long testLongParseUnsignedLongWithRadix() {
+    return UnsignedLongs.parseUnsignedLong("1", 2);
+  }
+
+  ImmutableSet<String> testIntegerToUnsignedString() {
+    return ImmutableSet.of(UnsignedInts.toString(1), Integer.toUnsignedString(2, 10));
+  }
+
+  ImmutableSet<String> testLongToUnsignedString() {
+    return ImmutableSet.of(UnsignedLongs.toString(1), Long.toUnsignedString(2, 10));
+  }
+
+  String testIntegerToUnsignedStringWithRadix() {
+    return UnsignedInts.toString(1, 2);
+  }
+
+  String testLongToUnsignedStringWithRadix() {
+    return UnsignedLongs.toString(1, 2);
+  }
 }

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

@@ -9,6 +9,8 @@ import com.google.common.primitives.Floats;
 import com.google.common.primitives.Ints;
 import com.google.common.primitives.Longs;
 import com.google.common.primitives.Shorts;
+import com.google.common.primitives.UnsignedInts;
+import com.google.common.primitives.UnsignedLongs;
 import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
 
 final class PrimitiveRulesTest implements RefasterRuleCollectionTestCase {
@@ -22,7 +24,9 @@ final class PrimitiveRulesTest implements RefasterRuleCollectionTestCase {
         Floats.class,
         Ints.class,
         Longs.class,
-        Shorts.class);
+        Shorts.class,
+        UnsignedInts.class,
+        UnsignedLongs.class);
   }
 
   ImmutableSet<Boolean> testLessThan() {
@@ -105,26 +109,6 @@ final class PrimitiveRulesTest implements RefasterRuleCollectionTestCase {
     return Double.hashCode(1);
   }
 
-  int testBooleanCompare() {
-    return Boolean.compare(false, true);
-  }
-
-  int testCharacterCompare() {
-    return Character.compare('a', 'b');
-  }
-
-  int testShortCompare() {
-    return Short.compare((short) 1, (short) 2);
-  }
-
-  int testIntegerCompare() {
-    return Integer.compare(1, 2);
-  }
-
-  int testLongCompare() {
-    return Long.compare(1, 2);
-  }
-
   int testFloatCompare() {
     return Float.compare(1, 2);
   }
@@ -190,4 +174,60 @@ final class PrimitiveRulesTest implements RefasterRuleCollectionTestCase {
     return ImmutableSet.of(
         Long.signum(1L) == -1, Long.signum(2L) == -1, Long.signum(3L) != -1, Long.signum(4L) != -1);
   }
+
+  int testIntegerCompareUnsigned() {
+    return Integer.compareUnsigned(1, 2);
+  }
+
+  long testLongCompareUnsigned() {
+    return Long.compareUnsigned(1, 2);
+  }
+
+  int testIntegerDivideUnsigned() {
+    return Integer.divideUnsigned(1, 2);
+  }
+
+  long testLongDivideUnsigned() {
+    return Long.divideUnsigned(1, 2);
+  }
+
+  int testIntegerRemainderUnsigned() {
+    return Integer.remainderUnsigned(1, 2);
+  }
+
+  long testLongRemainderUnsigned() {
+    return Long.remainderUnsigned(1, 2);
+  }
+
+  ImmutableSet<Integer> testIntegerParseUnsignedInt() {
+    return ImmutableSet.of(Integer.parseUnsignedInt("1"), Integer.parseUnsignedInt("2"));
+  }
+
+  ImmutableSet<Long> testLongParseUnsignedLong() {
+    return ImmutableSet.of(Long.parseUnsignedLong("1"), Long.parseUnsignedLong("2"));
+  }
+
+  int testIntegerParseUnsignedIntWithRadix() {
+    return Integer.parseUnsignedInt("1", 2);
+  }
+
+  long testLongParseUnsignedLongWithRadix() {
+    return Long.parseUnsignedLong("1", 2);
+  }
+
+  ImmutableSet<String> testIntegerToUnsignedString() {
+    return ImmutableSet.of(Integer.toUnsignedString(1), Integer.toUnsignedString(2));
+  }
+
+  ImmutableSet<String> testLongToUnsignedString() {
+    return ImmutableSet.of(Long.toUnsignedString(1), Long.toUnsignedString(2));
+  }
+
+  String testIntegerToUnsignedStringWithRadix() {
+    return Integer.toUnsignedString(1, 2);
+  }
+
+  String testLongToUnsignedStringWithRadix() {
+    return Long.toUnsignedString(1, 2);
+  }
 }

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

@@ -10,6 +10,7 @@ import static java.util.stream.Collectors.minBy;
 import static java.util.stream.Collectors.toCollection;
 import static org.assertj.core.api.Assertions.assertThat;
 
+import com.github.benmanes.caffeine.cache.AsyncLoadingCache;
 import com.google.common.collect.ImmutableCollection;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
@@ -23,6 +24,7 @@ import java.util.Optional;
 import java.util.concurrent.Callable;
 import java.util.concurrent.CompletableFuture;
 import java.util.function.Supplier;
+import java.util.stream.Stream;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.math.MathFlux;
@@ -434,8 +436,10 @@ final class ReactorRulesTest implements RefasterRuleCollectionTestCase {
         Flux.just(ImmutableList.of("bar")).concatMap(Flux::fromIterable, 2));
   }
 
-  Flux<String> testFluxFromIterable() {
-    return Flux.fromStream(ImmutableList.of("foo").stream());
+  ImmutableSet<Flux<String>> testFluxFromIterable() {
+    return ImmutableSet.of(
+        Flux.fromStream(ImmutableList.of("foo")::stream),
+        Flux.fromStream(() -> ImmutableList.of("bar").stream()));
   }
 
   ImmutableSet<Mono<Integer>> testFluxCountMapMathToIntExact() {
@@ -660,4 +664,12 @@ final class ReactorRulesTest implements RefasterRuleCollectionTestCase {
   Mono<Void> testMonoFromFutureSupplierBoolean() {
     return Mono.fromFuture(CompletableFuture.completedFuture(null), true);
   }
+
+  Mono<String> testMonoFromFutureAsyncLoadingCacheGet() {
+    return Mono.fromFuture(() -> ((AsyncLoadingCache<Integer, String>) null).get(0));
+  }
+
+  Flux<Integer> testFluxFromStreamSupplier() {
+    return Flux.fromStream(Stream.of(1));
+  }
 }

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

@@ -12,6 +12,7 @@ import static java.util.stream.Collectors.toCollection;
 import static org.assertj.core.api.Assertions.assertThat;
 import static reactor.function.TupleUtils.function;
 
+import com.github.benmanes.caffeine.cache.AsyncLoadingCache;
 import com.google.common.collect.ImmutableCollection;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
@@ -25,6 +26,7 @@ import java.util.Optional;
 import java.util.concurrent.Callable;
 import java.util.concurrent.CompletableFuture;
 import java.util.function.Supplier;
+import java.util.stream.Stream;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.function.TupleUtils;
@@ -429,8 +431,9 @@ final class ReactorRulesTest implements RefasterRuleCollectionTestCase {
         Flux.just(ImmutableList.of("bar")).concatMapIterable(identity(), 2));
   }
 
-  Flux<String> testFluxFromIterable() {
-    return Flux.fromIterable(ImmutableList.of("foo"));
+  ImmutableSet<Flux<String>> testFluxFromIterable() {
+    return ImmutableSet.of(
+        Flux.fromIterable(ImmutableList.of("foo")), Flux.fromIterable(ImmutableList.of("bar")));
   }
 
   ImmutableSet<Mono<Integer>> testFluxCountMapMathToIntExact() {
@@ -641,4 +644,12 @@ final class ReactorRulesTest implements RefasterRuleCollectionTestCase {
   Mono<Void> testMonoFromFutureSupplierBoolean() {
     return Mono.fromFuture(() -> CompletableFuture.completedFuture(null), true);
   }
+
+  Mono<String> testMonoFromFutureAsyncLoadingCacheGet() {
+    return Mono.fromFuture(() -> ((AsyncLoadingCache<Integer, String>) null).get(0), true);
+  }
+
+  Flux<Integer> testFluxFromStreamSupplier() {
+    return Flux.fromStream(() -> Stream.of(1));
+  }
 }

error-prone-experimental/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.17.0</version>
+        <version>0.18.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>error-prone-experimental</artifactId>

error-prone-guidelines/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.17.0</version>
+        <version>0.18.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>error-prone-guidelines</artifactId>

error-prone-utils/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.17.0</version>
+        <version>0.18.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>error-prone-utils</artifactId>

generate-docs.sh

@@ -1,27 +0,0 @@
-#!/usr/bin/env bash
-
-set -e -u -o pipefail
-
-REPOSITORY_ROOT="$(git rev-parse --show-toplevel)"
-WEBSITE_ROOT="${REPOSITORY_ROOT}/website"
-
-generate_homepage() {
-    local homepage="${WEBSITE_ROOT}/index.md"
-
-    echo "Generating ${homepage}..."
-    cat - "${REPOSITORY_ROOT}/README.md" > "${homepage}" << EOF
----
-layout: default
-title: Home
-nav_order: 1
----
-EOF
-
-    local macos_compat=""
-    [[ "${OSTYPE}" == "darwin"* ]] && macos_compat="yes"
-    sed -i ${macos_compat:+".bak"} 's/src="website\//src="/g' "${homepage}"
-    sed -i ${macos_compat:+".bak"} 's/srcset="website\//srcset="/g' "${homepage}"
-}
-
-# Generate the website.
-generate_homepage

integration-tests/checkstyle.sh

@@ -2,205 +2,35 @@
 
 set -e -u -o pipefail
 
-integration_test_root="$(cd "$(dirname -- "${0}")" && pwd)"
-error_prone_support_root="${integration_test_root}/.."
-repos_root="${integration_test_root}/.repos"
-
 test_name="$(basename "${0}" .sh)"
-project=checkstyle
-repository=https://github.com/checkstyle/checkstyle.git
-revision=checkstyle-10.14.0
-
-if [ "${#}" -gt 2 ] || ([ "${#}" = 2 ] && [ "${1:---sync}" != '--sync' ]); then
-  echo "Usage: ${0} [--sync] [<report_directory>]"
-  exit 1
-fi
-do_sync="$([ "${#}" = 0 ] || [ "${1:-}" != '--sync' ] || echo 1)"
-report_directory="$([ "${#}" = 0 ] || ([ -z "${do_sync}" ] && echo "${1}") || ([ "${#}" = 1 ] || echo "${2}"))"
-
-if [ -n "${report_directory}" ]; then
-  mkdir -p "${report_directory}"
-else
-  report_directory="$(mktemp -d)"
-  trap 'rm -rf -- "${report_directory}"' INT TERM HUP EXIT
-fi
-
-case "$(uname -s)" in
-  Linux*)
-    grep_command=grep
-    sed_command=sed
-    ;;
-  Darwin*)
-    grep_command=ggrep
-    sed_command=gsed
-    ;;
-  *)
-    echo "Unsupported distribution $(uname -s) for this script."
-    exit 1
-    ;;
-esac
-
+project='checkstyle'
+repository='https://github.com/checkstyle/checkstyle.git'
+revision='checkstyle-10.14.0'
 # XXX: Configure Renovate to manage the AssertJ version declared here.
-shared_build_flags="
-  -Perror-prone-compile,error-prone-test-compile
-  -Dassertj.version=3.24.2
-  -Derror-prone.version=$(
-    mvn -f "${error_prone_support_root}" help:evaluate -Dexpression=version.error-prone -q -DforceStdout
-  )
-  -Derror-prone-support.version=$(
-    mvn -f "${error_prone_support_root}" help:evaluate -Dexpression=project.version -q -DforceStdout
-  )
-  -DadditionalSourceDirectories=\${project.basedir}\${file.separator}src\${file.separator}it\${file.separator}java,\${project.basedir}\${file.separator}src\${file.separator}xdocs-examples\${file.separator}java
-  "
-
-# XXX: Configure Renovate to manage the fmt-maven-plugin version declared here.
-# XXX: Once GitHub actions uses Maven 3.9.2+, we can inline this variable with
-# version reference `${fmt.version}`, and `-Dfmt.version=2.21.1` added to
-# `shared_build_flags`.
-format_goal='com.spotify.fmt:fmt-maven-plugin:2.21.1:format'
-
-error_prone_shared_flags='-XepExcludedPaths:(\Q${project.basedir}${file.separator}src${file.separator}\E(it|test|xdocs-examples)\Q${file.separator}resources\E|\Q${project.build.directory}${file.separator}\E).*'
-
-error_prone_patch_flags="${error_prone_shared_flags} -XepPatchLocation:IN_PLACE -XepPatchChecks:$(
-  find "${error_prone_support_root}" \
-     -path "*/META-INF/services/com.google.errorprone.bugpatterns.BugChecker" \
-     -not -path "*/error-prone-experimental/*" \
-     -not -path "*/error-prone-guidelines/*" \
-     -print0 \
-    | xargs -0 "${grep_command}" -hoP '[^.]+$' \
-    | paste -s -d ',' -
-)"
-
-error_prone_validation_flags="${error_prone_shared_flags} -XepDisableAllChecks $(
-  find "${error_prone_support_root}" \
-     -path "*/META-INF/services/com.google.errorprone.bugpatterns.BugChecker" \
-     -not -path "*/error-prone-experimental/*" \
-     -not -path "*/error-prone-guidelines/*" \
-     -print0 \
-    | xargs -0 "${grep_command}" -hoP '[^.]+$' \
-    | "${sed_command}" -r 's,(.*),-Xep:\1:WARN,' \
-    | paste -s -d ' ' -
-)"
-
-echo "Shared build flags: ${shared_build_flags}"
-echo "Error Prone patch flags: ${error_prone_patch_flags}"
-echo "Error Prone validation flags: ${error_prone_validation_flags}"
-
-mkdir -p "${repos_root}"
-
-# Make sure that the targeted tag of the project's Git repository is checked
-# out.
-project_root="${repos_root}/${project}"
-if [ ! -d "${project_root}" ]; then
-  # The repository has not yet been cloned; create a shallow clone.
-  git clone --branch "${revision}" --depth 1 "${repository}" "${project_root}"
-else
-  # The repository does already appear to exist. Try to check out the requested
-  # tag if possible, and fetch it otherwise.
-  #
-  # Under certain circumstances this does not cause the relevant tag to be
-  # created, so if necessary we manually create it.
-  git -C "${project_root}" checkout --force "${revision}" 2>/dev/null \
-    || (
-         git -C "${project_root}" fetch --depth 1 "${repository}" "${revision}" \
-           && git -C "${project_root}" checkout --force FETCH_HEAD \
-           && (git -C "${project_root}" tag "${revision}" || true)
-       )
-fi
-
-pushd "${project_root}"
-
-# Make sure that Git is sufficiently configured to enable committing to the
-# project's Git repository.
-git config user.email || git config user.email "integration-test@example.com"
-git config user.name || git config user.name "Integration Test"
-
-# Prepare the code for analysis by (a) applying the minimal set of changes
-# required to run Error Prone with Error Prone Support and (b) formatting the
-# code using the same method by which it will be formatted after each
-# compilation round. The initial formatting operation ensures that subsequent
-# modifications can be rendered in a clean manner.
-git clean -fdx
-git apply < "${integration_test_root}/${test_name}-init.patch"
-git commit -m 'dependency: Introduce Error Prone Support' .
-mvn ${shared_build_flags} "${format_goal}"
-git commit -m 'minor: Reformat using Google Java Format' .
-diff_base="$(git rev-parse HEAD)"
-
-# Apply Error Prone Support-suggested changes until a fixed point is reached.
-function apply_patch() {
-  local extra_build_args="${1}"
-
-  mvn ${shared_build_flags} ${extra_build_args} \
-    package "${format_goal}" \
-    -Derror-prone.configuration-args="${error_prone_patch_flags}" \
-    -DskipTests
-
-  if ! git diff --exit-code; then
-    git commit -m 'minor: Apply patches' .
-
-    # Changes were applied, so another compilation round may apply yet more
-    # changes. For performance reasons we perform incremental compilation,
-    # enabled using a misleading flag. (See
-    # https://issues.apache.org/jira/browse/MCOMPILER-209 for details.)
-    apply_patch '-Dmaven.compiler.useIncrementalCompilation=false'
-  elif [ "${extra_build_args}" != 'clean' ]; then
-    # No changes were applied. We'll attempt one more round in which all files
-    # are recompiled, because there are cases in which violations are missed
-    # during incremental compilation.
-    apply_patch 'clean'
-  fi
-}
-apply_patch ''
-
-# Run one more full build and log the output.
-#
-# By also running the tests, we validate that the (majority of) applied changes
-# are behavior preserving. Some tests are skipped:
+additional_build_flags='-Dassertj.version=3.24.2'
+additional_source_directories='${project.basedir}${file.separator}src${file.separator}it${file.separator}java,${project.basedir}${file.separator}src${file.separator}xdocs-examples${file.separator}java'
+patch_error_prone_flags=''
+validation_error_prone_flags=''
+# Validation skips some tests:
 # - The `metadataFilesGenerationAllFiles` test is skipped because it makes line
 #   number assertions that will fail when the code is formatted or patched.
-# - The `allCheckSectionJavaDocs` test is skipped because is validates that
+# - The `allCheckSectionJavaDocs` test is skipped because it validates that
 #   Javadoc has certain closing tags that are removed by Google Java Format.
-validation_build_log="${report_directory}/${test_name}-validation-build-log.txt"
-mvn ${shared_build_flags} \
-      clean package \
-      -Derror-prone.configuration-args="${error_prone_validation_flags}" \
-      -Dtest='
-        !MetadataGeneratorUtilTest#metadataFilesGenerationAllFiles,
-        !XdocsJavaDocsTest#allCheckSectionJavaDocs' \
-    | tee "${validation_build_log}" \
-  || failure=1
+validation_build_flags='-Dtest=!MetadataGeneratorUtilTest#metadataFilesGenerationAllFiles,!XdocsJavaDocsTest#allCheckSectionJavaDocs'
 
-# Collect the applied changes.
-expected_changes="${integration_test_root}/${test_name}-expected-changes.patch"
-actual_changes="${report_directory}/${test_name}-changes.patch"
-(git diff "${diff_base}"..HEAD | "${grep_command}" -vP '^(diff|index)' || true) > "${actual_changes}"
-
-# Collect the warnings reported by Error Prone Support checks.
-expected_warnings="${integration_test_root}/${test_name}-expected-warnings.txt"
-actual_warnings="${report_directory}/${test_name}-validation-build-warnings.txt"
-("${grep_command}" -oP "(?<=^\\Q[WARNING] ${PWD}/\\E).*" "${validation_build_log}" | "${grep_command}" -P '\] \[' || true) | LC_ALL=C sort > "${actual_warnings}"
-
-# Persist or validate the applied changes and reported warnings.
-if [ -n "${do_sync}" ]; then
-  echo 'Saving changes...'
-  cp "${actual_changes}" "${expected_changes}"
-  cp "${actual_warnings}" "${expected_warnings}"
-else
-  echo 'Inspecting changes...'
-  # XXX: This "diff of diffs" also contains vacuous sections, introduced due to
-  # line offset differences. Try to omit those from the final output.
-  if ! diff -u "${expected_changes}" "${actual_changes}"; then
-    echo 'There are unexpected changes. Inspect the preceding output for details.'
-    failure=1
-  fi
-  echo 'Inspecting emitted warnings...'
-  if ! diff -u "${expected_warnings}" "${actual_warnings}"; then
-    echo 'Diagnostics output changed. Inspect the preceding output for details.'
-    failure=1
-  fi
-fi
-
-if [ -n "${failure:-}" ]; then
+if [ "${#}" -gt 2 ] || ([ "${#}" = 2 ] && [ "${1:---sync}" != '--sync' ]); then
+  >&2 echo "Usage: ${0} [--sync] [<report_directory>]"
   exit 1
 fi
+
+"$(dirname "${0}")/run-integration-test.sh" \
+  "${test_name}" \
+  "${project}" \
+  "${repository}" \
+  "${revision}" \
+  "${additional_build_flags}" \
+  "${additional_source_directories}" \
+  "${patch_error_prone_flags}" \
+  "${validation_error_prone_flags}" \
+  "${validation_build_flags}" \
+  $@

integration-tests/run-integration-test.sh

@@ -0,0 +1,210 @@
+#!/usr/bin/env bash
+
+# Integration test framework for Maven builds.
+#
+# This script is not meant to be invoked manually. Instead it should be invoked
+# through one of the top-level integration test scripts, such as
+# `checkstyle.sh`.
+
+set -e -u -o pipefail
+
+integration_test_root="$(cd "$(dirname -- "${0}")" && pwd)"
+error_prone_support_root="${integration_test_root}/.."
+repos_root="${integration_test_root}/.repos"
+
+if [ "${#}" -lt 9 ] || [ "${#}" -gt 11 ] || ([ "${#}" = 11 ] && [ "${10:---sync}" != '--sync' ]); then
+  >&2 echo "Usage: $(basename "${0}") <test_name> <project> <repository> <revision> <additional_build_flags> <additional_source_directories> <patch_error_prone_flags> <validation_error_prone_flags> <validation_build_flags> [--sync] [<report_directory>]"
+  exit 1
+fi
+
+test_name="${1}"
+project="${2}"
+repository="${3}"
+revision="${4}"
+additional_build_flags="${5}"
+additional_source_directories="${6}"
+patch_error_prone_flags="${7}"
+validation_error_prone_flags="${8}"
+validation_build_flags="${9}"
+do_sync="$([ "${#}" = 9 ] || [ "${10:-}" != '--sync' ] || echo 1)"
+report_directory="$([ "${#}" = 9 ] || ([ -z "${do_sync}" ] && echo "${10}") || ([ "${#}" = 10 ] || echo "${11}"))"
+
+if [ -n "${report_directory}" ]; then
+  mkdir -p "${report_directory}"
+else
+  report_directory="$(mktemp -d)"
+  trap 'rm -rf -- "${report_directory}"' INT TERM HUP EXIT
+fi
+
+case "$(uname -s)" in
+  Linux*)
+    grep_command=grep
+    sed_command=sed
+    ;;
+  Darwin*)
+    grep_command=ggrep
+    sed_command=gsed
+    ;;
+  *)
+    echo "Unsupported distribution $(uname -s) for this script."
+    exit 1
+    ;;
+esac
+
+shared_build_flags="
+  -Perror-prone-compile,error-prone-test-compile
+  -Derror-prone.version=$(
+    mvn -f "${error_prone_support_root}" help:evaluate -Dexpression=version.error-prone -q -DforceStdout
+  )
+  -Derror-prone-support.version=$(
+    mvn -f "${error_prone_support_root}" help:evaluate -Dexpression=project.version -q -DforceStdout
+  )
+  -DadditionalSourceDirectories=${additional_source_directories}
+  ${additional_build_flags}
+  "
+
+# XXX: Configure Renovate to manage the fmt-maven-plugin version declared here.
+# XXX: Once GitHub actions uses Maven 3.9.2+, we can inline this variable with
+# version reference `${fmt.version}`, and `-Dfmt.version=2.21.1` added to
+# `shared_build_flags`.
+format_goal='com.spotify.fmt:fmt-maven-plugin:2.21.1:format'
+
+error_prone_shared_flags='-XepExcludedPaths:(\Q${project.basedir}${file.separator}src${file.separator}\E(it|test|xdocs-examples)\Q${file.separator}resources\E|\Q${project.build.directory}${file.separator}\E).*'
+
+error_prone_patch_flags="${error_prone_shared_flags} -XepPatchLocation:IN_PLACE -XepPatchChecks:$(
+   find "${error_prone_support_root}" \
+      -path "*/META-INF/services/com.google.errorprone.bugpatterns.BugChecker" \
+      -not -path "*/error-prone-experimental/*" \
+      -not -path "*/error-prone-guidelines/*" \
+      -print0 \
+    | xargs -0 "${grep_command}" -hoP '[^.]+$' \
+    | paste -s -d ',' -
+) ${patch_error_prone_flags}"
+
+error_prone_validation_flags="${error_prone_shared_flags} -XepDisableAllChecks $(
+   find "${error_prone_support_root}" \
+      -path "*/META-INF/services/com.google.errorprone.bugpatterns.BugChecker" \
+      -not -path "*/error-prone-experimental/*" \
+      -not -path "*/error-prone-guidelines/*" \
+      -print0 \
+    | xargs -0 "${grep_command}" -hoP '[^.]+$' \
+    | "${sed_command}" -r 's,(.*),-Xep:\1:WARN,' \
+    | paste -s -d ' ' -
+) ${validation_error_prone_flags}"
+
+echo "Shared build flags: ${shared_build_flags}"
+echo "Error Prone patch flags: ${error_prone_patch_flags}"
+echo "Error Prone validation flags: ${error_prone_validation_flags}"
+
+mkdir -p "${repos_root}"
+
+# Make sure that the targeted tag of the project's Git repository is checked
+# out.
+project_root="${repos_root}/${project}"
+if [ ! -d "${project_root}" ]; then
+  # The repository has not yet been cloned; create a shallow clone.
+  git clone --branch "${revision}" --depth 1 "${repository}" "${project_root}"
+else
+  # The repository does already appear to exist. Try to check out the requested
+  # tag if possible, and fetch it otherwise.
+  #
+  # Under certain circumstances this does not cause the relevant tag to be
+  # created, so if necessary we manually create it.
+  git -C "${project_root}" checkout --force "${revision}" 2>/dev/null \
+    || (
+         git -C "${project_root}" fetch --depth 1 "${repository}" "${revision}" \
+           && git -C "${project_root}" checkout --force FETCH_HEAD \
+           && (git -C "${project_root}" tag "${revision}" || true)
+       )
+fi
+
+pushd "${project_root}"
+
+# Make sure that Git is sufficiently configured to enable committing to the
+# project's Git repository.
+git config user.email || git config user.email 'integration-test@example.com'
+git config user.name || git config user.name 'Integration Test'
+
+# Prepare the code for analysis by (a) applying the minimal set of changes
+# required to run Error Prone with Error Prone Support and (b) formatting the
+# code using the same method by which it will be formatted after each
+# compilation round. The initial formatting operation ensures that subsequent
+# modifications can be rendered in a clean manner.
+git clean -fdx
+git apply < "${integration_test_root}/${test_name}-init.patch"
+git commit -m 'dependency: Introduce Error Prone Support' .
+mvn ${shared_build_flags} "${format_goal}"
+git commit -m 'minor: Reformat using Google Java Format' .
+diff_base="$(git rev-parse HEAD)"
+
+# Apply Error Prone Support-suggested changes until a fixed point is reached.
+function apply_patch() {
+  local extra_build_args="${1}"
+
+  mvn ${shared_build_flags} ${extra_build_args} \
+    package "${format_goal}" \
+    -Derror-prone.configuration-args="${error_prone_patch_flags}" \
+    -DskipTests
+
+  if ! git diff --exit-code; then
+    git commit -m 'minor: Apply patches' .
+
+    # Changes were applied, so another compilation round may apply yet more
+    # changes. For performance reasons we perform incremental compilation,
+    # enabled using a misleading flag. (See
+    # https://issues.apache.org/jira/browse/MCOMPILER-209 for details.)
+    apply_patch '-Dmaven.compiler.useIncrementalCompilation=false'
+  elif [ "${extra_build_args}" != 'clean' ]; then
+    # No changes were applied. We'll attempt one more round in which all files
+    # are recompiled, because there are cases in which violations are missed
+    # during incremental compilation.
+    apply_patch 'clean'
+  fi
+}
+apply_patch ''
+
+# Run one more full build and log the output.
+#
+# By also running the tests, we validate that the (majority of) applied changes
+# are behavior preserving.
+validation_build_log="${report_directory}/${test_name}-validation-build-log.txt"
+mvn ${shared_build_flags} \
+      clean package \
+      -Derror-prone.configuration-args="${error_prone_validation_flags}" \
+      ${validation_build_flags} \
+    | tee "${validation_build_log}" \
+  || failure=1
+
+# Collect the applied changes.
+expected_changes="${integration_test_root}/${test_name}-expected-changes.patch"
+actual_changes="${report_directory}/${test_name}-changes.patch"
+(git diff "${diff_base}"..HEAD | "${grep_command}" -vP '^(diff|index)' || true) > "${actual_changes}"
+
+# Collect the warnings reported by Error Prone Support checks.
+expected_warnings="${integration_test_root}/${test_name}-expected-warnings.txt"
+actual_warnings="${report_directory}/${test_name}-validation-build-warnings.txt"
+("${grep_command}" -oP "(?<=^\\Q[WARNING] ${PWD}/\\E).*" "${validation_build_log}" | "${grep_command}" -P '\] \[' || true) | LC_ALL=C sort > "${actual_warnings}"
+
+# Persist or validate the applied changes and reported warnings.
+if [ -n "${do_sync}" ]; then
+  echo 'Saving changes...'
+  cp "${actual_changes}" "${expected_changes}"
+  cp "${actual_warnings}" "${expected_warnings}"
+else
+  echo 'Inspecting changes...'
+  # XXX: This "diff of diffs" also contains vacuous sections, introduced due to
+  # line offset differences. Try to omit those from the final output.
+  if ! diff -u "${expected_changes}" "${actual_changes}"; then
+    echo 'There are unexpected changes. Inspect the preceding output for details.'
+    failure=1
+  fi
+  echo 'Inspecting emitted warnings...'
+  if ! diff -u "${expected_warnings}" "${actual_warnings}"; then
+    echo 'Diagnostics output changed. Inspect the preceding output for details.'
+    failure=1
+  fi
+fi
+
+if [ -n "${failure:-}" ]; then
+  exit 1
+fi

pom.xml

@@ -4,7 +4,7 @@
 
     <groupId>tech.picnic.error-prone-support</groupId>
     <artifactId>error-prone-support</artifactId>
-    <version>0.17.0</version>
+    <version>0.18.1-SNAPSHOT</version>
     <packaging>pom</packaging>
 
     <name>Picnic :: Error Prone Support</name>
@@ -52,7 +52,7 @@
 
     <scm child.scm.developerConnection.inherit.append.path="false" child.scm.url.inherit.append.path="false">
         <developerConnection>scm:git:git@github.com:PicnicSupermarket/error-prone-support.git</developerConnection>
-        <tag>v0.17.0</tag>
+        <tag>HEAD</tag>
         <url>https://github.com/PicnicSupermarket/error-prone-support</url>
     </scm>
     <issueManagement>
@@ -148,7 +148,7 @@
         <groupId.error-prone>com.google.errorprone</groupId.error-prone>
         <!-- The build timestamp is derived from the most recent commit
         timestamp in support of reproducible builds. -->
-        <project.build.outputTimestamp>2024-07-20T12:12:19Z</project.build.outputTimestamp>
+        <project.build.outputTimestamp>2024-08-11T13:05:54Z</project.build.outputTimestamp>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <!-- Glob pattern identifying Refaster rule definition files. These
         Java classes don't contain "regular" code, and thus require special
@@ -208,16 +208,16 @@
         <version.auto-value>1.11.0</version.auto-value>
         <version.error-prone>${version.error-prone-orig}</version.error-prone>
         <version.error-prone-fork>v${version.error-prone-orig}-picnic-1</version.error-prone-fork>
-        <version.error-prone-orig>2.29.2</version.error-prone-orig>
-        <version.error-prone-slf4j>0.1.25</version.error-prone-slf4j>
+        <version.error-prone-orig>2.32.0</version.error-prone-orig>
+        <version.error-prone-slf4j>0.1.28</version.error-prone-slf4j>
         <version.guava-beta-checker>1.0</version.guava-beta-checker>
         <version.jdk>17</version.jdk>
-        <version.maven>3.9.5</version.maven>
-        <version.mockito>5.12.0</version.mockito>
+        <version.maven>3.9.9</version.maven>
+        <version.mockito>5.13.0</version.mockito>
         <version.nopen-checker>1.0.1</version.nopen-checker>
-        <version.nullaway>0.11.0</version.nullaway>
+        <version.nullaway>0.11.2</version.nullaway>
         <version.pitest-git>1.1.4</version.pitest-git>
-        <version.rewrite-templating>1.12.0</version.rewrite-templating>
+        <version.rewrite-templating>1.14.1</version.rewrite-templating>
         <version.surefire>3.2.3</version.surefire>
     </properties>
 
@@ -300,6 +300,11 @@
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
+            <dependency>
+                <groupId>com.github.ben-manes.caffeine</groupId>
+                <artifactId>caffeine</artifactId>
+                <version>3.1.8</version>
+            </dependency>
             <dependency>
                 <groupId>com.google.auto</groupId>
                 <artifactId>auto-common</artifactId>
@@ -328,7 +333,7 @@
             <dependency>
                 <groupId>com.google.googlejavaformat</groupId>
                 <artifactId>google-java-format</artifactId>
-                <version>1.22.0</version>
+                <version>1.23.0</version>
             </dependency>
             <dependency>
                 <groupId>com.google.guava</groupId>
@@ -338,7 +343,7 @@
             <dependency>
                 <groupId>com.google.guava</groupId>
                 <artifactId>guava-bom</artifactId>
-                <version>33.2.1-jre</version>
+                <version>33.3.0-jre</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
@@ -357,10 +362,15 @@
                 <artifactId>nullaway</artifactId>
                 <version>${version.nullaway}</version>
             </dependency>
+            <dependency>
+                <groupId>io.github.java-diff-utils</groupId>
+                <artifactId>java-diff-utils</artifactId>
+                <version>4.12</version>
+            </dependency>
             <dependency>
                 <groupId>io.projectreactor</groupId>
                 <artifactId>reactor-bom</artifactId>
-                <version>2023.0.8</version>
+                <version>2023.0.10</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
@@ -377,7 +387,7 @@
             <dependency>
                 <groupId>io.swagger.core.v3</groupId>
                 <artifactId>swagger-annotations</artifactId>
-                <version>2.2.22</version>
+                <version>2.2.23</version>
             </dependency>
             <dependency>
                 <groupId>jakarta.servlet</groupId>
@@ -412,7 +422,7 @@
             <dependency>
                 <groupId>net.bytebuddy</groupId>
                 <artifactId>byte-buddy</artifactId>
-                <version>1.14.18</version>
+                <version>1.15.1</version>
             </dependency>
             <!-- Specified so that Renovate will file Maven upgrade PRs, which
             subsequently will cause `maven-enforcer-plugin` to require that
@@ -437,12 +447,12 @@
             <dependency>
                 <groupId>org.checkerframework</groupId>
                 <artifactId>checker-qual</artifactId>
-                <version>3.45.0</version>
+                <version>3.47.0</version>
             </dependency>
             <dependency>
                 <groupId>org.hamcrest</groupId>
                 <artifactId>hamcrest-core</artifactId>
-                <version>2.2</version>
+                <version>3.0</version>
             </dependency>
             <dependency>
                 <groupId>org.immutables</groupId>
@@ -457,7 +467,7 @@
             <dependency>
                 <groupId>org.junit</groupId>
                 <artifactId>junit-bom</artifactId>
-                <version>5.10.3</version>
+                <version>5.11.0</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
@@ -471,7 +481,7 @@
             <dependency>
                 <groupId>org.mongodb</groupId>
                 <artifactId>mongodb-driver-core</artifactId>
-                <version>5.1.2</version>
+                <version>5.1.4</version>
             </dependency>
             <dependency>
                 <groupId>org.openrewrite</groupId>
@@ -481,33 +491,33 @@
             <dependency>
                 <groupId>org.openrewrite.recipe</groupId>
                 <artifactId>rewrite-recipe-bom</artifactId>
-                <version>2.15.0</version>
+                <version>2.18.0</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
             <dependency>
                 <groupId>org.slf4j</groupId>
                 <artifactId>slf4j-bom</artifactId>
-                <version>2.0.13</version>
+                <version>2.0.16</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
             <dependency>
                 <groupId>org.springframework</groupId>
                 <artifactId>spring-framework-bom</artifactId>
-                <version>6.1.11</version>
+                <version>6.1.12</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
             <dependency>
                 <groupId>org.springframework.boot</groupId>
                 <artifactId>spring-boot-test</artifactId>
-                <version>3.3.2</version>
+                <version>3.3.3</version>
             </dependency>
             <dependency>
                 <groupId>org.springframework.security</groupId>
                 <artifactId>spring-security-bom</artifactId>
-                <version>6.3.1</version>
+                <version>6.3.3</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
@@ -562,7 +572,7 @@
                 <plugin>
                     <groupId>com.spotify.fmt</groupId>
                     <artifactId>fmt-maven-plugin</artifactId>
-                    <version>2.22.1</version>
+                    <version>2.24</version>
                     <configuration>
                         <additionalSourceDirectories>
                             <additionalSourceDirectory>${basedir}/src/test/resources</additionalSourceDirectory>
@@ -648,7 +658,7 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-checkstyle-plugin</artifactId>
-                    <version>3.4.0</version>
+                    <version>3.5.0</version>
                     <configuration>
                         <checkstyleRules>
                             <!-- We only enable rules that are not enforced by
@@ -897,7 +907,7 @@
                         <dependency>
                             <groupId>com.puppycrawl.tools</groupId>
                             <artifactId>checkstyle</artifactId>
-                            <version>10.17.0</version>
+                            <version>10.18.1</version>
                         </dependency>
                         <dependency>
                             <groupId>io.spring.nohttp</groupId>
@@ -965,11 +975,43 @@
                         https://issues.apache.org/jira/browse/MCOMPILER-209. -->
                         <useIncrementalCompilation>false</useIncrementalCompilation>
                     </configuration>
+                    <executions>
+                        <!-- OpenRewrite recipe sources, generated by the
+                        `rewrite-templating` annotation processor and
+                        identified as classes whose name ends in `Recipes`, are
+                        compiled to target Java 8 for compatibility with the
+                        wider OpenRewrite ecosystem. The `maven-jar-plugin` is
+                        configured to package these files into a separate JAR. -->
+                        <execution>
+                            <id>compile-recipes</id>
+                            <goals>
+                                <goal>compile</goal>
+                            </goals>
+                            <configuration>
+                                <compilerArgs combine.self="override">
+                                    <!-- When Java 8 is targeted we can't use
+                                    the `add-exports` flag. And since this goal
+                                    only recompiles already-compiled code,
+                                    static analysis is irrelevant. As such we
+                                    clear all compiler arguments, and only
+                                    suppress source/target/bootstrap classpath
+                                    warnings. -->
+                                    <arg>-Xlint:-options</arg>
+                                </compilerArgs>
+                                <source>8</source>
+                                <target>8</target>
+                                <includes>
+                                    <include>**/*Recipes.java</include>
+                                </includes>
+                                <outputDirectory>${project.build.directory}/openrewrite-recipes</outputDirectory>
+                            </configuration>
+                        </execution>
+                    </executions>
                 </plugin>
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-dependency-plugin</artifactId>
-                    <version>3.7.1</version>
+                    <version>3.8.0</version>
                     <configuration>
                         <!-- XXX: Drop `ignoreAllNonTestScoped` once
                         https://issues.apache.org/jira/browse/MNG-6058 is
@@ -984,7 +1026,7 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-deploy-plugin</artifactId>
-                    <version>3.1.2</version>
+                    <version>3.1.3</version>
                     <configuration>
                         <retryFailedDeploymentCount>3</retryFailedDeploymentCount>
                     </configuration>
@@ -1077,7 +1119,7 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-gpg-plugin</artifactId>
-                    <version>3.2.4</version>
+                    <version>3.2.5</version>
                     <executions>
                         <execution>
                             <id>sign-artifacts</id>
@@ -1090,7 +1132,7 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-install-plugin</artifactId>
-                    <version>3.1.2</version>
+                    <version>3.1.3</version>
                 </plugin>
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
@@ -1112,6 +1154,39 @@
                         </archive>
                     </configuration>
                     <executions>
+                        <execution>
+                            <id>default-jar</id>
+                            <goals>
+                                <goal>jar</goal>
+                            </goals>
+                            <configuration>
+                                <!-- These Java 17 bytecode classes are omitted
+                                from the default JAR, as instead we produce a
+                                separate artifact with Java 8 bytecode variants. -->
+                                <excludes>
+                                    <excludes>**/*Recipe$*.class</excludes>
+                                    <excludes>**/*Recipe.class</excludes>
+                                    <excludes>**/*Recipes.class</excludes>
+                                </excludes>
+                            </configuration>
+                        </execution>
+                        <execution>
+                            <!-- Creates a custom JAR with Java 8-compatible
+                            OpenRewrite recipe classes. -->
+                            <id>create-openrewrite-recipes-jar</id>
+                            <goals>
+                                <goal>jar</goal>
+                            </goals>
+                            <configuration>
+                                <classesDirectory>${project.build.directory}/openrewrite-recipes</classesDirectory>
+                                <classifier>recipes</classifier>
+                                <includes>
+                                    <includes>**/*Recipe$*.class</includes>
+                                    <includes>**/*Recipe.class</includes>
+                                    <includes>**/*Recipes.class</includes>
+                                </includes>
+                            </configuration>
+                        </execution>
                         <execution>
                             <id>create-test-jar</id>
                             <goals>
@@ -1123,7 +1198,7 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-javadoc-plugin</artifactId>
-                    <version>3.7.0</version>
+                    <version>3.10.0</version>
                     <configuration>
                         <additionalJOptions>
                             <additionalJOption>--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED</additionalJOption>
@@ -1193,7 +1268,7 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-surefire-plugin</artifactId>
-                    <version>3.3.1</version>
+                    <version>3.5.0</version>
                     <configuration>
                         <includes>
                             <include>**/*Test.java</include>
@@ -1404,7 +1479,7 @@
                 <plugin>
                     <groupId>org.kordamp.maven</groupId>
                     <artifactId>pomchecker-maven-plugin</artifactId>
-                    <version>1.11.0</version>
+                    <version>1.13.0</version>
                     <configuration>
                         <failOnError>false</failOnError>
                         <release>false</release>
@@ -1753,6 +1828,11 @@
                         <groupId>org.apache.maven.plugins</groupId>
                         <artifactId>maven-enforcer-plugin</artifactId>
                     </plugin>
+                    <plugin>
+                        <groupId>org.codehaus.mojo</groupId>
+                        <artifactId>exec-maven-plugin</artifactId>
+                        <version>3.4.1</version>
+                    </plugin>
                     <plugin>
                         <groupId>org.codehaus.mojo</groupId>
                         <artifactId>license-maven-plugin</artifactId>

refaster-compiler/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.17.0</version>
+        <version>0.18.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>refaster-compiler</artifactId>

refaster-compiler/src/main/java/tech/picnic/errorprone/refaster/plugin/RefasterRuleCompilerTaskListener.java

@@ -21,7 +21,6 @@ import com.sun.tools.javac.code.Symbol.ClassSymbol;
 import com.sun.tools.javac.code.Symbol.PackageSymbol;
 import com.sun.tools.javac.main.JavaCompiler;
 import com.sun.tools.javac.util.Context;
-import com.sun.tools.javac.util.Name;
 import java.io.IOException;
 import java.io.ObjectOutput;
 import java.io.ObjectOutputStream;
@@ -137,10 +136,10 @@ final class RefasterRuleCompilerTaskListener implements TaskListener {
     return enclosingPackage == null ? "" : enclosingPackage.toString();
   }
 
-  private static CharSequence toSimpleFlatName(ClassSymbol symbol) {
-    Name flatName = symbol.flatName();
+  private static String toSimpleFlatName(ClassSymbol symbol) {
+    String flatName = symbol.flatName().toString();
     int lastDot = flatName.lastIndexOf((byte) '.');
-    return lastDot < 0 ? flatName : flatName.subSequence(lastDot + 1, flatName.length());
+    return lastDot < 0 ? flatName : flatName.substring(lastDot + 1);
   }
 
   private static void outputCodeTransformer(CodeTransformer codeTransformer, FileObject target)

refaster-runner/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.17.0</version>
+        <version>0.18.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>refaster-runner</artifactId>

refaster-support/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.17.0</version>
+        <version>0.18.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>refaster-support</artifactId>

refaster-support/src/main/java/tech/picnic/errorprone/refaster/matchers/RequiresComputation.java

@@ -2,6 +2,7 @@ package tech.picnic.errorprone.refaster.matchers;
 
 import com.google.errorprone.VisitorState;
 import com.google.errorprone.matchers.Matcher;
+import com.google.errorprone.util.ASTHelpers;
 import com.sun.source.tree.ArrayAccessTree;
 import com.sun.source.tree.ExpressionTree;
 import com.sun.source.tree.IdentifierTree;
@@ -9,34 +10,19 @@ import com.sun.source.tree.LambdaExpressionTree;
 import com.sun.source.tree.LiteralTree;
 import com.sun.source.tree.MemberReferenceTree;
 import com.sun.source.tree.MemberSelectTree;
-import com.sun.source.tree.MethodInvocationTree;
 import com.sun.source.tree.ParenthesizedTree;
 import com.sun.source.tree.TypeCastTree;
 import com.sun.source.tree.UnaryTree;
 
-/** A matcher of expressions that likely require little to no computation. */
-public final class IsLikelyTrivialComputation implements Matcher<ExpressionTree> {
+/** A matcher of expressions that may a non-trivial amount of computation. */
+public final class RequiresComputation implements Matcher<ExpressionTree> {
   private static final long serialVersionUID = 1L;
 
-  /** Instantiates a new {@link IsLikelyTrivialComputation} instance. */
-  public IsLikelyTrivialComputation() {}
+  /** Instantiates a new {@link RequiresComputation} instance. */
+  public RequiresComputation() {}
 
   @Override
   public boolean matches(ExpressionTree expressionTree, VisitorState state) {
-    if (expressionTree instanceof MethodInvocationTree methodInvocation) {
-      // XXX: Method invocations are generally *not* trivial computations, but we make an exception
-      // for nullary method invocations on the result of a trivial computation. This exception
-      // allows this `Matcher` to by the `OptionalOrElseGet` Refaster rule, such that it does not
-      // suggest the introduction of lambda expressions that are better expressed as method
-      // references. Once the `MethodReferenceUsage` bug checker is production-ready, this exception
-      // should be removed. (But at that point, instead defining a `RequiresComputation` matcher may
-      // be more appropriate.)
-      if (methodInvocation.getArguments().isEmpty()
-          && matches(methodInvocation.getMethodSelect())) {
-        return true;
-      }
-    }
-
     return matches(expressionTree);
   }
 
@@ -44,11 +30,11 @@ public final class IsLikelyTrivialComputation implements Matcher<ExpressionTree>
   // Depending on feedback such trees may be matched in the future.
   private static boolean matches(ExpressionTree expressionTree) {
     if (expressionTree instanceof ArrayAccessTree arrayAccess) {
-      return matches(arrayAccess.getExpression()) && matches(arrayAccess.getIndex());
+      return matches(arrayAccess.getExpression()) || matches(arrayAccess.getIndex());
     }
 
     if (expressionTree instanceof LiteralTree) {
-      return true;
+      return false;
     }
 
     if (expressionTree instanceof LambdaExpressionTree) {
@@ -56,11 +42,14 @@ public final class IsLikelyTrivialComputation implements Matcher<ExpressionTree>
        * Lambda expressions encapsulate computations, but their definition does not involve
        * significant computation.
        */
-      return true;
+      return false;
     }
 
     if (expressionTree instanceof IdentifierTree) {
-      return true;
+      // XXX: Generally identifiers don't by themselves represent a computation, though they may be
+      // a stand-in for one if they are a Refaster template method argument. Can we identify such
+      // cases, also when the `Matcher` is invoked by Refaster?
+      return false;
     }
 
     if (expressionTree instanceof MemberReferenceTree memberReference) {
@@ -80,11 +69,11 @@ public final class IsLikelyTrivialComputation implements Matcher<ExpressionTree>
     }
 
     if (expressionTree instanceof UnaryTree unary) {
-      // XXX: Arguably side-effectful options such as pre- and post-increment and -decrement are not
-      // trivial.
+      // XXX: Arguably side-effectful options such as pre- and post-increment and -decrement
+      // represent non-trivial computations.
       return matches(unary.getExpression());
     }
 
-    return false;
+    return ASTHelpers.constValue(expressionTree) == null;
   }
 }

refaster-support/src/test/java/tech/picnic/errorprone/refaster/matchers/RequiresComputationTest.java

@@ -8,54 +8,69 @@ import com.google.errorprone.bugpatterns.BugChecker;
 import com.sun.source.tree.ReturnTree;
 import org.junit.jupiter.api.Test;
 
-final class IsLikelyTrivialComputationTest {
+final class RequiresComputationTest {
   @Test
   void matches() {
     CompilationTestHelper.newInstance(MatcherTestChecker.class, getClass())
         .addSourceLines(
             "A.java",
+            "import java.io.OutputStream;",
+            "import java.util.Comparator;",
             "import java.util.function.Predicate;",
             "",
             "class A {",
-            "  String negative1() {",
-            "    return String.valueOf(1);",
+            "  int negative1() {",
+            "    int[] arr = new int[0];",
+            "    return arr[0];",
             "  }",
             "",
             "  String negative2() {",
-            "    return toString().toString();",
+            "    return null;",
             "  }",
             "",
-            "  String negative3() {",
-            "    return \"foo\" + toString();",
+            "  boolean negative3() {",
+            "    return false;",
             "  }",
             "",
-            "  byte negative4() {",
-            "    return \"foo\".getBytes()[0];",
+            "  int negative4() {",
+            "    return 0;",
             "  }",
             "",
-            "  int negative5() {",
-            "    int[] arr = new int[0];",
-            "    return arr[hashCode()];",
+            "  String negative5() {",
+            "    return \"foo\" + \"bar\";",
             "  }",
             "",
-            "  int negative6() {",
-            "    return 1 * 2;",
+            "  Predicate<String> negative6() {",
+            "    return v -> \"foo\".equals(v);",
             "  }",
             "",
-            "  Predicate<String> negative7() {",
-            "    return toString()::equals;",
+            "  A negative7() {",
+            "    return this;",
             "  }",
             "",
-            "  String negative8() {",
-            "    return (toString());",
+            "  Predicate<String> negative8() {",
+            "    return \"foo\"::equals;",
             "  }",
             "",
-            "  Object negative9() {",
-            "    return (Object) toString();",
+            "  OutputStream negative9() {",
+            "    return System.out;",
             "  }",
             "",
-            "  int negative10() {",
-            "    return -hashCode();",
+            "  A negative10() {",
+            "    return (this);",
+            "  }",
+            "",
+            "  Object negative11() {",
+            "    return (Object) this;",
+            "  }",
+            "",
+            "  boolean negative12() {",
+            "    boolean[] arr = new boolean[0];",
+            "    return !arr[0];",
+            "  }",
+            "",
+            "  String negative13() {",
+            "    return \"foo\" + 0;",
             "  }",
             "",
             "  String positive1() {",
@@ -68,68 +83,63 @@ final class IsLikelyTrivialComputationTest {
             "    return this.toString();",
             "  }",
             "",
-            "  int positive3() {",
-            "    int[] arr = new int[0];",
+            "  String positive3() {",
             "    // BUG: Diagnostic contains:",
-            "    return arr[0];",
+            "    return String.valueOf(1);",
             "  }",
             "",
             "  String positive4() {",
             "    // BUG: Diagnostic contains:",
-            "    return null;",
+            "    return toString().toString();",
             "  }",
             "",
-            "  boolean positive5() {",
+            "  String positive5() {",
             "    // BUG: Diagnostic contains:",
-            "    return false;",
+            "    return \"foo\" + toString();",
             "  }",
             "",
-            "  int positive6() {",
+            "  byte positive6() {",
             "    // BUG: Diagnostic contains:",
-            "    return 0;",
+            "    return \"foo\".getBytes()[0];",
             "  }",
             "",
-            "  String positive7() {",
+            "  int positive7() {",
+            "    int[] arr = new int[0];",
             "    // BUG: Diagnostic contains:",
-            "    return \"foo\" + \"bar\";",
+            "    return arr[hashCode()];",
             "  }",
             "",
             "  Predicate<String> positive8() {",
             "    // BUG: Diagnostic contains:",
-            "    return v -> \"foo\".equals(v);",
+            "    return toString()::equals;",
             "  }",
             "",
-            "  A positive9() {",
+            "  Comparator<String> positive9() {",
             "    // BUG: Diagnostic contains:",
-            "    return this;",
+            "    return toString().CASE_INSENSITIVE_ORDER;",
             "  }",
             "",
-            "  Predicate<String> positive10() {",
+            "  String positive10() {",
             "    // BUG: Diagnostic contains:",
-            "    return \"foo\"::equals;",
+            "    return (toString());",
             "  }",
             "",
-            "  A positive11() {",
+            "  Object positive11() {",
             "    // BUG: Diagnostic contains:",
-            "    return (this);",
+            "    return (Object) toString();",
             "  }",
             "",
-            "  Object positive12() {",
+            "  int positive12() {",
             "    // BUG: Diagnostic contains:",
-            "    return (Object) this;",
-            "  }",
-            "",
-            "  boolean positive13() {",
-            "    // BUG: Diagnostic contains:",
-            "    return !false;",
+            "    return -hashCode();",
             "  }",
             "}")
         .doTest();
   }
 
-  /** A {@link BugChecker} that simply delegates to {@link IsLikelyTrivialComputation}. */
+  /** A {@link BugChecker} that simply delegates to {@link RequiresComputation}. */
   @BugPattern(
-      summary = "Flags return statement expressions matched by `IsLikelyTrivialComputation`",
+      summary = "Flags return statement expressions matched by `RequiresComputation`",
       severity = ERROR)
   public static final class MatcherTestChecker extends AbstractMatcherTestChecker {
     private static final long serialVersionUID = 1L;
@@ -141,7 +151,7 @@ final class IsLikelyTrivialComputationTest {
       super(
           (expressionTree, state) ->
               state.getPath().getParentPath().getLeaf() instanceof ReturnTree
-                  && new IsLikelyTrivialComputation().matches(expressionTree, state));
+                  && new RequiresComputation().matches(expressionTree, state));
     }
   }
 }

refaster-test-support/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.17.0</version>
+        <version>0.18.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>refaster-test-support</artifactId>

refaster-test-support/src/main/java/tech/picnic/errorprone/refaster/test/RefasterRuleCollection.java

@@ -61,6 +61,9 @@ import tech.picnic.errorprone.refaster.runner.Refaster;
 // XXX: This check currently only validates that one `Refaster.anyOf` branch in one
 // `@BeforeTemplate` method is covered by a test. Review how we can make sure that _all_
 // `@BeforeTemplate` methods and `Refaster.anyOf` branches are covered.
+// XXX: Look into replacing this setup with another that allows test cases to be co-located
+// with/nested within the rules. This way any rule change only requires modifications in a single
+// place, rather than in three.
 @BugPattern(summary = "Exercises a Refaster rule collection", linkType = NONE, severity = ERROR)
 @SuppressWarnings("java:S2160" /* Super class equality definition suffices. */)
 public final class RefasterRuleCollection extends BugChecker implements CompilationUnitTreeMatcher {

website/.gitignore

@@ -1,12 +1,13 @@
 # Generated by Bundler and Jekyll.
 .bundle/
-Gemfile.lock
 .jekyll-cache/
 .jekyll-metadata
 .sass-cache/
 _site/
 vendor/
 
-# Generated by `../generate-docs.sh`.
-*.bak
+# XXX: Update generator name when it's renamed.
+# Generated by `JekyllCollectionGenerator`.
 index.md
+_bugpatterns/
+_refasterrules/

website/Gemfile

@@ -1,8 +1,15 @@
 ruby File.read(".ruby-version").strip
 
 source "https://rubygems.org"
-gem "html-proofer", "4.4.1"
-gem "jekyll", "4.2.2"
-gem "jekyll-sitemap", "1.4"
-gem "just-the-docs", "0.4.0.rc2"
-gem "webrick", "1.7"
+
+group :jekyll_site_dependencies do
+  gem "jekyll", "4.3.2"
+  gem "jekyll-sitemap", "1.4.0"
+  gem "just-the-docs", "0.6.2"
+  gem "rake", "13.0.6"
+  gem "webrick", "1.8.1"
+end
+
+group :website_validation_dependencies do
+  gem "html-proofer", "5.0.8"
+end

website/Gemfile.lock

@@ -0,0 +1,133 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    Ascii85 (1.1.0)
+    addressable (2.8.5)
+      public_suffix (>= 2.0.2, < 6.0)
+    afm (0.2.2)
+    async (2.6.4)
+      console (~> 1.10)
+      fiber-annotation
+      io-event (~> 1.1)
+      timers (~> 4.1)
+    colorator (1.1.0)
+    concurrent-ruby (1.2.2)
+    console (1.23.2)
+      fiber-annotation
+      fiber-local
+    em-websocket (0.5.3)
+      eventmachine (>= 0.12.9)
+      http_parser.rb (~> 0)
+    ethon (0.16.0)
+      ffi (>= 1.15.0)
+    eventmachine (1.2.7)
+    ffi (1.16.3)
+    fiber-annotation (0.2.0)
+    fiber-local (1.0.0)
+    forwardable-extended (2.6.0)
+    google-protobuf (3.24.4-x86_64-linux)
+    hashery (2.1.2)
+    html-proofer (5.0.8)
+      addressable (~> 2.3)
+      async (~> 2.1)
+      nokogiri (~> 1.13)
+      pdf-reader (~> 2.11)
+      rainbow (~> 3.0)
+      typhoeus (~> 1.3)
+      yell (~> 2.0)
+      zeitwerk (~> 2.5)
+    http_parser.rb (0.8.0)
+    i18n (1.14.1)
+      concurrent-ruby (~> 1.0)
+    io-event (1.3.2)
+    jekyll (4.3.2)
+      addressable (~> 2.4)
+      colorator (~> 1.0)
+      em-websocket (~> 0.5)
+      i18n (~> 1.0)
+      jekyll-sass-converter (>= 2.0, < 4.0)
+      jekyll-watch (~> 2.0)
+      kramdown (~> 2.3, >= 2.3.1)
+      kramdown-parser-gfm (~> 1.0)
+      liquid (~> 4.0)
+      mercenary (>= 0.3.6, < 0.5)
+      pathutil (~> 0.9)
+      rouge (>= 3.0, < 5.0)
+      safe_yaml (~> 1.0)
+      terminal-table (>= 1.8, < 4.0)
+      webrick (~> 1.7)
+    jekyll-include-cache (0.2.1)
+      jekyll (>= 3.7, < 5.0)
+    jekyll-sass-converter (3.0.0)
+      sass-embedded (~> 1.54)
+    jekyll-seo-tag (2.8.0)
+      jekyll (>= 3.8, < 5.0)
+    jekyll-sitemap (1.4.0)
+      jekyll (>= 3.7, < 5.0)
+    jekyll-watch (2.2.1)
+      listen (~> 3.0)
+    just-the-docs (0.6.2)
+      jekyll (>= 3.8.5)
+      jekyll-include-cache
+      jekyll-seo-tag (>= 2.0)
+      rake (>= 12.3.1)
+    kramdown (2.4.0)
+      rexml
+    kramdown-parser-gfm (1.1.0)
+      kramdown (~> 2.0)
+    liquid (4.0.4)
+    listen (3.8.0)
+      rb-fsevent (~> 0.10, >= 0.10.3)
+      rb-inotify (~> 0.9, >= 0.9.10)
+    mercenary (0.4.0)
+    nokogiri (1.15.4-x86_64-linux)
+      racc (~> 1.4)
+    pathutil (0.16.2)
+      forwardable-extended (~> 2.6)
+    pdf-reader (2.11.0)
+      Ascii85 (~> 1.0)
+      afm (~> 0.2.1)
+      hashery (~> 2.0)
+      ruby-rc4
+      ttfunk
+    public_suffix (5.0.3)
+    racc (1.7.1)
+    rainbow (3.1.1)
+    rake (13.0.6)
+    rb-fsevent (0.11.2)
+    rb-inotify (0.10.1)
+      ffi (~> 1.0)
+    rexml (3.2.6)
+    rouge (4.1.3)
+    ruby-rc4 (0.1.5)
+    safe_yaml (1.0.5)
+    sass-embedded (1.69.4)
+      google-protobuf (~> 3.23)
+      rake (>= 13.0.0)
+    terminal-table (3.0.2)
+      unicode-display_width (>= 1.1.1, < 3)
+    timers (4.3.5)
+    ttfunk (1.7.0)
+    typhoeus (1.4.0)
+      ethon (>= 0.9.0)
+    unicode-display_width (2.5.0)
+    webrick (1.8.1)
+    yell (2.2.2)
+    zeitwerk (2.6.12)
+
+PLATFORMS
+  x86_64-linux
+
+DEPENDENCIES
+  html-proofer (= 5.0.8)
+  jekyll (= 4.3.2)
+  jekyll-sitemap (= 1.4.0)
+  just-the-docs (= 0.6.2)
+  rake (= 13.0.6)
+  webrick (= 1.8.1)
+
+RUBY VERSION
+   ruby 3.1.2p20
+
+BUNDLED WITH
+   2.3.7

website/README.md

@@ -7,18 +7,30 @@ statically generated using [Jekyll][jekyll].
 # Local development
 
 To view the website on `localhost`, first follow the [Jekyll installation
-instructions][jekyll-docs-installation]. Once done, in this directory execute:
+instructions][jekyll-docs-installation]. Once done, run the following Maven
+commands in the root of the repository to extract the (test) data from the bug
+patterns and Refaster rule collections and to transform this data into a
+Jekyll-digestible format. Unless and relevant Java code has been changed, these
+commands needs to be executed once.
+
+```sh
+mvn -T1C clean install -DskipTests -Dverification.skip
+mvn exec:java@generate-docs -pl documentation-support
+```
+
+Then to build the website for local development, execute in this directory:
 
 ```sh
 bundle install
-../generate-docs.sh && bundle exec jekyll serve --livereload
+bundle exec jekyll serve --livereload
 ```
 
 The website will now be [available][localhost-port-4000] on port 4000. Source
-code modifications (including the result of rerunning `../generate-docs.sh`)
-will automatically be reflected. (An exception is `_config.yml`: changes to
-this file require a server restart.) Subsequent server restarts do not require
-running `bundle install`, unless `Gemfile` has been updated in the interim.
+code modifications (including the result of rerunning `mvn
+exec:java@generate-docs -pl documentation-support`) will automatically be
+reflected. (An exception is `_config.yml`: changes to this file require a
+server restart.) Subsequent server restarts do not require running `bundle
+install`, unless `Gemfile` has been updated in the interim.
 
 If you are not familiar with Jekyll, be sure to check out its
 [documentation][jekyll-docs]. It is recommended to follow the provided

website/_config.yml

@@ -8,15 +8,40 @@ description: >-
 
 theme: just-the-docs
 plugins:
-  - jekyll-sitemap
+- jekyll-sitemap
 
 # Files and directories not to be deployed through GitHub pages.
 exclude:
-  - Gemfile
-  - Gemfile.lock
-  - generate-version-compatibility-overview.sh
-  - README.md
-  - vendor
+- Gemfile
+- Gemfile.lock
+- generate-version-compatibility-overview.sh
+- README.md
+- vendor
+
+collections:
+  bugpatterns:
+    output: true
+  refasterrules:
+    output: true
+
+defaults:
+- scope:
+    type: "bugpatterns"
+  values:
+    layout: "bugpattern"
+- scope:
+    type: "refasterrules"
+  values:
+    layout: "refasterrule"
+
+just_the_docs:
+  collections:
+    bugpatterns:
+      name: Bug Patterns
+      nav_fold: true
+    refasterrules:
+      name: Refaster Rules
+      nav_fold: true
 
 # See https://jekyllrb.com/docs/permalinks/#built-in-formats.
 permalink: pretty
@@ -25,9 +50,9 @@ permalink: pretty
 # See
 # https://just-the-docs.github.io/just-the-docs/docs/navigation-structure/#external-navigation-links.
 nav_external_links:
-  - title: Error Prone Support on GitHub
-    url: https://github.com/PicnicSupermarket/error-prone-support
-    hide_icon: false
+- title: Error Prone Support on GitHub
+  url: https://github.com/PicnicSupermarket/error-prone-support
+  hide_icon: false
 
 callouts:
   summary:
@@ -40,9 +65,9 @@ callouts:
 social:
   name: Picnic
   links:
-    - https://github.com/PicnicSupermarket
-    - https://twitter.com/picnic
-    - https://www.linkedin.com/company/picnictechnologies
+  - https://github.com/PicnicSupermarket
+  - https://twitter.com/picnic
+  - https://www.linkedin.com/company/picnictechnologies
 twitter:
   username: picnic
   card: summary

website/_data/compatibility.yml

@@ -1,6 +1,25 @@
 # An overview of Error Prone Support releases, along with compatible Error
 # Prone releases. This data was generated by `generate-version-compatibility-overview.sh`.
 releases:
+  - version: 0.18.0
+    compatible:
+      - "2.30.0"
+      - "2.31.0"
+      - "2.32.0"
+  - version: 0.17.0
+    compatible:
+      - "2.29.2"
+      - "2.29.1"
+      - "2.29.0"
+      - "2.28.0"
+      - "2.27.1"
+      - "2.27.0"
+      - "2.26.1"
+      - "2.26.0"
+      - "2.25.0"
+      - "2.24.1"
+      - "2.24.0"
+      - "2.23.0"
   - version: 0.16.1
     compatible:
       - "2.29.2"

website/_data/severities.yml

@@ -0,0 +1,6 @@
+ERROR:
+  color: red
+WARNING:
+  color: yellow
+SUGGESTION:
+  color: green

website/_layouts/bugpattern.md

@@ -0,0 +1,94 @@
+---
+# XXX: To be implemented:
+# - Support for alt names.
+# - Support for explanations.
+# - Support for "can disable".
+# - Support for custom suppression annotations.
+layout: default
+---
+
+{% capture markdown_layout %}
+
+# {{ page.name }}
+
+{{ page.severity }}
+  {: .label .label-{{ site.data.severities[page.severity].color }} }
+
+{% for tag in page.tags %}
+{{ tag }}
+  {: .label }
+{% endfor %}
+
+<a href="https://github.com/PicnicSupermarket/error-prone-support/blob/master/{{ page.source }}" class="fs-3 btn external" target="_blank">
+    View source code on GitHub
+    <svg viewBox="0 0 24 24" aria-labelledby="svg-external-link-title">
+        <use xlink:href="#svg-external-link"></use>
+    </svg>
+</a>
+
+{: .summary-title }
+> Summary
+>
+> {{ page.summary }}
+
+{% comment %}
+  # XXX: Here, include a more elaborate explantion, if available.
+{% endcomment %}
+
+{: .note-title }
+> Suppression
+>
+> Suppress false positives by adding the suppression annotation `@SuppressWarnings("{{ page.name }}")` to
+> the enclosing element.
+>
+> Disable this pattern completely by adding `-Xep:{{ page.name }}:OFF` as compiler argument.
+> [Learn more][error-prone-flags].
+{% comment %}
+  # XXX: Create an internal page on documenting the usage of compiler flags.
+{% endcomment %}
+
+{% if page.replacement or page.identification %}
+
+## Samples
+
+{% comment %}
+  # XXX: Either make this "Samples" header useful, or drop it. (In which case
+  # the wrapping conjunctive guard should also go.)
+{% endcomment %}
+
+{% if page.replacement %}
+
+### Replacement
+
+Shows the difference in example code before and after the bug pattern is
+applied.
+
+{% for diff in page.replacement %}
+{% highlight diff %}
+{{ diff }}
+{% endhighlight %}
+{% endfor %}
+
+{% endif %}
+
+{% if page.identification %}
+
+### Identification
+
+Shows code lines which will (not) be flagged by this bug pattern. \
+A `//BUG: Diagnostic contains:` comment is placed above any violating line.
+
+{% for source in page.identification %}
+{% highlight java %}
+{{ source }}
+{% endhighlight %}
+{% endfor %}
+
+{% endif %}
+
+{% endif %}
+
+[error-prone-flags]: https://errorprone.info/docs/flags
+
+{% endcapture %}
+{{ markdown_layout | markdownify }}

website/_layouts/refasterrule.md

@@ -0,0 +1,78 @@
+---
+layout: default
+---
+
+{% capture markdown_layout %}
+
+# {{ page.name }}
+{: .no_toc }
+
+{{ page.severity }}
+  {: .label .label-{{ site.data.severities[page.severity].color }} }
+
+{% for tag in page.tags %}
+{{ tag }}
+  {: .label }
+{% endfor %}
+
+<a href="https://github.com/PicnicSupermarket/error-prone-support/blob/master/{{ page.source }}" class="fs-3 btn external" target="_blank">
+    View source code on GitHub
+    <svg viewBox="0 0 24 24" aria-labelledby="svg-external-link-title">
+        <use xlink:href="#svg-external-link"></use>
+    </svg>
+</a>
+
+{: .note-title }
+> Suppression
+>
+> Disable all rules by adding `-XepOpt:Refaster:NamePattern=^(?!{{page.name}}\$).*` as
+> compiler argument.
+{% comment %}
+  # XXX: Create an internal page on documenting the usage of compiler flags.
+{% endcomment %}
+
+<details open markdown="block">
+  <summary>
+    Table of contents
+  </summary>
+  {: .text-delta }
+  1. TOC
+  {:toc}
+</details>
+
+{% for rule in page.rules %}
+## {{rule.name}}
+
+{{ page.severity }}
+  {: .label .label-{{ site.data.severities[rule.severity].color }} }
+
+{% for tag in rule.tags %}
+{{ tag }}
+  {: .label }
+{% endfor %}
+
+{: .note-title }
+> Suppression
+>
+> Suppress false positives by adding the suppression annotation `@SuppressWarnings("{{rule.name}}")` to
+> the enclosing element.
+>
+> Disable this rule by adding `-XepOpt:Refaster:NamePattern=^(?!{{page.name}}\${{rule.name}}).*`
+> as compiler argument.
+{% comment %}
+  # XXX: Create an internal page on documenting the usage of compiler flags.
+{% endcomment %}
+
+### Samples
+{: .no_toc .text-delta }
+
+Shows the difference in example code before and after the Refaster rule is
+applied.
+
+{% highlight diff %}
+{{ rule.diff }}
+{% endhighlight %}
+{% endfor %}
+
+{% endcapture %}
+{{ markdown_layout | markdownify }}

website/_sass/color_schemes/_variables.scss

@@ -2,4 +2,4 @@
 // https://github.com/just-the-docs/just-the-docs/blob/main/_sass/support/_variables.scss.
 
 // Grid system.
-$nav-width: 400px;
+$nav-width: 25rem;

website/bugpatterns.md

@@ -1,8 +0,0 @@
----
-layout: default
-title: Bug Patterns
-nav_order: 2
-has_children: true
----
-
-# Bug Patterns

website/refasterrules.md

@@ -1,8 +0,0 @@
----
-layout: default
-title: Refaster Rules
-nav_order: 2
-has_children: true
----
-
-# Refaster Rules