Update EP and version on workshop branch

See:
- https://github.com/micrometer-metrics/micrometer/releases/tag/v1.14.6
- https://github.com/micrometer-metrics/micrometer/compare/v1.14.5...v1.14.6

.github/workflows/build.yml

@@ -26,7 +26,7 @@ jobs:
     continue-on-error: ${{ matrix.experimental }}
     steps:
       - name: Install Harden-Runner
-        uses: step-security/harden-runner@4d991eb9b905ef189e4c376166672c3f2f230481 # v2.11.0
+        uses: step-security/harden-runner@c6295a65d1254861815972266d5933fd6e532bdf # v2.11.1
         with:
           disable-sudo: true
           egress-policy: block

.github/workflows/codeql.yml

@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       - name: Install Harden-Runner
-        uses: step-security/harden-runner@4d991eb9b905ef189e4c376166672c3f2f230481 # v2.11.0
+        uses: step-security/harden-runner@c6295a65d1254861815972266d5933fd6e532bdf # v2.11.1
         with:
           disable-sudo: true
           egress-policy: block

.github/workflows/deploy-website.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       - name: Install Harden-Runner
-        uses: step-security/harden-runner@4d991eb9b905ef189e4c376166672c3f2f230481 # v2.11.0
+        uses: step-security/harden-runner@c6295a65d1254861815972266d5933fd6e532bdf # v2.11.1
         with:
           disable-sudo: true
           egress-policy: block
@@ -75,7 +75,7 @@ jobs:
       url: ${{ steps.deployment.outputs.page_url }}
     steps:
       - name: Install Harden-Runner
-        uses: step-security/harden-runner@4d991eb9b905ef189e4c376166672c3f2f230481 # v2.11.0
+        uses: step-security/harden-runner@c6295a65d1254861815972266d5933fd6e532bdf # v2.11.1
         with:
           disable-sudo: true
           egress-policy: block

.github/workflows/openssf-scorecard.yml

@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       - name: Install Harden-Runner
-        uses: step-security/harden-runner@4d991eb9b905ef189e4c376166672c3f2f230481 # v2.11.0
+        uses: step-security/harden-runner@c6295a65d1254861815972266d5933fd6e532bdf # v2.11.1
         with:
           disable-sudo: true
           egress-policy: block

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

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       - name: Install Harden-Runner
-        uses: step-security/harden-runner@4d991eb9b905ef189e4c376166672c3f2f230481 # v2.11.0
+        uses: step-security/harden-runner@c6295a65d1254861815972266d5933fd6e532bdf # v2.11.1
         with:
           disable-sudo: true
           egress-policy: block

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

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       - name: Install Harden-Runner
-        uses: step-security/harden-runner@4d991eb9b905ef189e4c376166672c3f2f230481 # v2.11.0
+        uses: step-security/harden-runner@c6295a65d1254861815972266d5933fd6e532bdf # v2.11.1
         with:
           disable-sudo: true
           egress-policy: block

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

@@ -22,7 +22,7 @@ jobs:
         integration-test: [ "checkstyle", "metrics", "prometheus-java-client" ]
     steps:
       - name: Install Harden-Runner
-        uses: step-security/harden-runner@4d991eb9b905ef189e4c376166672c3f2f230481 # v2.11.0
+        uses: step-security/harden-runner@c6295a65d1254861815972266d5933fd6e532bdf # v2.11.1
         with:
           disable-sudo: true
           egress-policy: block

.github/workflows/sonarcloud.yml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       - name: Install Harden-Runner
-        uses: step-security/harden-runner@4d991eb9b905ef189e4c376166672c3f2f230481 # v2.11.0
+        uses: step-security/harden-runner@c6295a65d1254861815972266d5933fd6e532bdf # v2.11.1
         with:
           disable-sudo: true
           egress-policy: block

.mvn/maven.config

@@ -1,3 +1,4 @@
 --batch-mode
 --errors
 --strict-checksums
+-Dstyle.color=always

.mvn/wrapper/maven-wrapper.properties

@@ -0,0 +1,18 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.6/apache-maven-3.9.6-bin.zip
+wrapperUrl=https://repo.maven.apache.org/maven2/org/apache/maven/wrapper/maven-wrapper/3.2.0/maven-wrapper-3.2.0.jar

documentation-support/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.21.1-SNAPSHOT</version>
+        <version>0.22.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>documentation-support</artifactId>

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

@@ -2,6 +2,7 @@ package tech.picnic.errorprone.documentation;
 
 import static com.google.errorprone.matchers.Matchers.instanceMethod;
 import static com.google.errorprone.matchers.method.MethodMatchers.staticMethod;
+import static java.util.Objects.requireNonNull;
 import static java.util.function.Predicate.not;
 
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
@@ -167,7 +168,10 @@ public final class BugPatternTestExtractor implements Extractor<BugPatternTestCa
          * is safe, because this code is guarded by an earlier call to `#getClassUnderTest(..)`,
          * which ensures that `tree` is part of a longer method invocation chain.
          */
-        MethodInvocationTree inputTree = (MethodInvocationTree) ASTHelpers.getReceiver(tree);
+        MethodInvocationTree inputTree =
+            (MethodInvocationTree)
+                requireNonNull(
+                    ASTHelpers.getReceiver(tree), "Instance method invocation must have receiver");
 
         String path = ASTHelpers.constValue(inputTree.getArguments().get(0), String.class);
         Optional<String> inputCode = getSourceCode(inputTree);

error-prone-contrib/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.21.1-SNAPSHOT</version>
+        <version>0.22.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>error-prone-contrib</artifactId>
@@ -62,6 +62,16 @@
             <artifactId>auto-value-annotations</artifactId>
             <scope>provided</scope>
         </dependency>
+        <!-- XXX: JSR-305 (meta-)annotation usage by some dependencies triggers
+        NullAway to attempt to load said annotations. As such some modules
+        require these annotations to be on the classpath. Periodically review
+        whether we can drop this dependeny declaration. See
+        https://github.com/uber/NullAway/issues/1171. -->
+        <dependency>
+            <groupId>com.google.code.findbugs</groupId>
+            <artifactId>jsr305</artifactId>
+            <scope>provided</scope>
+        </dependency>
         <dependency>
             <groupId>com.google.errorprone</groupId>
             <artifactId>error_prone_annotation</artifactId>
@@ -303,9 +313,6 @@
                                 <version>${project.version}</version>
                             </path>
                         </annotationProcessorPaths>
-                        <compilerArgs combine.children="append">
-                            <arg>-Xplugin:DocumentationGenerator -XoutputDirectory=${project.build.directory}/docs</arg>
-                        </compilerArgs>
                     </configuration>
                     <executions>
                         <!-- The Refaster input/output test classes used by

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

@@ -11,6 +11,7 @@ import static com.google.errorprone.matchers.Matchers.not;
 import static com.google.errorprone.matchers.Matchers.returnStatement;
 import static com.google.errorprone.matchers.Matchers.staticMethod;
 import static com.google.errorprone.matchers.Matchers.toType;
+import static java.util.Objects.requireNonNull;
 import static tech.picnic.errorprone.utils.Documentation.BUG_PATTERNS_BASE_URL;
 
 import com.google.auto.service.AutoService;
@@ -79,7 +80,10 @@ public final class DirectReturn extends BugChecker implements BlockTreeMatcher {
       return Description.NO_MATCH;
     }
 
-    Symbol variableSymbol = ASTHelpers.getSymbol(((ReturnTree) finalStatement).getExpression());
+    Symbol variableSymbol =
+        requireNonNull(
+            ASTHelpers.getSymbol(((ReturnTree) finalStatement).getExpression()),
+            "Missing symbol for returned variable");
     StatementTree precedingStatement = statements.get(statements.size() - 2);
 
     return tryMatchAssignment(variableSymbol, precedingStatement)

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

@@ -18,6 +18,7 @@ import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMultiset;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.ImmutableTable;
+import com.google.common.collect.Iterables;
 import com.google.errorprone.BugPattern;
 import com.google.errorprone.VisitorState;
 import com.google.errorprone.bugpatterns.BugChecker;
@@ -33,6 +34,8 @@ import com.sun.source.tree.MethodInvocationTree;
 import com.sun.source.tree.MethodTree;
 import com.sun.tools.javac.code.Symbol.MethodSymbol;
 import com.sun.tools.javac.code.Symbol.VarSymbol;
+import com.sun.tools.javac.code.Type;
+import com.sun.tools.javac.code.Types;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
@@ -178,30 +181,45 @@ public final class ExplicitArgumentEnumeration extends BugChecker
                 state.getTypes())
             .collect(toImmutableList());
 
-    /*
-     * If all overloads have a single parameter, and at least one of them is a varargs method, then
-     * we assume that unwrapping the iterable argument will cause a suitable overload to be invoked.
-     * (Note that there may be multiple varargs overloads, either with different parameter types, or
-     * due to method overriding; this check does not attempt to determine which exact method or
-     * overload will be invoked as a result of the suggested simplification.)
-     *
-     * Note that this is a (highly!) imperfect heuristic, but it is sufficient to prevent e.g.
-     * unwrapping of arguments to `org.jooq.impl.DSL#row`, which can cause the expression's return
-     * type to change from `RowN` to (e.g.) `Row2`.
-     */
-    // XXX: There are certainly cases where it _would_ be nice to unwrap the arguments to
-    // `org.jooq.impl.DSL#row(Collection<?>)`. Look into this.
-    // XXX: Ideally we do check that one of the overloads accepts the unwrapped arguments.
-    // XXX: Ideally we validate that eligible overloads have compatible return types.
-    boolean hasLikelySuitableVarargsOverload =
-        overloads.stream().allMatch(m -> m.params().size() == 1)
-            && overloads.stream().anyMatch(MethodSymbol::isVarArgs);
-
-    return hasLikelySuitableVarargsOverload
+    return hasLikelySuitableVarargsOverload(method, overloads, state)
         ? Optional.of(SourceCode.unwrapMethodInvocation(argument, state))
         : Optional.empty();
   }
 
+  /**
+   * Tells whether it is likely that, if the argument to the given method is unwrapped, a suitable
+   * varargs overload will be invoked instead.
+   *
+   * <p>If all overloads have a single parameter, and at least one of them is a suitably-typed
+   * varargs method, then we assume that unwrapping the iterable argument will cause a suitable
+   * overload to be invoked. (Note that there may be multiple varargs overloads due to method
+   * overriding; this check does not attempt to determine which exact method or overload will be
+   * invoked as a result of the suggested simplification.)
+   *
+   * <p>Note that this is a (highly!) imperfect heuristic, but it is sufficient to prevent e.g.
+   * unwrapping of arguments to `org.jooq.impl.DSL#row`, which can cause the expression's return
+   * type to change from `RowN` to (e.g.) `Row2`.
+   */
+  // XXX: There are certainly cases where it _would_ be nice to unwrap the arguments to
+  // `org.jooq.impl.DSL#row(Collection<?>)`. Look into this.
+  // XXX: Ideally we validate that eligible overloads have compatible return types.
+  private static boolean hasLikelySuitableVarargsOverload(
+      MethodSymbol method, ImmutableList<MethodSymbol> overloads, VisitorState state) {
+    Types types = state.getTypes();
+    // XXX: This logic is fragile, as it assumes that the method parameter's type is of the form
+    // `X<T>`, where `T` is the type of the explicitly enumerated values passed to the expression to
+    // be unwrapped. This should generally hold, given the types returned by the
+    // `EXPLICIT_ITERABLE_CREATOR` expressions: `Iterable<T>`, `List<T>`, `Set<T>`, etc.
+    Type parameterType =
+        Iterables.getOnlyElement(
+            Iterables.getOnlyElement(method.getParameters()).type.getTypeArguments());
+    return overloads.stream().allMatch(m -> m.params().size() == 1)
+        && overloads.stream()
+            .filter(MethodSymbol::isVarArgs)
+            .map(m -> types.elemtype(Iterables.getOnlyElement(m.getParameters()).type))
+            .anyMatch(varArgsType -> types.containsType(parameterType, varArgsType));
+  }
+
   private static Optional<SuggestedFix> trySuggestCallingCustomAlternative(
       MethodInvocationTree tree, MethodInvocationTree argument, VisitorState state) {
     return ALTERNATIVE_METHODS.rowMap().entrySet().stream()

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

@@ -17,6 +17,7 @@ import static com.google.errorprone.matchers.Matchers.isSameType;
 import static com.google.errorprone.matchers.Matchers.methodHasParameters;
 import static com.google.errorprone.matchers.Matchers.staticMethod;
 import static com.google.errorprone.matchers.Matchers.toType;
+import static java.util.Objects.requireNonNull;
 import static java.util.function.Predicate.not;
 import static java.util.stream.Collectors.joining;
 import static tech.picnic.errorprone.utils.Documentation.BUG_PATTERNS_BASE_URL;
@@ -129,7 +130,10 @@ public final class JUnitValueSource extends BugChecker implements MethodTreeMatc
       return Description.NO_MATCH;
     }
 
-    Type parameterType = ASTHelpers.getType(Iterables.getOnlyElement(tree.getParameters()));
+    Type parameterType =
+        requireNonNull(
+            ASTHelpers.getType(Iterables.getOnlyElement(tree.getParameters())),
+            "Missing type for method parameter");
 
     return findMethodSourceAnnotation(tree, state)
         .flatMap(
@@ -173,7 +177,9 @@ public final class JUnitValueSource extends BugChecker implements MethodTreeMatc
 
   private static Optional<MethodTree> findMatchingSibling(
       MethodTree tree, Predicate<? super MethodTree> predicate, VisitorState state) {
-    return state.findEnclosing(ClassTree.class).getMembers().stream()
+    return requireNonNull(state.findEnclosing(ClassTree.class), "No class enclosing method")
+        .getMembers()
+        .stream()
         .filter(MethodTree.class::isInstance)
         .map(MethodTree.class::cast)
         .filter(not(tree::equals))

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

@@ -5,6 +5,7 @@ import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
 import static com.google.errorprone.BugPattern.StandardTags.SIMPLIFICATION;
 import static com.google.errorprone.matchers.Matchers.anyOf;
 import static com.google.errorprone.matchers.Matchers.instanceMethod;
+import static java.util.Objects.requireNonNull;
 import static tech.picnic.errorprone.utils.Documentation.BUG_PATTERNS_BASE_URL;
 
 import com.google.auto.service.AutoService;
@@ -86,7 +87,9 @@ public final class NonEmptyMono extends BugChecker implements MethodInvocationTr
       return Description.NO_MATCH;
     }
 
-    ExpressionTree receiver = ASTHelpers.getReceiver(tree);
+    ExpressionTree receiver =
+        requireNonNull(
+            ASTHelpers.getReceiver(tree), "Instance method invocation must have receiver");
     if (!NON_EMPTY_MONO.matches(receiver, state)) {
       return Description.NO_MATCH;
     }

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

@@ -204,6 +204,11 @@ final class AssertJEnumerableRules {
       return enumAssert.hasSize(iterable.length);
     }
 
+    @BeforeTemplate
+    EnumerableAssert<?, S> before(EnumerableAssert<?, S> enumAssert, CharSequence iterable) {
+      return enumAssert.hasSize(iterable.length());
+    }
+
     @AfterTemplate
     EnumerableAssert<?, S> after(EnumerableAssert<?, S> enumAssert, Iterable<E> iterable) {
       return enumAssert.hasSameSizeAs(iterable);

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

@@ -515,8 +515,14 @@ final class ReactorRules {
           mono.switchIfEmpty(Mono.empty()), mono.flux().next(), mono.flux().singleOrEmpty());
     }
 
+    // XXX: Consider filing a SonarCloud issue for the S2637 false positive.
     @BeforeTemplate
-    Mono<@Nullable Void> before2(Mono<@Nullable Void> mono) {
+    @SuppressWarnings({
+      "java:S2637" /* False positive: result is never `null`. */,
+      "java:S4968" /* Result may be `Mono<Void>`. */,
+      "key-to-resolve-AnnotationUseStyle-and-TrailingComment-check-conflict"
+    })
+    Mono<? extends @Nullable Void> before2(Mono<@Nullable Void> mono) {
       return Refaster.anyOf(mono.ignoreElement(), mono.then());
     }
 
@@ -945,7 +951,8 @@ final class ReactorRules {
   /** Prefer direct invocation of {@link Mono#then()}} over more contrived alternatives. */
   static final class MonoThen<T> {
     @BeforeTemplate
-    Mono<@Nullable Void> before(Mono<T> mono) {
+    @SuppressWarnings("java:S4968" /* Result may be `Mono<Void>`. */)
+    Mono<? extends @Nullable Void> before(Mono<T> mono) {
       return Refaster.anyOf(
           mono.ignoreElement().then(),
           mono.flux().then(),
@@ -954,7 +961,8 @@ final class ReactorRules {
     }
 
     @AfterTemplate
-    Mono<@Nullable Void> after(Mono<T> mono) {
+    @SuppressWarnings("java:S4968" /* Result may be `Mono<Void>`. */)
+    Mono<? extends @Nullable Void> after(Mono<T> mono) {
       return mono.then();
     }
   }
@@ -962,17 +970,25 @@ final class ReactorRules {
   /** Avoid vacuous invocations of {@link Flux#ignoreElements()}. */
   static final class FluxThen<T> {
     @BeforeTemplate
-    Mono<@Nullable Void> before(Flux<T> flux) {
+    @SuppressWarnings("java:S4968" /* Result may be `Mono<Void>`. */)
+    Mono<? extends @Nullable Void> before(Flux<T> flux) {
       return flux.ignoreElements().then();
     }
 
+    // XXX: Consider filing a SonarCloud issue for the S2637 false positive.
     @BeforeTemplate
-    Mono<@Nullable Void> before2(Flux<@Nullable Void> flux) {
+    @SuppressWarnings({
+      "java:S2637" /* False positive: result is never `null`. */,
+      "java:S4968" /* Result may be `Mono<Void>`. */,
+      "key-to-resolve-AnnotationUseStyle-and-TrailingComment-check-conflict"
+    })
+    Mono<? extends @Nullable Void> before2(Flux<@Nullable Void> flux) {
       return flux.ignoreElements();
     }
 
     @AfterTemplate
-    Mono<@Nullable Void> after(Flux<T> flux) {
+    @SuppressWarnings("java:S4968" /* Result may be `Mono<Void>`. */)
+    Mono<? extends @Nullable Void> after(Flux<T> flux) {
       return flux.then();
     }
   }
@@ -980,12 +996,14 @@ final class ReactorRules {
   /** Avoid vacuous invocations of {@link Mono#ignoreElement()}. */
   static final class MonoThenEmpty<T> {
     @BeforeTemplate
-    Mono<@Nullable Void> before(Mono<T> mono, Publisher<@Nullable Void> publisher) {
+    @SuppressWarnings("java:S4968" /* Result may be `Mono<Void>`. */)
+    Mono<? extends @Nullable Void> before(Mono<T> mono, Publisher<@Nullable Void> publisher) {
       return mono.ignoreElement().thenEmpty(publisher);
     }
 
     @AfterTemplate
-    Mono<@Nullable Void> after(Mono<T> mono, Publisher<@Nullable Void> publisher) {
+    @SuppressWarnings("java:S4968" /* Result may be `Mono<Void>`. */)
+    Mono<? extends @Nullable Void> after(Mono<T> mono, Publisher<@Nullable Void> publisher) {
       return mono.thenEmpty(publisher);
     }
   }
@@ -993,12 +1011,14 @@ final class ReactorRules {
   /** Avoid vacuous invocations of {@link Flux#ignoreElements()}. */
   static final class FluxThenEmpty<T> {
     @BeforeTemplate
-    Mono<@Nullable Void> before(Flux<T> flux, Publisher<@Nullable Void> publisher) {
+    @SuppressWarnings("java:S4968" /* Result may be `Mono<Void>`. */)
+    Mono<? extends @Nullable Void> before(Flux<T> flux, Publisher<@Nullable Void> publisher) {
       return flux.ignoreElements().thenEmpty(publisher);
     }
 
     @AfterTemplate
-    Mono<@Nullable Void> after(Flux<T> flux, Publisher<@Nullable Void> publisher) {
+    @SuppressWarnings("java:S4968" /* Result may be `Mono<Void>`. */)
+    Mono<? extends @Nullable Void> after(Flux<T> flux, Publisher<@Nullable Void> publisher) {
       return flux.thenEmpty(publisher);
     }
   }
@@ -1054,7 +1074,8 @@ final class ReactorRules {
     }
 
     @BeforeTemplate
-    Mono<@Nullable Void> before2(Mono<T> mono1, Mono<@Nullable Void> mono2) {
+    @SuppressWarnings("java:S4968" /* Result may be `Mono<Void>`. */)
+    Mono<? extends @Nullable Void> before2(Mono<T> mono1, Mono<@Nullable Void> mono2) {
       return mono1.thenEmpty(mono2);
     }
 
@@ -1072,7 +1093,8 @@ final class ReactorRules {
     }
 
     @BeforeTemplate
-    Mono<@Nullable Void> before2(Flux<T> flux, Mono<@Nullable Void> mono) {
+    @SuppressWarnings("java:S4968" /* Result may be `Mono<Void>`. */)
+    Mono<? extends @Nullable Void> before2(Flux<T> flux, Mono<@Nullable Void> mono) {
       return flux.thenEmpty(mono);
     }
 

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

@@ -23,14 +23,16 @@ final class RxJava2AdapterRules {
   /** Use the fluent API style when using {@link RxJava2Adapter#completableToMono}. */
   static final class CompletableToMono {
     @BeforeTemplate
-    Mono<@Nullable Void> before(Completable completable) {
+    @SuppressWarnings("java:S4968" /* Result may be `Mono<Void>`. */)
+    Mono<? extends @Nullable Void> before(Completable completable) {
       return Refaster.anyOf(
           RxJava2Adapter.completableToMono(completable),
           completable.to(RxJava2Adapter::completableToMono));
     }
 
     @AfterTemplate
-    Mono<@Nullable Void> after(Completable completable) {
+    @SuppressWarnings("java:S4968" /* Result may be `Mono<Void>`. */)
+    Mono<? extends @Nullable Void> after(Completable completable) {
       return completable.as(RxJava2Adapter::completableToMono);
     }
   }

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

@@ -16,6 +16,8 @@ final class ExplicitArgumentEnumerationTest {
             "import com.google.common.collect.ImmutableList;",
             "import com.google.errorprone.CompilationTestHelper;",
             "import com.google.errorprone.bugpatterns.BugChecker;",
+            "import io.micrometer.core.instrument.Counter;",
+            "import io.micrometer.core.instrument.Tag;",
             "import org.jooq.impl.DSL;",
             "import reactor.core.publisher.Flux;",
             "import reactor.test.StepVerifier;",
@@ -32,6 +34,8 @@ final class ExplicitArgumentEnumerationTest {
             "",
             "    DSL.row(ImmutableList.of(1, 2));",
             "",
+            "    Counter.builder(\"foo\").tags(ImmutableList.of(Tag.of(\"bar\", \"baz\")));",
+            "",
             "    // BUG: Diagnostic contains:",
             "    unaryMethod(ImmutableList.of(1, 2));",
             "    unaryMethodWithLessVisibleOverload(ImmutableList.of(1, 2));",

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

@@ -67,10 +67,11 @@ final class AssertJEnumerableRulesTest implements RefasterRuleCollectionTestCase
         assertThat(ImmutableSet.of(4)).size().isBetween(5, 6));
   }
 
-  ImmutableSet<EnumerableAssert<?, Integer>> testEnumerableAssertHasSameSizeAs() {
+  ImmutableSet<EnumerableAssert<?, Character>> testEnumerableAssertHasSameSizeAs() {
     return ImmutableSet.of(
-        assertThat(ImmutableSet.of(1)).hasSize(Iterables.size(ImmutableSet.of(2))),
-        assertThat(ImmutableSet.of(3)).hasSize(ImmutableSet.of(4).size()),
-        assertThat(ImmutableSet.of(5)).hasSize(new Integer[0].length));
+        assertThat("foo").hasSize(Iterables.size(ImmutableSet.of(1))),
+        assertThat("bar").hasSize(ImmutableSet.of(2).size()),
+        assertThat("baz").hasSize(new Integer[0].length),
+        assertThat("qux").hasSize("quux".length()));
   }
 }

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

@@ -66,10 +66,11 @@ final class AssertJEnumerableRulesTest implements RefasterRuleCollectionTestCase
         assertThat(ImmutableSet.of(4)).hasSizeBetween(5, 6));
   }
 
-  ImmutableSet<EnumerableAssert<?, Integer>> testEnumerableAssertHasSameSizeAs() {
+  ImmutableSet<EnumerableAssert<?, Character>> testEnumerableAssertHasSameSizeAs() {
     return ImmutableSet.of(
-        assertThat(ImmutableSet.of(1)).hasSameSizeAs(ImmutableSet.of(2)),
-        assertThat(ImmutableSet.of(3)).hasSameSizeAs(ImmutableSet.of(4)),
-        assertThat(ImmutableSet.of(5)).hasSameSizeAs(new Integer[0]));
+        assertThat("foo").hasSameSizeAs(ImmutableSet.of(1)),
+        assertThat("bar").hasSameSizeAs(ImmutableSet.of(2)),
+        assertThat("baz").hasSameSizeAs(new Integer[0]),
+        assertThat("qux").hasSameSizeAs("quux"));
   }
 }

error-prone-experimental/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.21.1-SNAPSHOT</version>
+        <version>0.22.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>error-prone-experimental</artifactId>

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

@@ -29,6 +29,7 @@ import com.sun.source.tree.ReturnTree;
 import com.sun.source.tree.Tree;
 import com.sun.source.tree.VariableTree;
 import com.sun.tools.javac.code.Symbol;
+import com.sun.tools.javac.code.Symbol.PackageSymbol;
 import com.sun.tools.javac.code.Type;
 import java.util.List;
 import java.util.Optional;
@@ -126,7 +127,7 @@ public final class MethodReferenceUsage extends BugChecker implements LambdaExpr
         return Optional.empty();
       }
 
-      Symbol sym = ASTHelpers.getSymbol(methodSelect);
+      Symbol sym = ASTHelpers.getSymbol(subTree);
       return ASTHelpers.isStatic(sym)
           ? constructFix(lambdaExpr, sym.owner, methodSelect)
           : constructFix(lambdaExpr, "this", methodSelect);
@@ -200,7 +201,8 @@ public final class MethodReferenceUsage extends BugChecker implements LambdaExpr
     Name sName = target.getSimpleName();
     Optional<SuggestedFix.Builder> fix = constructFix(lambdaExpr, sName, methodName);
 
-    if (!"java.lang".equals(ASTHelpers.enclosingPackage(target).toString())) {
+    PackageSymbol pkg = ASTHelpers.enclosingPackage(target);
+    if (pkg != null && !"java.lang".equals(pkg.toString())) {
       Name fqName = target.getQualifiedName();
       if (!sName.equals(fqName)) {
         return fix.map(b -> b.addImport(fqName.toString()));

error-prone-guidelines/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.21.1-SNAPSHOT</version>
+        <version>0.22.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>error-prone-guidelines</artifactId>
@@ -118,9 +118,6 @@
                                 <version>${project.version}</version>
                             </path>
                         </annotationProcessorPaths>
-                        <compilerArgs combine.children="append">
-                            <arg>-Xplugin:DocumentationGenerator -XoutputDirectory=${project.build.directory}/docs</arg>
-                        </compilerArgs>
                     </configuration>
                 </plugin>
             </plugins>

error-prone-utils/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.21.1-SNAPSHOT</version>
+        <version>0.22.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>error-prone-utils</artifactId>

error-prone-utils/src/main/java/tech/picnic/errorprone/utils/AnnotationAttributeMatcher.java

@@ -1,5 +1,7 @@
 package tech.picnic.errorprone.utils;
 
+import static java.util.Objects.requireNonNull;
+
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.HashMultimap;
 import com.google.common.collect.ImmutableSet;
@@ -115,9 +117,15 @@ public final class AnnotationAttributeMatcher implements Serializable {
   }
 
   private static String extractAttributeName(ExpressionTree expr) {
-    return (expr instanceof AssignmentTree assignment)
-        ? ASTHelpers.getSymbol(assignment.getVariable()).getSimpleName().toString()
-        : "value";
+    if (!(expr instanceof AssignmentTree assignment)) {
+      return "value";
+    }
+
+    return requireNonNull(
+            ASTHelpers.getSymbol(assignment.getVariable()),
+            "Missing symbol for annotation attribute")
+        .getSimpleName()
+        .toString();
   }
 
   // XXX: The caller of this method can be implemented more efficiently in case of a "wholeTypes"

integration-tests/checkstyle.sh

@@ -11,6 +11,8 @@ additional_source_directories='${project.basedir}${file.separator}src${file.sepa
 shared_error_prone_flags='-XepExcludedPaths:(\Q${project.basedir}${file.separator}src${file.separator}\E(it|test|xdocs-examples)\Q${file.separator}resources\E|\Q${project.build.directory}${file.separator}\E).*'
 patch_error_prone_flags=''
 validation_error_prone_flags=''
+patch_error_prone_flags='-XepOpt:Refaster:NamePattern=.*Workshop.*"'
+validation_error_prone_flags='-XepOpt:Refaster:NamePattern=.*Workshop.*"'
 # 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.

integration-tests/metrics-init.patch

@@ -38,7 +38,7 @@
 +            <dependency>
 +                <groupId>com.google.guava</groupId>
 +                <artifactId>guava</artifactId>
-+                <version>33.4.0-jre<!-- Renovate: com.google.guava:guava-bom --></version>
++                <version>33.4.7-jre<!-- Renovate: com.google.guava:guava-bom --></version>
 +            </dependency>
 +        </dependencies>
 +    </dependencyManagement>

mvnw

@@ -0,0 +1,308 @@
+#!/bin/sh
+# ----------------------------------------------------------------------------
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+# ----------------------------------------------------------------------------
+
+# ----------------------------------------------------------------------------
+# Apache Maven Wrapper startup batch script, version 3.2.0
+#
+# Required ENV vars:
+# ------------------
+#   JAVA_HOME - location of a JDK home dir
+#
+# Optional ENV vars
+# -----------------
+#   MAVEN_OPTS - parameters passed to the Java VM when running Maven
+#     e.g. to debug Maven itself, use
+#       set MAVEN_OPTS=-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000
+#   MAVEN_SKIP_RC - flag to disable loading of mavenrc files
+# ----------------------------------------------------------------------------
+
+if [ -z "$MAVEN_SKIP_RC" ] ; then
+
+  if [ -f /usr/local/etc/mavenrc ] ; then
+    . /usr/local/etc/mavenrc
+  fi
+
+  if [ -f /etc/mavenrc ] ; then
+    . /etc/mavenrc
+  fi
+
+  if [ -f "$HOME/.mavenrc" ] ; then
+    . "$HOME/.mavenrc"
+  fi
+
+fi
+
+# OS specific support.  $var _must_ be set to either true or false.
+cygwin=false;
+darwin=false;
+mingw=false
+case "$(uname)" in
+  CYGWIN*) cygwin=true ;;
+  MINGW*) mingw=true;;
+  Darwin*) darwin=true
+    # Use /usr/libexec/java_home if available, otherwise fall back to /Library/Java/Home
+    # See https://developer.apple.com/library/mac/qa/qa1170/_index.html
+    if [ -z "$JAVA_HOME" ]; then
+      if [ -x "/usr/libexec/java_home" ]; then
+        JAVA_HOME="$(/usr/libexec/java_home)"; export JAVA_HOME
+      else
+        JAVA_HOME="/Library/Java/Home"; export JAVA_HOME
+      fi
+    fi
+    ;;
+esac
+
+if [ -z "$JAVA_HOME" ] ; then
+  if [ -r /etc/gentoo-release ] ; then
+    JAVA_HOME=$(java-config --jre-home)
+  fi
+fi
+
+# For Cygwin, ensure paths are in UNIX format before anything is touched
+if $cygwin ; then
+  [ -n "$JAVA_HOME" ] &&
+    JAVA_HOME=$(cygpath --unix "$JAVA_HOME")
+  [ -n "$CLASSPATH" ] &&
+    CLASSPATH=$(cygpath --path --unix "$CLASSPATH")
+fi
+
+# For Mingw, ensure paths are in UNIX format before anything is touched
+if $mingw ; then
+  [ -n "$JAVA_HOME" ] && [ -d "$JAVA_HOME" ] &&
+    JAVA_HOME="$(cd "$JAVA_HOME" || (echo "cannot cd into $JAVA_HOME."; exit 1); pwd)"
+fi
+
+if [ -z "$JAVA_HOME" ]; then
+  javaExecutable="$(which javac)"
+  if [ -n "$javaExecutable" ] && ! [ "$(expr "\"$javaExecutable\"" : '\([^ ]*\)')" = "no" ]; then
+    # readlink(1) is not available as standard on Solaris 10.
+    readLink=$(which readlink)
+    if [ ! "$(expr "$readLink" : '\([^ ]*\)')" = "no" ]; then
+      if $darwin ; then
+        javaHome="$(dirname "\"$javaExecutable\"")"
+        javaExecutable="$(cd "\"$javaHome\"" && pwd -P)/javac"
+      else
+        javaExecutable="$(readlink -f "\"$javaExecutable\"")"
+      fi
+      javaHome="$(dirname "\"$javaExecutable\"")"
+      javaHome=$(expr "$javaHome" : '\(.*\)/bin')
+      JAVA_HOME="$javaHome"
+      export JAVA_HOME
+    fi
+  fi
+fi
+
+if [ -z "$JAVACMD" ] ; then
+  if [ -n "$JAVA_HOME"  ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+      # IBM's JDK on AIX uses strange locations for the executables
+      JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+      JAVACMD="$JAVA_HOME/bin/java"
+    fi
+  else
+    JAVACMD="$(\unset -f command 2>/dev/null; \command -v java)"
+  fi
+fi
+
+if [ ! -x "$JAVACMD" ] ; then
+  echo "Error: JAVA_HOME is not defined correctly." >&2
+  echo "  We cannot execute $JAVACMD" >&2
+  exit 1
+fi
+
+if [ -z "$JAVA_HOME" ] ; then
+  echo "Warning: JAVA_HOME environment variable is not set."
+fi
+
+# traverses directory structure from process work directory to filesystem root
+# first directory with .mvn subdirectory is considered project base directory
+find_maven_basedir() {
+  if [ -z "$1" ]
+  then
+    echo "Path not specified to find_maven_basedir"
+    return 1
+  fi
+
+  basedir="$1"
+  wdir="$1"
+  while [ "$wdir" != '/' ] ; do
+    if [ -d "$wdir"/.mvn ] ; then
+      basedir=$wdir
+      break
+    fi
+    # workaround for JBEAP-8937 (on Solaris 10/Sparc)
+    if [ -d "${wdir}" ]; then
+      wdir=$(cd "$wdir/.." || exit 1; pwd)
+    fi
+    # end of workaround
+  done
+  printf '%s' "$(cd "$basedir" || exit 1; pwd)"
+}
+
+# concatenates all lines of a file
+concat_lines() {
+  if [ -f "$1" ]; then
+    # Remove \r in case we run on Windows within Git Bash
+    # and check out the repository with auto CRLF management
+    # enabled. Otherwise, we may read lines that are delimited with
+    # \r\n and produce $'-Xarg\r' rather than -Xarg due to word
+    # splitting rules.
+    tr -s '\r\n' ' ' < "$1"
+  fi
+}
+
+log() {
+  if [ "$MVNW_VERBOSE" = true ]; then
+    printf '%s\n' "$1"
+  fi
+}
+
+BASE_DIR=$(find_maven_basedir "$(dirname "$0")")
+if [ -z "$BASE_DIR" ]; then
+  exit 1;
+fi
+
+MAVEN_PROJECTBASEDIR=${MAVEN_BASEDIR:-"$BASE_DIR"}; export MAVEN_PROJECTBASEDIR
+log "$MAVEN_PROJECTBASEDIR"
+
+##########################################################################################
+# Extension to allow automatically downloading the maven-wrapper.jar from Maven-central
+# This allows using the maven wrapper in projects that prohibit checking in binary data.
+##########################################################################################
+wrapperJarPath="$MAVEN_PROJECTBASEDIR/.mvn/wrapper/maven-wrapper.jar"
+if [ -r "$wrapperJarPath" ]; then
+    log "Found $wrapperJarPath"
+else
+    log "Couldn't find $wrapperJarPath, downloading it ..."
+
+    if [ -n "$MVNW_REPOURL" ]; then
+      wrapperUrl="$MVNW_REPOURL/org/apache/maven/wrapper/maven-wrapper/3.2.0/maven-wrapper-3.2.0.jar"
+    else
+      wrapperUrl="https://repo.maven.apache.org/maven2/org/apache/maven/wrapper/maven-wrapper/3.2.0/maven-wrapper-3.2.0.jar"
+    fi
+    while IFS="=" read -r key value; do
+      # Remove '\r' from value to allow usage on windows as IFS does not consider '\r' as a separator ( considers space, tab, new line ('\n'), and custom '=' )
+      safeValue=$(echo "$value" | tr -d '\r')
+      case "$key" in (wrapperUrl) wrapperUrl="$safeValue"; break ;;
+      esac
+    done < "$MAVEN_PROJECTBASEDIR/.mvn/wrapper/maven-wrapper.properties"
+    log "Downloading from: $wrapperUrl"
+
+    if $cygwin; then
+      wrapperJarPath=$(cygpath --path --windows "$wrapperJarPath")
+    fi
+
+    if command -v wget > /dev/null; then
+        log "Found wget ... using wget"
+        [ "$MVNW_VERBOSE" = true ] && QUIET="" || QUIET="--quiet"
+        if [ -z "$MVNW_USERNAME" ] || [ -z "$MVNW_PASSWORD" ]; then
+            wget $QUIET "$wrapperUrl" -O "$wrapperJarPath" || rm -f "$wrapperJarPath"
+        else
+            wget $QUIET --http-user="$MVNW_USERNAME" --http-password="$MVNW_PASSWORD" "$wrapperUrl" -O "$wrapperJarPath" || rm -f "$wrapperJarPath"
+        fi
+    elif command -v curl > /dev/null; then
+        log "Found curl ... using curl"
+        [ "$MVNW_VERBOSE" = true ] && QUIET="" || QUIET="--silent"
+        if [ -z "$MVNW_USERNAME" ] || [ -z "$MVNW_PASSWORD" ]; then
+            curl $QUIET -o "$wrapperJarPath" "$wrapperUrl" -f -L || rm -f "$wrapperJarPath"
+        else
+            curl $QUIET --user "$MVNW_USERNAME:$MVNW_PASSWORD" -o "$wrapperJarPath" "$wrapperUrl" -f -L || rm -f "$wrapperJarPath"
+        fi
+    else
+        log "Falling back to using Java to download"
+        javaSource="$MAVEN_PROJECTBASEDIR/.mvn/wrapper/MavenWrapperDownloader.java"
+        javaClass="$MAVEN_PROJECTBASEDIR/.mvn/wrapper/MavenWrapperDownloader.class"
+        # For Cygwin, switch paths to Windows format before running javac
+        if $cygwin; then
+          javaSource=$(cygpath --path --windows "$javaSource")
+          javaClass=$(cygpath --path --windows "$javaClass")
+        fi
+        if [ -e "$javaSource" ]; then
+            if [ ! -e "$javaClass" ]; then
+                log " - Compiling MavenWrapperDownloader.java ..."
+                ("$JAVA_HOME/bin/javac" "$javaSource")
+            fi
+            if [ -e "$javaClass" ]; then
+                log " - Running MavenWrapperDownloader.java ..."
+                ("$JAVA_HOME/bin/java" -cp .mvn/wrapper MavenWrapperDownloader "$wrapperUrl" "$wrapperJarPath") || rm -f "$wrapperJarPath"
+            fi
+        fi
+    fi
+fi
+##########################################################################################
+# End of extension
+##########################################################################################
+
+# If specified, validate the SHA-256 sum of the Maven wrapper jar file
+wrapperSha256Sum=""
+while IFS="=" read -r key value; do
+  case "$key" in (wrapperSha256Sum) wrapperSha256Sum=$value; break ;;
+  esac
+done < "$MAVEN_PROJECTBASEDIR/.mvn/wrapper/maven-wrapper.properties"
+if [ -n "$wrapperSha256Sum" ]; then
+  wrapperSha256Result=false
+  if command -v sha256sum > /dev/null; then
+    if echo "$wrapperSha256Sum  $wrapperJarPath" | sha256sum -c > /dev/null 2>&1; then
+      wrapperSha256Result=true
+    fi
+  elif command -v shasum > /dev/null; then
+    if echo "$wrapperSha256Sum  $wrapperJarPath" | shasum -a 256 -c > /dev/null 2>&1; then
+      wrapperSha256Result=true
+    fi
+  else
+    echo "Checksum validation was requested but neither 'sha256sum' or 'shasum' are available."
+    echo "Please install either command, or disable validation by removing 'wrapperSha256Sum' from your maven-wrapper.properties."
+    exit 1
+  fi
+  if [ $wrapperSha256Result = false ]; then
+    echo "Error: Failed to validate Maven wrapper SHA-256, your Maven wrapper might be compromised." >&2
+    echo "Investigate or delete $wrapperJarPath to attempt a clean download." >&2
+    echo "If you updated your Maven version, you need to update the specified wrapperSha256Sum property." >&2
+    exit 1
+  fi
+fi
+
+MAVEN_OPTS="$(concat_lines "$MAVEN_PROJECTBASEDIR/.mvn/jvm.config") $MAVEN_OPTS"
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin; then
+  [ -n "$JAVA_HOME" ] &&
+    JAVA_HOME=$(cygpath --path --windows "$JAVA_HOME")
+  [ -n "$CLASSPATH" ] &&
+    CLASSPATH=$(cygpath --path --windows "$CLASSPATH")
+  [ -n "$MAVEN_PROJECTBASEDIR" ] &&
+    MAVEN_PROJECTBASEDIR=$(cygpath --path --windows "$MAVEN_PROJECTBASEDIR")
+fi
+
+# Provide a "standardized" way to retrieve the CLI args that will
+# work with both Windows and non-Windows executions.
+MAVEN_CMD_LINE_ARGS="$MAVEN_CONFIG $*"
+export MAVEN_CMD_LINE_ARGS
+
+WRAPPER_LAUNCHER=org.apache.maven.wrapper.MavenWrapperMain
+
+# shellcheck disable=SC2086 # safe args
+exec "$JAVACMD" \
+  $MAVEN_OPTS \
+  $MAVEN_DEBUG_OPTS \
+  -classpath "$MAVEN_PROJECTBASEDIR/.mvn/wrapper/maven-wrapper.jar" \
+  "-Dmaven.multiModuleProjectDirectory=${MAVEN_PROJECTBASEDIR}" \
+  ${WRAPPER_LAUNCHER} $MAVEN_CONFIG "$@"

mvnw.cmd

@@ -0,0 +1,205 @@
+@REM ----------------------------------------------------------------------------
+@REM Licensed to the Apache Software Foundation (ASF) under one
+@REM or more contributor license agreements.  See the NOTICE file
+@REM distributed with this work for additional information
+@REM regarding copyright ownership.  The ASF licenses this file
+@REM to you under the Apache License, Version 2.0 (the
+@REM "License"); you may not use this file except in compliance
+@REM with the License.  You may obtain a copy of the License at
+@REM
+@REM    http://www.apache.org/licenses/LICENSE-2.0
+@REM
+@REM Unless required by applicable law or agreed to in writing,
+@REM software distributed under the License is distributed on an
+@REM "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+@REM KIND, either express or implied.  See the License for the
+@REM specific language governing permissions and limitations
+@REM under the License.
+@REM ----------------------------------------------------------------------------
+
+@REM ----------------------------------------------------------------------------
+@REM Apache Maven Wrapper startup batch script, version 3.2.0
+@REM
+@REM Required ENV vars:
+@REM JAVA_HOME - location of a JDK home dir
+@REM
+@REM Optional ENV vars
+@REM MAVEN_BATCH_ECHO - set to 'on' to enable the echoing of the batch commands
+@REM MAVEN_BATCH_PAUSE - set to 'on' to wait for a keystroke before ending
+@REM MAVEN_OPTS - parameters passed to the Java VM when running Maven
+@REM     e.g. to debug Maven itself, use
+@REM set MAVEN_OPTS=-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000
+@REM MAVEN_SKIP_RC - flag to disable loading of mavenrc files
+@REM ----------------------------------------------------------------------------
+
+@REM Begin all REM lines with '@' in case MAVEN_BATCH_ECHO is 'on'
+@echo off
+@REM set title of command window
+title %0
+@REM enable echoing by setting MAVEN_BATCH_ECHO to 'on'
+@if "%MAVEN_BATCH_ECHO%" == "on"  echo %MAVEN_BATCH_ECHO%
+
+@REM set %HOME% to equivalent of $HOME
+if "%HOME%" == "" (set "HOME=%HOMEDRIVE%%HOMEPATH%")
+
+@REM Execute a user defined script before this one
+if not "%MAVEN_SKIP_RC%" == "" goto skipRcPre
+@REM check for pre script, once with legacy .bat ending and once with .cmd ending
+if exist "%USERPROFILE%\mavenrc_pre.bat" call "%USERPROFILE%\mavenrc_pre.bat" %*
+if exist "%USERPROFILE%\mavenrc_pre.cmd" call "%USERPROFILE%\mavenrc_pre.cmd" %*
+:skipRcPre
+
+@setlocal
+
+set ERROR_CODE=0
+
+@REM To isolate internal variables from possible post scripts, we use another setlocal
+@setlocal
+
+@REM ==== START VALIDATION ====
+if not "%JAVA_HOME%" == "" goto OkJHome
+
+echo.
+echo Error: JAVA_HOME not found in your environment. >&2
+echo Please set the JAVA_HOME variable in your environment to match the >&2
+echo location of your Java installation. >&2
+echo.
+goto error
+
+:OkJHome
+if exist "%JAVA_HOME%\bin\java.exe" goto init
+
+echo.
+echo Error: JAVA_HOME is set to an invalid directory. >&2
+echo JAVA_HOME = "%JAVA_HOME%" >&2
+echo Please set the JAVA_HOME variable in your environment to match the >&2
+echo location of your Java installation. >&2
+echo.
+goto error
+
+@REM ==== END VALIDATION ====
+
+:init
+
+@REM Find the project base dir, i.e. the directory that contains the folder ".mvn".
+@REM Fallback to current working directory if not found.
+
+set MAVEN_PROJECTBASEDIR=%MAVEN_BASEDIR%
+IF NOT "%MAVEN_PROJECTBASEDIR%"=="" goto endDetectBaseDir
+
+set EXEC_DIR=%CD%
+set WDIR=%EXEC_DIR%
+:findBaseDir
+IF EXIST "%WDIR%"\.mvn goto baseDirFound
+cd ..
+IF "%WDIR%"=="%CD%" goto baseDirNotFound
+set WDIR=%CD%
+goto findBaseDir
+
+:baseDirFound
+set MAVEN_PROJECTBASEDIR=%WDIR%
+cd "%EXEC_DIR%"
+goto endDetectBaseDir
+
+:baseDirNotFound
+set MAVEN_PROJECTBASEDIR=%EXEC_DIR%
+cd "%EXEC_DIR%"
+
+:endDetectBaseDir
+
+IF NOT EXIST "%MAVEN_PROJECTBASEDIR%\.mvn\jvm.config" goto endReadAdditionalConfig
+
+@setlocal EnableExtensions EnableDelayedExpansion
+for /F "usebackq delims=" %%a in ("%MAVEN_PROJECTBASEDIR%\.mvn\jvm.config") do set JVM_CONFIG_MAVEN_PROPS=!JVM_CONFIG_MAVEN_PROPS! %%a
+@endlocal & set JVM_CONFIG_MAVEN_PROPS=%JVM_CONFIG_MAVEN_PROPS%
+
+:endReadAdditionalConfig
+
+SET MAVEN_JAVA_EXE="%JAVA_HOME%\bin\java.exe"
+set WRAPPER_JAR="%MAVEN_PROJECTBASEDIR%\.mvn\wrapper\maven-wrapper.jar"
+set WRAPPER_LAUNCHER=org.apache.maven.wrapper.MavenWrapperMain
+
+set WRAPPER_URL="https://repo.maven.apache.org/maven2/org/apache/maven/wrapper/maven-wrapper/3.2.0/maven-wrapper-3.2.0.jar"
+
+FOR /F "usebackq tokens=1,2 delims==" %%A IN ("%MAVEN_PROJECTBASEDIR%\.mvn\wrapper\maven-wrapper.properties") DO (
+    IF "%%A"=="wrapperUrl" SET WRAPPER_URL=%%B
+)
+
+@REM Extension to allow automatically downloading the maven-wrapper.jar from Maven-central
+@REM This allows using the maven wrapper in projects that prohibit checking in binary data.
+if exist %WRAPPER_JAR% (
+    if "%MVNW_VERBOSE%" == "true" (
+        echo Found %WRAPPER_JAR%
+    )
+) else (
+    if not "%MVNW_REPOURL%" == "" (
+        SET WRAPPER_URL="%MVNW_REPOURL%/org/apache/maven/wrapper/maven-wrapper/3.2.0/maven-wrapper-3.2.0.jar"
+    )
+    if "%MVNW_VERBOSE%" == "true" (
+        echo Couldn't find %WRAPPER_JAR%, downloading it ...
+        echo Downloading from: %WRAPPER_URL%
+    )
+
+    powershell -Command "&{"^
+		"$webclient = new-object System.Net.WebClient;"^
+		"if (-not ([string]::IsNullOrEmpty('%MVNW_USERNAME%') -and [string]::IsNullOrEmpty('%MVNW_PASSWORD%'))) {"^
+		"$webclient.Credentials = new-object System.Net.NetworkCredential('%MVNW_USERNAME%', '%MVNW_PASSWORD%');"^
+		"}"^
+		"[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; $webclient.DownloadFile('%WRAPPER_URL%', '%WRAPPER_JAR%')"^
+		"}"
+    if "%MVNW_VERBOSE%" == "true" (
+        echo Finished downloading %WRAPPER_JAR%
+    )
+)
+@REM End of extension
+
+@REM If specified, validate the SHA-256 sum of the Maven wrapper jar file
+SET WRAPPER_SHA_256_SUM=""
+FOR /F "usebackq tokens=1,2 delims==" %%A IN ("%MAVEN_PROJECTBASEDIR%\.mvn\wrapper\maven-wrapper.properties") DO (
+    IF "%%A"=="wrapperSha256Sum" SET WRAPPER_SHA_256_SUM=%%B
+)
+IF NOT %WRAPPER_SHA_256_SUM%=="" (
+    powershell -Command "&{"^
+       "$hash = (Get-FileHash \"%WRAPPER_JAR%\" -Algorithm SHA256).Hash.ToLower();"^
+       "If('%WRAPPER_SHA_256_SUM%' -ne $hash){"^
+       "  Write-Output 'Error: Failed to validate Maven wrapper SHA-256, your Maven wrapper might be compromised.';"^
+       "  Write-Output 'Investigate or delete %WRAPPER_JAR% to attempt a clean download.';"^
+       "  Write-Output 'If you updated your Maven version, you need to update the specified wrapperSha256Sum property.';"^
+       "  exit 1;"^
+       "}"^
+       "}"
+    if ERRORLEVEL 1 goto error
+)
+
+@REM Provide a "standardized" way to retrieve the CLI args that will
+@REM work with both Windows and non-Windows executions.
+set MAVEN_CMD_LINE_ARGS=%*
+
+%MAVEN_JAVA_EXE% ^
+  %JVM_CONFIG_MAVEN_PROPS% ^
+  %MAVEN_OPTS% ^
+  %MAVEN_DEBUG_OPTS% ^
+  -classpath %WRAPPER_JAR% ^
+  "-Dmaven.multiModuleProjectDirectory=%MAVEN_PROJECTBASEDIR%" ^
+  %WRAPPER_LAUNCHER% %MAVEN_CONFIG% %*
+if ERRORLEVEL 1 goto error
+goto end
+
+:error
+set ERROR_CODE=1
+
+:end
+@endlocal & set ERROR_CODE=%ERROR_CODE%
+
+if not "%MAVEN_SKIP_RC%"=="" goto skipRcPost
+@REM check for post script, once with legacy .bat ending and once with .cmd ending
+if exist "%USERPROFILE%\mavenrc_post.bat" call "%USERPROFILE%\mavenrc_post.bat"
+if exist "%USERPROFILE%\mavenrc_post.cmd" call "%USERPROFILE%\mavenrc_post.cmd"
+:skipRcPost
+
+@REM pause the script if MAVEN_BATCH_PAUSE is set to 'on'
+if "%MAVEN_BATCH_PAUSE%"=="on" pause
+
+if "%MAVEN_TERMINATE_CMD%"=="on" exit %ERROR_CODE%
+
+cmd /C exit /B %ERROR_CODE%

pom.xml

@@ -4,7 +4,7 @@
 
     <groupId>tech.picnic.error-prone-support</groupId>
     <artifactId>error-prone-support</artifactId>
-    <version>0.21.1-SNAPSHOT</version>
+    <version>0.22.1-SNAPSHOT</version>
     <packaging>pom</packaging>
 
     <name>Picnic :: Error Prone Support</name>
@@ -48,6 +48,7 @@
         <module>refaster-runner</module>
         <module>refaster-support</module>
         <module>refaster-test-support</module>
+        <module>workshop</module>
     </modules>
 
     <scm child.scm.developerConnection.inherit.append.path="false" child.scm.url.inherit.append.path="false">
@@ -146,7 +147,7 @@
         <error-prone.self-check-args />
         <!-- The build timestamp is derived from the most recent commit
         timestamp in support of reproducible builds. -->
-        <project.build.outputTimestamp>2025-03-24T10:41:07Z</project.build.outputTimestamp>
+        <project.build.outputTimestamp>2025-04-14T09:36:15Z</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
@@ -211,11 +212,11 @@
         <version.guava-beta-checker>1.0</version.guava-beta-checker>
         <version.jdk>17</version.jdk>
         <version.maven>3.9.9</version.maven>
-        <version.mockito>5.16.1</version.mockito>
+        <version.mockito>5.17.0</version.mockito>
         <version.nopen-checker>1.0.1</version.nopen-checker>
-        <version.nullaway>0.12.5</version.nullaway>
-        <version.pitest-git>2.2.0</version.pitest-git>
-        <version.rewrite-templating>1.24.1</version.rewrite-templating>
+        <version.nullaway>0.12.6</version.nullaway>
+        <version.pitest-git>2.2.1</version.pitest-git>
+        <version.rewrite-templating>1.25.1</version.rewrite-templating>
         <version.surefire>3.2.3</version.surefire>
     </properties>
 
@@ -303,6 +304,16 @@
                 <artifactId>auto-value-annotations</artifactId>
                 <version>${version.auto-value}</version>
             </dependency>
+            <!-- XXX: JSR-305 (meta-)annotation usage by some dependencies
+            triggers NullAway to attempt to load said annotations. As such
+            some modules require these annotations to be on the classpath.
+            Periodically review whether we can drop this dependeny version
+            declaration. See https://github.com/uber/NullAway/issues/1171. -->
+            <dependency>
+                <groupId>com.google.code.findbugs</groupId>
+                <artifactId>jsr305</artifactId>
+                <version>3.0.2</version>
+            </dependency>
             <dependency>
                 <groupId>com.google.errorprone</groupId>
                 <artifactId>error_prone_annotation</artifactId>
@@ -331,7 +342,7 @@
             <dependency>
                 <groupId>com.google.googlejavaformat</groupId>
                 <artifactId>google-java-format</artifactId>
-                <version>1.25.2</version>
+                <version>1.26.0</version>
             </dependency>
             <dependency>
                 <groupId>com.google.guava</groupId>
@@ -341,7 +352,7 @@
             <dependency>
                 <groupId>com.google.guava</groupId>
                 <artifactId>guava-bom</artifactId>
-                <version>33.4.0-jre</version>
+                <version>33.4.7-jre</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
@@ -363,7 +374,7 @@
             <dependency>
                 <groupId>io.micrometer</groupId>
                 <artifactId>micrometer-bom</artifactId>
-                <version>1.14.5</version>
+                <version>1.14.6</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
@@ -387,7 +398,7 @@
             <dependency>
                 <groupId>io.swagger.core.v3</groupId>
                 <artifactId>swagger-annotations</artifactId>
-                <version>2.2.29</version>
+                <version>2.2.30</version>
             </dependency>
             <dependency>
                 <groupId>jakarta.servlet</groupId>
@@ -422,20 +433,12 @@
             <dependency>
                 <groupId>net.bytebuddy</groupId>
                 <artifactId>byte-buddy</artifactId>
-                <version>1.17.4</version>
-            </dependency>
-            <!-- Specified so that Renovate will file Maven upgrade PRs, which
-            subsequently will cause `maven-enforcer-plugin` to require that
-            developers build the project using the latest Maven release. -->
-            <dependency>
-                <groupId>org.apache.maven</groupId>
-                <artifactId>maven-plugin-api</artifactId>
-                <version>${version.maven}</version>
+                <version>1.17.5</version>
             </dependency>
             <dependency>
                 <groupId>org.aspectj</groupId>
                 <artifactId>aspectjweaver</artifactId>
-                <version>1.9.23</version>
+                <version>1.9.24</version>
             </dependency>
             <dependency>
                 <groupId>org.assertj</groupId>
@@ -447,7 +450,7 @@
             <dependency>
                 <groupId>org.checkerframework</groupId>
                 <artifactId>checker-qual</artifactId>
-                <version>3.49.1</version>
+                <version>3.49.2</version>
             </dependency>
             <dependency>
                 <groupId>org.hamcrest</groupId>
@@ -472,7 +475,7 @@
             <dependency>
                 <groupId>org.junit</groupId>
                 <artifactId>junit-bom</artifactId>
-                <version>5.12.1</version>
+                <version>5.12.2</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
@@ -498,7 +501,7 @@
             <dependency>
                 <groupId>org.openrewrite.recipe</groupId>
                 <artifactId>rewrite-recipe-bom</artifactId>
-                <version>3.4.0</version>
+                <version>3.6.1</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
@@ -610,7 +613,7 @@
                 <plugin>
                     <groupId>de.thetaphi</groupId>
                     <artifactId>forbiddenapis</artifactId>
-                    <version>3.8</version>
+                    <version>3.9</version>
                     <configuration>
                         <bundledSignatures>
                             <bundledSignature>jdk-internal</bundledSignature>
@@ -925,7 +928,7 @@
                         <dependency>
                             <groupId>com.puppycrawl.tools</groupId>
                             <artifactId>checkstyle</artifactId>
-                            <version>10.21.4</version>
+                            <version>10.23.0</version>
                         </dependency>
                         <dependency>
                             <groupId>io.spring.nohttp</groupId>
@@ -1124,9 +1127,6 @@
                             <requireMatchingCoordinates>
                                 <moduleNameMustMatchArtifactId>true</moduleNameMustMatchArtifactId>
                             </requireMatchingCoordinates>
-                            <requireMavenVersion>
-                                <version>${version.maven}</version>
-                            </requireMavenVersion>
                             <requireNoRepositories />
                             <requirePluginVersions />
                             <requireUpperBoundDeps />
@@ -1136,7 +1136,7 @@
                         <dependency>
                             <groupId>org.codehaus.mojo</groupId>
                             <artifactId>extra-enforcer-rules</artifactId>
-                            <version>1.9.0</version>
+                            <version>1.10.0</version>
                         </dependency>
                     </dependencies>
                     <executions>
@@ -1300,7 +1300,7 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-surefire-plugin</artifactId>
-                    <version>3.5.2</version>
+                    <version>3.5.3</version>
                     <configuration>
                         <includes>
                             <include>**/*Test.java</include>
@@ -1463,41 +1463,10 @@
                         <updateBuildOutputTimestampPolicy>never</updateBuildOutputTimestampPolicy>
                     </configuration>
                 </plugin>
-                <plugin>
-                    <groupId>org.gaul</groupId>
-                    <artifactId>modernizer-maven-plugin</artifactId>
-                    <version>3.1.0</version>
-                    <configuration>
-                        <exclusionPatterns>
-                            <!-- The plugin suggests replacing usages of
-                            Guava's `Iterables` class with
-                            `java.util.stream.Stream` equivalents, but the
-                            alternative is often more verbose, requiring
-                            unnecessary conversions to and from streams. -->
-                            <exclusionPattern>com/google/common/collect/Iterables\..*</exclusionPattern>
-                        </exclusionPatterns>
-                        <failOnViolations>false</failOnViolations>
-                        <ignorePackages>
-                            <!-- Some Refaster rules purposefully use outdated
-                            patterns in their `@BeforeTemplate` methods. -->
-                            <ignorePackage>tech.picnic.errorprone.refasterrules</ignorePackage>
-                        </ignorePackages>
-                        <javaVersion>${version.jdk}</javaVersion>
-                    </configuration>
-                    <executions>
-                        <execution>
-                            <id>run-modernizer</id>
-                            <goals>
-                                <goal>modernizer</goal>
-                            </goals>
-                            <phase>process-test-classes</phase>
-                        </execution>
-                    </executions>
-                </plugin>
                 <plugin>
                     <groupId>org.jacoco</groupId>
                     <artifactId>jacoco-maven-plugin</artifactId>
-                    <version>0.8.12</version>
+                    <version>0.8.13</version>
                     <configuration>
                         <excludes>
                             <!-- Refaster rules are tested using a custom method
@@ -1506,28 +1475,10 @@
                         </excludes>
                     </configuration>
                 </plugin>
-                <plugin>
-                    <groupId>org.kordamp.maven</groupId>
-                    <artifactId>pomchecker-maven-plugin</artifactId>
-                    <version>1.14.0</version>
-                    <configuration>
-                        <failOnError>false</failOnError>
-                        <release>false</release>
-                    </configuration>
-                    <executions>
-                        <execution>
-                            <id>check-maven-central-compliance</id>
-                            <goals>
-                                <goal>check-maven-central</goal>
-                            </goals>
-                            <phase>verify</phase>
-                        </execution>
-                    </executions>
-                </plugin>
                 <plugin>
                     <groupId>org.pitest</groupId>
                     <artifactId>pitest-maven</artifactId>
-                    <version>1.19.0</version>
+                    <version>1.19.1</version>
                     <configuration>
                         <excludedClasses>
                             <!-- AutoValue generated classes. -->
@@ -1581,7 +1532,7 @@
                 <plugin>
                     <groupId>org.sonarsource.scanner.maven</groupId>
                     <artifactId>sonar-maven-plugin</artifactId>
-                    <version>5.0.0.4389</version>
+                    <version>5.1.0.4751</version>
                 </plugin>
             </plugins>
         </pluginManagement>
@@ -1702,11 +1653,6 @@
             profile. Necessary for dealing with plugins that default to failing
             the build upon encountering a violation. -->
             <id>avoid-errors</id>
-            <activation>
-                <property>
-                    <name>verification.warn</name>
-                </property>
-            </activation>
             <build>
                 <pluginManagement>
                     <plugins>
@@ -1727,11 +1673,6 @@
             that they can be disabled during development. See also the
             `error-prone` profile defined below. -->
             <id>build-checks</id>
-            <activation>
-                <property>
-                    <name>!verification.skip</name>
-                </property>
-            </activation>
             <build>
                 <plugins>
                     <plugin>
@@ -1823,14 +1764,6 @@
                         <groupId>org.codehaus.mojo</groupId>
                         <artifactId>tidy-maven-plugin</artifactId>
                     </plugin>
-                    <plugin>
-                        <groupId>org.gaul</groupId>
-                        <artifactId>modernizer-maven-plugin</artifactId>
-                    </plugin>
-                    <plugin>
-                        <groupId>org.kordamp.maven</groupId>
-                        <artifactId>pomchecker-maven-plugin</artifactId>
-                    </plugin>
                 </plugins>
             </build>
         </profile>
@@ -1940,6 +1873,7 @@
                                     -XepOpt:NullAway:AnnotatedPackages=tech.picnic
                                     -XepOpt:NullAway:AssertsEnabled=true
                                     -XepOpt:NullAway:CheckOptionalEmptiness=true
+                                    -XepOpt:NullAway:JSpecifyMode=true
                                     -XepOpt:Nullness:Conservative=false
                                     -XepOpt:StatementSwitchToExpressionSwitch:EnableDirectConversion=true
                                     <!-- Append additional custom arguments. -->
@@ -1986,11 +1920,6 @@
             This profile allows one to collect all violations without failing
             the build. -->
             <id>disallow-warnings</id>
-            <activation>
-                <property>
-                    <name>!verification.warn</name>
-                </property>
-            </activation>
             <build>
                 <pluginManagement>
                     <plugins>
@@ -2059,21 +1988,6 @@
                                 <failOnMissing>true</failOnMissing>
                             </configuration>
                         </plugin>
-                        <plugin>
-                            <groupId>org.gaul</groupId>
-                            <artifactId>modernizer-maven-plugin</artifactId>
-                            <configuration>
-                                <failOnViolations>true</failOnViolations>
-                            </configuration>
-                        </plugin>
-                        <plugin>
-                            <groupId>org.kordamp.maven</groupId>
-                            <artifactId>pomchecker-maven-plugin</artifactId>
-                            <configuration>
-                                <failOnError>true</failOnError>
-                                <failOnWarning>true</failOnWarning>
-                            </configuration>
-                        </plugin>
                     </plugins>
                 </pluginManagement>
             </build>
@@ -2145,13 +2059,6 @@
                         <artifactId>maven-gpg-plugin</artifactId>
                     </plugin>
                     <?SORTPOM RESUME?>
-                    <plugin>
-                        <groupId>org.kordamp.maven</groupId>
-                        <artifactId>pomchecker-maven-plugin</artifactId>
-                        <configuration>
-                            <release>true</release>
-                        </configuration>
-                    </plugin>
                 </plugins>
             </build>
         </profile>

refaster-compiler/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.21.1-SNAPSHOT</version>
+        <version>0.22.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>refaster-compiler</artifactId>

refaster-runner/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.21.1-SNAPSHOT</version>
+        <version>0.22.1-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>0.21.1-SNAPSHOT</version>
+        <version>0.22.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>refaster-support</artifactId>

refaster-test-support/pom.xml

@@ -5,7 +5,7 @@
     <parent>
         <groupId>tech.picnic.error-prone-support</groupId>
         <artifactId>error-prone-support</artifactId>
-        <version>0.21.1-SNAPSHOT</version>
+        <version>0.22.1-SNAPSHOT</version>
     </parent>
 
     <artifactId>refaster-test-support</artifactId>

website/_data/compatibility.yml

@@ -1,6 +1,9 @@
 # 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: 0.22.0
+    compatible:
+      - "2.37.0"
   - version: 0.21.0
     compatible:
       - "2.37.0"

workshop/README.md

@@ -0,0 +1,104 @@
+# Error Prone Workshop
+
+Download the slides [here][eps-workshop-slides].
+
+## Initial setup of the workshop
+
+1. Start by cloning this repository locally from GitHub.
+2. Checkout the `workshop` branch.
+3. Make sure to run `mvn clean install` in the root of this repository.
+4. Open your code editor and familiarize yourself with the project structure.
+
+In IntelliJ IDEA (or your preferred editor), try to run the
+`WorkshopRefasterRulesTest` test. You might see the following error:
+
+```
+java: exporting a package from system module jdk.compiler is not allowed with --release
+```
+
+If this happens, go to _File -> Settings... -> Build, Execution, Deployment ->
+Compiler -> Java Compiler_ and deselect the option _Use '--release' option for
+cross-compilation (Java 9 and later)_.
+
+If you encounter any other bugs when running `mvn clean install`, make sure you
+are using a recent release of JDK 17.
+
+Now the project is ready for the workshop.
+
+## Part 1: Writing Refaster rules
+
+During this part of the workshop we will implement multiple Refaster rules.
+
+Go to the `workshop` module and navigate to the
+`tech.picnic.errorprone.workshop.refasterrules` package. There you can find one
+example and five different exercises to do. Make sure to open the
+`WorkshopRefasterRulesTest` class where you can enable tests. Per assignment
+there is a test in this class that you can enable (by dropping the `@Disabled`
+annotation) to validate your changes. The goal is to implement or improve the
+Refaster rules such that the enabled tests pass.
+
+Tips:
+
+* Go through the exercises in the proposed order.
+* The `XXX:` comments explain what needs to happen.
+* Find the test case for each Refaster rule by looking for the name of the
+  Refaster rule, prefixed with `test`. For example, the
+  `WorkshopAssignment0Rules.java` rule collection has a Refaster rule named
+  `ExampleStringIsEmpty`. In the `WorkshopAssignment0RulesTestInput.java` and
+  `WorkshopAssignment0RulesTestOutput.java` files there is a
+  `testExampleStringIsEmpty` method that shows the input and output to test the
+  Refaster rule.
+
+## Part 2: Writing Error Prone checks
+
+During this part of the workshop we will implement parts of multiple Error
+Prone `BugChecker`s. Each of these classes contain `XXX` comments explaining
+what needs to be implemented. However, before diving in, make sure to first
+navigate to a check's associated test class to drop the class-level `@Disabled`
+annotation. Upon initial execution the tests will fail; the goal is to get then
+to pass.
+
+Some utility classes that you can use:
+
+* `com.google.errorprone.util.ASTHelpers`: contains many common operations on
+  the Abstract Syntax Tree.
+* `com.google.errorprone.fixes.SuggestedFixes`: contains helper methods for
+  creating `Fix`es.
+
+### Tips and tricks
+
+If you are working from the command line, it is suggested to run commands in
+the `workshop` directory. To do this, navigate to the root of the repository
+and run:
+
+```bash
+cd workshop
+```
+
+In case you want to do a fast build to just compile the project, run:
+
+```bash
+mvn clean install -DskipTests -Dverification.skip
+```
+
+In case you want to run one test from the command line, run the following
+commands:
+
+```bash
+mvn clean install -Dtest=WorkshopRefasterRulesTest -Dverification.skip
+```
+
+### Troubleshooting
+
+Make sure to use the latest version of JDK 21 or 17.
+
+In some specific cases the `-Dverification.skip` is not correctly processed. In
+that case, use `-D"verification.skip"`.
+
+In case there is an error mentioning the `BetaApi` check, please rebuild or try
+to `Reload All Maven projects`.
+
+
+[eps-github]: https://github.com/PicnicSupermarket/error-prone-support
+
+[eps-workshop-slides]: https://docs.google.com/presentation/d/16MnDk6eW5dxKrLfG7TNUKAX-UVDJwbMz55UvKUkzeHc/edit?usp=sharing

workshop/pom.xml

@@ -0,0 +1,155 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>tech.picnic.error-prone-support</groupId>
+        <artifactId>error-prone-support</artifactId>
+        <version>0.22.1-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>workshop</artifactId>
+
+    <name>Picnic :: Error Prone Support :: Workshop</name>
+    <description>Project for the Error Prone Workshop.</description>
+    <url>https://error-prone.picnic.tech</url>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.google.errorprone</groupId>
+            <artifactId>error_prone_annotation</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.errorprone</groupId>
+            <artifactId>error_prone_annotations</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.errorprone</groupId>
+            <artifactId>error_prone_check_api</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.errorprone</groupId>
+            <artifactId>error_prone_core</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.errorprone</groupId>
+            <artifactId>error_prone_test_helpers</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>error-prone-utils</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>refaster-compiler</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>refaster-support</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>${project.groupId}</groupId>
+            <artifactId>refaster-test-support</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.google.auto.service</groupId>
+            <artifactId>auto-service-annotations</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>javax.annotation</groupId>
+            <artifactId>javax.annotation-api</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.aspectj</groupId>
+            <artifactId>aspectjweaver</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-api</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter-params</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.openrewrite</groupId>
+            <artifactId>rewrite-core</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.openrewrite</groupId>
+            <artifactId>rewrite-java</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.openrewrite</groupId>
+            <artifactId>rewrite-java-11</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.openrewrite</groupId>
+            <artifactId>rewrite-templating</artifactId>
+            <scope>provided</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-context</artifactId>
+            <scope>provided</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <pluginManagement>
+            <plugins>
+                <plugin>
+                    <groupId>org.apache.maven.plugins</groupId>
+                    <artifactId>maven-compiler-plugin</artifactId>
+                    <configuration>
+                        <annotationProcessorPaths combine.children="append">
+                            <path>
+                                <groupId>${project.groupId}</groupId>
+                                <artifactId>refaster-compiler</artifactId>
+                                <version>${project.version}</version>
+                            </path>
+                            <path>
+                                <groupId>${project.groupId}</groupId>
+                                <artifactId>refaster-support</artifactId>
+                                <version>${project.version}</version>
+                            </path>
+                        </annotationProcessorPaths>
+                        <compilerArgs combine.children="append">
+                            <arg>-Xplugin:RefasterRuleCompiler</arg>
+                        </compilerArgs>
+                    </configuration>
+                </plugin>
+            </plugins>
+        </pluginManagement>
+    </build>
+</project>

workshop/src/main/java/tech/picnic/errorprone/workshop/bugpatterns/Assignment0DeleteEmptyMethod.java

@@ -0,0 +1,33 @@
+package tech.picnic.errorprone.workshop.bugpatterns;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.BugPattern.StandardTags.SIMPLIFICATION;
+
+import com.google.auto.service.AutoService;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
+import com.google.errorprone.matchers.Description;
+import com.sun.source.tree.MethodTree;
+
+/** A {@link BugChecker} that flags empty methods that seemingly can simply be deleted. */
+@AutoService(BugChecker.class)
+@BugPattern(
+    summary = "Empty method can likely be deleted",
+    severity = WARNING,
+    tags = SIMPLIFICATION)
+public final class Assignment0DeleteEmptyMethod extends BugChecker implements MethodTreeMatcher {
+  private static final long serialVersionUID = 1L;
+
+  /** Instantiates a new {@link Assignment0DeleteEmptyMethod} instance. */
+  public Assignment0DeleteEmptyMethod() {}
+
+  @Override
+  public Description matchMethod(MethodTree tree, VisitorState state) {
+    // XXX: Part 1: Ensure that we only delete methods that contain no statements.
+    // XXX: Part 2: Don't delete methods that are annotated with `@Override`.
+
+    return Description.NO_MATCH;
+  }
+}

workshop/src/main/java/tech/picnic/errorprone/workshop/bugpatterns/Assignment1AssertJIsNullMethod.java

@@ -0,0 +1,61 @@
+package tech.picnic.errorprone.workshop.bugpatterns;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
+import static com.google.errorprone.BugPattern.StandardTags.SIMPLIFICATION;
+import static com.google.errorprone.matchers.Matchers.allOf;
+import static com.google.errorprone.matchers.Matchers.argument;
+import static com.google.errorprone.matchers.Matchers.argumentCount;
+import static com.google.errorprone.matchers.Matchers.instanceMethod;
+import static com.google.errorprone.matchers.Matchers.nullLiteral;
+
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
+import com.google.errorprone.fixes.SuggestedFix;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.sun.source.tree.MethodInvocationTree;
+
+/**
+ * A {@link BugChecker} that flags AssertJ {@code isEqualTo(null)} checks for simplification.
+ *
+ * <p>This bug checker cannot be replaced with a simple Refaster rule, as the Refaster approach
+ * would require that all overloads of {@link org.assertj.core.api.Assert#isEqualTo(Object)} (such
+ * as {@link org.assertj.core.api.AbstractStringAssert#isEqualTo(String)}) are explicitly
+ * enumerated. This bug checker generically matches all such current and future overloads.
+ */
+@BugPattern(
+    summary = "Prefer `.isNull()` over `.isEqualTo(null)`",
+    severity = SUGGESTION,
+    tags = SIMPLIFICATION)
+public final class Assignment1AssertJIsNullMethod extends BugChecker
+    implements MethodInvocationTreeMatcher {
+  private static final long serialVersionUID = 1L;
+  private static final Matcher<MethodInvocationTree> ASSERT_IS_EQUAL_TO_NULL =
+      allOf(
+          instanceMethod().onDescendantOf("org.assertj.core.api.Assert").named("isEqualTo"),
+          argumentCount(1),
+          argument(0, nullLiteral()));
+
+  /** Instantiates a new {@link Assignment1AssertJIsNullMethod} instance. */
+  public Assignment1AssertJIsNullMethod() {}
+
+  @Override
+  public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+    // This statement filters out `MethodInvocation`s that are *not* `assertThat().isEqualTo(null)`
+    // statements.
+    if (!ASSERT_IS_EQUAL_TO_NULL.matches(tree, state)) {
+      return Description.NO_MATCH;
+    }
+
+    SuggestedFix.Builder fix = SuggestedFix.builder();
+
+    // XXX: Using `fix.merge(<some code>);` make sure we rename the method invocation to `isNull`.
+    // See the `SuggestedFixes` class ;).
+
+    tree.getArguments().forEach(arg -> fix.merge(SuggestedFix.delete(arg)));
+
+    return describeMatch(tree, fix.build());
+  }
+}

workshop/src/main/java/tech/picnic/errorprone/workshop/bugpatterns/Assignment2DropMockitoEq.java

@@ -0,0 +1,56 @@
+package tech.picnic.errorprone.workshop.bugpatterns;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
+import static com.google.errorprone.BugPattern.StandardTags.SIMPLIFICATION;
+import static com.google.errorprone.matchers.Matchers.staticMethod;
+
+import com.google.common.collect.Iterables;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
+import com.google.errorprone.fixes.SuggestedFix;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.MethodInvocationTree;
+import tech.picnic.errorprone.utils.SourceCode;
+
+/**
+ * A {@link BugChecker} that flags method invocations for which all arguments are wrapped using
+ * {@link org.mockito.Mockito#eq}; this is redundant.
+ */
+@BugPattern(
+    summary = "Don't unnecessarily use Mockito's `eq(...)`",
+    severity = SUGGESTION,
+    tags = SIMPLIFICATION)
+public final class Assignment2DropMockitoEq extends BugChecker
+    implements MethodInvocationTreeMatcher {
+  private static final long serialVersionUID = 1L;
+  private static final Matcher<ExpressionTree> MOCKITO_EQ_METHOD =
+      staticMethod().onClass("org.mockito.ArgumentMatchers").named("eq");
+
+  /** Instantiates a new {@link Assignment2DropMockitoEq} instance. */
+  public Assignment2DropMockitoEq() {}
+
+  @Override
+  public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+    // XXX: Make sure to return `Description.NO_MATCH` if the `tree` doesn't have arguments, or if
+    // the `isEqInvocation` method below returns `false` for at least one of the arguments.
+
+    SuggestedFix.Builder suggestedFix = SuggestedFix.builder();
+    for (ExpressionTree arg : tree.getArguments()) {
+      suggestedFix.replace(
+          arg,
+          SourceCode.treeToString(
+              Iterables.getOnlyElement(((MethodInvocationTree) arg).getArguments()), state));
+    }
+
+    return describeMatch(tree, suggestedFix.build());
+  }
+
+  @SuppressWarnings("UnusedMethod" /* Recommended to use when implementing this assignment. */)
+  private static boolean isEqInvocation(ExpressionTree tree, VisitorState state) {
+    return tree instanceof MethodInvocationTree && MOCKITO_EQ_METHOD.matches(tree, state);
+  }
+}

workshop/src/main/java/tech/picnic/errorprone/workshop/bugpatterns/Assignment3DropAutowiredConstructorAnnotation.java

@@ -0,0 +1,54 @@
+package tech.picnic.errorprone.workshop.bugpatterns;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
+import static com.google.errorprone.BugPattern.StandardTags.SIMPLIFICATION;
+import static com.google.errorprone.matchers.ChildMultiMatcher.MatchType.AT_LEAST_ONE;
+import static com.google.errorprone.matchers.Matchers.annotations;
+import static com.google.errorprone.matchers.Matchers.isType;
+
+import com.google.common.collect.Iterables;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.MultiMatcher;
+import com.google.errorprone.matchers.MultiMatcher.MultiMatchResult;
+import com.sun.source.tree.AnnotationTree;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.tree.MethodTree;
+import com.sun.source.tree.Tree;
+import java.util.ArrayList;
+import java.util.List;
+import tech.picnic.errorprone.utils.SourceCode;
+
+/** A {@link BugChecker} that flags redundant {@code @Autowired} constructor annotations. */
+@BugPattern(
+    summary = "Omit `@Autowired` on a class' sole constructor, as it is redundant",
+    severity = SUGGESTION,
+    tags = SIMPLIFICATION)
+public final class Assignment3DropAutowiredConstructorAnnotation extends BugChecker
+    implements ClassTreeMatcher {
+  private static final long serialVersionUID = 1L;
+  private static final MultiMatcher<Tree, AnnotationTree> AUTOWIRED_ANNOTATION =
+      annotations(AT_LEAST_ONE, isType("org.springframework.beans.factory.annotation.Autowired"));
+
+  /** Instantiates a new {@link Assignment3DropAutowiredConstructorAnnotation} instance. */
+  public Assignment3DropAutowiredConstructorAnnotation() {}
+
+  @Override
+  public Description matchClass(ClassTree tree, VisitorState state) {
+    // XXX: Using the `ASTHelpers#getConstructors` method, return `Description.NO_MATCH` if we do
+    // not have exactly 1 constructor (start by dropping `new ArrayList<>()` on the next line).
+    List<MethodTree> constructors = new ArrayList<>();
+
+    MultiMatchResult<AnnotationTree> hasAutowiredAnnotation =
+        AUTOWIRED_ANNOTATION.multiMatchResult(Iterables.getOnlyElement(constructors), state);
+    if (!hasAutowiredAnnotation.matches()) {
+      return Description.NO_MATCH;
+    }
+
+    AnnotationTree annotation = hasAutowiredAnnotation.onlyMatchingNode();
+    return describeMatch(annotation, SourceCode.deleteWithTrailingWhitespace(annotation, state));
+  }
+}

workshop/src/main/java/tech/picnic/errorprone/workshop/bugpatterns/Assignment4JUnitTestMethodDeclaration.java

@@ -0,0 +1,61 @@
+package tech.picnic.errorprone.workshop.bugpatterns;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.BugPattern.StandardTags.SIMPLIFICATION;
+import static com.google.errorprone.matchers.ChildMultiMatcher.MatchType.AT_LEAST_ONE;
+import static com.google.errorprone.matchers.Matchers.annotations;
+import static com.google.errorprone.matchers.Matchers.anyOf;
+import static com.google.errorprone.matchers.Matchers.isType;
+
+import com.google.auto.service.AutoService;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Sets;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
+import com.google.errorprone.fixes.SuggestedFix;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.MultiMatcher;
+import com.sun.source.tree.AnnotationTree;
+import com.sun.source.tree.MethodTree;
+import javax.lang.model.element.Modifier;
+
+/** A {@link BugChecker} that flags non-canonical JUnit method declarations. */
+@AutoService(BugChecker.class)
+@BugPattern(
+    summary = "JUnit method declaration can likely be improved",
+    severity = WARNING,
+    tags = SIMPLIFICATION)
+@SuppressWarnings({
+  "UnusedMethod",
+  "UnusedVariable"
+} /* This check is yet to be implemented as part of the demo. */)
+public final class Assignment4JUnitTestMethodDeclaration extends BugChecker
+    implements MethodTreeMatcher {
+  private static final long serialVersionUID = 1L;
+  private static final ImmutableSet<Modifier> ILLEGAL_MODIFIERS =
+      Sets.immutableEnumSet(Modifier.PRIVATE, Modifier.PROTECTED, Modifier.PUBLIC);
+  private static final MultiMatcher<MethodTree, AnnotationTree> TEST_METHOD =
+      annotations(AT_LEAST_ONE, anyOf(isType("org.junit.jupiter.api.Test")));
+
+  /** Instantiates a new {@link Assignment4JUnitTestMethodDeclaration} instance. */
+  public Assignment4JUnitTestMethodDeclaration() {}
+
+  @Override
+  public Description matchMethod(MethodTree tree, VisitorState state) {
+    // XXX: Part 1: Return `Description.NO_MATCH` if the method is not a `TEST_METHOD`.
+
+    SuggestedFix.Builder fixBuilder = SuggestedFix.builder();
+
+    // XXX: Part 2: Make sure that JUnit test methods don't use any of the modifiers from the
+    // `ILLEGAL_MODIFIERS` field, by using `SuggestedFixes#removeModifiers` and
+    // `SuggestedFix.Builder#merge`.
+
+    if (fixBuilder.isEmpty()) {
+      return Description.NO_MATCH;
+    }
+
+    return describeMatch(tree, fixBuilder.build());
+  }
+}

workshop/src/main/java/tech/picnic/errorprone/workshop/bugpatterns/Assignment5DeleteIdentityConversion.java

@@ -0,0 +1,108 @@
+package tech.picnic.errorprone.workshop.bugpatterns;
+
+import static com.google.common.collect.ImmutableSet.toImmutableSet;
+import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.BugPattern.StandardTags.SIMPLIFICATION;
+import static com.google.errorprone.matchers.Matchers.anyOf;
+import static com.google.errorprone.matchers.Matchers.staticMethod;
+import static com.google.errorprone.suppliers.Suppliers.OBJECT_TYPE;
+
+import com.google.common.primitives.Primitives;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
+import com.google.errorprone.bugpatterns.TypesWithUndefinedEquality;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.google.errorprone.util.ASTHelpers;
+import com.google.errorprone.util.ASTHelpers.TargetType;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.MemberSelectTree;
+import com.sun.source.tree.MethodInvocationTree;
+import com.sun.tools.javac.code.Type;
+import com.sun.tools.javac.code.Types;
+import java.util.Arrays;
+import java.util.List;
+
+/** A {@link BugChecker} that flags redundant identity conversions. */
+@BugPattern(
+    summary = "Avoid or clarify identity conversions",
+    severity = WARNING,
+    tags = SIMPLIFICATION)
+public final class Assignment5DeleteIdentityConversion extends BugChecker
+    implements MethodInvocationTreeMatcher {
+  private static final long serialVersionUID = 1L;
+  private static final Matcher<ExpressionTree> IS_CONVERSION_METHOD =
+      anyOf(
+          staticMethod()
+              .onClassAny(
+                  Primitives.allWrapperTypes().stream()
+                      .map(Class::getName)
+                      .collect(toImmutableSet()))
+              .named("valueOf"),
+          staticMethod().onClass(String.class.getName()).named("valueOf"),
+          staticMethod()
+              .onClassAny(
+                  "com.google.common.collect.ImmutableBiMap",
+                  "com.google.common.collect.ImmutableList",
+                  "com.google.common.collect.ImmutableListMultimap",
+                  "com.google.common.collect.ImmutableMap",
+                  "com.google.common.collect.ImmutableMultimap",
+                  "com.google.common.collect.ImmutableMultiset",
+                  "com.google.common.collect.ImmutableRangeMap",
+                  "com.google.common.collect.ImmutableRangeSet",
+                  "com.google.common.collect.ImmutableSet",
+                  "com.google.common.collect.ImmutableSetMultimap",
+                  "com.google.common.collect.ImmutableTable")
+              .named("copyOf"),
+          staticMethod()
+              .onClass("com.google.errorprone.matchers.Matchers")
+              .namedAnyOf("allOf", "anyOf"));
+
+  /** Instantiates a new {@link Assignment5DeleteIdentityConversion} instance. */
+  public Assignment5DeleteIdentityConversion() {}
+
+  @Override
+  public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+    List<? extends ExpressionTree> arguments = tree.getArguments();
+    // XXX: Make sure we skip invocations that do not pass exactly one argument, by using the
+    // `tree`.
+    if (!IS_CONVERSION_METHOD.matches(tree, state)) {
+      return Description.NO_MATCH;
+    }
+
+    ExpressionTree sourceTree = arguments.get(0);
+    Type sourceType = ASTHelpers.getType(sourceTree);
+    Type resultType = ASTHelpers.getType(tree);
+    TargetType targetType = ASTHelpers.targetType(state);
+    if (sourceType == null || resultType == null || targetType == null) {
+      return Description.NO_MATCH;
+    }
+
+    if (!state.getTypes().isSameType(sourceType, resultType)
+        && !isConvertibleWithWellDefinedEquality(sourceType, targetType.type(), state)) {
+      return Description.NO_MATCH;
+    }
+
+    if (sourceType.isPrimitive()
+        && state.getPath().getParentPath().getLeaf() instanceof MemberSelectTree) {
+      return Description.NO_MATCH;
+    }
+
+    return buildDescription(tree)
+        // XXX: Use the `.addFix()` to suggest replacing the original `tree` with the `sourceTree`.
+        // Tip: You can get the actual String representation of a Tree by using the
+        // `SourceCode#treeToString`.
+        .build();
+  }
+
+  private static boolean isConvertibleWithWellDefinedEquality(
+      Type sourceType, Type targetType, VisitorState state) {
+    Types types = state.getTypes();
+    return !types.isSameType(targetType, OBJECT_TYPE.get(state))
+        && types.isConvertible(sourceType, targetType)
+        && Arrays.stream(TypesWithUndefinedEquality.values())
+            .noneMatch(b -> b.matchesType(sourceType, state) || b.matchesType(targetType, state));
+  }
+}

workshop/src/main/java/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment0Rules.java

@@ -0,0 +1,22 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import com.google.errorprone.refaster.annotation.AfterTemplate;
+import com.google.errorprone.refaster.annotation.BeforeTemplate;
+
+/** Refaster rule used as example for the assignments of the workshop. */
+final class WorkshopAssignment0Rules {
+  private WorkshopAssignment0Rules() {}
+
+  /** Prefer {@link String#isEmpty()} over alternatives that consult the string's length. */
+  static final class ExampleStringIsEmpty {
+    @BeforeTemplate
+    boolean before(String str) {
+      return str.length() == 0;
+    }
+
+    @AfterTemplate
+    boolean after(String str) {
+      return str.isEmpty();
+    }
+  }
+}

workshop/src/main/java/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment1Rules.java

@@ -0,0 +1,11 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+/** Refaster rules for the first assignment of the workshop. */
+final class WorkshopAssignment1Rules {
+  private WorkshopAssignment1Rules() {}
+
+  /** Prefer {@link String#String(char[])} over {@link String#copyValueOf(char[])}. */
+  static final class NewStringCharArray {
+    // XXX: Implement this Refaster rule.
+  }
+}

workshop/src/main/java/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment2Rules.java

@@ -0,0 +1,18 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import com.google.common.collect.ImmutableList;
+
+/** Refaster rules for the second assignment of the workshop. */
+@SuppressWarnings("UnusedTypeParameter" /* Ignore this for demo purposes. */)
+final class WorkshopAssignment2Rules {
+  private WorkshopAssignment2Rules() {}
+
+  /**
+   * Prefer {@link ImmutableList#of(Object)} over alternatives that don't communicate the
+   * immutability of the resulting list at the type level.
+   */
+  static final class ImmutableListOfOne<T> {
+    // XXX: Implement this Refaster rule, preferably by using only one `@BeforeTemplate`.
+    // Tip: use the type argument.
+  }
+}

workshop/src/main/java/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment3Rules.java

@@ -0,0 +1,21 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import com.google.common.base.Preconditions;
+
+/** Refaster rules for the third assignment of the workshop. */
+@SuppressWarnings("UnusedTypeParameter" /* Ignore this for demo purposes. */)
+final class WorkshopAssignment3Rules {
+  private WorkshopAssignment3Rules() {}
+
+  // XXX: Tip: check the input and output files to see the *expected* refactoring.
+
+  /** Prefer {@link Preconditions#checkArgument(boolean)} over if statements. */
+  static final class CheckArgumentWithoutMessage {
+    // XXX: Implement the Refaster rule to get the test green.
+  }
+
+  /** Prefer {@link Preconditions#checkArgument(boolean, Object)} over if statements. */
+  static final class CheckArgumentWithMessage {
+    // XXX: Implement the Refaster rule to get the test green.
+  }
+}

workshop/src/main/java/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment4Rules.java

@@ -0,0 +1,25 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+/** Refaster rules for the fourth assignment of the workshop. */
+@SuppressWarnings("java:S1698" /* Reference comparison is valid for enums. */)
+final class WorkshopAssignment4Rules {
+  private WorkshopAssignment4Rules() {}
+
+  // The test fails because non Enum comparisons are also rewritten.
+  // Fix the test by tweaking the type parameters.
+
+  // XXX: Get the test to pass by improving the Refaster rule (uncommented it first).
+
+  //  static final class PrimitiveOrReferenceEqualityEnum<T> {
+  //    @BeforeTemplate
+  //    boolean before(T a, T b) {
+  //      return Refaster.anyOf(a.equals(b), Objects.equals(a, b));
+  //    }
+  //
+  //    @AfterTemplate
+  //    @AlsoNegation
+  //    boolean after(T a, T b) {
+  //      return a == b;
+  //    }
+  //  }
+}

workshop/src/main/java/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment5Rules.java

@@ -0,0 +1,12 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+/** Refaster rules for the fifth assignment of the workshop. */
+@SuppressWarnings("UnusedTypeParameter" /* Ignore this for demo purposes. */)
+final class WorkshopAssignment5Rules {
+  private WorkshopAssignment5Rules() {}
+
+  abstract static class StreamDoAllMatch<T> {
+    // XXX: Implement the Refaster rule to get the test green.
+    // Tip: use the `@Placeholder` annotation.
+  }
+}

workshop/src/test/java/tech/picnic/errorprone/workshop/bugpatterns/Assignment0DeleteEmptyMethodTest.java

@@ -0,0 +1,70 @@
+package tech.picnic.errorprone.workshop.bugpatterns;
+
+import com.google.errorprone.BugCheckerRefactoringTestHelper;
+import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+@Disabled("Enable this when implementing the BugChecker.")
+final class Assignment0DeleteEmptyMethodTest {
+  @Test
+  void identification() {
+    CompilationTestHelper.newInstance(Assignment0DeleteEmptyMethod.class, getClass())
+        .addSourceLines(
+            "A.java",
+            "class A {",
+            "  Object m1() {",
+            "    return null;",
+            "  }",
+            "",
+            "  void m2() {",
+            "    System.out.println(42);",
+            "  }",
+            "",
+            "  // BUG: Diagnostic contains:",
+            "  static void m3() {}",
+            "",
+            "  interface F {",
+            "    void fun();",
+            "  }",
+            "}")
+        .addSourceLines(
+            "B.java",
+            "final class B implements A.F {",
+            "  @Override",
+            "  public void fun() {}",
+            "",
+            "  /** Javadoc. */",
+            "  // BUG: Diagnostic contains:",
+            "  void m4() {}",
+            "}")
+        .doTest();
+  }
+
+  @Test
+  void replacement() {
+    BugCheckerRefactoringTestHelper.newInstance(Assignment0DeleteEmptyMethod.class, getClass())
+        .addInputLines(
+            "A.java",
+            "final class A {",
+            "",
+            "  void instanceMethod() {}",
+            "",
+            "  static void staticMethod() {}",
+            "",
+            "  static void staticMethodWithComment() {",
+            "    System.out.println(42);",
+            "  }",
+            "}")
+        .addOutputLines(
+            "A.java",
+            "final class A {",
+            "",
+            "  static void staticMethodWithComment() {",
+            "    System.out.println(42);",
+            "  }",
+            "}")
+        .doTest(TestMode.TEXT_MATCH);
+  }
+}

workshop/src/test/java/tech/picnic/errorprone/workshop/bugpatterns/Assignment1AssertJIsNullMethodTest.java

@@ -0,0 +1,60 @@
+package tech.picnic.errorprone.workshop.bugpatterns;
+
+import com.google.errorprone.BugCheckerRefactoringTestHelper;
+import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+@Disabled("Enable this when implementing the BugChecker.")
+final class Assignment1AssertJIsNullMethodTest {
+  @Test
+  void identification() {
+    CompilationTestHelper.newInstance(Assignment1AssertJIsNullMethod.class, getClass())
+        .addSourceLines(
+            "A.java",
+            "import static org.assertj.core.api.Assertions.assertThat;",
+            "",
+            "class A {",
+            "  void m() {",
+            "    assertThat(1).isEqualTo(1);",
+            "    // BUG: Diagnostic contains:",
+            "    assertThat(1).isEqualTo(null);",
+            "    // BUG: Diagnostic contains:",
+            "    assertThat(\"foo\").isEqualTo(null);",
+            "    isEqualTo(null);",
+            "  }",
+            "",
+            "  private boolean isEqualTo(Object value) {",
+            "    return value.equals(\"bar\");",
+            "  }",
+            "}")
+        .doTest();
+  }
+
+  @Test
+  void replacement() {
+    BugCheckerRefactoringTestHelper.newInstance(Assignment1AssertJIsNullMethod.class, getClass())
+        .addInputLines(
+            "A.java",
+            "import static org.assertj.core.api.Assertions.assertThat;",
+            "",
+            "class A {",
+            "  void m() {",
+            "    assertThat(1).isEqualTo(null);",
+            "    assertThat(\"foo\").isEqualTo(null);",
+            "  }",
+            "}")
+        .addOutputLines(
+            "A.java",
+            "import static org.assertj.core.api.Assertions.assertThat;",
+            "",
+            "class A {",
+            "  void m() {",
+            "    assertThat(1).isNull();",
+            "    assertThat(\"foo\").isNull();",
+            "  }",
+            "}")
+        .doTest(TestMode.TEXT_MATCH);
+  }
+}

workshop/src/test/java/tech/picnic/errorprone/workshop/bugpatterns/Assignment2DropMockitoEqTest.java

@@ -0,0 +1,102 @@
+package tech.picnic.errorprone.workshop.bugpatterns;
+
+import com.google.errorprone.BugCheckerRefactoringTestHelper;
+import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+@Disabled("Enable this when implementing the BugChecker.")
+final class Assignment2DropMockitoEqTest {
+  @Test
+  void identification() {
+    CompilationTestHelper.newInstance(Assignment2DropMockitoEq.class, getClass())
+        .addSourceLines(
+            "A.java",
+            "import static org.mockito.ArgumentMatchers.eq;",
+            "import static org.mockito.ArgumentMatchers.notNull;",
+            "import static org.mockito.Mockito.doAnswer;",
+            "import static org.mockito.Mockito.mock;",
+            "",
+            "import java.util.function.BiConsumer;",
+            "import java.util.function.Consumer;",
+            "import org.mockito.ArgumentMatchers;",
+            "",
+            "class A {",
+            "  void m() {",
+            "    Runnable runnable = mock(Runnable.class);",
+            "    doAnswer(inv -> null).when(runnable).run();",
+            "",
+            "    Consumer<String> consumer = mock(Consumer.class);",
+            "    doAnswer(inv -> null).when(consumer).accept(\"foo\");",
+            "    doAnswer(inv -> null).when(consumer).accept(notNull());",
+            "    // BUG: Diagnostic contains:",
+            "    doAnswer(inv -> null).when(consumer).accept(ArgumentMatchers.eq(\"foo\"));",
+            "    // BUG: Diagnostic contains:",
+            "    doAnswer(inv -> null).when(consumer).accept(eq(toString()));",
+            "",
+            "    BiConsumer<Integer, String> biConsumer = mock(BiConsumer.class);",
+            "    doAnswer(inv -> null).when(biConsumer).accept(0, \"foo\");",
+            "    doAnswer(inv -> null).when(biConsumer).accept(eq(0), notNull());",
+            "    doAnswer(inv -> null).when(biConsumer).accept(notNull(), eq(\"foo\"));",
+            "    doAnswer(inv -> null)",
+            "        .when(biConsumer)",
+            "        // BUG: Diagnostic contains:",
+            "        .accept(ArgumentMatchers.eq(0), ArgumentMatchers.eq(\"foo\"));",
+            "    // BUG: Diagnostic contains:",
+            "    doAnswer(inv -> null).when(biConsumer).accept(eq(hashCode()), eq(toString()));",
+            "  }",
+            "}")
+        .doTest();
+  }
+
+  @Test
+  void replacement() {
+    BugCheckerRefactoringTestHelper.newInstance(Assignment2DropMockitoEq.class, getClass())
+        .addInputLines(
+            "A.java",
+            "import static org.mockito.ArgumentMatchers.eq;",
+            "import static org.mockito.Mockito.doAnswer;",
+            "import static org.mockito.Mockito.mock;",
+            "",
+            "import java.util.function.BiConsumer;",
+            "import java.util.function.Consumer;",
+            "import org.mockito.ArgumentMatchers;",
+            "",
+            "class A {",
+            "  void m() {",
+            "    Consumer<String> consumer = mock(Consumer.class);",
+            "    doAnswer(inv -> null).when(consumer).accept(ArgumentMatchers.eq(\"foo\"));",
+            "    doAnswer(inv -> null).when(consumer).accept(eq(toString()));",
+            "",
+            "    BiConsumer<Integer, String> biConsumer = mock(BiConsumer.class);",
+            "    doAnswer(inv -> null)",
+            "        .when(biConsumer)",
+            "        .accept(ArgumentMatchers.eq(0), ArgumentMatchers.eq(\"foo\"));",
+            "    doAnswer(inv -> null).when(biConsumer).accept(eq(hashCode()), eq(toString()));",
+            "  }",
+            "}")
+        .addOutputLines(
+            "A.java",
+            "import static org.mockito.ArgumentMatchers.eq;",
+            "import static org.mockito.Mockito.doAnswer;",
+            "import static org.mockito.Mockito.mock;",
+            "",
+            "import java.util.function.BiConsumer;",
+            "import java.util.function.Consumer;",
+            "import org.mockito.ArgumentMatchers;",
+            "",
+            "class A {",
+            "  void m() {",
+            "    Consumer<String> consumer = mock(Consumer.class);",
+            "    doAnswer(inv -> null).when(consumer).accept(\"foo\");",
+            "    doAnswer(inv -> null).when(consumer).accept(toString());",
+            "",
+            "    BiConsumer<Integer, String> biConsumer = mock(BiConsumer.class);",
+            "    doAnswer(inv -> null).when(biConsumer).accept(0, \"foo\");",
+            "    doAnswer(inv -> null).when(biConsumer).accept(hashCode(), toString());",
+            "  }",
+            "}")
+        .doTest(TestMode.TEXT_MATCH);
+  }
+}

workshop/src/test/java/tech/picnic/errorprone/workshop/bugpatterns/Assignment3DropAutowiredConstructorAnnotationTest.java

@@ -0,0 +1,106 @@
+package tech.picnic.errorprone.workshop.bugpatterns;
+
+import com.google.errorprone.BugCheckerRefactoringTestHelper;
+import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+@Disabled("Enable this when implementing the BugChecker.")
+final class Assignment3DropAutowiredConstructorAnnotationTest {
+  @Test
+  void identification() {
+    CompilationTestHelper.newInstance(
+            Assignment3DropAutowiredConstructorAnnotation.class, getClass())
+        .addSourceLines(
+            "Container.java",
+            "import com.google.errorprone.annotations.Immutable;",
+            "import java.util.List;",
+            "import org.springframework.beans.factory.annotation.Autowired;",
+            "",
+            "interface Container {",
+            "  @Immutable",
+            "  class A {",
+            "    A() {}",
+            "  }",
+            "",
+            "  class B {",
+            "    @Autowired",
+            "    void setProperty(Object o) {}",
+            "  }",
+            "",
+            "  class C {",
+            "    // BUG: Diagnostic contains:",
+            "    @Autowired",
+            "    C() {}",
+            "  }",
+            "",
+            "  class D {",
+            "    // BUG: Diagnostic contains:",
+            "    @Autowired",
+            "    D(String x) {}",
+            "  }",
+            "",
+            "  class E {",
+            "    @Autowired",
+            "    E() {}",
+            "",
+            "    E(String x) {}",
+            "  }",
+            "",
+            "  class F {",
+            "    F() {}",
+            "",
+            "    @Autowired",
+            "    F(String x) {}",
+            "  }",
+            "",
+            "  class G {",
+            "    @Autowired private Object o;",
+            "  }",
+            "",
+            "  class H {",
+            "    @SafeVarargs",
+            "    H(List<String>... lists) {}",
+            "  }",
+            "}")
+        .doTest();
+  }
+
+  @Test
+  void replacement() {
+    BugCheckerRefactoringTestHelper.newInstance(
+            Assignment3DropAutowiredConstructorAnnotation.class, getClass())
+        .addInputLines(
+            "Container.java",
+            "import org.springframework.beans.factory.annotation.Autowired;",
+            "",
+            "interface Container {",
+            "  class A {",
+            "    @Autowired",
+            "    @Deprecated",
+            "    A() {}",
+            "  }",
+            "",
+            "  class B {",
+            "    @Autowired",
+            "    B(String x) {}",
+            "  }",
+            "}")
+        .addOutputLines(
+            "Container.java",
+            "import org.springframework.beans.factory.annotation.Autowired;",
+            "",
+            "interface Container {",
+            "  class A {",
+            "    @Deprecated",
+            "    A() {}",
+            "  }",
+            "",
+            "  class B {",
+            "    B(String x) {}",
+            "  }",
+            "}")
+        .doTest(TestMode.TEXT_MATCH);
+  }
+}

workshop/src/test/java/tech/picnic/errorprone/workshop/bugpatterns/Assignment4JUnitTestMethodDeclarationTest.java

@@ -0,0 +1,91 @@
+package tech.picnic.errorprone.workshop.bugpatterns;
+
+import com.google.errorprone.BugCheckerRefactoringTestHelper;
+import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+@Disabled("Enable this to validate part 1.")
+final class Assignment4JUnitTestMethodDeclarationTest {
+  @Test
+  void identificationIllegalModifiers() {
+    CompilationTestHelper.newInstance(Assignment4JUnitTestMethodDeclaration.class, getClass())
+        .addSourceLines(
+            "A.java",
+            "import org.junit.jupiter.api.Test;",
+            "",
+            "class A {",
+            "  @Test",
+            "  void method1() {}",
+            "",
+            "  @Test",
+            "  // BUG: Diagnostic contains:",
+            "  public void method2() {}",
+            "",
+            "  @Test",
+            "  // BUG: Diagnostic contains:",
+            "  protected void method3() {}",
+            "",
+            "  @Test",
+            "  // BUG: Diagnostic contains:",
+            "  private void method4() {}",
+            "",
+            "  public void method5() {}",
+            "",
+            "  protected void method6() {}",
+            "",
+            "  private void method7() {}",
+            "}")
+        .doTest();
+  }
+
+  @Test
+  void replacementIllegalModifiers() {
+    BugCheckerRefactoringTestHelper.newInstance(
+            Assignment4JUnitTestMethodDeclaration.class, getClass())
+        .addInputLines(
+            "A.java",
+            "import org.junit.jupiter.api.Test;",
+            "",
+            "class A {",
+            "  @Test",
+            "  void foo() {}",
+            "",
+            "  @Test",
+            "  public void bar() {}",
+            "",
+            "  @Test",
+            "  protected void baz() {}",
+            "",
+            "  @Test",
+            "  private void qux() {}",
+            "",
+            "  public void quux() {}",
+            "",
+            "  private void quuz() {}",
+            "}")
+        .addOutputLines(
+            "A.java",
+            "import org.junit.jupiter.api.Test;",
+            "",
+            "class A {",
+            "  @Test",
+            "  void foo() {}",
+            "",
+            "  @Test",
+            "  void bar() {}",
+            "",
+            "  @Test",
+            "  void baz() {}",
+            "",
+            "  @Test",
+            "  void qux() {}",
+            "",
+            "  public void quux() {}",
+            "",
+            "  private void quuz() {}",
+            "}")
+        .doTest(TestMode.TEXT_MATCH);
+  }
+}

workshop/src/test/java/tech/picnic/errorprone/workshop/bugpatterns/Assignment5DeleteIdentityConversionTest.java

@@ -0,0 +1,223 @@
+package tech.picnic.errorprone.workshop.bugpatterns;
+
+import com.google.errorprone.BugCheckerRefactoringTestHelper;
+import com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode;
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+@Disabled("Enable this when implementing the BugChecker.")
+final class Assignment5DeleteIdentityConversionTest {
+  @Test
+  void identification() {
+    CompilationTestHelper.newInstance(Assignment5DeleteIdentityConversion.class, getClass())
+        .addSourceLines(
+            "A.java",
+            "import static com.google.errorprone.matchers.Matchers.instanceMethod;",
+            "import static com.google.errorprone.matchers.Matchers.staticMethod;",
+            "",
+            "import com.google.common.collect.ImmutableBiMap;",
+            "import com.google.common.collect.ImmutableList;",
+            "import com.google.common.collect.ImmutableListMultimap;",
+            "import com.google.common.collect.ImmutableMap;",
+            "import com.google.common.collect.ImmutableMultimap;",
+            "import com.google.common.collect.ImmutableMultiset;",
+            "import com.google.common.collect.ImmutableRangeMap;",
+            "import com.google.common.collect.ImmutableRangeSet;",
+            "import com.google.common.collect.ImmutableSet;",
+            "import com.google.common.collect.ImmutableSetMultimap;",
+            "import com.google.common.collect.ImmutableTable;",
+            "import com.google.errorprone.matchers.Matcher;",
+            "import com.google.errorprone.matchers.Matchers;",
+            "",
+            "public final class A {",
+            "  public void m() {",
+            "    // BUG: Diagnostic contains:",
+            "    Matcher allOf1 = Matchers.allOf(instanceMethod());",
+            "    Matcher allOf2 = Matchers.allOf(instanceMethod(), staticMethod());",
+            "    // BUG: Diagnostic contains:",
+            "    Matcher anyOf1 = Matchers.anyOf(staticMethod());",
+            "    Matcher anyOf2 = Matchers.anyOf(instanceMethod(), staticMethod());",
+            "",
+            "    // BUG: Diagnostic contains:",
+            "    Boolean b1 = Boolean.valueOf(Boolean.FALSE);",
+            "    // BUG: Diagnostic contains:",
+            "    Boolean b2 = Boolean.valueOf(false);",
+            "    // BUG: Diagnostic contains:",
+            "    boolean b3 = Boolean.valueOf(Boolean.FALSE);",
+            "    // BUG: Diagnostic contains:",
+            "    boolean b4 = Boolean.valueOf(false);",
+            "",
+            "    // BUG: Diagnostic contains:",
+            "    Byte byte1 = Byte.valueOf((Byte) Byte.MIN_VALUE);",
+            "    // BUG: Diagnostic contains:",
+            "    Byte byte2 = Byte.valueOf(Byte.MIN_VALUE);",
+            "    // BUG: Diagnostic contains:",
+            "    byte byte3 = Byte.valueOf((Byte) Byte.MIN_VALUE);",
+            "    // BUG: Diagnostic contains:",
+            "    byte byte4 = Byte.valueOf(Byte.MIN_VALUE);",
+            "",
+            "    // BUG: Diagnostic contains:",
+            "    Character c1 = Character.valueOf((Character) 'a');",
+            "    // BUG: Diagnostic contains:",
+            "    Character c2 = Character.valueOf('a');",
+            "    // BUG: Diagnostic contains:",
+            "    char c3 = Character.valueOf((Character) 'a');",
+            "    // BUG: Diagnostic contains:",
+            "    char c4 = Character.valueOf('a');",
+            "",
+            "    // BUG: Diagnostic contains:",
+            "    Double d1 = Double.valueOf((Double) 0.0);",
+            "    // BUG: Diagnostic contains:",
+            "    Double d2 = Double.valueOf(0.0);",
+            "    // BUG: Diagnostic contains:",
+            "    double d3 = Double.valueOf((Double) 0.0);",
+            "    // BUG: Diagnostic contains:",
+            "    double d4 = Double.valueOf(0.0);",
+            "",
+            "    // BUG: Diagnostic contains:",
+            "    Float f1 = Float.valueOf((Float) 0.0F);",
+            "    // BUG: Diagnostic contains:",
+            "    Float f2 = Float.valueOf(0.0F);",
+            "    // BUG: Diagnostic contains:",
+            "    float f3 = Float.valueOf((Float) 0.0F);",
+            "    // BUG: Diagnostic contains:",
+            "    float f4 = Float.valueOf(0.0F);",
+            "",
+            "    // BUG: Diagnostic contains:",
+            "    Integer i1 = Integer.valueOf((Integer) 1);",
+            "    // BUG: Diagnostic contains:",
+            "    Integer i2 = Integer.valueOf(1);",
+            "    // BUG: Diagnostic contains:",
+            "    int i3 = Integer.valueOf((Integer) 1);",
+            "    // BUG: Diagnostic contains:",
+            "    int i4 = Integer.valueOf(1);",
+            "",
+            "    // BUG: Diagnostic contains:",
+            "    Long l1 = Long.valueOf((Long) 1L);",
+            "    // BUG: Diagnostic contains:",
+            "    Long l2 = Long.valueOf(1L);",
+            "    // BUG: Diagnostic contains:",
+            "    long l3 = Long.valueOf((Long) 1L);",
+            "    // BUG: Diagnostic contains:",
+            "    long l4 = Long.valueOf(1L);",
+            "",
+            "    Long l5 = Long.valueOf((Integer) 1);",
+            "    Long l6 = Long.valueOf(1);",
+            "    // BUG: Diagnostic contains:",
+            "    long l7 = Long.valueOf((Integer) 1);",
+            "    // BUG: Diagnostic contains:",
+            "    long l8 = Long.valueOf(1);",
+            "",
+            "    // BUG: Diagnostic contains:",
+            "    Short s1 = Short.valueOf((Short) Short.MIN_VALUE);",
+            "    // BUG: Diagnostic contains:",
+            "    Short s2 = Short.valueOf(Short.MIN_VALUE);",
+            "    // BUG: Diagnostic contains:",
+            "    short s3 = Short.valueOf((Short) Short.MIN_VALUE);",
+            "    // BUG: Diagnostic contains:",
+            "    short s4 = Short.valueOf(Short.MIN_VALUE);",
+            "",
+            "    // BUG: Diagnostic contains:",
+            "    String boolStr = Boolean.valueOf(Boolean.FALSE).toString();",
+            "    int boolHash = Boolean.valueOf(false).hashCode();",
+            "    // BUG: Diagnostic contains:",
+            "    int byteHash = Byte.valueOf((Byte) Byte.MIN_VALUE).hashCode();",
+            "    String byteStr = Byte.valueOf(Byte.MIN_VALUE).toString();",
+            "",
+            "    String str1 = String.valueOf(0);",
+            "    // BUG: Diagnostic contains:",
+            "    String str2 = String.valueOf(\"1\");",
+            "",
+            "    // BUG: Diagnostic contains:",
+            "    ImmutableBiMap<Object, Object> o1 = ImmutableBiMap.copyOf(ImmutableBiMap.of());",
+            "    // BUG: Diagnostic contains:",
+            "    ImmutableList<Object> o2 = ImmutableList.copyOf(ImmutableList.of());",
+            "    ImmutableListMultimap<Object, Object> o3 =",
+            "        // BUG: Diagnostic contains:",
+            "        ImmutableListMultimap.copyOf(ImmutableListMultimap.of());",
+            "    // BUG: Diagnostic contains:",
+            "    ImmutableMap<Object, Object> o4 = ImmutableMap.copyOf(ImmutableMap.of());",
+            "    // BUG: Diagnostic contains:",
+            "    ImmutableMultimap<Object, Object> o5 = ImmutableMultimap.copyOf(ImmutableMultimap.of());",
+            "    // BUG: Diagnostic contains:",
+            "    ImmutableMultiset<Object> o6 = ImmutableMultiset.copyOf(ImmutableMultiset.of());",
+            "    // BUG: Diagnostic contains:",
+            "    ImmutableRangeMap<String, Object> o7 = ImmutableRangeMap.copyOf(ImmutableRangeMap.of());",
+            "    // BUG: Diagnostic contains:",
+            "    ImmutableRangeSet<String> o8 = ImmutableRangeSet.copyOf(ImmutableRangeSet.of());",
+            "    // BUG: Diagnostic contains:",
+            "    ImmutableSet<Object> o9 = ImmutableSet.copyOf(ImmutableSet.of());",
+            "    ImmutableSetMultimap<Object, Object> o10 =",
+            "        // BUG: Diagnostic contains:",
+            "        ImmutableSetMultimap.copyOf(ImmutableSetMultimap.of());",
+            "    // BUG: Diagnostic contains:",
+            "    ImmutableTable<Object, Object, Object> o11 = ImmutableTable.copyOf(ImmutableTable.of());",
+            "  }",
+            "}")
+        .doTest();
+  }
+
+  @Test
+  void replacement() {
+    BugCheckerRefactoringTestHelper.newInstance(
+            Assignment5DeleteIdentityConversion.class, getClass())
+        .addInputLines(
+            "A.java",
+            "import static com.google.errorprone.matchers.Matchers.staticMethod;",
+            "import static org.mockito.Mockito.when;",
+            "",
+            "import com.google.common.collect.ImmutableCollection;",
+            "import com.google.common.collect.ImmutableList;",
+            "import com.google.common.collect.ImmutableSet;",
+            "import java.util.ArrayList;",
+            "import java.util.Collection;",
+            "",
+            "public final class A {",
+            "  public void m() {",
+            "    ImmutableSet<Object> set1 = ImmutableSet.copyOf(ImmutableSet.of());",
+            "    ImmutableSet<Object> set2 = ImmutableSet.copyOf(ImmutableList.of());",
+            "",
+            "    ImmutableCollection<Integer> list1 = ImmutableList.copyOf(ImmutableList.of(1));",
+            "    ImmutableCollection<Integer> list2 = ImmutableList.copyOf(new ArrayList<>(ImmutableList.of(1)));",
+            "",
+            "    Collection<Integer> c1 = ImmutableSet.copyOf(ImmutableSet.of(1));",
+            "    Collection<Integer> c2 = ImmutableList.copyOf(new ArrayList<>(ImmutableList.of(1)));",
+            "",
+            "    Object o1 = ImmutableSet.copyOf(ImmutableList.of());",
+            "    Object o2 = ImmutableSet.copyOf(ImmutableSet.of());",
+            "",
+            "    when(\"foo\".contains(\"f\")).thenAnswer(inv -> ImmutableSet.copyOf(ImmutableList.of(1)));",
+            "  }",
+            "}")
+        .addOutputLines(
+            "A.java",
+            "import static com.google.errorprone.matchers.Matchers.staticMethod;",
+            "import static org.mockito.Mockito.when;",
+            "",
+            "import com.google.common.collect.ImmutableCollection;",
+            "import com.google.common.collect.ImmutableList;",
+            "import com.google.common.collect.ImmutableSet;",
+            "import java.util.ArrayList;",
+            "import java.util.Collection;",
+            "",
+            "public final class A {",
+            "  public void m() {",
+            "    ImmutableSet<Object> set1 = ImmutableSet.of();",
+            "    ImmutableSet<Object> set2 = ImmutableSet.copyOf(ImmutableList.of());",
+            "",
+            "    ImmutableCollection<Integer> list1 = ImmutableList.of(1);",
+            "    ImmutableCollection<Integer> list2 = ImmutableList.copyOf(new ArrayList<>(ImmutableList.of(1)));",
+            "",
+            "    Collection<Integer> c1 = ImmutableSet.of(1);",
+            "    Collection<Integer> c2 = ImmutableList.copyOf(new ArrayList<>(ImmutableList.of(1)));",
+            "",
+            "    Object o1 = ImmutableSet.copyOf(ImmutableList.of());",
+            "    Object o2 = ImmutableSet.of();",
+            "",
+            "    when(\"foo\".contains(\"f\")).thenAnswer(inv -> ImmutableSet.copyOf(ImmutableList.of(1)));",
+            "  }",
+            "}")
+        .doTest(TestMode.TEXT_MATCH);
+  }
+}

workshop/src/test/java/tech/picnic/errorprone/workshop/refasterrules/WorkshopRefasterRulesTest.java

@@ -0,0 +1,42 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollection;
+
+final class WorkshopRefasterRulesTest {
+  @Test
+  void validateExampleRuleCollection() {
+    RefasterRuleCollection.validate(WorkshopAssignment0Rules.class);
+  }
+
+  @Disabled("Needs to be implemented in `WorkshopAssignment1Rules.java`.")
+  @Test
+  void validateFirstWorkshopAssignment() {
+    RefasterRuleCollection.validate(WorkshopAssignment1Rules.class);
+  }
+
+  @Disabled("Needs to be implemented in `WorkshopAssignment2Rules.java`.")
+  @Test
+  void validateSecondWorkshopAssignment() {
+    RefasterRuleCollection.validate(WorkshopAssignment2Rules.class);
+  }
+
+  @Disabled("Needs to be implemented in `WorkshopAssignment3Rules.java`.")
+  @Test
+  void validateThirdWorkshopAssignment() {
+    RefasterRuleCollection.validate(WorkshopAssignment3Rules.class);
+  }
+
+  @Disabled("Needs to be implemented in `WorkshopAssignment4Rules.java`.")
+  @Test
+  void validateFourthWorkshopAssignment() {
+    RefasterRuleCollection.validate(WorkshopAssignment4Rules.class);
+  }
+
+  @Disabled("Needs to be implemented in `WorkshopAssignment5Rules.java`.")
+  @Test
+  void validateFifthWorkshopAssignment() {
+    RefasterRuleCollection.validate(WorkshopAssignment5Rules.class);
+  }
+}

workshop/src/test/resources/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment0RulesTestInput.java

@@ -0,0 +1,10 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class WorkshopAssignment0RulesTest implements RefasterRuleCollectionTestCase {
+  boolean testExampleStringIsEmpty() {
+    boolean b = "foo".length() == 0;
+    return "bar".length() == 0;
+  }
+}

workshop/src/test/resources/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment0RulesTestOutput.java

@@ -0,0 +1,10 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class WorkshopAssignment0RulesTest implements RefasterRuleCollectionTestCase {
+  boolean testExampleStringIsEmpty() {
+    boolean b = "foo".isEmpty();
+    return "bar".isEmpty();
+  }
+}

workshop/src/test/resources/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment1RulesTestInput.java

@@ -0,0 +1,11 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class WorkshopAssignment1RulesTest implements RefasterRuleCollectionTestCase {
+  String testNewStringCharArray() {
+    String.copyValueOf(new char[] {});
+    String.copyValueOf(new char[] {'f', 'o', 'o'});
+    return String.copyValueOf(new char[] {'b', 'a', 'r'});
+  }
+}

workshop/src/test/resources/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment1RulesTestOutput.java

@@ -0,0 +1,11 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class WorkshopAssignment1RulesTest implements RefasterRuleCollectionTestCase {
+  String testNewStringCharArray() {
+    new String(new char[] {});
+    new String(new char[] {'f', 'o', 'o'});
+    return new String(new char[] {'b', 'a', 'r'});
+  }
+}

workshop/src/test/resources/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment2RulesTestInput.java

@@ -0,0 +1,20 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import com.google.common.collect.ImmutableSet;
+import java.util.Collections;
+import java.util.List;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class WorkshopAssignment2RulesTest implements RefasterRuleCollectionTestCase {
+  @Override
+  public ImmutableSet<Object> elidedTypesAndStaticImports() {
+    return ImmutableSet.of(Collections.class);
+  }
+
+  List<Object> testImmutableListOfOne() {
+    Collections.singletonList(1);
+    Collections.singletonList("foo");
+    List.of(1);
+    return List.of("bar");
+  }
+}

workshop/src/test/resources/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment2RulesTestOutput.java

@@ -0,0 +1,21 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
+import java.util.Collections;
+import java.util.List;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class WorkshopAssignment2RulesTest implements RefasterRuleCollectionTestCase {
+  @Override
+  public ImmutableSet<Object> elidedTypesAndStaticImports() {
+    return ImmutableSet.of(Collections.class);
+  }
+
+  List<Object> testImmutableListOfOne() {
+    ImmutableList.of(1);
+    ImmutableList.of("foo");
+    ImmutableList.of(1);
+    return ImmutableList.of("bar");
+  }
+}

workshop/src/test/resources/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment3RulesTestInput.java

@@ -0,0 +1,25 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import java.util.concurrent.ThreadLocalRandom;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class WorkshopAssignment3RulesTest implements RefasterRuleCollectionTestCase {
+  void testCheckArgumentWithoutMessage() {
+    if (!"foo".isEmpty()) {
+      throw new IllegalArgumentException();
+    }
+    if (!ThreadLocalRandom.current().nextBoolean()) {
+      throw new IllegalArgumentException();
+    }
+  }
+
+  void testCheckArgumentWithMessage() {
+    if (!"foo".isEmpty()) {
+      throw new IllegalArgumentException("The string is not empty");
+    }
+    if (!ThreadLocalRandom.current().nextBoolean()) {
+      throw new IllegalArgumentException(
+          "The rule should be able rewrite all kinds of messages ;).");
+    }
+  }
+}

workshop/src/test/resources/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment3RulesTestOutput.java

@@ -0,0 +1,20 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import java.util.concurrent.ThreadLocalRandom;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class WorkshopAssignment3RulesTest implements RefasterRuleCollectionTestCase {
+  void testCheckArgumentWithoutMessage() {
+    checkArgument("foo".isEmpty());
+    checkArgument(ThreadLocalRandom.current().nextBoolean());
+  }
+
+  void testCheckArgumentWithMessage() {
+    checkArgument("foo".isEmpty(), "The string is not empty");
+    checkArgument(
+        ThreadLocalRandom.current().nextBoolean(),
+        "The rule should be able rewrite all kinds of messages ;).");
+  }
+}

workshop/src/test/resources/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment4RulesTestInput.java

@@ -0,0 +1,25 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import com.google.common.collect.ImmutableSet;
+import java.math.RoundingMode;
+import java.util.Objects;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class WorkshopAssignment4RulesTest implements RefasterRuleCollectionTestCase {
+  @Override
+  public ImmutableSet<Object> elidedTypesAndStaticImports() {
+    return ImmutableSet.of(Objects.class);
+  }
+
+  ImmutableSet<Boolean> testPrimitiveOrReferenceEqualityEnum() {
+    // Don't pay attention to the `ImmutableSet#of` here, it's just syntactical sugar for the
+    // testing framework.
+    return ImmutableSet.of(
+        "foo".equals("bar"),
+        Integer.valueOf(1).equals(2),
+        RoundingMode.UP.equals(RoundingMode.DOWN),
+        Objects.equals(RoundingMode.UP, RoundingMode.DOWN),
+        !RoundingMode.UP.equals(RoundingMode.DOWN),
+        !Objects.equals(RoundingMode.UP, RoundingMode.DOWN));
+  }
+}

workshop/src/test/resources/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment4RulesTestOutput.java

@@ -0,0 +1,25 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import com.google.common.collect.ImmutableSet;
+import java.math.RoundingMode;
+import java.util.Objects;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class WorkshopAssignment4RulesTest implements RefasterRuleCollectionTestCase {
+  @Override
+  public ImmutableSet<Object> elidedTypesAndStaticImports() {
+    return ImmutableSet.of(Objects.class);
+  }
+
+  ImmutableSet<Boolean> testPrimitiveOrReferenceEqualityEnum() {
+    // Don't pay attention to the `ImmutableSet#of` here, it's just syntactical sugar for the
+    // testing framework.
+    return ImmutableSet.of(
+        "foo".equals("bar"),
+        Integer.valueOf(1).equals(2),
+        RoundingMode.UP == RoundingMode.DOWN,
+        RoundingMode.UP == RoundingMode.DOWN,
+        RoundingMode.UP != RoundingMode.DOWN,
+        RoundingMode.UP != RoundingMode.DOWN);
+  }
+}

workshop/src/test/resources/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment5RulesTestInput.java

@@ -0,0 +1,11 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class WorkshopAssignment5RulesTest implements RefasterRuleCollectionTestCase {
+  boolean testStreamDoAllMatch() {
+    boolean example = Stream.of("foo").noneMatch(s -> !s.isBlank());
+    return Stream.of("bar").noneMatch(b -> !b.startsWith("b"));
+  }
+}

workshop/src/test/resources/tech/picnic/errorprone/workshop/refasterrules/WorkshopAssignment5RulesTestOutput.java

@@ -0,0 +1,11 @@
+package tech.picnic.errorprone.workshop.refasterrules;
+
+import java.util.stream.Stream;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class WorkshopAssignment5RulesTest implements RefasterRuleCollectionTestCase {
+  boolean testStreamDoAllMatch() {
+    boolean example = Stream.of("foo").allMatch(s -> s.isBlank());
+    return Stream.of("bar").allMatch(b -> b.startsWith("b"));
+  }
+}