ClassCanBeStatic: Exclude JUnit @Nested classes

Exclude inner classes annotated with JUnit's `@Nested` annotation from the `ClassCanBeStatic` check. JUnit requires them to not be `static`. From the [JUnit docs](https://junit.org/junit5/docs/current/user-guide/#writing-tests-nested): > Only non-static nested classes (i.e. inner classes) can serve as `@Nested` test classes. Fixes #956. Fixes #3654 FUTURE_COPYBARA_INTEGRATE_REVIEW=#3654 from ljrmorgan:junit_nested_test_classes_cannot_be_static 3a5bd67 PiperOrigin-RevId: 503544057
google · Jan 23, 2023 · 7f8fde1 · 7f8fde1
1 parent 1b8bf17
commit 7f8fde1
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Showing 3 changed files with 29 additions and 1 deletion.
diff --git a/check_api/src/main/java/com/google/errorprone/util/ASTHelpers.java b/check_api/src/main/java/com/google/errorprone/util/ASTHelpers.java
@@ -1041,7 +1041,8 @@ public static boolean shouldKeep(Tree tree) {
    * though they are.
    */
   private static final ImmutableSet<String> ANNOTATIONS_CONSIDERED_KEEP =
-      ImmutableSet.of("org.apache.beam.sdk.transforms.DoFn.ProcessElement");
+      ImmutableSet.of(
+          "org.apache.beam.sdk.transforms.DoFn.ProcessElement", "org.junit.jupiter.api.Nested");
 
   private static final String USED_REFLECTIVELY = "UsedReflectively";
 

diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/ClassCanBeStatic.java b/core/src/main/java/com/google/errorprone/bugpatterns/ClassCanBeStatic.java
@@ -77,6 +77,9 @@ public Description matchClass(ClassTree tree, VisitorState state) {
     if (CanBeStaticAnalyzer.referencesOuter(tree, currentClass, state)) {
       return NO_MATCH;
     }
+    if (ASTHelpers.shouldKeep(tree)) {
+      return NO_MATCH;
+    }
     if (tree.getMembers().stream().anyMatch(m -> hasAnnotation(m, REFASTER_ANNOTATION, state))) {
       return NO_MATCH;
     }

diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/ClassCanBeStaticTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/ClassCanBeStaticTest.java
@@ -401,4 +401,28 @@ public void refaster() {
             "}")
         .doTest();
   }
+
+  @Test
+  public void junitNestedClass() {
+    compilationHelper
+        .addSourceLines(
+            "Nested.java",
+            "package org.junit.jupiter.api;",
+            "import java.lang.annotation.ElementType;",
+            "import java.lang.annotation.Retention;",
+            "import java.lang.annotation.RetentionPolicy;",
+            "import java.lang.annotation.Target;",
+            "@Target(ElementType.TYPE)",
+            "@Retention(RetentionPolicy.RUNTIME)",
+            "public @interface Nested {}")
+        .addSourceLines(
+            "A.java",
+            "import org.junit.jupiter.api.Nested;",
+            "public class A {",
+            "  @Nested class Inner {",
+            "    void f() {}",
+            "  }",
+            "}")
+        .doTest();
+  }
 }