Introduce MissingRefasterAnnotation checker

core/src/main/java/com/google/errorprone/bugpatterns/MissingRefasterAnnotation.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2022 The Error Prone Authors.
+ *
+ * Licensed 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.
+ */
+
+package com.google.errorprone.bugpatterns;
+
+import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.BugPattern.StandardTags.LIKELY_ERROR;
+import static com.google.errorprone.matchers.ChildMultiMatcher.MatchType.AT_LEAST_ONE;
+import static com.google.errorprone.matchers.Matchers.annotations;
+import static com.google.errorprone.matchers.Matchers.anyOf;
+import static com.google.errorprone.matchers.Matchers.isType;
+
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.MultiMatcher;
+import com.google.errorprone.util.ASTHelpers;
+import com.sun.source.tree.AnnotationTree;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.tree.MethodTree;
+import com.sun.source.tree.Tree;
+
+/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
+@BugPattern(
+    summary = "The Refaster template contains a method without any Refaster annotations",
+    severity = WARNING,
+    tags = LIKELY_ERROR)
+public final class MissingRefasterAnnotation extends BugChecker implements ClassTreeMatcher {
+  private static final MultiMatcher<Tree, AnnotationTree> HAS_REFASTER_ANNOTATION =
+      annotations(
+          AT_LEAST_ONE,
+          anyOf(
+              isType("com.google.errorprone.refaster.annotation.Placeholder"),
+              isType("com.google.errorprone.refaster.annotation.BeforeTemplate"),
+              isType("com.google.errorprone.refaster.annotation.AfterTemplate")));
+
+  @Override
+  public Description matchClass(ClassTree tree, VisitorState state) {
+    long methodTypeCount =
+        tree.getMembers().stream()
+            .filter(member -> member.getKind() == Tree.Kind.METHOD)
+            .map(MethodTree.class::cast)
+            .filter(method -> !ASTHelpers.isGeneratedConstructor(method))
+            .map(method -> HAS_REFASTER_ANNOTATION.matches(method, state))
+            .distinct()
+            .count();
+
+    return methodTypeCount < 2 ? Description.NO_MATCH : buildDescription(tree).build();
+  }
+}

core/src/main/java/com/google/errorprone/scanner/BuiltInCheckerSuppliers.java

@@ -219,6 +219,7 @@
 import com.google.errorprone.bugpatterns.MissingFail;
 import com.google.errorprone.bugpatterns.MissingImplementsComparable;
 import com.google.errorprone.bugpatterns.MissingOverride;
+import com.google.errorprone.bugpatterns.MissingRefasterAnnotation;
 import com.google.errorprone.bugpatterns.MissingSuperCall;
 import com.google.errorprone.bugpatterns.MissingTestCall;
 import com.google.errorprone.bugpatterns.MisusedDayOfYear;
@@ -916,6 +917,7 @@ public static ScannerSupplier errorChecks() {
           MissingFail.class,
           MissingImplementsComparable.class,
           MissingOverride.class,
+          MissingRefasterAnnotation.class,
           MissingSummary.class,
           MixedMutabilityReturnType.class,
           MockNotUsedInProduction.class,

core/src/test/java/com/google/errorprone/bugpatterns/MissingRefasterAnnotationTest.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright 2022 The Error Prone Authors.
+ *
+ * Licensed 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.
+ */
+
+package com.google.errorprone.bugpatterns;
+
+import com.google.common.base.Predicates;
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for {@link MissingRefasterAnnotation}. */
+@RunWith(JUnit4.class)
+public final class MissingRefasterAnnotationTest {
+  private final CompilationTestHelper compilationTestHelper =
+      CompilationTestHelper.newInstance(MissingRefasterAnnotation.class, getClass())
+          .expectErrorMessage(
+              "X",
+              Predicates.containsPattern(
+                  "The Refaster template contains a method without any Refaster annotations"));
+
+  @Test
+  public void testIdentification() {
+    compilationTestHelper
+        .addSourceLines(
+            "A.java",
+            "import com.google.errorprone.refaster.annotation.AfterTemplate;",
+            "import com.google.errorprone.refaster.annotation.AlsoNegation;",
+            "import com.google.errorprone.refaster.annotation.BeforeTemplate;",
+            "import java.util.Map;",
+            "",
+            "class A {",
+            "  // BUG: Diagnostic matches: X",
+            "  static final class MethodLacksBeforeTemplateAnnotation {",
+            "    @BeforeTemplate",
+            "    boolean before1(String string) {",
+            "      return string.equals(\"\");",
+            "    }",
+            "",
+            "    // @BeforeTemplate is missing",
+            "    boolean before2(String string) {",
+            "      return string.length() == 0;",
+            "    }",
+            "",
+            "    @AfterTemplate",
+            "    @AlsoNegation",
+            "    boolean after(String string) {",
+            "      return string.isEmpty();",
+            "    }",
+            "  }",
+            "",
+            "  // BUG: Diagnostic matches: X",
+            "  static final class MethodLacksAfterTemplateAnnotation {",
+            "    @BeforeTemplate",
+            "    boolean before(String string) {",
+            "      return string.equals(\"\");",
+            "    }",
+            "",
+            "    // @AfterTemplate is missing",
+            "    boolean after(String string) {",
+            "      return string.isEmpty();",
+            "    }",
+            "  }",
+            "",
+            "  // BUG: Diagnostic matches: X",
+            "  abstract class MethodLacksPlaceholderAnnotation<K, V> {",
+            "    // @Placeholder is missing",
+            "    abstract V function(K key);",
+            "",
+            "    @BeforeTemplate",
+            "    void before(Map<K, V> map, K key) {",
+            "      if (!map.containsKey(key)) {",
+            "        map.put(key, function(key));",
+            "      }",
+            "    }",
+            "",
+            "    @AfterTemplate",
+            "    void after(Map<K, V> map, K key) {",
+            "      map.computeIfAbsent(key, k -> function(k));",
+            "    }",
+            "  }",
+            "",
+            "  static final class ValidRefasterTemplate {",
+            "    @BeforeTemplate",
+            "    void unusedPureFunctionCall(Object o) {",
+            "      o.toString();",
+            "    }",
+            "  }",
+            "",
+            "  static final class NotARefasterTemplate {",
+            "    @Override",
+            "    public String toString() {",
+            "      return \"This is not a Refaster template\";",
+            "    }",
+            "  }",
+            "}")
+        .doTest();
+  }
+}

docs/bugpattern/MissingRefasterAnnotation.md

@@ -0,0 +1,23 @@
+A Refaster template consists of multiple methods. Typically, each method in the
+class has an annotation. If a method has no annotation, this is likely an
+oversight.
+
+```java
+static final class MethodLacksBeforeTemplateAnnotation {
+  @BeforeTemplate
+  boolean before1(String string) {
+    return string.equals("");
+  }
+
+  // @BeforeTemplate is missing
+  boolean before2(String string) {
+    return string.length() == 0;
+  }
+
+  @AfterTemplate
+  @AlsoNegation
+  boolean after(String string) {
+    return string.isEmpty();
+  }
+}
+```