Implement error-prone ObjectsHashCodeUnnecessaryVarargs migration (#1522

)

Implement error-prone ObjectsHashCodeUnnecessaryVarargs migration

README.md

@@ -190,6 +190,7 @@ Safe Logging can be found at [github.com/palantir/safe-logging](https://github.c
 - `ExtendsErrorOrThrowable`: Avoid extending Error (or subclasses of it) or Throwable directly.
 - `ImmutablesStyleCollision`: Prevent unintentionally voiding immutables Style meta-annotations through the introduction of inline style annotations.
 - `TooManyArguments`: Prefer Interface that take few arguments rather than many.
+- `ObjectsHashCodeUnnecessaryVarargs`: java.util.Objects.hash(non-varargs) should be replaced with java.util.Objects.hashCode(value) to avoid unnecessary varargs array allocations.
 - `PreferStaticLoggers`: Prefer static loggers over instance loggers.
 - `LogsafeArgName`: Prevent certain named arguments as being logged as safe. Specify unsafe argument names using `LogsafeArgName:UnsafeArgNames` errorProne flag.
 - `ImplicitPublicBuilderConstructor`: Prevent builders from unintentionally leaking public constructors.

baseline-error-prone/src/main/java/com/palantir/baseline/errorprone/ObjectsHashCodeUnnecessaryVarargs.java

@@ -0,0 +1,61 @@
+/*
+ * (c) Copyright 2020 Palantir Technologies Inc. All rights reserved.
+ *
+ * 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.palantir.baseline.errorprone;
+
+import com.google.auto.service.AutoService;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.BugPattern.LinkType;
+import com.google.errorprone.BugPattern.SeverityLevel;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.fixes.SuggestedFixes;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.Matcher;
+import com.google.errorprone.matchers.Matchers;
+import com.google.errorprone.matchers.method.MethodMatchers;
+import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.MethodInvocationTree;
+
+@AutoService(BugChecker.class)
+@BugPattern(
+        name = "ObjectsHashCodeUnnecessaryVarargs",
+        link = "https://github.com/palantir/gradle-baseline#baseline-error-prone-checks",
+        linkType = LinkType.CUSTOM,
+        severity = SeverityLevel.WARNING,
+        summary = "java.util.Objects.hash(non-varargs) should be replaced with java.util.Objects.hashCode(value) "
+                + "to avoid unnecessary varargs array allocations.")
+public final class ObjectsHashCodeUnnecessaryVarargs extends BugChecker
+        implements BugChecker.MethodInvocationTreeMatcher {
+
+    private static final Matcher<ExpressionTree> HASH_MATCHER =
+            MethodMatchers.staticMethod().onClass("java.util.Objects").named("hash");
+
+    private static final Matcher<ExpressionTree> ARRAY_MATCHER = Matchers.isArrayType();
+
+    @Override
+    public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
+        if (HASH_MATCHER.matches(tree, state) && tree.getArguments().size() == 1) {
+            ExpressionTree argument = tree.getArguments().get(0);
+            if (!ARRAY_MATCHER.matches(argument, state)) {
+                return buildDescription(tree)
+                        .addFix(SuggestedFixes.renameMethodInvocation(tree, "hashCode", state))
+                        .build();
+            }
+        }
+        return Description.NO_MATCH;
+    }
+}

baseline-error-prone/src/test/java/com/palantir/baseline/errorprone/ObjectsHashCodeUnnecessaryVarargsTest.java

@@ -0,0 +1,61 @@
+/*
+ * (c) Copyright 2020 Palantir Technologies Inc. All rights reserved.
+ *
+ * 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.palantir.baseline.errorprone;
+
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.jupiter.api.Test;
+
+class ObjectsHashCodeUnnecessaryVarargsTest {
+
+    @Test
+    public void test() {
+        fix().addInputLines(
+                        "Test.java",
+                        "import java.util.Objects;",
+                        "public class Test {",
+                        "  void f(Object a, Object[] b, String[] c, String d) {",
+                        "    Objects.hash(a);",
+                        "    Objects.hash(a, a);",
+                        "    Objects.hash(b);",
+                        "    Objects.hash(c);",
+                        "    Objects.hash(d);",
+                        "  }",
+                        "}")
+                .addOutputLines(
+                        "Test.java",
+                        "import java.util.Objects;",
+                        "public class Test {",
+                        "  void f(Object a, Object[] b, String[] c, String d) {",
+                        "    Objects.hashCode(a);",
+                        "    Objects.hash(a, a);",
+                        "    Objects.hash(b);",
+                        "    // BUG: Diagnostic contains: non-varargs call of varargs method",
+                        "    Objects.hash(c);",
+                        "    Objects.hashCode(d);",
+                        "  }",
+                        "}")
+                .doTest();
+    }
+
+    private RefactoringValidator fix() {
+        return RefactoringValidator.of(new ObjectsHashCodeUnnecessaryVarargs(), getClass());
+    }
+
+    public CompilationTestHelper helper() {
+        return CompilationTestHelper.newInstance(ObjectsHashCodeUnnecessaryVarargs.class, getClass());
+    }
+}

baseline-error-prone/src/test/java/com/palantir/baseline/errorprone/RefactoringValidator.java

@@ -88,13 +88,15 @@ void doTest() {
             delegate.doTest();
             helper.compilationHelper
                     .addSourceLines(helper.outputPath, helper.outputLines)
+                    .matchAllDiagnostics()
                     .doTest();
         }
 
         void doTest(BugCheckerRefactoringTestHelper.TestMode testMode) {
             delegate.doTest(testMode);
             helper.compilationHelper
                     .addSourceLines(helper.outputPath, helper.outputLines)
+                    .matchAllDiagnostics()
                     .doTest();
         }
 

changelog/@unreleased/pr-1522.v2.yml

@@ -0,0 +1,5 @@
+type: improvement
+improvement:
+  description: Implement error-prone ObjectsHashCodeUnnecessaryVarargs migration
+  links:
+  - https://github.com/palantir/gradle-baseline/pull/1522

gradle-baseline-java/src/main/groovy/com/palantir/baseline/extensions/BaselineErrorProneExtension.java

@@ -41,6 +41,7 @@ public class BaselineErrorProneExtension {
             "LambdaMethodReference",
             "LoggerEnclosingClass",
             "LogsafeArgName",
+            "ObjectsHashCodeUnnecessaryVarargs",
             "OptionalFlatMapOfNullable",
             "OptionalOrElseMethodInvocation",
             "PreferBuiltInConcurrentKeySet",