Add a check for missing braces
PiperOrigin-RevId: 368113953
diff --git a/core/src/main/java/com/google/errorprone/bugpatterns/MissingBraces.java b/core/src/main/java/com/google/errorprone/bugpatterns/MissingBraces.java
new file mode 100644
index 0000000..55ae172
--- /dev/null
+++ b/core/src/main/java/com/google/errorprone/bugpatterns/MissingBraces.java
@@ -0,0 +1,101 @@
+/*
+ * Copyright 2021 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.matchers.Description.NO_MATCH;
+
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.BugPattern.LinkType;
+import com.google.errorprone.BugPattern.SeverityLevel;
+import com.google.errorprone.BugPattern.StandardTags;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker.DoWhileLoopTreeMatcher;
+import com.google.errorprone.bugpatterns.BugChecker.EnhancedForLoopTreeMatcher;
+import com.google.errorprone.bugpatterns.BugChecker.ForLoopTreeMatcher;
+import com.google.errorprone.bugpatterns.BugChecker.IfTreeMatcher;
+import com.google.errorprone.bugpatterns.BugChecker.WhileLoopTreeMatcher;
+import com.google.errorprone.fixes.SuggestedFix;
+import com.google.errorprone.matchers.Description;
+import com.sun.source.tree.BlockTree;
+import com.sun.source.tree.DoWhileLoopTree;
+import com.sun.source.tree.EnhancedForLoopTree;
+import com.sun.source.tree.ForLoopTree;
+import com.sun.source.tree.IfTree;
+import com.sun.source.tree.StatementTree;
+import com.sun.source.tree.Tree;
+import com.sun.source.tree.WhileLoopTree;
+
+/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
+@BugPattern(
+ name = "MissingBraces",
+ summary =
+ "The Google Java Style Guide requires braces to be used with if, else, for, do and while"
+ + " statements, even when the body is empty or contains only a single statement.",
+ severity = SeverityLevel.SUGGESTION,
+ tags = StandardTags.STYLE,
+ linkType = LinkType.CUSTOM,
+ link = "https://google.github.io/styleguide/javaguide.html#s4.1.1-braces-always-used"
+ )
+public class MissingBraces extends BugChecker
+ implements IfTreeMatcher,
+ ForLoopTreeMatcher,
+ DoWhileLoopTreeMatcher,
+ WhileLoopTreeMatcher,
+ EnhancedForLoopTreeMatcher {
+
+ @Override
+ public Description matchIf(IfTree tree, VisitorState state) {
+ check(tree.getThenStatement(), state);
+ if (tree.getElseStatement() != null
+ && !tree.getElseStatement().getKind().equals(Tree.Kind.IF)) {
+ check(tree.getElseStatement(), state);
+ }
+ return NO_MATCH;
+ }
+
+ @Override
+ public Description matchDoWhileLoop(DoWhileLoopTree tree, VisitorState state) {
+ check(tree.getStatement(), state);
+ return NO_MATCH;
+ }
+
+ @Override
+ public Description matchForLoop(ForLoopTree tree, VisitorState state) {
+ check(tree.getStatement(), state);
+ return NO_MATCH;
+ }
+
+ @Override
+ public Description matchEnhancedForLoop(EnhancedForLoopTree tree, VisitorState state) {
+ check(tree.getStatement(), state);
+ return NO_MATCH;
+ }
+
+ @Override
+ public Description matchWhileLoop(WhileLoopTree tree, VisitorState state) {
+ check(tree.getStatement(), state);
+ return NO_MATCH;
+ }
+
+ void check(StatementTree tree, VisitorState state) {
+ if (tree != null && !(tree instanceof BlockTree)) {
+ state.reportMatch(
+ describeMatch(
+ tree, SuggestedFix.builder().prefixWith(tree, "{").postfixWith(tree, "}").build()));
+ }
+ }
+}
diff --git a/core/src/main/java/com/google/errorprone/scanner/BuiltInCheckerSuppliers.java b/core/src/main/java/com/google/errorprone/scanner/BuiltInCheckerSuppliers.java
index 50e8fa6..177024d 100644
--- a/core/src/main/java/com/google/errorprone/scanner/BuiltInCheckerSuppliers.java
+++ b/core/src/main/java/com/google/errorprone/scanner/BuiltInCheckerSuppliers.java
@@ -197,6 +197,7 @@
import com.google.errorprone.bugpatterns.MathRoundIntLong;
import com.google.errorprone.bugpatterns.MemberName;
import com.google.errorprone.bugpatterns.MethodCanBeStatic;
+import com.google.errorprone.bugpatterns.MissingBraces;
import com.google.errorprone.bugpatterns.MissingCasesInEnumSwitch;
import com.google.errorprone.bugpatterns.MissingDefault;
import com.google.errorprone.bugpatterns.MissingFail;
@@ -994,6 +995,7 @@
LongLiteralLowerCaseSuffix.class,
MemberName.class,
MethodCanBeStatic.class,
+ MissingBraces.class,
MissingDefault.class,
MixedArrayDimensions.class,
MoreThanOneQualifier.class,
diff --git a/core/src/test/java/com/google/errorprone/bugpatterns/MissingBracesTest.java b/core/src/test/java/com/google/errorprone/bugpatterns/MissingBracesTest.java
new file mode 100644
index 0000000..961e30a
--- /dev/null
+++ b/core/src/test/java/com/google/errorprone/bugpatterns/MissingBracesTest.java
@@ -0,0 +1,79 @@
+/*
+ * Copyright 2021 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.errorprone.BugCheckerRefactoringTestHelper;
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** {@link MissingBraces}Test */
+@RunWith(JUnit4.class)
+public class MissingBracesTest {
+ @Test
+ public void positive() {
+ BugCheckerRefactoringTestHelper.newInstance(MissingBraces.class, getClass())
+ .addInputLines(
+ "Test.java",
+ "import java.util.List;",
+ "class Test {",
+ " void f(boolean x, List<Integer> is) {",
+ " if (x) throw new AssertionError();",
+ " else x = !x;",
+ " while (x) g();",
+ " do g(); while (x);",
+ " for ( ; x; ) g();",
+ " for (int i : is) g();",
+ " }",
+ " void g() {}",
+ "}")
+ .addOutputLines(
+ "Test.java",
+ "import java.util.List;",
+ "class Test {",
+ " void f(boolean x, List<Integer> is) {",
+ " if (x) { throw new AssertionError(); }",
+ " else { x = !x; }",
+ " while (x) { g(); }",
+ " do { g(); } while (x);",
+ " for ( ; x; ) { g(); }",
+ " for (int i : is) { g(); }",
+ " }",
+ " void g() {}",
+ "}")
+ .doTest();
+ }
+
+ @Test
+ public void negative() {
+ CompilationTestHelper.newInstance(MissingBraces.class, getClass())
+ .addSourceLines(
+ "Test.java",
+ "class Test {",
+ " void f(boolean x) {",
+ " if (x) { g(); }",
+ " else { g(); }",
+ " while (x) { g(); }",
+ " do { g(); } while (x);",
+ " for (;;) { g(); }",
+ " }",
+ " void g() {}",
+ "}")
+ .doTest();
+ }
+}
