com.google.errorprone.bugpatterns.MultiVariableDeclaration Maven / Gradle / Ivy
/*
* Copyright 2015 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.LinkType.CUSTOM;
import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.util.ASTHelpers.getStartPosition;
import static java.util.stream.Collectors.joining;
import com.google.common.collect.Iterables;
import com.google.common.collect.Iterators;
import com.google.common.collect.PeekingIterator;
import com.google.errorprone.BugPattern;
import com.google.errorprone.BugPattern.StandardTags;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.BlockTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
import com.google.errorprone.fixes.Fix;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.sun.source.tree.BlockTree;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.VariableTree;
import com.sun.tools.javac.tree.JCTree.JCAnnotation;
import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
import com.sun.tools.javac.tree.Pretty;
import java.io.IOException;
import java.io.StringWriter;
import java.io.UncheckedIOException;
import java.util.ArrayList;
import java.util.List;
/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
@BugPattern(
name = "MultiVariableDeclaration",
summary = "Variable declarations should declare only one variable",
severity = SUGGESTION,
linkType = CUSTOM,
tags = StandardTags.STYLE,
link = "https://google.github.io/styleguide/javaguide.html#s4.8.2.1-variables-per-declaration")
public class MultiVariableDeclaration extends BugChecker
implements ClassTreeMatcher, BlockTreeMatcher {
@Override
public Description matchBlock(BlockTree tree, VisitorState state) {
return checkDeclarations(tree.getStatements(), state);
}
@Override
public Description matchClass(ClassTree tree, VisitorState state) {
return checkDeclarations(tree.getMembers(), state);
}
private Description checkDeclarations(List children, VisitorState state) {
PeekingIterator it = Iterators.peekingIterator(children.iterator());
while (it.hasNext()) {
if (it.peek().getKind() != Tree.Kind.VARIABLE) {
it.next();
continue;
}
VariableTree variableTree = (VariableTree) it.next();
ArrayList fragments = new ArrayList<>();
fragments.add((JCVariableDecl) variableTree);
// Javac handles multi-variable declarations by lowering them in the parser into a series of
// individual declarations, all of which have the same start position. We search for the first
// declaration in the group, which is either the first variable declared in this scope or has
// a distinct end position from the previous declaration.
while (it.hasNext()
&& it.peek().getKind() == Tree.Kind.VARIABLE
&& getStartPosition(variableTree) == getStartPosition(it.peek())) {
fragments.add((JCVariableDecl) it.next());
}
if (fragments.size() == 1) {
continue;
}
Fix fix =
SuggestedFix.replace(
fragments.get(0).getStartPosition(),
state.getEndPosition(Iterables.getLast(fragments)),
fragments.stream().map(this::pretty).collect(joining("")));
state.reportMatch(describeMatch(fragments.get(0), fix));
}
return NO_MATCH;
}
private String pretty(JCVariableDecl variableDecl) {
StringWriter sw = new StringWriter();
try {
new Pretty(sw, true) {
@Override
public void visitAnnotation(JCAnnotation anno) {
if (anno.getArguments().isEmpty()) {
try {
print("@");
printExpr(anno.annotationType);
} catch (IOException e) {
throw new UncheckedIOException(e);
}
} else {
super.visitAnnotation(anno);
}
}
}.printStat(variableDecl);
} catch (IOException e) {
throw new UncheckedIOException(e);
}
return sw.toString();
}
}