com.google.errorprone.bugpatterns.MultiVariableDeclaration.java Source code

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Here is the source code for com.google.errorprone.bugpatterns.MultiVariableDeclaration.java

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/*
 * Copyright 2015 Google 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.google.errorprone.bugpatterns;

import static com.google.errorprone.BugPattern.Category.JDK;
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 com.google.common.base.Joiner;
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.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;
import java.util.ArrayList;
import java.util.List;

/** @author cushon@google.com (Liam Miller-Cushon) */
@BugPattern(name = "MultiVariableDeclaration", summary = "Variable declarations should declare only one variable", category = JDK, severity = SUGGESTION,

        linkType = CUSTOM, 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<? extends Tree> children, VisitorState state) {
        PeekingIterator<Tree> it = Iterators.<Tree>peekingIterator(children.iterator());
        while (it.hasNext()) {
            if (it.peek().getKind() != Tree.Kind.VARIABLE) {
                it.next();
                continue;
            }
            VariableTree variableTree = (VariableTree) it.next();
            ArrayList<VariableTree> fragments = new ArrayList<>();
            fragments.add(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
                    && ((JCTree) variableTree).getStartPosition() == ((JCTree) it.peek()).getStartPosition()) {
                fragments.add((VariableTree) it.next());
            }
            if (fragments.size() == 1) {
                continue;
            }
            Fix fix = SuggestedFix.replace(((JCTree) fragments.get(0)).getStartPosition(),
                    state.getEndPosition(Iterables.getLast(fragments)), Joiner.on("; ").join(fragments) + ";");
            state.reportMatch(describeMatch(fragments.get(0), fix));
        }
        return NO_MATCH;
    }
}