com.google.errorprone.bugpatterns.RemoveUnusedImports Maven / Gradle / Ivy
/*
* Copyright 2016 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.common.collect.ImmutableList.toImmutableList;
import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ImmutableSetMultimap;
import com.google.errorprone.BugPattern;
import com.google.errorprone.BugPattern.StandardTags;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.CompilationUnitTreeMatcher;
import com.google.errorprone.bugpatterns.StaticImports.StaticImportInfo;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.doctree.DocCommentTree;
import com.sun.source.doctree.ReferenceTree;
import com.sun.source.tree.CompilationUnitTree;
import com.sun.source.tree.IdentifierTree;
import com.sun.source.tree.ImportTree;
import com.sun.source.tree.Tree;
import com.sun.source.util.DocTreePath;
import com.sun.source.util.DocTreePathScanner;
import com.sun.source.util.TreePathScanner;
import com.sun.source.util.TreeScanner;
import com.sun.tools.javac.api.JavacTrees;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.tree.DCTree.DCReference;
import java.util.LinkedHashSet;
import javax.annotation.Nullable;
/**
* @author [email protected] (Gregory Kick)
*/
@BugPattern(
summary = "Unused imports",
severity = SUGGESTION,
documentSuppression = false,
tags = StandardTags.STYLE)
public final class RemoveUnusedImports extends BugChecker implements CompilationUnitTreeMatcher {
private static final Joiner COMMA_JOINER = Joiner.on(", ");
@Override
public Description matchCompilationUnit(
CompilationUnitTree compilationUnitTree, VisitorState state) {
ImmutableSetMultimap importedSymbols =
getImportedSymbols(compilationUnitTree, state);
if (importedSymbols.isEmpty()) {
return NO_MATCH;
}
LinkedHashSet unusedImports = new LinkedHashSet<>(importedSymbols.keySet());
new TreeSymbolScanner(JavacTrees.instance(state.context))
.scan(
compilationUnitTree,
new SymbolSink() {
@Override
public boolean keepScanning() {
return !unusedImports.isEmpty();
}
@Override
public void accept(Symbol symbol) {
unusedImports.removeAll(importedSymbols.inverse().get(symbol));
}
});
if (unusedImports.isEmpty()) {
return NO_MATCH;
}
SuggestedFix.Builder fixBuilder = SuggestedFix.builder();
for (ImportTree unusedImport : unusedImports) {
fixBuilder.delete(unusedImport);
}
ImmutableList unusedImportQualifiedNames =
unusedImports.stream()
.map(tree -> state.getSourceForNode(tree.getQualifiedIdentifier()))
.collect(toImmutableList());
return buildDescription(unusedImports.iterator().next())
.addFix(fixBuilder.build())
.setMessage(
String.format("Unused imports: %s", COMMA_JOINER.join(unusedImportQualifiedNames)))
.build();
}
/**
* A callback that provides actions for whenever you encounter a {@link Symbol}. Also provides a
* hook by which you can stop scanning.
*/
private interface SymbolSink {
boolean keepScanning();
void accept(Symbol symbol);
}
private static final class TreeSymbolScanner extends TreePathScanner {
final DocTreeSymbolScanner docTreeSymbolScanner;
final JavacTrees trees;
private TreeSymbolScanner(JavacTrees trees) {
this.docTreeSymbolScanner = new DocTreeSymbolScanner();
this.trees = trees;
}
/** Skip the imports themselves when checking for usage. */
@Override
public Void visitImport(ImportTree importTree, SymbolSink usedSymbols) {
return null;
}
@Override
public Void visitIdentifier(IdentifierTree tree, SymbolSink sink) {
if (tree == null) {
return null;
}
Symbol symbol = getSymbol(tree);
if (symbol == null) {
return null;
}
sink.accept(symbol.baseSymbol());
return null;
}
@Override
public Void scan(Tree tree, SymbolSink sink) {
if (!sink.keepScanning()) {
return null;
}
if (tree == null) {
return null;
}
scanJavadoc(sink);
return super.scan(tree, sink);
}
private void scanJavadoc(SymbolSink sink) {
if (getCurrentPath() == null) {
return;
}
DocCommentTree commentTree = trees.getDocCommentTree(getCurrentPath());
if (commentTree == null) {
return;
}
docTreeSymbolScanner.scan(new DocTreePath(getCurrentPath(), commentTree), sink);
}
/**
* For the time being, this will just report any symbol referenced from javadoc as a usage.
* TODO(gak): improve this so that we can remove imports used only from javadoc and replace the
* usages with fully-qualified names.
*/
final class DocTreeSymbolScanner extends DocTreePathScanner {
@Override
public Void visitReference(ReferenceTree referenceTree, SymbolSink sink) {
// do this first, it attributes the referenceTree as a side-effect
trees.getElement(getCurrentPath());
TreeScanner nonRecursiveScanner =
new TreeScanner() {
@Override
public Void visitIdentifier(IdentifierTree tree, SymbolSink sink) {
Symbol sym = ASTHelpers.getSymbol(tree);
if (sym != null) {
sink.accept(sym);
}
return null;
}
};
DCReference reference = (DCReference) referenceTree;
nonRecursiveScanner.scan(reference.qualifierExpression, sink);
nonRecursiveScanner.scan(reference.paramTypes, sink);
return null;
}
}
}
private static ImmutableSetMultimap getImportedSymbols(
CompilationUnitTree compilationUnitTree, VisitorState state) {
ImmutableSetMultimap.Builder builder = ImmutableSetMultimap.builder();
for (ImportTree importTree : compilationUnitTree.getImports()) {
builder.putAll(importTree, getImportedSymbols(importTree, state));
}
return builder.build();
}
private static ImmutableSet getImportedSymbols(
ImportTree importTree, VisitorState state) {
if (importTree.isStatic()) {
StaticImportInfo staticImportInfo = StaticImports.tryCreate(importTree, state);
return staticImportInfo == null ? ImmutableSet.of() : staticImportInfo.members();
} else {
@Nullable Symbol importedSymbol = getSymbol(importTree.getQualifiedIdentifier());
return importedSymbol == null ? ImmutableSet.of() : ImmutableSet.of(importedSymbol);
}
}
}