com.google.errorprone.bugpatterns.UnusedNestedClass Maven / Gradle / Ivy
/*
* Copyright 2019 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.base.Ascii.toLowerCase;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.util.ASTHelpers.canBeRemoved;
import static com.google.errorprone.util.ASTHelpers.enclosingClass;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.shouldKeep;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.CompilationUnitTreeMatcher;
import com.google.errorprone.fixes.SuggestedFixes;
import com.google.errorprone.matchers.Description;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.CompilationUnitTree;
import com.sun.source.tree.IdentifierTree;
import com.sun.source.tree.MemberSelectTree;
import com.sun.source.tree.Tree;
import com.sun.source.util.TreePath;
import com.sun.source.util.TreePathScanner;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Symbol.ClassSymbol;
import com.sun.tools.javac.code.Symbol.MethodSymbol;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
/** Bugpattern to detect unused nested classes. */
@BugPattern(
altNames = "unused",
summary = "This nested class is unused, and can be removed.",
severity = WARNING,
documentSuppression = false)
public final class UnusedNestedClass extends BugChecker implements CompilationUnitTreeMatcher {
@Override
public Description matchCompilationUnit(CompilationUnitTree tree, VisitorState state) {
PrivateNestedClassScanner privateNestedClassScanner = new PrivateNestedClassScanner(state);
privateNestedClassScanner.scan(state.getPath(), null);
Map privateNestedClasses = privateNestedClassScanner.classes;
ClassUsageScanner classUsageScanner = new ClassUsageScanner();
classUsageScanner.scan(state.getPath(), null);
privateNestedClasses.keySet().removeAll(classUsageScanner.usedClasses);
for (TreePath path : privateNestedClasses.values()) {
state.reportMatch(
describeMatch(path.getLeaf(), SuggestedFixes.replaceIncludingComments(path, "", state)));
}
return NO_MATCH;
}
private final class PrivateNestedClassScanner extends TreePathScanner {
private final Map classes = new HashMap<>();
private final VisitorState state;
private PrivateNestedClassScanner(VisitorState state) {
this.state = state;
}
@Override
public Void visitClass(ClassTree classTree, Void unused) {
if (ignoreUnusedClass(classTree, state)) {
return null;
}
ClassSymbol symbol = getSymbol(classTree);
boolean isAnonymous = classTree.getSimpleName().length() == 0;
if (!isAnonymous && (canBeRemoved(symbol) || symbol.owner instanceof MethodSymbol)) {
classes.put(symbol, getCurrentPath());
}
return super.visitClass(classTree, null);
}
private boolean ignoreUnusedClass(ClassTree classTree, VisitorState state) {
return isSuppressed(classTree, state)
|| shouldKeep(classTree)
|| toLowerCase(classTree.getSimpleName().toString()).startsWith("unused");
}
}
private static final class ClassUsageScanner extends TreePathScanner {
private final Set withinClasses = new HashSet<>();
private final Set usedClasses = new HashSet<>();
@Override
public Void visitClass(ClassTree classTree, Void unused) {
ClassSymbol symbol = getSymbol(classTree);
withinClasses.add(symbol);
super.visitClass(classTree, null);
withinClasses.remove(symbol);
return null;
}
@Override
public Void visitMemberSelect(MemberSelectTree memberSelectTree, Void unused) {
handle(memberSelectTree);
return super.visitMemberSelect(memberSelectTree, null);
}
@Override
public Void visitIdentifier(IdentifierTree identifierTree, Void unused) {
handle(identifierTree);
return super.visitIdentifier(identifierTree, null);
}
private void handle(Tree node) {
for (Symbol symbol = getSymbol(node); symbol != null; symbol = enclosingClass(symbol)) {
if (symbol instanceof ClassSymbol && !withinClasses.contains(symbol)) {
usedClasses.add((ClassSymbol) symbol);
}
}
}
}
}