com.google.errorprone.bugpatterns.MutableMethodReturnType Maven / Gradle / Ivy
/*
* Copyright 2017 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.Preconditions.checkState;
import static com.google.common.base.Verify.verify;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.util.ASTHelpers.findSuperMethods;
import static com.google.errorprone.util.ASTHelpers.getErasedTypeTree;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.getType;
import static com.google.errorprone.util.ASTHelpers.methodCanBeOverridden;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.fixes.SuggestedFixes;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.InjectMatchers;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.LambdaExpressionTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.ReturnTree;
import com.sun.source.tree.Tree;
import com.sun.source.util.TreeScanner;
import com.sun.tools.javac.code.Symbol.MethodSymbol;
import com.sun.tools.javac.code.Type;
import com.sun.tools.javac.code.Type.ClassType;
import java.util.Optional;
import java.util.function.Predicate;
/** @author [email protected] (Dori Reuveni) */
@BugPattern(
name = "MutableMethodReturnType",
summary =
"Method return type should use the immutable type (such as ImmutableList) instead of"
+ " the general collection interface type (such as List).",
severity = WARNING)
public final class MutableMethodReturnType extends BugChecker implements MethodTreeMatcher {
private static final Matcher ANNOTATED_WITH_PRODUCES_OR_PROVIDES =
InjectMatchers.hasProvidesAnnotation();
private static final String OVERRIDE_NOTE =
" Note that it is legal to narrow the return type when overriding a parent method. And"
+ " because this method cannot be overridden, doing so cannot cause problems for any"
+ " subclasses.";
@Override
public Description matchMethod(MethodTree methodTree, VisitorState state) {
MethodSymbol methodSymbol = getSymbol(methodTree);
if (methodSymbol.isConstructor()) {
return Description.NO_MATCH;
}
if (methodCanBeOverridden(methodSymbol)) {
return Description.NO_MATCH;
}
if (ANNOTATED_WITH_PRODUCES_OR_PROVIDES.matches(methodTree, state)) {
return Description.NO_MATCH;
}
Type returnType = methodSymbol.getReturnType();
if (ImmutableCollections.isImmutableType(returnType)) {
return Description.NO_MATCH;
}
// Iterable is technically mutable, but there isn't an Immutable* equivalent, and switching
// to an immutable list or set may not be the right choice for all APIs
if (ASTHelpers.isSameType(returnType, state.getSymtab().iterableType, state)) {
return Description.NO_MATCH;
}
ImmutableSet returnStatementsTypes = getMethodReturnTypes(methodTree);
if (returnStatementsTypes.isEmpty()) {
return Description.NO_MATCH;
}
boolean alwaysReturnsImmutableType =
returnStatementsTypes.stream().allMatch(ImmutableCollections::isImmutableType);
if (!alwaysReturnsImmutableType) {
return Description.NO_MATCH;
}
Optional immutableReturnType =
ImmutableCollections.mutableToImmutable(getTypeQualifiedName(returnType));
if (!immutableReturnType.isPresent()) {
immutableReturnType =
getCommonImmutableTypeForAllReturnStatementsTypes(returnStatementsTypes);
}
if (!immutableReturnType.isPresent()) {
return Description.NO_MATCH;
}
Type newReturnType = state.getTypeFromString(immutableReturnType.get());
SuggestedFix.Builder fixBuilder = SuggestedFix.builder();
Tree typeTree = getErasedTypeTree(methodTree.getReturnType());
verify(typeTree != null, "Could not find return type of %s", methodTree);
fixBuilder.replace(
typeTree, SuggestedFixes.qualifyType(state, fixBuilder, newReturnType.asElement()));
String message =
message()
+ (findSuperMethods(getSymbol(methodTree), state.getTypes()).isEmpty()
? ""
: OVERRIDE_NOTE);
return buildDescription(methodTree.getReturnType())
.setMessage(message)
.addFix(fixBuilder.build())
.build();
}
private static Optional getCommonImmutableTypeForAllReturnStatementsTypes(
ImmutableSet returnStatementsTypes) {
checkState(!returnStatementsTypes.isEmpty());
ClassType arbitraryClassType = returnStatementsTypes.asList().get(0);
ImmutableList superTypes = getImmutableSuperTypesForClassType(arbitraryClassType);
return superTypes.stream()
.filter(areAllReturnStatementsAssignable(returnStatementsTypes))
.findFirst();
}
private static Predicate areAllReturnStatementsAssignable(
ImmutableSet returnStatementsTypes) {
return s ->
returnStatementsTypes.stream()
.map(MutableMethodReturnType::getImmutableSuperTypesForClassType)
.allMatch(c -> c.contains(s));
}
private static ImmutableList getImmutableSuperTypesForClassType(ClassType classType) {
ImmutableList.Builder immutableSuperTypes = ImmutableList.builder();
ClassType superType = classType;
while (superType.supertype_field instanceof ClassType) {
if (ImmutableCollections.isImmutableType(superType)) {
immutableSuperTypes.add(getTypeQualifiedName(superType.asElement().type));
}
superType = (ClassType) superType.supertype_field;
}
return immutableSuperTypes.build();
}
private static String getTypeQualifiedName(Type type) {
return type.tsym.getQualifiedName().toString();
}
private static ImmutableSet getMethodReturnTypes(MethodTree methodTree) {
ImmutableSet.Builder returnTypes = ImmutableSet.builder();
methodTree.accept(
new TreeScanner() {
@Override
public Void visitReturn(ReturnTree node, Void unused) {
Type type = getType(node.getExpression());
if (type instanceof ClassType) {
returnTypes.add((ClassType) type);
}
return null;
}
@Override
public Void visitClass(ClassTree tree, Void unused) {
// Don't continue into nested classes.
return null;
}
@Override
public Void visitLambdaExpression(LambdaExpressionTree tree, Void unused) {
// Don't continue into nested lambdas.
return null;
}
},
null /* unused */);
return returnTypes.build();
}
}