com.google.errorprone.bugpatterns.StreamToIterable Maven / Gradle / Ivy
/*
* Copyright 2020 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.SeverityLevel.WARNING;
import static com.google.errorprone.BugPattern.StandardTags.FRAGILE_CODE;
import static com.google.errorprone.fixes.SuggestedFixes.qualifyStaticImport;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.matchers.method.MethodMatchers.instanceMethod;
import static com.google.errorprone.util.ASTHelpers.getReceiver;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.getType;
import static com.google.errorprone.util.ASTHelpers.isSameType;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.LambdaExpressionTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.MemberReferenceTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.sun.source.tree.EnhancedForLoopTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.LambdaExpressionTree;
import com.sun.source.tree.LambdaExpressionTree.BodyKind;
import com.sun.source.tree.MemberReferenceTree;
import com.sun.source.tree.TypeCastTree;
import com.sun.tools.javac.code.Symbol.VarSymbol;
/** Discourage {@code stream::iterator} to create {@link Iterable}s. */
@BugPattern(
summary =
"Using stream::iterator creates a one-shot Iterable, which may cause surprising failures.",
severity = WARNING,
tags = FRAGILE_CODE,
documentSuppression = false)
public final class StreamToIterable extends BugChecker
implements LambdaExpressionTreeMatcher, MemberReferenceTreeMatcher {
private static final Matcher STREAM_ITERATOR =
instanceMethod().onDescendantOf("java.util.stream.Stream").named("iterator");
@Override
public Description matchLambdaExpression(LambdaExpressionTree tree, VisitorState state) {
if (!isSameType(getType(tree), state.getSymtab().iterableType, state)) {
return NO_MATCH;
}
if (!tree.getBodyKind().equals(BodyKind.EXPRESSION)) {
return NO_MATCH;
}
ExpressionTree body = (ExpressionTree) tree.getBody();
if (!STREAM_ITERATOR.matches(body, state)) {
return NO_MATCH;
}
// Only match variables, which we can be sure aren't being re-created.
if (!(getSymbol(getReceiver(body)) instanceof VarSymbol)) {
return NO_MATCH;
}
return describeMatch(tree, body, state);
}
@Override
public Description matchMemberReference(MemberReferenceTree tree, VisitorState state) {
if (!STREAM_ITERATOR.matches(tree, state)) {
return NO_MATCH;
}
if (!isSameType(getType(tree), state.getSymtab().iterableType, state)) {
return NO_MATCH;
}
return describeMatch(tree, tree, state);
}
private Description describeMatch(
ExpressionTree tree, ExpressionTree invocation, VisitorState state) {
if (state.getPath().getParentPath().getLeaf() instanceof TypeCastTree
&& state.getPath().getParentPath().getParentPath().getLeaf()
instanceof EnhancedForLoopTree) {
return NO_MATCH;
}
SuggestedFix.Builder fix =
SuggestedFix.builder()
.setShortDescription(
"Collect to an ImmutableList (caveat: this materializes the contents into memory"
+ " at once)");
fix.replace(
tree,
String.format(
"%s.collect(%s())",
state.getSourceForNode(getReceiver(invocation)),
qualifyStaticImport(
"com.google.common.collect.ImmutableList.toImmutableList", fix, state)));
return describeMatch(tree, fix.build());
}
}