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/*
* 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.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.util.ASTHelpers.getStartPosition;
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.Matcher;
import com.google.errorprone.matchers.method.MethodMatchers;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.BlockTree;
import com.sun.source.tree.EnhancedForLoopTree;
import com.sun.source.tree.ExpressionStatementTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.IdentifierTree;
import com.sun.source.tree.MemberSelectTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.StatementTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.VariableTree;
import com.sun.source.util.TreePath;
import com.sun.source.util.TreeScanner;
import java.util.List;
import java.util.Objects;
import java.util.Optional;
/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
@BugPattern(
altNames = "FilesLinesLeak",
summary =
"Streams that encapsulate a closeable resource should be closed using"
+ " try-with-resources",
severity = WARNING)
public class StreamResourceLeak extends AbstractMustBeClosedChecker implements MethodTreeMatcher {
public static final Matcher MATCHER =
MethodMatchers.staticMethod()
.onClass("java.nio.file.Files")
.namedAnyOf("lines", "newDirectoryStream", "list", "walk", "find");
@Override
public Description matchMethod(MethodTree tree, VisitorState state) {
return scanEntireMethodFor(MATCHER, tree, state);
}
@Override
protected Optional fix(ExpressionTree tree, VisitorState state, NameSuggester suggester) {
return Change.of(definiteFix(tree, state));
}
private static SuggestedFix definiteFix(ExpressionTree tree, VisitorState state) {
TreePath parentPath = state.getPath().getParentPath();
Tree parent = parentPath.getLeaf();
SuggestedFix.Builder fix = SuggestedFix.builder();
String streamType = SuggestedFixes.prettyType(state, fix, ASTHelpers.getReturnType(tree));
if (parent instanceof MemberSelectTree) {
StatementTree statement = state.findEnclosing(StatementTree.class);
if (statement instanceof VariableTree) {
// Variables need to be declared outside the try-with-resources:
// e.g. `int count = Files.lines(p).count();`
// -> `int count; try (Stream stream = Files.lines(p)) { count = stream.count(); }`
VariableTree var = (VariableTree) statement;
int pos = getStartPosition(var);
int initPos = getStartPosition(var.getInitializer());
int eqPos = pos + state.getSourceForNode(var).substring(0, initPos - pos).lastIndexOf('=');
fix.replace(
eqPos,
initPos,
String.format(
";\ntry (%s stream = %s) {\n%s =",
streamType, state.getSourceForNode(tree), var.getName()));
} else {
// the non-variable case, e.g. `return Files.lines(p).count()`
// -> try (Stream stream = Files.lines(p)) { return stream.count(); }`
fix.prefixWith(
statement,
String.format("try (%s stream = %s) {\n", streamType, state.getSourceForNode(tree)));
}
fix.replace(tree, "stream");
fix.postfixWith(statement, "}");
return fix.build();
} else if (parent instanceof VariableTree) {
// If the stream is assigned to a variable, wrap the variable in a try-with-resources
// that includes all statements in the same block that reference the variable.
Tree grandParent = parentPath.getParentPath().getLeaf();
if (!(grandParent instanceof BlockTree)) {
return SuggestedFix.emptyFix();
}
List statements = ((BlockTree) grandParent).getStatements();
int idx = statements.indexOf(parent);
int lastUse = idx;
for (int i = idx + 1; i < statements.size(); i++) {
boolean[] found = {false};
statements
.get(i)
.accept(
new TreeScanner() {
@Override
public Void visitIdentifier(IdentifierTree tree, Void unused) {
if (Objects.equals(ASTHelpers.getSymbol(tree), ASTHelpers.getSymbol(parent))) {
found[0] = true;
}
return null;
}
},
null);
if (found[0]) {
lastUse = i;
}
}
fix.prefixWith(parent, "try (");
fix.replace(
state.getEndPosition(((VariableTree) parent).getInitializer()),
state.getEndPosition(parent),
") {");
fix.postfixWith(statements.get(lastUse), "}");
return fix.build();
} else if (parent instanceof EnhancedForLoopTree) {
// If the stream is used in a loop (e.g. directory streams), wrap the loop in
// try-with-resources.
fix.prefixWith(
parent,
String.format("try (%s stream = %s) {\n", streamType, state.getSourceForNode(tree)));
fix.replace(tree, "stream");
fix.postfixWith(parent, "}");
return fix.build();
} else if (parent instanceof MethodInvocationTree) {
// If the stream is used in a method that is called in an expression statement, wrap it in
// try-with-resources.
Tree grandParent = parentPath.getParentPath().getLeaf();
if (!(grandParent instanceof ExpressionStatementTree)) {
return SuggestedFix.emptyFix();
}
fix.prefixWith(
parent,
String.format("try (%s stream = %s) {\n", streamType, state.getSourceForNode(tree)));
fix.replace(tree, "stream");
fix.postfixWith(grandParent, "}");
return fix.build();
}
return SuggestedFix.emptyFix();
}
}
