com.google.errorprone.bugpatterns.StaticAssignmentOfThrowable Maven / Gradle / Ivy
/*
* Copyright 2022 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.matchers.Description.NO_MATCH;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.getType;
import static com.google.errorprone.util.ASTHelpers.isSubtype;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
import com.google.errorprone.bugpatterns.BugChecker.VariableTreeMatcher;
import com.google.errorprone.matchers.Description;
import com.sun.source.tree.AssignmentTree;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.VariableTree;
import com.sun.source.util.TreeScanner;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Symbol.MethodSymbol;
import com.sun.tools.javac.code.Type;
import javax.lang.model.element.Modifier;
/** Checks for static fields being assigned with {@code Throwable}. */
@BugPattern(
severity = WARNING,
summary =
"Saving instances of Throwable in static fields is discouraged, prefer to create them"
+ " on-demand when an exception is thrown")
public final class StaticAssignmentOfThrowable extends BugChecker
implements MethodTreeMatcher, VariableTreeMatcher {
@Override
public Description matchVariable(VariableTree variableTree, VisitorState state) {
if (state.errorProneOptions().isTestOnlyTarget()
|| !variableTree.getModifiers().getFlags().contains(Modifier.STATIC)) {
return NO_MATCH;
}
ExpressionTree initializer = variableTree.getInitializer();
if (initializer == null) {
return NO_MATCH;
}
Type throwableType = state.getSymtab().throwableType;
Type variableType = getType(variableTree.getType());
if (!isSubtype(variableType, throwableType, state)) {
return NO_MATCH;
}
return describeMatch(variableTree);
}
@Override
public Description matchMethod(MethodTree tree, VisitorState state) {
if (state.errorProneOptions().isTestOnlyTarget()) {
return NO_MATCH;
}
MethodSymbol methodSymbol = getSymbol(tree);
if (methodSymbol.isConstructor()) {
// To avoid duplicate/conflicting findings, this scenario delegated to
// StaticAssignmentInConstructor
return NO_MATCH;
}
buildTreeScanner(state).scan(tree.getBody(), null);
return NO_MATCH;
}
/* Builds a {@code TreeScanner} that searches for assignments to static {@code Throwable} fields,
* and reports matches. */
private final TreeScanner buildTreeScanner(VisitorState state) {
Type throwableType = state.getSymtab().throwableType;
return new TreeScanner() {
@Override
public Void visitClass(ClassTree classTree, Void unused) {
return null;
}
@Override
public Void visitMethod(MethodTree methodTree, Void unused) {
return null;
}
@Override
public Void visitAssignment(AssignmentTree assignmentTree, Void unused) {
Symbol variableSymbol = getSymbol(assignmentTree.getVariable());
Type variableType = getType(assignmentTree.getVariable());
if (variableSymbol != null
&& variableSymbol.isStatic()
&& isSubtype(variableType, throwableType, state)) {
state.reportMatch(describeMatch(assignmentTree));
}
return super.visitAssignment(assignmentTree, null);
}
};
}
}