com.google.errorprone.bugpatterns.Varifier Maven / Gradle / Ivy
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* Copyright 2022 Google Inc. All Rights Reserved.
*
* 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.matchers.Matchers.allOf;
import static com.google.errorprone.matchers.Matchers.anyOf;
import static com.google.errorprone.matchers.method.MethodMatchers.instanceMethod;
import static com.google.errorprone.matchers.method.MethodMatchers.staticMethod;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.getType;
import static com.google.errorprone.util.ASTHelpers.hasImplicitType;
import static com.google.errorprone.util.ASTHelpers.isConsideredFinal;
import static com.google.errorprone.util.ASTHelpers.isSameType;
import static com.google.errorprone.util.ASTHelpers.streamReceivers;
import static javax.lang.model.element.ElementKind.LOCAL_VARIABLE;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.VariableTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.matchers.Matcher;
import com.google.errorprone.matchers.method.MethodMatchers;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.NewClassTree;
import com.sun.source.tree.ParameterizedTypeTree;
import com.sun.source.tree.TypeCastTree;
import com.sun.source.tree.VariableTree;
import com.sun.tools.javac.code.Symbol.MethodSymbol;
import java.util.regex.Pattern;
/** Converts some local variables to use {@code var}. */
@BugPattern(severity = WARNING, summary = "Consider using `var` here to avoid boilerplate.")
public final class Varifier extends BugChecker implements VariableTreeMatcher {
private static final Matcher BUILD_METHOD =
instanceMethod().anyClass().withNameMatching(Pattern.compile("build.*"));
private static final Matcher BUILDER_FACTORY =
anyOf(
staticMethod().anyClass().withNameMatching(Pattern.compile("(builder|newBuilder).*")),
MethodMatchers.constructor()
.forClass(
(type, state) -> type.tsym.getSimpleName().toString().startsWith("Builder")));
private static final Matcher FACTORY_METHOD =
allOf(
staticMethod().anyClass().withNameMatching(Pattern.compile("(new|create|of).*")),
(t, s) -> {
var symbol = getSymbol(t);
return symbol instanceof MethodSymbol
&& isSameType(((MethodSymbol) symbol).getReturnType(), symbol.owner.type, s);
});
private static final Matcher ASSERT_THROWS =
staticMethod().onClass("org.junit.Assert").named("assertThrows");
@Override
public Description matchVariable(VariableTree tree, VisitorState state) {
var symbol = getSymbol(tree);
ExpressionTree initializer = tree.getInitializer();
if (!symbol.getKind().equals(LOCAL_VARIABLE)
|| !isConsideredFinal(symbol)
|| initializer == null
|| hasImplicitType(tree, state)) {
return NO_MATCH;
}
// Foo unused = ...;
if (symbol.getSimpleName().contentEquals("unused")) {
return fix(tree);
}
// MyException exception = assertThrows(MyException.class, () -> ...);
if (ASSERT_THROWS.matches(initializer, state)) {
return fix(tree);
}
// Foo foo = (Foo) bar;
if (initializer instanceof TypeCastTree
&& isSameType(
getType(((TypeCastTree) initializer).getType()), getType(tree.getType()), state)) {
return fix(tree);
}
// Foo foo = new Foo(...);
if (initializer instanceof NewClassTree
&& isSameType(
getType(((NewClassTree) initializer).getIdentifier()),
getType(tree.getType()),
state)) {
var identifier = ((NewClassTree) initializer).getIdentifier();
if (identifier instanceof ParameterizedTypeTree
&& ((ParameterizedTypeTree) identifier).getTypeArguments().isEmpty()) {
return NO_MATCH;
}
return fix(tree);
}
// Foo foo = Foo.builder()...build();
if (BUILD_METHOD.matches(initializer, state)
&& streamReceivers(initializer).anyMatch(t -> BUILDER_FACTORY.matches(t, state))) {
return fix(tree);
}
// Foo foo = Foo.createFoo(..);
if (FACTORY_METHOD.matches(initializer, state)) {
return fix(tree);
}
return NO_MATCH;
}
private Description fix(VariableTree tree) {
return describeMatch(tree, SuggestedFix.replace(tree.getType(), "var"));
}
}