com.google.errorprone.bugpatterns.RedundantThrows Maven / Gradle / Ivy
/*
* 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.matchers.Description.NO_MATCH;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.getType;
import com.google.common.base.Joiner;
import com.google.common.base.Predicates;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.LinkedHashMultimap;
import com.google.common.collect.SetMultimap;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher;
import com.google.errorprone.fixes.SuggestedFixes;
import com.google.errorprone.matchers.Description;
import com.sun.source.tree.ExpressionTree;
import com.sun.source.tree.MethodTree;
import com.sun.tools.javac.code.Symbol;
import com.sun.tools.javac.code.Type;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
@BugPattern(
name = "RedundantThrows",
summary = "Thrown exception is a subtype of another",
severity = WARNING)
public class RedundantThrows extends BugChecker implements MethodTreeMatcher {
@Override
public Description matchMethod(MethodTree tree, VisitorState state) {
List thrown = tree.getThrows();
if (thrown.isEmpty()) {
return NO_MATCH;
}
SetMultimap exceptionsBySuper = LinkedHashMultimap.create();
for (ExpressionTree exception : thrown) {
Type type = getType(exception);
do {
type = state.getTypes().supertype(type);
exceptionsBySuper.put(type.tsym, exception);
} while (!state.getTypes().isSameType(type, state.getSymtab().objectType));
}
Set toRemove = new HashSet<>();
List messages = new ArrayList<>();
for (ExpressionTree exception : thrown) {
Symbol sym = getSymbol(exception);
if (exceptionsBySuper.containsKey(sym)) {
Set sub = exceptionsBySuper.get(sym);
messages.add(
String.format(
"%s %s of %s",
oxfordJoin(", ", sub),
sub.size() == 1 ? "is a subtype" : "are subtypes",
sym.getSimpleName()));
toRemove.addAll(sub);
}
}
if (toRemove.isEmpty()) {
return NO_MATCH;
}
// sort by order in input
List delete =
ImmutableList.copyOf(
Iterables.filter(tree.getThrows(), Predicates.in(toRemove)));
return buildDescription(delete.get(0))
.setMessage("Redundant throws clause: " + oxfordJoin("; ", messages))
.addFix(SuggestedFixes.deleteExceptions(tree, state, delete))
.build();
}
static String oxfordJoin(String on, Iterable pieces) {
StringBuilder result = new StringBuilder();
int size = Iterables.size(pieces);
if (size == 2) {
return Joiner.on(" and ").join(pieces);
}
int idx = 0;
for (Object piece : pieces) {
if (idx > 0) {
result.append(on);
if (idx == size - 1) {
result.append("and ");
}
}
result.append(piece);
idx++;
}
return result.toString();
}
}