com.google.errorprone.bugpatterns.PrivateConstructorForUtilityClass 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.common.collect.ImmutableList.toImmutableList;
import static com.google.common.collect.Streams.stream;
import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
import static com.google.errorprone.fixes.SuggestedFixes.addMembers;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.util.ASTHelpers.createPrivateConstructor;
import static com.google.errorprone.util.ASTHelpers.getSymbol;
import static com.google.errorprone.util.ASTHelpers.hasAnnotation;
import static com.google.errorprone.util.ASTHelpers.isGeneratedConstructor;
import static com.sun.source.tree.Tree.Kind.CLASS;
import static com.sun.source.tree.Tree.Kind.METHOD;
import static javax.lang.model.element.Modifier.PRIVATE;
import static javax.lang.model.element.Modifier.STATIC;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.fixes.SuggestedFixes;
import com.google.errorprone.matchers.Description;
import com.sun.source.tree.BlockTree;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.VariableTree;
import com.sun.tools.javac.code.Symbol.ClassSymbol;
import javax.lang.model.element.Modifier;
/** @author [email protected] (Gregory Kick) */
@BugPattern(
name = "PrivateConstructorForUtilityClass",
summary =
"Classes which are not intended to be instantiated should be made non-instantiable with a"
+ " private constructor. This includes utility classes (classes with only static"
+ " members), and the main class.",
severity = SUGGESTION)
public final class PrivateConstructorForUtilityClass extends BugChecker
implements ClassTreeMatcher {
private static final ImmutableSet ANNOTATIONS_TO_IGNORE =
ImmutableSet.of(
"org.junit.runner.RunWith",
"org.robolectric.annotation.Implements",
"com.google.auto.value.AutoValue");
@Override
public Description matchClass(ClassTree classTree, VisitorState state) {
if (!classTree.getKind().equals(CLASS)
|| classTree.getModifiers().getFlags().contains(Modifier.ABSTRACT)
|| classTree.getExtendsClause() != null
|| !classTree.getImplementsClause().isEmpty()
|| isInPrivateScope(state)) {
return NO_MATCH;
}
ClassSymbol sym = getSymbol(classTree);
for (String annotation : ANNOTATIONS_TO_IGNORE) {
if (hasAnnotation(sym, annotation, state)) {
return NO_MATCH;
}
}
ImmutableList nonSyntheticMembers =
classTree.getMembers().stream()
.filter(
tree ->
!(tree.getKind().equals(METHOD) && isGeneratedConstructor((MethodTree) tree)))
.collect(toImmutableList());
if (nonSyntheticMembers.isEmpty()
|| nonSyntheticMembers.stream().anyMatch(PrivateConstructorForUtilityClass::isInstance)) {
return NO_MATCH;
}
SuggestedFix.Builder fix =
SuggestedFix.builder()
.merge(addMembers(classTree, state, createPrivateConstructor(classTree)));
SuggestedFixes.addModifiers(classTree, state, Modifier.FINAL).ifPresent(fix::merge);
return describeMatch(classTree, fix.build());
}
private static boolean isInPrivateScope(VisitorState state) {
return stream(state.getPath())
.anyMatch(
currentLeaf ->
// Checking instanceof rather than Kind given (e.g.) enums are ClassTrees.
currentLeaf instanceof ClassTree
&& ((ClassTree) currentLeaf).getModifiers().getFlags().contains(PRIVATE));
}
private static boolean isInstance(Tree tree) {
switch (tree.getKind()) {
case CLASS:
return !((ClassTree) tree).getModifiers().getFlags().contains(STATIC);
case METHOD:
return !((MethodTree) tree).getModifiers().getFlags().contains(STATIC);
case VARIABLE:
return !((VariableTree) tree).getModifiers().getFlags().contains(STATIC);
case BLOCK:
return !((BlockTree) tree).isStatic();
case ENUM:
case ANNOTATION_TYPE:
case INTERFACE:
return false;
default:
if (tree.getKind().name().equals("RECORD")) {
return false;
}
throw new AssertionError("unknown member type:" + tree.getKind());
}
}
}