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Warn when accepting or returning object arrays in public APIs. See[]
[] #klippy4apis PiperOrigin-RevId: 496131604
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core/src/main/java/com/google/errorprone/bugpatterns/AvoidObjectArrays.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,153 @@ | ||
| /* | ||
| * 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.fixes.SuggestedFixes.prettyType; | ||
| import static com.google.errorprone.matchers.Description.NO_MATCH; | ||
| import static com.google.errorprone.matchers.Matchers.allOf; | ||
| import static com.google.errorprone.matchers.Matchers.hasModifier; | ||
| import static com.google.errorprone.matchers.Matchers.isSameType; | ||
| import static com.google.errorprone.matchers.Matchers.methodHasArity; | ||
| import static com.google.errorprone.matchers.Matchers.methodHasParameters; | ||
| import static com.google.errorprone.matchers.Matchers.methodHasVisibility; | ||
| import static com.google.errorprone.matchers.Matchers.methodIsNamed; | ||
| import static com.google.errorprone.matchers.Matchers.methodReturns; | ||
| import static com.google.errorprone.matchers.MethodVisibility.Visibility.PUBLIC; | ||
| import static com.google.errorprone.util.ASTHelpers.getSymbol; | ||
| import static com.google.errorprone.util.ASTHelpers.getType; | ||
| import static com.google.errorprone.util.ASTHelpers.hasAnnotation; | ||
| import static com.google.errorprone.util.ASTHelpers.isSameType; | ||
| import static com.google.errorprone.util.ASTHelpers.methodIsPublicAndNotAnOverride; | ||
| import static java.util.function.Predicate.isEqual; | ||
| import static javax.lang.model.element.Modifier.STATIC; | ||
|
|
||
| import com.google.common.collect.ImmutableSet; | ||
| import com.google.errorprone.BugPattern; | ||
| import com.google.errorprone.VisitorState; | ||
| import com.google.errorprone.bugpatterns.BugChecker.MethodTreeMatcher; | ||
| import com.google.errorprone.matchers.Description; | ||
| import com.google.errorprone.matchers.Matcher; | ||
| import com.google.errorprone.suppliers.Suppliers; | ||
| 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.MethodSymbol; | ||
| import com.sun.tools.javac.code.Type; | ||
| import com.sun.tools.javac.code.Type.ArrayType; | ||
| import javax.lang.model.element.ElementKind; | ||
|
|
||
| /** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */ | ||
| @BugPattern( | ||
| summary = | ||
| "Object arrays are inferior to collections in almost every way. Prefer immutable" | ||
| + " collections (e.g., ImmutableSet, ImmutableList, etc.) over an object array whenever" | ||
| + " possible.", | ||
| severity = WARNING) | ||
| public class AvoidObjectArrays extends BugChecker implements MethodTreeMatcher { | ||
| private static final ImmutableSet<String> ANNOTATIONS_TO_IGNORE = | ||
| ImmutableSet.of( | ||
| "com.tngtech.java.junit.dataprovider.DataProvider", | ||
| "org.junit.runners.Parameterized.Parameters", | ||
| "org.junit.experimental.theories.DataPoints", | ||
| "junitparams.Parameters"); | ||
|
|
||
| // copied from SystemExitOutsideMain | ||
| private static final Matcher<MethodTree> MAIN_METHOD = | ||
| allOf( | ||
| methodHasArity(1), | ||
| methodHasVisibility(PUBLIC), | ||
| hasModifier(STATIC), | ||
| methodReturns(Suppliers.VOID_TYPE), | ||
| methodIsNamed("main"), | ||
| methodHasParameters(isSameType(Suppliers.arrayOf(Suppliers.STRING_TYPE)))); | ||
|
|
||
| @Override | ||
| public Description matchMethod(MethodTree method, VisitorState state) { | ||
| if (shouldApplyApiChecks(method, state)) { | ||
| // check the return type | ||
| if (isObjectArray(method.getReturnType())) { | ||
| state.reportMatch( | ||
| createDescription(method.getReturnType(), state, "returning", "ImmutableList")); | ||
| } | ||
|
|
||
| // check each method parameter | ||
| for (int i = 0; i < method.getParameters().size(); i++) { | ||
| VariableTree varTree = method.getParameters().get(i); | ||
| if (isObjectArray(varTree)) { | ||
| // we allow an object array if it's the last parameter and it's var args | ||
| if (getSymbol(method).isVarArgs() && i == method.getParameters().size() - 1) { | ||
| continue; | ||
| } | ||
|
|
||
| // we _may_ want to eventually allow `String[] args` as a method param, since folks | ||
| // sometimes pass around command-line arguments to other methods | ||
| state.reportMatch(createDescription(varTree.getType(), state, "accepting", "Iterable")); | ||
| } | ||
| } | ||
| } | ||
| return NO_MATCH; | ||
| } | ||
|
|
||
| private Description createDescription( | ||
| Tree tree, VisitorState state, String verb, String newType) { | ||
| Type type = getType(tree); | ||
|
|
||
| String message = String.format("Avoid %s a %s", verb, prettyType(type, state)); | ||
|
|
||
| if (type instanceof ArrayType) { | ||
| type = ((ArrayType) type).getComponentType(); | ||
| boolean isMultiDimensional = (type instanceof ArrayType); | ||
| if (!isMultiDimensional) { | ||
| message += String.format("; consider an %s<%s> instead", newType, prettyType(type, state)); | ||
| } | ||
| } | ||
|
|
||
| return buildDescription(tree).setMessage(message).build(); | ||
| } | ||
|
|
||
| /** Returns whether the tree represents an object array or not. */ | ||
| private static boolean isObjectArray(Tree tree) { | ||
| Type type = getType(tree); | ||
| return (type instanceof ArrayType) && !((ArrayType) type).getComponentType().isPrimitive(); | ||
| } | ||
|
|
||
| private static boolean shouldApplyApiChecks(MethodTree methodTree, VisitorState state) { | ||
| // don't match main methods | ||
| if (MAIN_METHOD.matches(methodTree, state)) { | ||
| return false; | ||
| } | ||
|
|
||
| // don't match certain framework-y APIs like parameterized test data providers | ||
| for (String annotationName : ANNOTATIONS_TO_IGNORE) { | ||
| if (hasAnnotation(methodTree, annotationName, state)) { | ||
| return false; | ||
| } | ||
| } | ||
|
|
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| MethodSymbol method = getSymbol(methodTree); | ||
|
|
||
| // don't match methods inside an annotation type | ||
| if (state.getTypes().closure(method.owner.type).stream() | ||
| .map(superType -> superType.tsym.getKind()) | ||
| .anyMatch(isEqual(ElementKind.ANNOTATION_TYPE))) { | ||
| return false; | ||
| } | ||
|
|
||
| return methodIsPublicAndNotAnOverride(method, state); | ||
| } | ||
| } |
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