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Introduce
OptionalOrElseGet Refaster rule (#527)
While there, introduce `IsLikelyTrivialComputation` Matcher.
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92 changes: 92 additions & 0 deletions
92
...rt/src/main/java/tech/picnic/errorprone/refaster/matchers/IsLikelyTrivialComputation.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,92 @@ | ||
| package tech.picnic.errorprone.refaster.matchers; | ||
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| import com.google.errorprone.VisitorState; | ||
| import com.google.errorprone.matchers.Matcher; | ||
| import com.sun.source.tree.ArrayAccessTree; | ||
| import com.sun.source.tree.ExpressionTree; | ||
| import com.sun.source.tree.IdentifierTree; | ||
| import com.sun.source.tree.LambdaExpressionTree; | ||
| import com.sun.source.tree.LiteralTree; | ||
| import com.sun.source.tree.MemberReferenceTree; | ||
| import com.sun.source.tree.MemberSelectTree; | ||
| import com.sun.source.tree.MethodInvocationTree; | ||
| import com.sun.source.tree.ParenthesizedTree; | ||
| import com.sun.source.tree.TypeCastTree; | ||
| import com.sun.source.tree.UnaryTree; | ||
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| /** A matcher of expressions that likely require little to no computation. */ | ||
| public final class IsLikelyTrivialComputation implements Matcher<ExpressionTree> { | ||
| private static final long serialVersionUID = 1L; | ||
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| /** Instantiates a new {@link IsLikelyTrivialComputation} instance. */ | ||
| public IsLikelyTrivialComputation() {} | ||
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| @Override | ||
| public boolean matches(ExpressionTree expressionTree, VisitorState state) { | ||
| if (expressionTree instanceof MethodInvocationTree) { | ||
| // XXX: Method invocations are generally *not* trivial computations, but we make an exception | ||
| // for nullary method invocations on the result of a trivial computation. This exception | ||
| // allows this `Matcher` to by the `OptionalOrElseGet` Refaster rule, such that it does not | ||
| // suggest the introduction of lambda expressions that are better expressed as method | ||
| // references. Once the `MethodReferenceUsage` bug checker is production-ready, this exception | ||
| // should be removed. (But at that point, instead defining a `RequiresComputation` matcher may | ||
| // be more appropriate.) | ||
| MethodInvocationTree methodInvocation = (MethodInvocationTree) expressionTree; | ||
| if (methodInvocation.getArguments().isEmpty() | ||
| && matches(methodInvocation.getMethodSelect())) { | ||
| return true; | ||
| } | ||
| } | ||
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| return matches(expressionTree); | ||
| } | ||
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| // XXX: Some `BinaryTree`s may represent what could be considered "trivial computations". | ||
| // Depending on feedback such trees may be matched in the future. | ||
| private static boolean matches(ExpressionTree expressionTree) { | ||
| if (expressionTree instanceof ArrayAccessTree) { | ||
| return matches(((ArrayAccessTree) expressionTree).getExpression()) | ||
| && matches(((ArrayAccessTree) expressionTree).getIndex()); | ||
| } | ||
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| if (expressionTree instanceof LiteralTree) { | ||
| return true; | ||
| } | ||
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| if (expressionTree instanceof LambdaExpressionTree) { | ||
| /* | ||
| * Lambda expressions encapsulate computations, but their definition does not involve | ||
| * significant computation. | ||
| */ | ||
| return true; | ||
| } | ||
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| if (expressionTree instanceof IdentifierTree) { | ||
| return true; | ||
| } | ||
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| if (expressionTree instanceof MemberReferenceTree) { | ||
| return matches(((MemberReferenceTree) expressionTree).getQualifierExpression()); | ||
| } | ||
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| if (expressionTree instanceof MemberSelectTree) { | ||
| return matches(((MemberSelectTree) expressionTree).getExpression()); | ||
| } | ||
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| if (expressionTree instanceof ParenthesizedTree) { | ||
| return matches(((ParenthesizedTree) expressionTree).getExpression()); | ||
| } | ||
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| if (expressionTree instanceof TypeCastTree) { | ||
| return matches(((TypeCastTree) expressionTree).getExpression()); | ||
| } | ||
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| if (expressionTree instanceof UnaryTree) { | ||
| // XXX: Arguably side-effectful options such as pre- and post-increment and -decrement are not | ||
| // trivial. | ||
| return matches(((UnaryTree) expressionTree).getExpression()); | ||
| } | ||
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| return false; | ||
| } | ||
| } |
147 changes: 147 additions & 0 deletions
147
...rc/test/java/tech/picnic/errorprone/refaster/matchers/IsLikelyTrivialComputationTest.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,147 @@ | ||
| package tech.picnic.errorprone.refaster.matchers; | ||
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| import static com.google.errorprone.BugPattern.SeverityLevel.ERROR; | ||
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| import com.google.errorprone.BugPattern; | ||
| import com.google.errorprone.CompilationTestHelper; | ||
| import com.google.errorprone.bugpatterns.BugChecker; | ||
| import com.sun.source.tree.ReturnTree; | ||
| import org.junit.jupiter.api.Test; | ||
|
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| final class IsLikelyTrivialComputationTest { | ||
| @Test | ||
| void matches() { | ||
| CompilationTestHelper.newInstance(MatcherTestChecker.class, getClass()) | ||
| .addSourceLines( | ||
| "A.java", | ||
| "import java.util.function.Predicate;", | ||
| "", | ||
| "class A {", | ||
| " String negative1() {", | ||
| " return String.valueOf(1);", | ||
| " }", | ||
| "", | ||
| " String negative2() {", | ||
| " return toString().toString();", | ||
| " }", | ||
| "", | ||
| " String negative3() {", | ||
| " return \"foo\" + toString();", | ||
| " }", | ||
| "", | ||
| " byte negative4() {", | ||
| " return \"foo\".getBytes()[0];", | ||
| " }", | ||
| "", | ||
| " int negative5() {", | ||
| " int[] arr = new int[0];", | ||
| " return arr[hashCode()];", | ||
| " }", | ||
| "", | ||
| " int negative6() {", | ||
| " return 1 * 2;", | ||
| " }", | ||
| "", | ||
| " Predicate<String> negative7() {", | ||
| " return toString()::equals;", | ||
| " }", | ||
| "", | ||
| " String negative8() {", | ||
| " return (toString());", | ||
| " }", | ||
| "", | ||
| " Object negative9() {", | ||
| " return (Object) toString();", | ||
| " }", | ||
| "", | ||
| " int negative10() {", | ||
| " return -hashCode();", | ||
| " }", | ||
| "", | ||
| " String positive1() {", | ||
| " // BUG: Diagnostic contains:", | ||
| " return toString();", | ||
| " }", | ||
| "", | ||
| " String positive2() {", | ||
| " // BUG: Diagnostic contains:", | ||
| " return this.toString();", | ||
| " }", | ||
| "", | ||
| " int positive3() {", | ||
| " int[] arr = new int[0];", | ||
| " // BUG: Diagnostic contains:", | ||
| " return arr[0];", | ||
| " }", | ||
| "", | ||
| " String positive4() {", | ||
| " // BUG: Diagnostic contains:", | ||
| " return null;", | ||
| " }", | ||
| "", | ||
| " boolean positive5() {", | ||
| " // BUG: Diagnostic contains:", | ||
| " return false;", | ||
| " }", | ||
| "", | ||
| " int positive6() {", | ||
| " // BUG: Diagnostic contains:", | ||
| " return 0;", | ||
| " }", | ||
| "", | ||
| " String positive7() {", | ||
| " // BUG: Diagnostic contains:", | ||
| " return \"foo\" + \"bar\";", | ||
| " }", | ||
| "", | ||
| " Predicate<String> positive8() {", | ||
| " // BUG: Diagnostic contains:", | ||
| " return v -> \"foo\".equals(v);", | ||
| " }", | ||
| "", | ||
| " A positive9() {", | ||
| " // BUG: Diagnostic contains:", | ||
| " return this;", | ||
| " }", | ||
| "", | ||
| " Predicate<String> positive10() {", | ||
| " // BUG: Diagnostic contains:", | ||
| " return \"foo\"::equals;", | ||
| " }", | ||
| "", | ||
| " A positive11() {", | ||
| " // BUG: Diagnostic contains:", | ||
| " return (this);", | ||
| " }", | ||
| "", | ||
| " Object positive12() {", | ||
| " // BUG: Diagnostic contains:", | ||
| " return (Object) this;", | ||
| " }", | ||
| "", | ||
| " boolean positive13() {", | ||
| " // BUG: Diagnostic contains:", | ||
| " return !false;", | ||
| " }", | ||
| "}") | ||
| .doTest(); | ||
| } | ||
|
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| /** A {@link BugChecker} that simply delegates to {@link IsLikelyTrivialComputation}. */ | ||
| @BugPattern( | ||
| summary = "Flags return statement expressions matched by `IsLikelyTrivialComputation`", | ||
| severity = ERROR) | ||
| public static final class MatcherTestChecker extends AbstractMatcherTestChecker { | ||
| private static final long serialVersionUID = 1L; | ||
|
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| // XXX: This is a false positive reported by Checkstyle. See | ||
| // https://github.com/checkstyle/checkstyle/issues/10161#issuecomment-1242732120. | ||
| @SuppressWarnings("RedundantModifier") | ||
| public MatcherTestChecker() { | ||
| super( | ||
| (expressionTree, state) -> | ||
| state.getPath().getParentPath().getLeaf() instanceof ReturnTree | ||
| && new IsLikelyTrivialComputation().matches(expressionTree, state)); | ||
| } | ||
| } | ||
| } |