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https://issues.apache.org/jira/browse/GROOVY-12434?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18126662#comment-18126662
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ASF GitHub Bot commented on GROOVY-12434:
-----------------------------------------
paulk-asert merged PR #2961:
URL: https://github.com/apache/groovy/pull/2961
> Implementing a precompiled trait fails with "Duplicate annotation" when a
> trait method has a TYPE_USE annotation on its return type
> -----------------------------------------------------------------------------------------------------------------------------------
>
> Key: GROOVY-12434
> URL: https://issues.apache.org/jira/browse/GROOVY-12434
> Project: Groovy
> Issue Type: Bug
> Components: Compiler
> Affects Versions: 6.0.0
> Reporter: Mattias Reichel
> Assignee: Paul King
> Priority: Major
>
> When a trait method's return type carries a {{TYPE_USE}} annotation, such as
> JSpecify's {{@Nullable}}, the trait is written with that annotation twice. A
> class in a later compilation that implements the trait then fails to compile
> on Groovy 6.0.0 with {{java.lang.annotation.AnnotationFormatError: Duplicate
> annotation}}.
> This compiles on Groovy 5.1.3 and fails on 6.0.0. It does not happen when the
> trait and the implementing class are in the same compilation, or when the
> annotation is on a parameter instead of the return type. It fails whether the
> trait was compiled by 5.1.3 or by 6.0.0, so traits in existing jars built
> with Groovy 5 are affected too.
> h3. Steps to reproduce
> {code:title=trait/MaybeNull.java}
> import java.lang.annotation.ElementType;
> import java.lang.annotation.Retention;
> import java.lang.annotation.RetentionPolicy;
> import java.lang.annotation.Target;
> @Retention(RetentionPolicy.RUNTIME)
> @Target(ElementType.TYPE_USE)
> public @interface MaybeNull { }
> {code}
> {code:title=trait/Named.groovy}
> trait Named {
> @MaybeNull String getName() { null }
> }
> {code}
> {code:title=src/Person.groovy}
> class Person implements Named { }
> {code}
> {noformat}
> mkdir lib out
> javac -d lib trait/MaybeNull.java
> java -cp groovy-6.0.0.jar:lib org.codehaus.groovy.tools.FileSystemCompiler
> -cp lib -d lib trait/Named.groovy
> java -cp groovy-6.0.0.jar org.codehaus.groovy.tools.FileSystemCompiler -cp
> lib -d out src/Person.groovy
> {noformat}
> h3. Expected
> Compilation succeeds, as on Groovy 5.1.3.
> h3. Actual
> {noformat}
> >>> a serious error occurred: Duplicate annotation for class: interface
> >>> MaybeNull: @MaybeNull()
> >>> stacktrace:
> java.lang.annotation.AnnotationFormatError: Duplicate annotation for class:
> interface MaybeNull: @MaybeNull()
> at
> java.base/sun.reflect.annotation.TypeAnnotationParser.mapTypeAnnotations(TypeAnnotationParser.java:382)
> at
> java.base/sun.reflect.annotation.AnnotatedTypeFactory$AnnotatedTypeBaseImpl.<init>(AnnotatedTypeFactory.java:138)
> ...
> at
> org.codehaus.groovy.vmplugin.v8.Java8.configureClassNode(Java8.java:392)
> at org.codehaus.groovy.ast.ClassNode.lazyClassInit(ClassNode.java:192)
> at org.codehaus.groovy.ast.ClassNode.getMethods(ClassNode.java:1090)
> at org.codehaus.groovy.ast.ClassNode.getMethods(ClassNode.java:1089)
> at
> org.codehaus.groovy.transform.trait.TraitComposer.applyTrait(TraitComposer.java:134)
> at
> org.codehaus.groovy.transform.trait.TraitComposer.doExtendTraits(TraitComposer.java:110)
> ...
> {noformat}
> h3. Notes
> {{javap -v}} shows the return type annotation twice on the trait's interface
> method and on its helper method. The class files are the same whether the
> trait is compiled by 5.1.3 or by 6.0.0:
> {noformat}
> public abstract java.lang.String getName();
> descriptor: ()Ljava/lang/String;
> flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
> RuntimeVisibleAnnotations:
> 0: #9()
> org.codehaus.groovy.transform.trait.Traits$Implemented
> RuntimeVisibleTypeAnnotations:
> 0: #10(): METHOD_RETURN
> MaybeNull
> 1: #10(): METHOD_RETURN
> MaybeNull
> {noformat}
> {{Named$Trait$Helper.getName(Named)}} has the same two {{METHOD_RETURN}}
> entries. The same method on a plain class or interface is written with a
> single entry.
> Groovy 5.1.3 accepts the duplicate because it does not read the annotated
> return type when it initializes the trait's {{ClassNode}}. Groovy 6.0.0 reads
> it through reflection in {{Java8.configureClassNode}}, where the JDK rejects
> the duplicate. Groovy 5.1.3 can still implement a trait compiled by 6.0.0.
> GROOVY-12413 fixed similar duplicated {{TYPE_USE}} annotations on record
> components and tuple-constructor parameters. The trait transform seems to
> copy the return type annotations as well as the method annotations.
> Found while moving Apache Grails to Groovy 6: a JSpecify {{@Nullable}} on a
> return type in the Grails unit testing traits ({{ControllerUnitTest}},
> {{UrlMappingsUnitTest}}, {{InterceptorUnitTest}}) makes every test class that
> implements them fail to compile. The workaround is to leave {{TYPE_USE}}
> annotations off trait method return types.
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