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Java annotations don't show up using Scala reflection's getAnnotations #6356

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scabug opened this issue Sep 10, 2012 · 4 comments
Closed

Java annotations don't show up using Scala reflection's getAnnotations #6356

scabug opened this issue Sep 10, 2012 · 4 comments
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has PR reflection
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2.10.0-M7

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@scabug
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scabug commented Sep 10, 2012 •
edited by retronym

Consider the following Java files:

// FooAnnotation.java
import java.lang.annotation.Target;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD, ElementType.METHOD, ElementType.TYPE})
public @interface FooAnnotation {}
// Foo.java
@FooAnnotation
public class Foo {}

Compilation with javac succeeds as expected:
javac *.java

Starting the Scala REPL with those files on the classpath...
scala -cp .

Java reflection works:

scala> val javaFooClass = classOf[Foo]
javaFooClass: Class[Foo] = class Foo

scala> val javaFooClassAnnotations = javaFooClass.getAnnotations
javaFooClassAnnotations: Array[java.lang.annotation.Annotation] = Array(@FooAnnotation())

val javaFooAnnotationAnnotations = javaFooClassAnnotations(0).annotationType.getAnnotations
javaFooAnnotationAnnotations: Array[java.lang.annotation.Annotation] = Array(@java.lang.annotation.Retention(value=RUNTIME), @java.lang.annotation.Target(value=[FIELD, METHOD, TYPE]))

But Scala reflection doesn't see anything:

scala> import reflect.runtime.universe.typeOf
import reflect.runtime.universe.typeOf

scala> val scalaFooType = typeOf[Foo]
scalaFooType: reflect.runtime.universe.Type = Foo

scala> val scalaFooTypeAnnotations = scalaFooType.typeSymbol.getAnnotations
scalaFooTypeAnnotations: List[reflect.runtime.universe.AnnotationInfo] = List()

The annotations should show up in Scala reflection, because they are clearly present at runtime, as shown with Java reflection.

The problem is probably only slightly related to #32, because scalac's nonsupport of creating runtime-visible annotations doesn't get involved here (javac was used for that).
@scabug
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scabug commented Sep 10, 2012

Imported From: https://issues.scala-lang.org/browse/SI-6356?orig=1
Reporter: @soc
Affected Versions: 2.10.0-M7
See #32

@scabug
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scabug commented Sep 10, 2012

@soc said:
The cause of the issue is probably scala.tools.nsc.javac.JavaParsers around line 339.

The whole annotation handling there seems to be a large no-op ...

@scabug
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scabug commented Sep 11, 2012

@xeno-by said:
Probably the problem is that we understand only Scala annotations, i.e. the ones pickled by scalac. I'll discuss this today on a Scala meeting

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scabug commented Sep 16, 2012

@xeno-by said:
Fixed in scala/scala@cf819b7

@scabug scabug closed this as completed Sep 16, 2012
@scabug scabug added this to the 2.10.0-M7 milestone Apr 7, 2017
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