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Repeatable active annotations [message #1806092]

Thu, 02 May 2019 13:46

Udo Walker

Messages: 44
Registered: January 2013

Member

I created an active annotation like this:

@Target(ElementType.FIELD)
@Repeatable(MyAnnos)
@Active(MyAnnoProcessor)
annotation MyAnno {
	int group = 0
}

@Target(ElementType.FIELD)
annotation MyAnnos{
	MyAnno [] value
}

So I can write this in code:

@MyAnno(group=0)
@MyAnno(group=1)
String myField

In my MyAnnoProcessor I've overridden the method doTransform(MutableFieldDeclaration field, extension TransformationContext context) of the class AbstractFieldProcessor.

For each field I extract all annotations of type MyAnno and create for each annotation a new method.

When I look in the generated code then the methods are duplicated i.e. it looks like for 1 field and 2 annotations the doTransform-Method is called twice.

How can I use repeatable annotations in Xtend's active annotations correctly?

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Re: Repeatable active annotations [message #1806094 is a reply to message #1806092]

Thu, 02 May 2019 14:09

Karsten Thoms

Messages: 687
Registered: July 2009
Location: Dortmund, Germany

Senior Member

I'm quite sure that this is an implementation gap. I'm not aware of a scenario where AA's were used repeatably. Please file an issue to https://github.com/eclipse/xtext/issues

Could you provide a minimal example or better unit test? And even best, a patch? I think we won't have this on our short list. So if you are interested in that feature, please provide it. We would help you through the process & review.

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Re: Repeatable active annotations [message #1806095 is a reply to message #1806094]

Thu, 02 May 2019 14:13

Udo Walker

Messages: 44
Registered: January 2013

Member

Where do I start to implement it myself? Is there a readme on how to setup the sources and the build of Xtend?

First I'll try to prepare a minimal example project.

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Re: Repeatable active annotations [message #1806096 is a reply to message #1806095]

Thu, 02 May 2019 14:15

Karsten Thoms

Messages: 687
Registered: July 2009
Location: Dortmund, Germany

Senior Member

We have an Oomph setup that does all the setup automatically. Just use the Eclipse Installer, switch to Advanced mode and select all "Xtext" projects.

Read:
https://github.com/eclipse/xtext/blob/master/CONTRIBUTING.md

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Re: Repeatable active annotations [message #1806097 is a reply to message #1806096]

Thu, 02 May 2019 14:25

Christian Dietrich

Messages: 13071
Registered: July 2009

Senior Member

@udo maybe you can customize

public void doTransform(List<? extends MutableFieldDeclaration> annotatedfields, @Extension TransformationContext context) {
instead
and filter the duplicates youself

(dont know if this will be called n-times too

Need professional support for Xtext, Xpand, EMF?
Go to: https://www.itemis.com/en/xtext/
Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

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Re: Repeatable active annotations [message #1806098 is a reply to message #1806096]

Thu, 02 May 2019 14:45

Udo Walker

Messages: 44
Registered: January 2013

Member

Minimal example based on projects xtend-annotations-examples and xtend-annotations-examples-client created with project wizard "Xtend > Examples > Xtend Active Annotation Examples":

1. Add a new package called "repeatable" to both projects.
2. Add this Xtend class to first project in package repeatable:

package repeatable

import java.lang.annotation.Target
import java.lang.annotation.ElementType
import java.lang.annotation.Repeatable
import org.eclipse.xtend.lib.macro.Active
import org.eclipse.xtend.lib.macro.declaration.MutableFieldDeclaration
import org.eclipse.xtend.lib.macro.AbstractFieldProcessor
import org.eclipse.xtend.lib.macro.TransformationContext
import org.eclipse.xtend.lib.macro.declaration.AnnotationTarget
import org.eclipse.xtend.lib.macro.declaration.AnnotationReference
import org.eclipse.xtend.lib.annotations.Accessors

@Target(ElementType.FIELD)
@Repeatable(MyAnnos)
@Active(MyAnnoProcessor)
annotation MyAnno {
	int group = 0
}

@Target(ElementType.FIELD)
annotation MyAnnos {
	MyAnno[] value
}

class MyAnnoProcessor extends AbstractFieldProcessor {

	extension AnnotationExtensions = new AnnotationExtensions

	override doTransform(MutableFieldDeclaration field, extension TransformationContext context) {

		var annos = field.getAnnotations(context)
		for (anno : annos) {
			doTransformSingleAnnotation(anno, field, context)
		}
	}

	def doTransformSingleAnnotation(AnnotationReference annoRef, MutableFieldDeclaration field,
		extension TransformationContext context) {
		val group = annoRef.getValue("group") as Integer

		field.declaringType.addMethod("method" + group) [
			returnType = context.primitiveVoid
			body = ''''''
		]
	}

	private def getAnnotations(MutableFieldDeclaration field, extension TransformationContext context) {
		findAnnotations(
			new AnnotationSearch => [
				it.type = field
				it.context = context
				it.annotationClass = MyAnno
			],
			context
		)
	}
}

class AnnotationExtensions {

	def findAnnotations(extension AnnotationSearch annotationSearch, extension TransformationContext context) {
		type.annotations.filter [
			annotationTypeDeclaration.qualifiedName == annotationClass.newTypeReference.type.qualifiedName
		]
	}
}

class AnnotationSearch {
	@Accessors AnnotationTarget type
	@Accessors TransformationContext context
	@Accessors Class<?> annotationClass
}

3. Add this code to package repeatable in second project (client):

package repeatable

class RepeatableExample {
	
	
	@MyAnno(group=0)
	@MyAnno(group=1)
	@MyAnno(group=2)
	String field
}

To see the active annotation in client-project you have to extend the MANIFEST.MF of the first project with the package repeatable as exported.

And following code is generated:

package repeatable;

import repeatable.MyAnno;

@SuppressWarnings("all")
public class RepeatableExample {
  @MyAnno(group = 0)
  @MyAnno(group = 1)
  @MyAnno(group = 2)
  private String field;
  
  public void method0() {
  }
  public void method1() {
  }
  public void method2() {
  }
  public void method0() {
  }
  public void method1() {
  }
  public void method2() {
  }
  public void method0() {
  }
  public void method1() {
  }
  public void method2() {
  }
}

So the field generation is called too often.

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