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Xtext code generation using other JVM languages, e.g. Scala [message #1091924]

Thu, 22 August 2013 05:31

Shelby Moore III

Messages: 42
Registered: August 2013

Member

I want to use Scala for the code generation, because I am writing a fairly sophisticated compiler for a general purpose language (that builds on and outputs to Scala). For example, I want to use Scala's pattern matching on the AST to make the code more succinct. And eventually I will rewrite the compiler to use the language I am building for code generation.

How do I employ another JVM language for code generation?

The default settings apparently create a workflow which puts the source for code generation in a {ProjectName}Generator.xtend file in the org.xtext.{ProjectFileExt}.generator folder.

I have viewed the thread about using .java as the source language, but I didn't even understand what (if anything) was resolved in that thread.

I have seen the a mention of a mixed Scala and Xtext project, but that did not add any insight for me at least.

I have seen the thread about Xtext's Java integration and I don't understand it. I think this may have to do with the ability to embed Java in the grammar? Don't understand if or how this might apply to what I want to accomplish above.

The only other possible relevant pages I have found are:

voelterblog dot blogspot dot com/2009/09/using-scala-for-xtext-scope-definitions.html
www dot assembla dot com/wiki/show/scala-ide/Eclipse_Plugin_Development_using_the_Scala_IDE

I must say that I am lost in a vast sea of APIs that I don't think I could wrap my head around with a big picture understanding in any reasonable time frame.

Could someone offer me some pointers to shorten the learning curve? Or point me to the relevant documentation to read?

[Updated on: Thu, 22 August 2013 13:54]

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Re: Xtext code generation using other JVM languages, e.g. Scala [message #1092169 is a reply to message #1091924]

Thu, 22 August 2013 12:13

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

Hi,

i am not quite sure what your problem is
first you should note: there is the jvmmodelinferrer magic (and the generator that is based on that)
then there are normal generators that produce text.
i asume the second is fine for you.
if so have a look at "Writing a Code Generator With Xtend" in "15 Minutes Tutorial - Extended" from the docs.

Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

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Re: Xtext code generation using other JVM languages, e.g. Scala [message #1092181 is a reply to message #1092169]

Thu, 22 August 2013 12:28

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

P.S: if you ant to write the generator itself in scala,
simply delegate to your scala code from the doGenerate method ....

Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

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Re: Xtext code generation using other JVM languages, e.g. Scala [message #1092198 is a reply to message #1092181]

Thu, 22 August 2013 12:52

Shelby Moore III

Messages: 42
Registered: August 2013

Member

Christian Dietrich wrote on Thu, 22 August 2013 08:28

P.S: if you ant to write the generator itself in scala,
simply delegate to your scala code from the doGenerate method ....

I mentioned in the other thread, how to do this?

Christian Dietrich wrote on Thu, 22 August 2013 08:13

Hi,

i am not quite sure what your problem is
first you should note: there is the jvmmodelinferrer magic (and the generator that is based on that)
then there are normal generators that produce text.
i asume the second is fine for you.
if so have a look at "Writing a Code Generator With Xtend" in "15 Minutes Tutorial - Extended" from the docs.

Yes the second is what I want. I already reviewed that tutorial and successfully generated output with doGenerate from either .xtend and .java source files.

My question is how to integrate it with Scala code. The first issue I am asking about now is how to do the delegation to a Scala method from doGenerate.

After that, I want to learn how to do post processing on the EMF model to output Scala extractors for all the generated Java classes, so I can use Scala's pattern matching in the code generation method I want to delegate to above.

Thank you.

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Re: Xtext code generation using other JVM languages, e.g. Scala [message #1092204 is a reply to message #1092198]

Thu, 22 August 2013 13:04

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

Hmm

this sounds like:"how to call scala from java" and thus is not xtend related.

Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

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Re: Xtext code generation using other JVM languages, e.g. Scala [message #1092230 is a reply to message #1092204]

Thu, 22 August 2013 13:51

Shelby Moore III

Messages: 42
Registered: August 2013

Member

Perhaps that is where I have arrived, yet one issue in my mind is how to set the scala-library.jar[1] and the .jar for the Scala containing the delegate method on the classpath searched by the compilation of {ProjectName}Generator.java? Perhaps that is not Xtext related, rather a general Eclipse project configuration issue?

Later I will be concerned about how this all gets exported to various scenarios for using the editor (and do the Scala dependencies get pulled in correctly), yet for now I will just concern myself with the above.

P.S. This is my first time to use Eclipse, Xtext, and Java, although my proficiency with programming languages in general helps. As well my first time to code in Scala in a build environment (before only SimplyScala.com). So I may be conflating issues.

[1] lampwww dot epfl dot ch/~michelou/scala/using-scala-from-java.html

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Re: Xtext code generation using other JVM languages, e.g. Scala [message #1092236 is a reply to message #1092230]

Thu, 22 August 2013 13:56

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

Hi,

it would be preferred if the exist as osgi bundles. if not

- create a lib folder in the project
- drop the libs there.
- open the manifest file.
- add the libs on the runtime tab/classpath section
- add the lib folder on the build tab of the editor.

Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

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Re: Xtext code generation using other JVM languages, e.g. Scala [message #1093701 is a reply to message #1092236]

Sat, 24 August 2013 14:07

Shelby Moore III

Messages: 42
Registered: August 2013

Member

There was no need for importing .jar files.

Xtend can't resolve the type. This should probably be filed as a bug report.

Quote:

package org.xtext.copu.generator

import org.eclipse.emf.ecore.resource.Resource
import org.eclipse.xtext.generator.IGenerator
import org.eclipse.xtext.generator.IFileSystemAccess

import org.xtext.copu.copute.File
import org.xtext.copu.generator.CoputeToScala

class CoputeGenerator implements IGenerator {

override void doGenerate(Resource r, IFileSystemAccess fsa) {
if (r.getContents.size == 1 && r.getContents.get(0) instanceof File)
fsa.generateFile("test.scala", CoputeToScala.apply((File)r.getContents.get(0)))
}
}

Yet Java can.

package org.xtext.copu.generator;


import org.eclipse.emf.ecore.resource.Resource;
import org.eclipse.xtext.generator.IGenerator;
import org.eclipse.xtext.generator.IFileSystemAccess;

import org.xtext.copu.copute.File;
import org.xtext.copu.generator.CoputeToScala;

class CoputeGenerator implements IGenerator {
   
   @Override
   public void doGenerate(Resource r, IFileSystemAccess fsa) {
      if (r.getContents().size() == 1 && r.getContents().get(0) instanceof File)
        fsa.generateFile("test.scala", CoputeToScala.apply((File)r.getContents().get(0)));
   }
}

Here is the Scala source.

package org.xtext.copu.generator

import org.xtext.copu.copute.File

object CoputeToScala {
   def apply(file: File): String = ""
}

-----------------------------------------------------

I ended up as follows using CoputeGenerator.xtend to call Java which calls my Scala code above.

package org.xtext.copu.generator


import org.eclipse.emf.ecore.resource.Resource
import org.eclipse.xtext.generator.IGenerator
import org.eclipse.xtext.generator.IFileSystemAccess

import org.xtext.copu.copute.File
import org.xtext.copu.generator.CoputeToScalaJ

class CoputeGenerator implements IGenerator {
	
	override void doGenerate(Resource r, IFileSystemAccess fsa) {
	   if (r.getContents.size == 1 && r.getContents.get(0) instanceof File)
	     fsa.generateFile("test.scala", CoputeToScalaJ.apply(r.getContents.get(0)))
	}
}

package org.xtext.copu.generator;

import org.xtext.copu.copute.File;
import org.xtext.copu.generator.CoputeToScala;

class CoputeToScalaJ {
   public static java.lang.String apply(java.lang.Object file) {
      return CoputeToScala.apply((File)file);
   }
}

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Re: Xtext code generation using other JVM languages, e.g. Scala [message #1744850 is a reply to message #1092230]

Fri, 30 September 2016 18:06

Andrzej Wasowski

Messages: 15
Registered: June 2015

Junior Member

I know this is an old thread, but I am also interested in this issue. So let me try.

Quote:

After that, I want to learn how to do post processing on the EMF model to output Scala extractors for all the generated Java classes, so I can use Scala's pattern matching in the code generation method I want to delegate to above.

OP, have you ever got to that?

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