Next stop: EclipseCon Europe 2017

As every year EclipseCon Europe is fixed in my schedule, and I am excited to go there. It is a melting pot for the Eclipse Community, a big family come together. I am in the last preparations before departure to Ludwigsburg, and can’t wait to finally go there.

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itemis is of course sponsoring EclipseCon Europe, and we will have a booth in front of the theater. With 12 talks, 8 speakers and about 20 attendees I am expecting that the it(emis)-Crowd is again the biggest party at EclipseCon Europe. The itemis booth will be the place where you will have the highest chance to meet me, but of course there is plenty of time to meet each other.

Meeting the Scout and Modeling community

As in the past years, I will start my journey already on sunday. I will again join the Eclipse Scout community’s pre-conference dinner at the Rossknecht. The past years I was joining on monday the Scout User Group meeting, but this year I committed to join the Guided Tour on Eclipse Modeling at the Unconference. At 14:40 I will give there my first talk, an insight on the Xtend language.

 

Xtext and Platform development

This Friday, Oct 20th, Xtext 2.13 was released finally and I have invested quite some time in the past months to find and resolve bugs. I have worked intensively with the Eclipse EARI system, and investigated together with Christian Dietrich the problem reports we are getting in. Until we now managed to get less problem reports in than we are processing. Christian and I are those who care most about user problems and we have fixed together the majority of bugs for this and the past releases. Christian does an incredible job! We will happily share insights on the current state on Xtext at the Unconference and all conference days.

The past months I starting getting involved into the Eclipse Platform itself. While before I completely focused on Xtext development and just used the platform, I thought it was time to give something back. I am using Eclipse every day and still love to work with it. I am recognizing that others prefer other IDEs, or even new ones are built, and there are reasons for that. But still for complex development tasks I believe that an extensible desktop IDE like Eclipse is the best tool. Eclipse has some flaws, and I could help there. Now I am frequently contributing to the Eclipse Platform (with focus on performance, usability and stability) and found into the development process, which took me some time. Because of this engagement I am expecting to have some interersting talks on platform development with some driving persons like Lars Vogel, Dani Megert, Alexander Kurtakov, Mickael Istria, Mikaël Barbero or Andrey Loskutov. I have to thank them for guiding me in the process and reviewing my changes carefully. Guys, I owe you a beer at the Nestor bar!

A conference day (almost) never ends

Nestor bar, the place to be after the long conference day! You will find me there each evening from monday on till late. Like every year it will be hard to celebrate long and get up early. But be sure, I’ll manage that. It isn’t the first time, and won’t be the last. The party ain’t over until it’s over.

I’m not staying at Nestor; like last year I reserved early a room at the nearby Villa Forêt. It is just a 5 minute walk (and some walking does not harm) and fine for me. It was in this hotel where I met Philip Wenig some years ago at breakfast. Ever since then I had nice talks with him and I always enjoy that. This year I already met him twice: At the Eclipse DemoCamp in Zurich, and at Eclipse Hackathon Hamburg.

Talks at the main conference

This year, besides my Xtend talk at the Unconference, I will give 2 talks at EclipseCon:

screenshot 21.png

“Introduction to Expression Languages with Xtext” (Tuesday 14:30, Silchersaal) will give you some patterns in Xtext grammers when you need to embed expressions in your language. Xtext ships with Xbase, which is a full expression langauge that you can easily integrate, but sometimes Xbase is not the right choice for you. Xbase is tightly bound to the Java typesystem and JDT, and for your language this could be undesired. Then you have to build your own expression language, which is a bit advanced. But you can learn a lot from Xbase, and in this talk I will show some grammar patterns that you could take from Xbase. I already gave this talk at EclipseCon France this year, so most of the slides are fortunately prepared.

screenshot 20.png

Different for my second talk: “Advanced Oomph Setup Authoring” (Wednesday 12:00, Silchersaal). This is completely new, and I am right now working on the slide deck. I was responsible for developing Xtext’s Oomph setup, which is compared to other setups at Eclipse more complex. But I have learned much from the other setups. Again, there are some patterns that can be recognized among the different setups. I will show and explain screenshots from different setups and discuss some advantages or disadvantages from then. Oomph is a mighty framework, and creating good setups is a time consuming and error prone work. The information given in this talk should give some help to author more robust setups, and build them faster. Advanced Oomph users might recognize that they do already much right, but even they might get the one or other idea to enhance their setups. Users rather new with Oomph will get the most out of this talk. They should at least have a basic idea about Oomph project setups.

Lightning Talks at the itemis booth

This year we will give some 5-Minute Lightning Talks at our booth in pauses. We have a lot of interesting small talks this time, from Xtext to Java 9, and even where plastic plants play a role. Just come around to the exhibitor’s area in front of the theater and get some inspiration.

Also here I have 2 slots:

  • Tuesday 15:50: “What’s new in Eclipse Photon?”: Let me show you a sneak preview on some features coming in Photon. You will see some of my contributions and some other.What's New in Eclipse Photon.001.jpeg
  • Wednesday 15:20: “A committer’s view on Eclipse Automated Error Reporting”: As said before, AERI helped me a lot to improve Xtext and Eclipse Platform. I’ll show you what committers see from problems reported to it and how it can help to find bugs. Also, a big Thank You to the guys from Codetrails for the support!ACommittersViewOnEARI.001.jpeg

Follow @itemis on Twitter to get notice on further talks from us!

The most important thing at EclipseCon is…

the people! I love to meet all the people again, from which most of them I only see once a year. This year I have already attended Eclipse Converge/, DevoXX US and EclipseCon France, so some of you folks I have already met again. But EclipseCon Europe is by far larger and more intensive. To all the people I already know, from year to year they become more.

Eclipse on the roll

It is a pleasure to see which companies and projects joined the Eclipse Foundation recently. Since I have a background in Java Enterprise development from early beginnings (yes, I had to implement bean managed persistence with EJB 1.0 in the ancient days and it was NOT funny!), I was delighted to see EE4J at Eclipse. Then IBM’s J9, Deeplearning4J, and the story is not over yet. If this continues, the Eclipse Foundation has a bright future and I am glad that itemis is a driving part of the story.

For this year’s EclipseCon Europe some of this hot new stuff might come a bit too late, but I expect more talks related to these exciting technologies next year. Yes, there are already some talks, but I think the focus will shift from now on.

And finally: Time to rest

After EclipseCon I’m taking a week off. I need this already, and will desperately need this after this exciting and exhausting week. Back to my beloved family, who is awaiting me after a long week. Who knows, maybe my second daughter Sophia is walking then? Can’t be long anymore.

 

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EclipseCon Europe 2016 – I’m coming!

130x130 I'm Speaking logo

I’m sitting now in the train on my way to Ludwigsburg. For sure I cannot miss this great event, where so many smart people and friends come together. Although ECE is always at the same time of the year and I knew for long that I want to go there again, it comes not at the best time for me – or better: for my family. The reason is a really positive one: Almost 3 weeks ago on October 4th I became for the second time father of a lovely daughter, Sophia.

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I am missing her already deeply, and my wife would need some supporting hands at home right now. However she understands that EclipseCon is important for me and supports me. The past weeks I did not get much sleep, but the reason was mostly not Sophia, but mainly preparing my talks – in the late evening and night it was most suitable. I will definitely enjoy EclipseCon, but this year I will also be happy when I can leave towards home again and will take 3 days off afterwards for regeneration and caring for the family.

This year’s EclipseCon will be fully packed for me. Today, on Sunday, it will start with a small pre-conference event at the Rossknecht, where the Eclipse Scout community comes together. Tomorrow at the Unconference day I will attend the Eclipse Scout User Day, which I attended the past two years already. At the moment I do not work with Scout, but I really enjoyed working with this framework in the past and would like to do another project with it again. The recent year Scout has much evolved, and I am keen to learn all the news.

On tuesday the Xtext developers plan to schedule a BoF Session. A beta of Xtext 2.11 was released this week, and we have to work much now to make the 2.11 release round. I plan to invest quite some time on this, and we have to talk about the concrete tasks and collaboration. Since we are now a team spanning several companies, it is important to have the chance to get the whole team together at EclipseCon.

On wednesday it is time for action. I was recently contacted that the proposal for the session “Recipes to build Code Generators for Non-Xtext Models with Xtend” got picked from the waiting list. I will perform the talk with my colleague and friend Holger Schill.

screenshot 68.png

We give this talk because Xtend is a very nice language when it comes to developing template based code generators, but is mostly only used in the context of Xtext. Xtext projects seamlessly integrate a generator infrastructure with Xtend, but it is not that common to use Xtend based generators with models that are not Xtext DSL files. We will show how simple it can be to integrate Xtend for other use cases, e.g. with JSON as input.

After that talk we will participate at the Modeling Symposium (17:45 Theater Stage). There we will shortly (7 minutes slot only) present a generator fragment that creates an extension package for VisualStudio Code to embed support for a DSL with an embedded language server. The Language Server Protocol support is the main feature for Xtext 2.11. We plan to contribute the created generator fragment to the Xtext project.

On thursday it is time for my talk “From stairway to heaven onto the highway to hell with Xtext” (11:00 Theater Stage). In this talk I will explain why I love Xtext and why it is used successfully in so many projects first, but then discuss where users have or run into trouble when using the framework. We see in many projects that first steps are easily done and don’t require much experience, but as requirements grow the complexity of DSL projects also grow and extensive experience with details of Xtext and the technologies behind is crucial. I hopefully compiled an informative set of issues.

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One Xpand user less, one happy Xtend user more

This week I am consulting a customer who had introduced a model based development approach based almost 10 years ago and used it with success since then. At the time back then Xpand was the most powerful code generation engine and UML models were often used to generate code from. Xtext did not even exist at that time. The customer uses Enterprise Architect and the Enterprise Architect exporter from the components4oaw. The last release was in 2011 and the project has not been developed further. For my customer the component just did what it should, so there was no direct need to change anything at the process. The EA exporter has its flaws, especially since it needs an Enterprise Architect installation and this means it only works on Windows machines. For Enterprise Architect users who do model based development, we therefore offer the YAKINDU Enterprise Architect Bridge, which scales better and can process .eap models on any platform.

My task was to help the customer to modernize their tool chain. To be fair, Xpand is not the right choice anymore. The Xtend Language combines the strengths from Xpand (great templating support, functional programming, static typing, polymorphic dispatch, mature Eclipse tooling) and resolved some weaknesses (performance, compiled code instead of interpreted, Java integration, extensibility of expressions).

For the customer who never had used Xtend so far, but was quite familiar with Xpand, it was quite a surprise how close both languages really are. Most of the concepts can be mapped 1:1 from good old Xpand to Xtend. We created a small generator from scratch and copied functions and templates and translated them manually for demonstration. They understood Xtend within minutes then. Most of the work is monkey-see-monkey-do. For such cases I wrote a small migration script which can translate Xpand,Xtend(1) and Check code to Xtend(2) classes. We used that script now for an initial translation.

One of the reasons why this migration script is not published is that cannot translate Xpand code completely to Xtend. The tool parses Xpand templates and traverses the AST to transform the expressions to Xtend equivalents. But it does not know about the type system which is used by the generator.

And here Xtend is not as powerful as Xpand, especially when using UML. In Xpand, the UML type system adapter analyzed the applied profiles of a model to create virtual types for stereotypes. Elements with stereotypes applied can be processed as if they were of a subtype of the extended type, and tagged values became attributes. In Xtend, there is only the Java type system, and for processing UML models this means that templates have to use the UML metamodel directly. The old “feeling” of a real type system can be simulated with a set of extension functions. I usually introduce an extension class per profile which offers for example a method per tagged value. The creation of such an extension class can again be automated by generating it from a profile .uml model.

Another disadvantage against the Xpand framework is that Xtend is not a code generation framework, but a general purpose programming language. How a generator component looks like that invokes the templates, where to produce output to, how to integrate constraint checks, this all is not provided.

What I usually do here is to use Xtext’s infrastructure like the IGenerator interface and validation based on Xtext’s AbstractDeclarativeValidator and @Check annotations. I reuse Xtext’s MWE Reader and Generator component. However, this requires some work and advanced knowledge. The basic approach is here to make UML models recognized by Xtext as a generic EMF resource. To actually use the Xtext components, a generator specific Guice module has to be created which extends AbstractGenericResourceRuntimeModule and satisfy several dependencies which an Xtext language already as configured by default. A good part of the approach was described by Christian Dietrich in his blog posts “Xtend2 Code Generators with Non-Xtext Models” and “Xtext 2.0 and UML“. I may go into details in a later blog post.

Although Xtend is such a natural choice for writing code generators and it is so well-integrated in the Xtext ecosystem, there is framework support missing for non-Xtext models. It is easy to write a trivial framework, but why should everyone start writing their own when good infrastructure already exists in the Xtext framework? From what I experienced again, there is need to have some more framework support for this use case. I doubt that it could be part of Xtext itself, but maybe we will provide a framework for Xtend based code generators in the future.

At the end we were able to show and demonstrate a migration path in one single workshop day. The customer was happy to save several days or weeks of time. The workshop costs were compensated by far for them. From a sales perspective it might not be wise to leave a customer in a state where he is not dependent on our services in the next time, but this is not how we work. For me it feels right.

Give a man a fish and you feed him for a day; teach a man to fish and you feed him for a lifetime.

Xbase Customization: Redefining operator keywords

If you use Xbase in your Xtext based DSL, you are usually satisfied with the set of operators the expression language defines. They are closely related to what you are used to in Java or similar languages.

However, in a customer’s workshop the customer wished to have custom keywords for some operators. For example, the operator && should be alternatively presented as AND, and the || operator as OR.

To demonstrate this customization we’ll start with Xtext’s famous Domainmodel Example. The Domainmodel.xtext grammar is derived from org.eclipse.xtext.xbase.Xbase and the Operation rule uses an XBlockExpression for the Operation’s body:

grammar org.eclipse.xtext.example.domainmodel.Domainmodel with org.eclipse.xtext.xbase.Xbase

...

Operation:
	'op' name=ValidID '(' (params+=FullJvmFormalParameter (',' params+=FullJvmFormalParameter)*)? ')' (':' type=JvmTypeReference)?
		body=XBlockExpression;

Unit Test

We’ll extend the language test-driven, thus we first create a unit test that uses the new feature, but will fail first until we have successfully implemented it. Fortunately there is already a suitable test class in project org.eclipse.xtext.example.domainmodel.tests.

We extend the class ParserTest.xtend:

	@Test
	def void testOverriddenKeyword() {
		val model = '''
			package example {
			  entity MyEntity {
			    property : String
			    op foo(String s) {
			    	return s!= null && s.length > 0 AND s.startsWith("bar")
			    }
			  }
			}
		'''.parse
		val pack = model.elements.head as PackageDeclaration
		val entity = pack.elements.head as Entity
		val op = entity.features.last as Operation
		val method = op.jvmElements.head as JvmOperation
		model.eResource.assertNoErrors
		Assert::assertEquals("boolean", method.returnType.simpleName)
	}

Note the Operation body, the expression uses both presentations of the And-operator.

return s!= null && s.length > 0 AND s.startsWith("bar")

When the ParserTest is executed it will now fail, of course, but only for the AND keyword:

java.lang.AssertionError: Expected no errors, but got :
ERROR (org.eclipse.xtext.diagnostics.Diagnostic.Linking) 
'The method or field AND is undefined' 
on XFeatureCall, offset 119, length 3
ERROR (org.eclipse.xtext.xbase.validation.IssueCodes.unreachable_code) 'Unreachable expression.' on XFeatureCall, offset 119, length 3

	at org.junit.Assert.fail(Assert.java:88)
	at org.eclipse.xtext.junit4.validation.ValidationTestHelper.assertNoErrors(ValidationTestHelper.java:187)
	at org.eclipse.xtext.example.domainmodel.tests.ParserTest.testOverriddenKeyword(ParserTest.java:268)
...

Overloading the operator rules

Looking at Xbase.xtext shows that Xbase defines separate data type rules for operators:

OpOr:
	'||';
OpAnd:
	'&&';

Xtext’s Grammar Mixin feature allows a redefinition of those rules. The obvious customization is in Domainmodel.xtext:

OpOr:
	'||' | 'OR';
OpAnd:
	'&&' | 'AND';

Regenerating the language’s Xtext implementation makes those keywords available to the syntax. However, the unit test still fails, but now with a different error:

java.lang.AssertionError: Expected no errors, but got :
ERROR (org.eclipse.xtext.diagnostics.Diagnostic.Linking) 
'AND cannot be resolved.' on XBinaryOperation, offset 119, length 3

	at org.junit.Assert.fail(Assert.java:88)
	at org.eclipse.xtext.junit4.validation.ValidationTestHelper.assertNoErrors(ValidationTestHelper.java:187)
	at org.eclipse.xtext.example.domainmodel.tests.ParserTest.testOverriddenKeyword(ParserTest.java:268)

OperatorMapping

The missing piece is a customization of class OperatorMapping. Thus we create a subclass OperatorMappingCustom with constant QualifiedNames for the additional operator keywords and bind it in DomainmodelRuntimeModule:

@Singleton
public class OperatorMappingCustom extends OperatorMapping {
	public static final QualifiedName AND_2 = create("AND");
	public static final QualifiedName OR_2 = create("OR");
}
public class DomainmodelRuntimeModule extends AbstractDomainmodelRuntimeModule {
	[...]
	public Class bindOperatorMapping() {
		return OperatorMappingCustom.class;
	}
}

A naive approach is here to overload the initializeMapping(), as the Javadoc suggests (“Clients may want to override #initializeMapping() to add other operators.“):

But this fails again:

com.google.inject.CreationException: Guice creation errors:

1) Error injecting constructor, java.lang.IllegalArgumentException: value already present: operator_and
  at org.eclipse.xtext.example.domainmodel.OperatorMappingCustom.(Unknown Source)
  at org.eclipse.xtext.example.domainmodel.OperatorMappingCustom.class(Unknown Source)
  while locating org.eclipse.xtext.example.domainmodel.OperatorMappingCustom
  while locating org.eclipse.xtext.xbase.scoping.featurecalls.OperatorMapping
    for field at org.eclipse.xtext.xbase.util.XExpressionHelper.operatorMapping(Unknown Source)
  while locating org.eclipse.xtext.xbase.util.XExpressionHelper
    for field at org.eclipse.xtext.xbase.validation.XbaseValidator.expressionHelper(Unknown Source)
  at org.eclipse.xtext.service.MethodBasedModule.configure(MethodBasedModule.java:57)
  while locating org.eclipse.xtext.example.domainmodel.validation.DomainmodelJavaValidator
Caused by: java.lang.IllegalArgumentException: value already present: operator_and
	at com.google.common.collect.HashBiMap.put(HashBiMap.java:237)
	at com.google.common.collect.HashBiMap.put(HashBiMap.java:214)
	at org.eclipse.xtext.example.domainmodel.OperatorMappingCustom.initializeMapping(OperatorMappingCustom.java:25)
	at org.eclipse.xtext.xbase.scoping.featurecalls.OperatorMapping.(OperatorMapping.java:121)
	at org.eclipse.xtext.example.domainmodel.OperatorMappingCustom.(OperatorMappingCustom.java:18)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	...

Instead, the method getMethodName() must be overridden and delegate the invocations of the new operators to the existing ones. The resulting OperatorMappingCustom is then:

@Singleton
public class OperatorMappingCustom extends OperatorMapping {
	public static final QualifiedName AND_2 = create("AND");
	public static final QualifiedName OR_2 = create("OR");

	@Override
	public QualifiedName getMethodName(QualifiedName operator) {
		if (AND_2.equals(operator)) {
			return getMethodName(AND);
		}
		if (OR_2.equals(operator)) {
			return getMethodName(OR);
		}
		return super.getMethodName(operator);
	}
}

Finally, the unit test will execute successful.

Summary

Xbase allows customization of operators by overriding the operator’s data type rule from Xbase.xtext. This adds the operator keywords to the language, but fails at runtime. Additionaly the class OperatorMapping must be customized and method getMethodName() overloaded.

Preparations for CodeGeneration 2013

As I am addicted to code generation and DSLs, the CodeGeneration conference in Cambridge is always a must each year. Last year I could not make it, since I had the chance to speak at EclipseCon North America, which was in the same week. This year Mark took EclipseCon into his considerations (it was last week), so me and my colleagues from itemis will be there again. Actually, this year we will be more itemis guys then ever. Mark already assumed in his opening words at CG2011 that almost everyone from itemis would be there, this year we prove itemis is larger. I think our company is so close related to the conference theme that it is natural that we have lots to present, and much interest to hear others about what they are doing and have learned in the past.

screenshot 2013-04-05 um 10.55.19

Before the actual CodeGeneration conference starts on Wednesday, there are some pre-conference activities. My colleagues Holger Schill and Moritz Eysholdt will hold an intensive 2-day Xtext workshop on monday and tuesday.

I will arrive monday noon, since I take the early flight directly from my hometown Dortmund to London Luton. From there, I have to take a 2 hour bus trip to Cambridge. In the evening, I plan to meet Holger, Moritz, Meinte Boersma and hopefully some others in the Castle Inn pub. When you arrive on monday, drop into the Castle Inn roughly at 20 PM (I guess we go to a restaurant before). You can reach me there on my mobile phone: screenshot 2013-04-05 um 12.30.02

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On tuesday this year’s Language Workbench Challenge summit takes place. We have 14 submissions (wow!) for the LWC13 assignment. I have been working on the Xtext submission together with 2 colleagues, Johannes Dicks and Thomas Kutz. The results are available as open-source project lwc13-xtext at Eclipselabs. We have prepared a detailed step-by-step tutorial as submission paper. The resulting document LWC13-XtextSubmission.pdf is available for download. On the project homepage I have placed today a quick start tutorial. Oh boy, this project did cost some time. The actual solution is not much code, but as often, it is harder to write less code than more. It could be even less, but we took care of that the code is readable and understandable. And writing the document is at least that much work as the implementation.

screenshot 2013-04-08 um 13.52.06

Every presenter has only 15 minutes to present their approach. 15 minutes presentation for that much work. I guess that the other participants did invest also quite some time. Both of my co-authors got the chance to visit the conference, and Thomas will support me with the presentation. He will demo the resulting JSF application and DSL source code while I do the main talking. We did a test run of the talk yesterday evening, and easily exceeded 20 minutes. I think Angelo will bring his egg timer again, which begs no pardon with the talk time of speakers. But only that way we will be able to run 14 talks on one day. We will have to restrict on the most important aspects only.

Besides my colleagues Thomas and Johannes also Sven Lange will join us then. I have the pleasure to work with him in my long-time project at Deutsche Börse (German Stock Exchange), now since over half a year. Sven is a highly motivated, skilled and smart person. It is still the same project I have reported about at CodeGeneration 2009 together with my former colleague Heiko Behrens. Sven is full-time working on this project, while I am for 20% scheduled. We have migrated here a huge code generator project from Xpand to Xtend. This alone would be worth an experience report session. Sven is working on Xtend support for IntelliJ, which he might present in a Lightning Talk on wednesday.

Wednesday the conference will start. I will have my main talk “Alive and Kicking with Code Generation” together with Dr. Boris Baginski from ATOSS Software AG after lunch at 13:45.

screenshot 2013-04-05 um 10.57.34

Currently we are finalizing our presentation slides. Boris has been ill for some days and busy with a new release of their ASES product, a workforce management suite. This is really an interesting customer and project. They are evolving this product now for 25 years, and they make use of code generation for ages. I think one can say that it helped them to survive in their business, some contestants did not manage to make larger platform shifts and died. Most of them tried a big-bang replacement, but the business is too fast evolving so that the target is moving steadily. Boris and I will speak about this product and how it has been evolved over the years. ATOSS was one of the first major projects using openArchitectureWare 4 (which mainly means Xpand), and now they are currently preparing a shift to Xtend.

I am glad that this talk is already on wednesday, I never come to rest until I finished some talk. After it, I can just relax and enjoy the conference. I am expecting some interesting insights on different approaches. Especially experience reports are interesting for me. I did not finally decide which sessions I will attend. At the moment I plan to see John Hutchinson with “The Use of Model-Driven Development in Industry” in the morning, and Darius Silingas with “Why MDA Fails: Analysis of Unsuccessful Cases” in the afternoon.

In the evening it is again time for the punting boat tour. I already attended three times, but it will be great fun again for sure. Let’s hope the weather is not too bad. I saw a prediction of ~10°C and possibility of light shower. In the past we had luck, and on a warm, sunny day the tour is double fun. However, I’ll better put an umbrella into the suitcase.

On thursday I have again an active part in the hands-on session “Have Your Language Built While You Wait”, which is hosted by Risto Pohjonen from MetaCase. The idea of this session is that attendees can get a DSL with the language workbench of their choice built with the help of experts for this workbench. Of course I will assist on Xtext. If you had no chance to visit the Xtext workshop this might be your chance to get some hands on Xtext. This session was already run last year successfully. Last year my colleague Benjamin Schwertfeger took over the Xtext part, since we were at EclipseCon.

There are also some other talks around Xtext and Xtend. Both have been released in version 2.4 on March 20th, which brings some interesting new features. Most notably in regard to code generation are the Active Annotations. I guess this is also part of what Sven Efftinge will adress as future of code generation in his keynote “The Past, Present and Future of Code Generation” wednesday morning. More details he will present together with Sebastian Zarnekow in the tutorial “Internal DSLs with Xtend” (thursday 10:45-12:00). The last Xtext related talk will be from Moritz Eysholdt, called “Executable Specifications for Xtext Languages” (friday 10:45-12:15). I am actually not sure which of these talks I will attend personally. They are most relevant for my work, and I don’t work close enough with them to catch everything new in Xtext on my own. Thus, I’ll definetely would learn important aspects. On the other side, there are also other interesting talks in parallel.

The coming week will be an intensive experience with lots to learn and interesting persons to meet. Although I will really enjoy this time, I will be glad when I finally come back home. At the moment, my family is ill and I hope that I get not infected these days. I have been looking forward and worked for this event, so I am crossing fingers when I can board monday morning healthy.

I am sure the organizing team around Mark and Jacqui will do again a great job.

DSC00363

See you there and let’s make this event special!

Xtext Content Assist: Filtering keyword proposals

Sometimes when I introduce template proposals in Xtext editors I want them to be a replacement for a keyword proposal. By default you would get a proposal for the template AND for the keyword. In the following screenshot a template for a “class” concept exists, and a proposal for the “class” keyword, which would be inserted as part of the template at the cursor position.

The key to the solution is to overwrite the completeKeyword() method from your proposal provider class, e.g. like this:

public class SprayProposalProvider extends AbstractSprayProposalProvider {
    private static final Set<String>      FILTERED_KEYWORDS = Sets.newHashSet("text", "line", "class", "behavior", "style", "custom");
    @Override
    public void completeKeyword(Keyword keyword, ContentAssistContext contentAssistContext, ICompletionProposalAcceptor acceptor) {
        if (FILTERED_KEYWORDS.contains(keyword.getValue())) {
            // don't propose keyword
            return;
        }
        super.completeKeyword(keyword, contentAssistContext, acceptor);
    }
}

Christian Dietrich added in a comment how to filter a keyword that may occur more than once in your grammar. If you want to filter specific occurances you need to use the IGrammarAccess of your language:

@Inject MyDslGrammarAccess grammarAccess;

@Override
public void completeKeyword(Keyword keyword,ContentAssistContext contentAssistContext,ICompletionProposalAcceptor acceptor) {
  if (!grammarAccess.getGreetingAccess().getHelloKeyword_0().equals(keyword)) {
    super.completeKeyword(keyword, contentAssistContext, acceptor);
  }
}

xtext-utils unittesting 0.9.4 released

I have just released the new version 0.9.4 of the xtext-utils unittesting framework. The release became necessary due to a too restrictive version constraint for Google Guice, which made the framework incompatible with the upcoming Xtext 2.3.0 release.

This little framework is a useful addition to Xtext which makes writing DSL tests quite easy. In my daily work on developing Xtext projects and coaching Xtext in workshops it became a useful tool which complements Xtext’s test support. It is not the only way to write tests for Xtext DSLs, but a real simple one. The main idea is that the best way to develop DSLs is to write prototype models. This framework allows you to read, parse, validate, format, serialize, and compare your models in a single line.

The framework can be installed from its update site.