xText - use custom properties in CustomOutputConfigurationProvider

Ok, that is a very special topic and I guess not many will need this.
My problem was that I created a properties-page and wanted to use the folders selected there or to use IProject-related paths or such. I had to hack a little bit to get it to work, but I did it. In the end I could have context-based CustomOutputConfigurations.

Ok, I got it to work but it feels a bit hacky. Here is what I did.

1. Write OutputConfigurationProvider that implements IContextualOutputProvider2 and place it somewhere in your MyDSL-Modules main-module

public class CustomOutputConfigurationProvider  implements IContextualOutputConfigurationProvider2 {

	override getOutputConfigurations(ResourceSet context) {
		if (context.resources.size()>0){
			// we are now context-aware. With the resource we can access the project
			val Resource res = context.resources.get(0);
			val path = res.URI.toPlatformString(true);
			val file = ResourcesPlugin.workspace.root.findMember(path) as IFile;
			val IProject project = file.project		
			// do what you want! e.g. read properties (as I intend to do)
			val OutputConfiguration defaultOutput = new OutputConfiguration(IFileSystemAccess.DEFAULT_OUTPUT);
			defaultOutput.setDescription("Default Output - Overwrite");
			defaultOutput.setOutputDirectory("./out-src/src-gen");
			defaultOutput.setOverrideExistingResources(true);
			defaultOutput.setCreateOutputDirectory(true);
			defaultOutput.setCleanUpDerivedResources(true);
			defaultOutput.setSetDerivedProperty(true);
			defaultOutput.useOutputPerSourceFolder = true;
			return newHashSet(defaultOutput);
		}
		return newHashSet();
	}
}

2. Bind it in your MyDSLRuntimeModule:

	def Class<? extends IContextualOutputConfigurationProvider2> bindIContextualOutputConfigurationProvider2() {
		CustomOutputConfigurationProvider
	}

3)In the UI-Module create a CustomBuilderParticipant that derives from BuilderPartiticpant:

public class CustomBuilderParticipant extends BuilderParticipant {

	@Inject
	private IContextualOutputConfigurationProvider2 outputConfigurationProvider;
	
	@Override
	protected Map<String, OutputConfiguration> getOutputConfigurations(IBuildContext context) {
		Set<OutputConfiguration> configurations = outputConfigurationProvider.getOutputConfigurations(context
				.getResourceSet());
		return uniqueIndex(configurations, new Function<OutputConfiguration, String>() {
			@Override
			public String apply(OutputConfiguration from) {
				return from.getName();
			}
		});
	}
}

4. Bind this in your UI-Modules MsDSLUIModule.xtend:

	override Class<? extends IXtextBuilderParticipant> bindIXtextBuilderParticipant() {
		return CustomBuilderParticipant;
	}

That's it. Seems to work. Also have a look at a corresponding forum-thread .