Is a CompilationParticipant bundle usable in a headless PDE build?

Question

I've written a plugin that uses the org.eclipse.jdt.core.compilationParticipant extension to gather some compile information to be used elsewhere. I've tested in multiple versions of the Eclipse IDE and it works like a charm. My ultimate goal is to be able to use it in a headless production PDE build. I've added some logging to the bundle so I am aware when it starts up, when it shuts down, and when source compilation occurs. The problem is that these events never get caught in my headless build buy the participant. The headless PDE build is kicked off by starting the equinox launcher from an ant script that runs the antrunner executing the PDE build script. There are so many scopes of execution involved I'm unsure where to start looking. My first question is, is what I'm trying to do even possible? It didn't seem like the CompilationParticipant would only work in the UI, but I want to make sure before I go down the road of debugging this. Has anyone ever done this?

I tried to add a comment, but I'm too wordy so I will try to clarify here a bit. Unfortunately I can't do much to change the build system except to apply hooks like I am attempting. I did spend some time running through the ant scripts that PDE generates and see the it is calling the JDT compiler adapter which made me curious if the JDT compiler adapter could reference the compilation participant since it is running ant from the plugin and should have access to the framework, and it seemed to be the intent of the participant API to allow the hooking of the JDT compiler to do things like the implementation of the APT processor and other DSL implementations. That was my read on the intent of the participants, and assume they would be available in a headless build since the APT processor works, but since I can't find a really good tutorial I'm kind of putting things together piecemeal and I'm guessing I'm missing something, or at least I hope so..

It is true that PDE is generating ant scripts and calling the javac task, but it is also setting the build.compiler property to use the JDT compiler and therefore I would assume have access to the OSGi framework. Here is a snippet from one of the generated build files to show what I am talking about:

<compilerarg line="-log '${temp.folder}/pde.example3.jar.bin${logExtension}'" compiler="org.eclipse.jdt.core.JDTCompilerAdapter"/>

Debugging org.eclipse.jdt.internal.core.JavaModelManager reveals that the JDT compiler is in fact being used but getRegisteredParticipants is not being called for some reason, startup() is however being called, so the question it why does it not try to register participants.

After spending hours in the debugger attaching to the various VMs that spawn during my build process I was able to determine the flow through a PDE build. I don't believe that CompilationParticipants come in to play, in fact I don't even think the JavaBuilder is called. It looks like the execution path is something like the following:

Ant spawns my VM which starts the Equinox Launcher which starts up the OSGi framework and instantiates the AntRunner application, this in turn starts ant from the Elcipse Ant plugin that runs the build.xml file from the PDE plugin, the Build.xml file generates all the ant scripting used to generate the eclipse plugins which includes setting the build.compiler to the JDTCompilerAdapter which wraps the Eclipse Java Compiler ( originally based on Visual Age for Java ). The JDTCompilerAdapter does some setup and instantiates the org.eclipse.jdt.internal.compiler.batch.Main class which does the real compilation, and also instantiates the org.eclipse.jdt.internal.compiler.apt.dispatch.BatchAnnotationProcessorManager class to handle annotation processing. Nowhere in this path of execution are participants notified, and the JDTCompilerAdapter seems to be specifically designed to be able to be used outside the OSGi environment in ant. so it looks like CompilationParticipants will not give me what I need in a headless PDE build using the antrunner..

Answer 1

Well after tons of debugging, reading docs, and stepping though the PDE sources it seems like this can NOT be done. It seems in a headless build the execution of the JDTCompilerAdapter is designed to work outside of OSGi and does not have access to the framework it is simply called from the javac task and does NOT involve the JavaBuilder and therefore does not call any participants.

Answer 2

AFAIK PDE build is "just" a fancy way of generating a lot of Ant-scripts, and I belive it just uses the javac target to compile files. You can check that after the PDE build has run, by going into your source folders, find the Ant-script, and check.

If what you do is important for the build, I would recommend that you check out Buckminster. It is a build tool designed of OSGi applications. It is special in the sense, that it actually builds in an Eclipse workspace, so it uses the same builders and stuff like CompilationParticipants as you do during development, assuming you have installed the plugins in the headless build-application.