Well, you probably won't be surprised to learn that the result is no different using the latest maven-eclipse-plugin version 1.5-SNAPSHOT, dated 30th November 2007. I had to create an entire Maven project to invoke the to-maven goal on the maven-eclipse-plugin, just so that I could specify the version I wanted to run. But this should be quite a useful asset in the long run anyway: I can now type
to invoke the corresponding actions. At the moment, however, there is no way to get beyond any plugin whose MANIFEST.MF specifies system.bundle as a required bundle.
The OSGI Bundle Repository Browser confirms that system.bundle does in fact refer to the org.eclipse.osgi jar file. I therefore decided to supply the missing artifact, by using file:deploy-file to create it from org.eclipse.osgi...jar. I added this to the POM of my eclipse-to-maven project and linked it to the initialize phase.
It still doesn't work. For some reason, because the Require-Bundle instruction in MANIFEST.MF does not specify a version number, the maven-eclipse-plugin cannot find the artifact I created. It tells me that it was unable to resolve the version range for version [0,).
So as an experiment, I altered the MANIFEST.MF of the Xerces plugin to explicitly require the actual version number of the org.eclipse.osgi bundle - and hey presto, this was resolved successfully. But we really can't go through all manifests of all Eclipse plugins every time we want to run this plugin and update the system.bundle requirement!
This must be a bug in the maven-eclipse-plugin (caused by a documented incompatibility between Eclipse 3.2 and 3.3, which has led a number of bundle committers to add "Require-bundle: system.bundle" to their manifests), so I have submitted a bug report about it.
In fact, on closer investigation it transpired that there are currently only two Eclipse plugins that fall into this category: org.eclipse.xerces and org.eclipse.xml.resolver. In fact it wasn't even necessary to create a system.bundle artifact - I just altered the two manifests temporarily to express a dependency on the exact version of the org.eclipse.osgi plugin supplied with the Eclipse installation in question. With this modification, the eclipse:to-maven goal was able to run successfully to completion.
On to the next stage! But first, there is a weekend to take care of...