In the commit f7b348c the Manifest.MF file was changed to include the groovyAntEclipse.jar in the Bundle-ClassPath.

This breaks the headless Eclipse ANT execution of the GroovyCompilerAdapter:

"Class org.codehaus.groovy.eclipse.ant.GroovyCompilerAdapter could not be loaded because of an invalid dependency."

See Stacktrace below.

The GroovyCompilerAdapter is loaded via the EquinoxBundleLoader of the groovy.eclipse.ant plug-in (due to the new entry), which then could not load the JDTCompilerAdapter, because the org.eclipse.jdt.core plugin has no Bundle-ClassPath entry for the jdtCompilerAdapter.jar file.

But it would work without the Bundle-ClassPath, because the AntClassLoader would find the GroovyCompilerAdapter and the JDTCompilerAdapter due to the plugin.xml entries for ANT.

When a remove the new entry the build works again.

I'm wondering why the new entry in the Manifest.MF file was made?

The stacktrace of the error is attached.
Stacktrace.txt

The tested version was org.codehaus.groovy.eclipse.feature_2.9.2.xx-201612082348-e46