JRuby debugging problem in eclipse

I’m trying to get some JRuby low-level debugging happening in Eclipse,
using Ganymede, jruby trunk, RadRails, and latest debug gems. Compiling
using jdk 1.6.0_07.

I’m almost there. I’m trying to debug the java code for
RubyFileStat.java, but Eclipse is complaining that line number info is
not available as soon as I start the debug session.

I gather this is because this source is run through apt before being
compiled. I noted that the ant script does not specify
debuglevel=“lines,vars,source” anywhere, even though it has
debug=“true”. The trick is to know exactly where in the Ant script this
should go? My first guess was on the apt element, but that didn’t work.

Any advice gratefully received…