How do I install a Scala compiler plugin so that it automatically works with Ant? - scala

Question

I'm writing a Scala compiler plugin that I want to be used whenever scalac is invoked, so I put it in the Scala distribution's plugins directory (misc/scala-devel/plugins) - this works perfectly when I write something simple like scalac HelloWorld.scala, but doesn't work when I try building using an Ant script with an embedded scalac task like:
<scalac srcdir="${src}" destdir="${bin}" classpathref="build.classpath" deprecation="on">
<include name="**/*.scala"/>
</scalac>
I can get it to work by changing the build script to specify the plugins directory, e.g.:
<scalac srcdir="${src}" destdir="${bin}" classpathref="build.classpath" deprecation="on"
addparams="-Xpluginsdir /Users/stuart/Downloads/scala-2.9.2/misc/scala-devel/plugins">
<include name="**/*.scala"/>
</scalac>
However, I need this to work for third-party build scripts that I am unable to change manually, so my simple fix doesn't cut it - any ideas please?
UPDATE:
After a bit more digging, I've found that you can override task definitions using presetdef, e.g.:
<presetdef name="scalac">
<scalac addparams="-Xpluginsdir /Users/stuart/Downloads/scala-2.9.2/misc/scala-devel/plugins"/>
</presetdef>
This doesn't directly solve the problem, but it's potentially interesting - my current line of investigation is whether it's possible to put this (or something like it) in a wrapper Ant script that imports the original one (no idea whether this will work, I don't use Ant that much).