How to invoke CompileTask without compiling?

Keith Lea wrote:

I want to invoke a CompileTask without compiling. I see
CompilerManager.executeTask, but it requires a CompileContext, and I
don't want to use DummyCompileContext because I want the messages
toolwindow to show any messages generated from the task.

I can't figure out a way to create a CompileContext, or to write
directly to the Messages toolwindow. Is there a way to do either of
these things?

It looks like passing null for the compile scope works. Some
documentation and nullable tags would be cool here.