Provide a way to see generated stub code

If a stub directory is set, the stub files will not be removed

How do I set a stub directory?

It is already possible to "keep the stubs".
This aspect, by the way, is used by the recent stub generator test infrastructure to verify the stubs which are generated.
On CompilerConfiguration, there's a setJointCompilationOptions() which takes a Map, with keys like keepStubs and stubDir.
You can do something like that:

def config = new CompilerConfiguration()
config.jointCompilationOptions = [stubDir: stubDir, keepStubs: true]

There should be a way to set this on the command line. That's what this issue is about.

I also always use FileSystemCompiler to look into joint compilation related things and I agree that it is very irritating that there is no way to specify keepStubs/stubDir options from the command line.

I think we should open this issue and use it to provide these important but missing options on the command line.

Feel free to reopen if you feel like working on it.

I feel like reopening because the requirement seems genuine to me. Then it can remain in the work queue of genuine issues and whoever has time can work on it. Why does it need to be tied to "me" working on it?

If you don't think it's a valid requirement, say so with your views.

Should this be a system property (-DkeepStubs) or a regular command-line option?

FileSystemCompiler uses command line options everywhere instead of system properties - so I guess that should be ok.

But I was thinking that instead of introducing separate command line options for stubDir and keepStubs options, may be we can introduce {{ -JCname=value }} series and push all such options to JointCompilationOptions map. That way tomorrow if joint compilation needs more configuration options, instead of maintaining specific command line options, this generic series may help.

I think that is a very good idea Roshan

This is now supported via the --configscript option.

Just create a config script (e.g. conf.groovy) like this:

configuration.jointCompilationOptions.keepStubs=true
configuration.jointCompilationOptions.stubDir=new File('/path/to/temp/stubdir')

Then call with something like:

groovyc --configscript conf.groovy -j MyJava.java MyGroovy.groovy

While it would be possible to try to emulate this with separate individual switches, it becomes cumbersome to try to support options in a generic way (allowing more to be added easily) while also providing rich typing (e.g. keepStubs and stubDir are Boolean and File rather than just Strings)

Just to mention it, for Gradle it's important that all compiler options can also be set programmatically. I assume this is still the plan? (I know it's true for keepStubs and stubDir.)

Yes, the above script is in fact calling the API - just making it more convenient to do so, e.g. the config script has the current CompilerConfiguration object predefined in the script as "configuration" as well as other conveniences.