Cannot generate internal documentation

[osbugs]

Perhaps I did miss something, but it seems to me that generating internal documentation is not possible.

With cabal, I just use the following command line: cabal haddock --internal. Is there some similar switch for stack?

[osbugs]

I think this bug/feature request is distinct from #2165. The difference is that I do not want to provide arguments to haddock but I do want haddock to be run on a different target than the one provided.

[mgsloan]

I see! Yes, currently I don't think we have a way to do --internal, but it'd be a great thing to add. Not sure if we want to call it that, though.

I'd almost want to have it be a default, but only if haddock made it clear they're for unexposed modules (doubtful)

[rickowens]

Hi guys. I really needed this for a project I'm working on, so I went ahead and took a swing at it. This is my first contribution to stack, so let me know if there is anything I missed in the way of completeness/style/policy. Thanks.

[osbugs]

Updated PR in #2598