Using a development snapshot of happy

[Vladislav Zavialov]

Hi ghc-devs,

I’m working on the unification of parsers for terms and types, and one of the things I’d really like to make use of is a feature I implemented in ‘happy’ in October 2019 (9 months ago):

  https://github.com/simonmar/happy/pull/153

It’s been merged upstream, but there has been no release of ‘happy’, despite repeated requests:

  1. I asked for a release in December: https://github.com/simonmar/happy/issues/164
  2. Ben asked for a release a month ago: https://github.com/simonmar/happy/issues/168

I see two solutions here:

  a) Find a co-maintainer for ‘happy’ who could make releases more frequently (I understand the current maintainers probably don’t have the time to do it).
  b) Use a development snapshot of ‘happy’ in GHC

Maybe we need to do both, but one reason I’d like to see (b) in particular happen is that I can imagine introducing more features to ‘happy’ for use in GHC, and it’d be nice not to wait for a release every time. For instance, there are some changes I’d like to make to happy/alex in order to implement #17750

So here are two questions I have:

  1. Are there any objections to this idea?
  2. If not, could someone more familiar with the build process guide me as to how this should be implemented? Do I add ‘happy’ as a submodule and change something in the ./configure script, or is there more to it? Do I need to modify make/hadrian, and if so, then how?

Thanks,
- Vlad