On Oct 1, 2019, at 18:19, Ben Gamari <ben@well-typed.com> wrote:

Your question is a very good one which, until quite recently, there was
not a particularly good answer to. However, in the past months we have
been working on infrastructure (in the form of head.hackage [0]) to make
GHC more testable in pre-release form.

I have a draft blog post explaining the currently state-of-play
here [1,2]. Unfortunately between ICFP, release things, vacation, and bug
fixing I've lacked the time to finish these off (the tutorial in particular).

Hi Ben,

Many thanks for your response—this infrastructure looks incredibly helpful! I’ll give it a try. One question I do have just from giving it a look involves the cabal.constraints file available here:

https://ghc.gitlab.haskell.org/head.hackage/cabal.constraints

A number of packages appear to be listed twice, and some of them (but not all of them) are pinned to different versions. Is that intentional? Or is it just a part of still being a bit of a work in progress?

In any case, this gets me quite a bit further, and though I’m not sure yet if my project will actually build, I can now at least construct a valid build plan. Thanks again!

Alexis