Re: GHC 8.4.3

[Ricardo Wurmus]

Hi Tim,

> Some of you may recall that I started work on updating all of our
> Haskell packages to their LTS 12 versions, and making sure they all
> build with GHC 8.4.3.  I think this work is ready to be included now (on
> a WIP branch, at least).

Thank you so much!

> The commits exist at
> <https://gitlab.com/samplet/guix/tree/wip-haskell> under the
> “wip-haskell” branch.  There are 258 commits, and they have been rebased
> on master (although that was a few days ago, but it should be fine
> because the Haskell packages have been relatively stable).  I figure
> that 258 commits is too many for guix-patches, so I’m hoping that
> someone (Ricardo?) can take them from the repo linked above.  There are
> about 450 packages that need to be rebuilt.

I have fetched the branch, rebased it onto current master, and pushed it
to “wip-haskell” on Savannah.

> Here are some notes that you might find interesting if you rely on our
> Haskell infrastructure.
>
>   • There are 21 failing packages.  They are agda, beast, corrode,
>     git-annex, ghc-aws, ghc-gnuplot, ghc-haddock-test,
>     ghc-hashable-bootstrap, ghc-indents, ghc-monadplus,
>     ghc-nats-bootstrap, ghc-packedstring, ghc-regex, ghc-regex-tdfa-rc,
>     ghc-statistics, ghc-vector-builder, ghc-wave, ghc-xmonad-contrib,
>     raincat, rapicorn, and shellcheck.  Some of these are abandoned
>     upstream, but most of them just need some extra attention.  I will
>     look through them (especially git-annex), but I would like the
>     stability of the build farm as I do it.  (Also, help wanted!)

“beast” and “rapicorn” belong together.  “beast” depends on “rapicorn”;
but they don’t seem to have Haskell dependencies.  In any case these two
packages are outdated and would need to be updated.  It’s fine if these
two are broken for now.

>   • The new Haskell no longer supports the “--allow-newer” flag, so it
>     has to be worked around with phases and “substitute*”.  However, I
>     have introduced a “#:cabal-revision” keyword that tells the build
>     system to patch in newer revisions of the package’s Cabal file from
>     Hackage.  This means that we can use this mechanism whenever
>     upstream has updated the dependency constraints (which is the main
>     reason we made so much use of “--allow-newer” in the first place).

Very good.  Thank you.

>   • I removed “ghc-mtl” since it is now included in GHC.

Okay.

I’ll try to go through the patches in the coming days and push fixes to
some of the failures if I can.

--
Ricardo