Dear friends,
the other day I've run into an issue where I could not build a package. It
turned out that
the underlying reason was that the packages ghc ships with are not necessarily
the same
as they are on hackage. Ryan was kind enough to open Ticket 16199[1].
My use case is that I reduce the set of packages I use from the package
database that ghc
ships, and build the others myself. Thus if packages in the package database
as shipped
with ghc do not match the ones found on hackage for the SAME VERSION, I run
into issues.
I've since devised a script to compute the difference between packages in GHC
and the ones
on hackage with the same version[2].
I've then sat out to compute the differences for ghc8.4 and ghc8.6 using the
following
approach:
for release in ghc-8.4.1-release ghc-8.4.2-release ghc-8.4.3-release
ghc-8.4.4-release \
ghc-8.6.4-release ghc-8.6.2-release ghc-8.6.3-release; do
git checkout $release
git reset --hard HEAD && git clean -xffd
git submodule update --init --recursive && git clean -xffd
../verify-packages.sh
mkdir -p ../$release
find package-diffs -not -empty -type f -exec cp {} ../$release \;
done
I've compiled them[3] for inspection (and because I need to patch my hackage
packages to
match the ones that ghc ships).
I'm sorry to report that I found discrepancies between the package we ship with
GHC and
the ones on haskell for each ghc release in 8.4 and 8.6. Some changes are
minor, such
as version bumps, as can be represented with revisions on hackage as well.
Other are not
so minor. The one over which I tripped was transformers-0.5.5.0. The diff[4]
is 20K.
I therefore propose that we make sure to only ship packages with GHC that match
their
respective versions on hackage.
Cheers,
Moritz
--
[1]: http://ghc.haskell.org/trac/ghc/ticket/16199
[2]: https://gitlab.haskell.org/ghc/ghc/merge_requests/139
[3]: https://github.com/angerman/haskell.nix/tree/master/patches
[4]:
https://github.com/angerman/haskell.nix/blob/master/patches/ghc863/transformers-0.5.5.0.patch
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