GHA fails with constraints on Cabal version

[andreasabel]

I am testing hpack that has constraint Cabal >= 3.0.0.0, see https://github.com/andreasabel/hpack/actions/runs/492023303.
This fails for the ghc instances that come with a smaller cabal version, e.g. 8.0, see https://github.com/andreasabel/hpack/runs/1717674161.

rejecting: Cabal-1.24.2.0/installed-1.24.2.0 (conflict: hpack => Cabal>=3.0.0.0)
[__1] rejecting: Cabal-3.2.1.0, ..., Cabal-1.24.1.0
(constraint from project config TODO requires installed instance)

How would that be fixed?
Can I work around that?

[phadej]

See https://github.com/haskell-CI/haskell-ci/blob/master/cabal.haskell-ci#L43-L45

[andreasabel]

Thanks for the hint!

A related problem that I have is if I e.g. specify cabal-version: 2.0 in the .cabal file it does not install a sufficiently new version of cabal-install. E.g. when testing under GHC 8.0, see https://github.com/BNFC/bnfc/runs/1751241734?check_suite_focus=true , I get the error

Configuring BNFC-2.9.1...
setup: This package description follows version 2.0 of the Cabal
specification. This tool only supports up to version 1.24.2.0.

I didn't see a way to set the version of cabal-install (see also #470).

UPDATE: I managed to fix my problem by also requiring Cabal >= 2.0 in setup-depends: https://github.com/BNFC/bnfc/runs/1751716416?check_suite_focus=true

[phadej]

setup: This package description follows version 2.0 of the Cabal
specification. This tool only supports up to version 1.24.2.0.

refers to Cabal-1.24.0.0 used to compile the custom setup. Why? I don't know. You should try to reproduce locally.

[andreasabel]

See also: #168.