Install fails with "cabal: unrecognized 'user-config' option `-a'"

[gallais]

github actions suddenly fails with an 'unrecognized option' error on a PR to
our project https://github.com/msp-strath/mary

The error is:

  /opt/cabal/2.0/bin/cabal user-config update -a http-transport: plain-http -v3
  cabal: unrecognized 'user-config' option `-a'

Has actions/setup-haskell@v1 been changed?

[hazelweakly]

Looks like cabal v2.0 doesn't support the -a flag to user-config. The action automatically runs cabal update and adds the http-transport on a recommendation from Herbert (hvr). I think I had tested this successfully with cabal v2.4 but had failed to see that it wasn't supported in cabal 2.0. (it doesn't help that I have read through the entire set of docs for cabal v3, and v2.4 and have failed to see any mention of the -a flag at all).

Between this issue and other issues about wanting to skip cabal update entirely if you're using stack, I'm thinking it might just be best to remove all implicit updating behavior. It seems to be getting in the way more than its helping, and many people include it in their pipelines anyway.

[gallais]

I'm not married to v2.0, I think I just picked version numbers based on what
I saw listed on the ghc download page of each version.

Looking at the README, I see that you are not listing 2.0 (anymore?) as a
supported version of cabal so it's probably my fault for relying on that.

I have just bumped the version number to 2.2 and it seems to be happily
building now.

[hazelweakly]

Excellent! I'm not sure why I "dropped" 2.0; I suspect it has to do with only supporting recent-ish GHC versions and I picked the versions of cabal that corresponded with those. That being said, I'm pretty sure cabal v2.0 was around when GHC 7.10 was?

Either way, I'm working on a fix to support cabal 2.0. The bigger goal here is remaining fully backwards compatible with v1.