Testing a new stack resolver

When there’s been a new GHC release, it can take a little while for there to be a stack resolver for it. The following procedure can be used for some local testing if you want to get ahead of the game¹.

Where stack looks for resolvers

If you execute the command,

    $stack setup --resolver ghc-x.y.z

you’ll see something like

    No setup information found for ghc-x.y.z on your platform.

if there isn’t yet a resolver for ghc-x.y.z.

The default set of resolvers stack “knows about” are those enumerated in the file stack-setup-2.yaml in the commericalhaskell/stackage-content repository.

Create a local stack setup file

• Start by downloading the release binary package tarball of interest from www.haskell.org and note its
  • size (in bytes):

         stat -f%z ghc-x.y.z-x86_64-apple-darwin.tar.xz

  • SHA1 hash:

         shasum -a 1 ghc-x.y.z-x86_64-apple-darwin.tar.xz

  • SHA256 hash:

         shasum -a 256 ghc-x.y.z-x86_64-apple-darwin.tar.xz

• Now, create stack-setup-2-ghc-x.y.z.yaml with contents along the lines of

        ghc:
          macosx:
            x.y.z:
              url: http://downloads.haskell.org/~ghc/x.y.z/ghc-x.y.z-x86_64-apple-darwin.tar.xz
              content-length: 177152992
              sha1: 2dbd726860ed2c0ea04c7aca29c22df20b952ee1
              sha256: f2e8366fd3754dd9388510792aba2d2abecb1c2f7f1e5555f6065c3c5e2ffec4

Update: Here’s an even easier way.

    ghc:
     macosx:
        x.y.z:
          url: /path/to/ghc-x.y.z-x86_64-apple-darwin.tar.xz

Install GHC version x.y.z via the setup file

The following stack setup command will use the setup file created above to download and install ghc-x.y.z:

  stack --setup-info-yaml stack-setup-2-ghc-x.y.z.yaml --resolver ghc-x.y.z setup

Once stack has got GHC installed, there’s no further any need to pass a setup-info-yaml argument to subsequent stack commands, it’s ready to go!

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1. Kindly explained to me by Mike Pilgrem in this ticket. This note is biased towards my needs on macOS. See the linked issue for further details especially for Windows installations.↩︎