Haskell installation not installing compiler

[StefanoDeVuono]

What happened?

The instructions for a Haskell install indicate that the following:

  "packages": [
    "stack@latest",
    "cabal-install@latest",
    "zlib@latest",
    "hpack@latest"
  ]

will install GHC. It does not. And it's not clear what the best practice is for a Devbox user:

• install GHC via stack
• try adding "nix aware" flags to stack and cabal
• installing a nix package for ghcup and using that to install GHC

Thanks!

Steps to reproduce

1. > devbox add stack cabal-install zlib hpack
2. > devbox shell
3. > which ghc
4. > which stack (To verify installation of stack, which seems to work fine.)

Command

shell

devbox.json

{
  "$schema": "https://raw.githubusercontent.com/jetify-com/devbox/0.15.0/.schema/devbox.schema.json",
  "packages": [
    "stack@latest",
    "cabal-install@latest",
    "zlib@latest",
    "hpack@latest"
  ],
  "shell": {
    "init_hook": [
      "echo -ne \"\\033]0;📦 𝚍𝚎𝚟𝚋𝚘𝚡 - $(basename \"$PWD\")\\007\"",
      "echo 'Welcome to devbox!' > /dev/null"
    ],
    "scripts": {
      "test": [
        "echo \"Error: no test specified\" && exit 1"
      ]
    }
  },
  "env": {
     "PATH": "$DEVBOX_PROJECT_ROOT/.bin:$PATH",
     "STACK_ROOT": "$DEVBOX_PROJECT_ROOT/.stack",
     "CABAL_DIR": "$DEVBOX_PROJECT_ROOT/.cabal"
  }
}

Devbox version

0.15.0

Nix version

2.29.0

What system does this bug occur on?

macOS (Apple Silicon)

Debug logs

No response

[savil]

Looks like the linked example repo includes ghc as its own package: https://github.com/jetify-com/devbox/blob/main/examples/development/haskell/devbox.json

does that work for you? if so, the docs should be updated

[StefanoDeVuono]

@savil Yeah, installing GHC as its own package works, but might it be cleaner just to install GHCup? This aligns with how the docs advise a rust install be done (with rustup).

[mikeland73]

Triage: looks easy, p3. This is a documentation bug.

examples/development/haskell/README.md (the source of the Haskell docs page) lists only stack, cabal-install, zlib and hpack, and then says "This will install GHC". None of those packages puts ghc on PATH. Stack would download its own GHC unless configured for Nix.

The example project next to it, examples/development/haskell/devbox.json, does include ghc@latest and gmp@latest, which is why it works.

Suggested fix. Update the README/docs snippet to match the example:

devbox add ghc stack cabal-install zlib hpack gmp

Also drop or qualify the "This will install GHC" sentence. Optionally, mention stack config set system-ghc --global true (or --system-ghc), so Stack uses the devbox-provided GHC instead of downloading one.

Using ghcup inside devbox is possible, but it bypasses Nix pinning. The ghc package is the more devbox-native approach.

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