[CDEC-383] Add stylish-haskell to nix and CI

[ruhatch]

Description

To bring the code base to a consistent style we want to add stylish-haskell checks to CI. This adds our custom version of stylish-haskell to stack.yaml and uses it in the stylish-haskell check in buildkite.

Linked issue

CDEC-383

Type of change

• [~] 🐞 Bug fix (non-breaking change which fixes an issue)
• 🛠 New feature (non-breaking change which adds functionality)
• [~] ⚠️ Breaking change (fix or feature that would cause existing functionality to change)
• [~] 🏭 Refactoring that does not change existing functionality but does improve things like code readability, structure etc
• [~] 🔨 New or improved tests for existing code
• [~] ⛑ git-flow chore (backport, hotfix, etc)

Developer checklist

• I have read the style guide document, and my code follows the code style of this project.
• If my code deals with exceptions, it follows the guidelines.
• I have updated any documentation accordingly, if needed. Documentation changes can be reflected in opening a PR on cardanodocs.com, amending the inline Haddock comments, any relevant README file or one of the document listed in the docs directory.

Testing checklist

• [~] I have added tests to cover my changes.
• All new and existing tests passed.

QA Steps

Screenshots (if available)

[parsonsmatt]

👏

[erikd]

I really don't think we should change that one. 80 characters is super narrow and the change is actually un-ncessary.

[ruhatch]

Hmm, 80 chars is the codebase-wide recommended style - it's only here that it was inconsistent. What does everyone else think?

Change made

[adinapoli-iohk]

@ruhatch Which version of stylish-haskell are you using? After this patch, even if I upgrade stylish-haskell to 0.9.2.0, I get the following when trying to style my code:

stylish-haskell: Language.Haskell.Stylish.Config.loadConfig: Error in $: Unknown option: with_module_name, should be one of: new_line, with_alias, after_alias^@CallStack (from HasCallStack):^
@  error, called at lib/Language/Haskell/Stylish/Config.hs:107:25 in stylish-haskell-0.9.2.0-LNY14uUlu9HBLMLNzIHZYc:Language.Haskell.Stylish.Config^@

[adinapoli-iohk]

Oh wow, didn't appreciate I needed to install our own custom version:

haskell/stylish-haskell#214

Alfredo proceeds to checkout and install the version

[parsonsmatt]

You can just do stack install stylish-haskell in the cardano-sl repo and it will pick up the right version, thanks to it being in the stack.yaml file.

[adinapoli-iohk]

You can just do stack install stylish-haskell in the cardano-sl repo and it will pick up the right version, thanks to it being in the stack.yaml file.

Ah, true enough!