Hlint: A handful of fixes to hints

[andys8]

Goal

Less existing warnings in pull requests - by addressing some of the issues.

Changes

• hlint fixes
• hlint config (Hlint: A handful of fixes to hints #3259 (comment))
• CI: rwe/actions-hlint-run@v2

Review

While most of the changes seem to be trivial (whitespace or parens removed), some changes prefer extra functions (as it has been configured). What I think is potentially critical is removing extensions as suggested by hlint: Is it possible that one of the removed extensions is actually changing functionality? If so, please comment.

[andys8]

ℹ️ Because of rule defined here

https://github.com/andys8/haskell-language-server/blob/ebb58eec6fb9817c163879800cf0c17dcb25e460/.hlint.yaml#L47

[michaelpj]

FWIW I personally disagree with this hlint rule pretty strongly. If anything I tend to replace fromMaybe and friends with explicit pattern matches unless there's something higher-order going on!

[andys8]

Main issue I think that needs to be addressed is the difference between what is configured in .hlint.yaml and the codebase. I myself am trying to be not opinionated in this PR. But I'm also not sure regarding defaults and capabilities of different hlint versions - and how hint levels are dealt with by different tools (hls, the github action in this repository and together with apply-refact). Currently I'm still looking into it.

E.g. for this specific file with hlint version 3.3.6 I see these hints (where this one is a suggestion):

hlint hie-compat/src-ghc86/Compat/HieDebug.hs
hie-compat/src-ghc86/Compat/HieDebug.hs:1:1: Warning: Use module export list
Found:
  module Compat.HieDebug where
Perhaps:
  module Compat.HieDebug (
          module Compat.HieDebug
      ) where
Note: an explicit list is usually better

hie-compat/src-ghc86/Compat/HieDebug.hs:4:1-35: Warning: Unused LANGUAGE pragma
Found:
  {-# LANGUAGE StandaloneDeriving #-}
Perhaps you should remove it.

hie-compat/src-ghc86/Compat/HieDebug.hs:(132,18)-(134,23): Suggestion: Replace case with fromMaybe
Found:
  case foldMap mapRef refs of
    Just xs -> xs
    Nothing -> []
Perhaps:
  Data.Maybe.fromMaybe [] (foldMap mapRef refs)

3 hints

Changed this in the hlint config: 5a68e9f

[michaelpj]

We can absolutely continue to tweak our hlint config, and I think turning off a rule is equally valid to fixing it if we don't think the rule clearly adds value.

[michaelpj]

In terms of getting our codebase clean: we have some hlint rules set to error, and those will fail the build, and hence they have a bunch of exceptions. Reducing the number of exceptions would be great: in that way the "error" rules are the ones we're really saying we don't want to happen ever.

I'm also very pro getting rid of warnings and pruning any rules that don't add value 👍

[kokobd]

modification to hls-code-range-plugin looks good to me.

[drsooch]

Lgtm on number formatting plugin