Switch to fourmolu formatter and reformat all sources (#1825)

* Switch to fourmolu formatter and reformat all sources

Some FOURMOLU_DISABLE directives were added in problematic cases
(mostly CPP conditional pragmas or foreign imports).

* Second pass to reduce amount of multi-line import lists

* Third pass, now with fourmolu-0.18.0.0

* Fix doctests

Author: zlondrej

.github/workflows/code-style.yaml

@@ -0,0 +1,23 @@
+name: Code style check
+
+concurrency:
+  group: formatting-${{ github.ref_name }}
+  cancel-in-progress: true
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  formatting:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+      - name: Install Nix
+        uses: cachix/install-nix-action@v31
+      - name: Check code formatting
+        run: |
+          nix develop '#haskellFormatter' --command fourmolu --mode=check --check-idempotence servant servant-*

.stylish-haskell.yaml

@@ -36,7 +36,9 @@ Some things we like:
 - Few dependencies
 - -Werror-compatible (7.8, 7.10 and 8.0)
 
-Though we aren't sticklers for style, the `.stylish-haskell.yaml` and `HLint.hs` files in the repository provide a good baseline for consistency.
+Haskell code should be formatted with `fourmolu` (`>= 0.18.0.0`).
+Please try to avoid introducing new `hlint` warnings.
+For Nix files, `nixfmt-rfc-style` is preferred.
 
 **Important**: please do not modify the versions of the servant packages you are sending patches for.
 

CONTRIBUTING.md

@@ -1,2 +1,3 @@
 import Distribution.Simple
+
 main = defaultMain

doc/tutorial/Setup.hs

@@ -2,13 +2,13 @@
 
 module JavascriptSpec where
 
-import           Data.List
-import           Data.String
-import           Data.String.Conversions
-import           Test.Hspec
-import           Test.Hspec.Wai
+import Data.List
+import Data.String
+import Data.String.Conversions
+import Test.Hspec
+import Test.Hspec.Wai
 
-import           Javascript
+import Javascript
 
 spec :: Spec
 spec = do

doc/tutorial/test/JavascriptSpec.hs

@@ -2,7 +2,7 @@ module Main where
 
 import qualified JavascriptSpec
 
-import Test.Hspec (Spec, hspec, describe)
+import Test.Hspec (Spec, describe, hspec)
 
 main :: IO ()
 main = hspec spec

doc/tutorial/test/Spec.hs

@@ -0,0 +1,15 @@
+indentation: 2
+comma-style: leading
+import-export-style: leading
+record-brace-space: false
+indent-wheres: true
+respectful: true # don't be too opinionated about newlines etc.
+haddock-style: single-line
+newlines-between-decls: 1
+fixities: []
+function-arrows: leading
+single-constraint-parens: never
+import-grouping: by-scope
+sort-constraints: true
+sort-derived-classes: true
+sort-deriving-clauses: true

flake.lock

@@ -1,2 +1,3 @@
 import Distribution.Simple
+
 main = defaultMain

fourmolu.yaml

@@ -1,3 +1,3 @@
-module Servant.Auth.Client (Token(..), Bearer) where
+module Servant.Auth.Client (Token (..), Bearer) where
 
-import Servant.Auth.Client.Internal (Bearer, Token(..))
+import Servant.Auth.Client.Internal (Bearer, Token (..))