Add fourmolu as formatter

.ci/gitlab/branch.yaml

@@ -75,6 +75,19 @@ nix-build:
   tags:
     - local
 
+fourmolu:
+  extends: .common-local
+  needs: []
+  stage: test
+  script:
+    - cabal v2-update
+    # Install the same version as Nix OS manages, 0.14.0.0.
+    # Installation failure should not make the job fail. This can happen if
+    # fourmolu was already in PATH for example.
+    - cabal v2-install --overwrite-policy=always fourmolu-0.14.0.0 || true
+    - export PATH="$HOME/.cabal/bin:$PATH"
+    - ./format.sh check
+
 haddock:
   extends: .common-local
   needs: []

.git-blame-ignore-revs

@@ -0,0 +1 @@
+d3d5a48394c28232c9d84e7a4d8e504dc0d2d0ad

Setup.hs

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

format.sh

@@ -0,0 +1,60 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Help message
+show_help() {
+  local script_name
+  script_name=$(basename "$0")
+  echo "Fourmolu formatting Script.
+
+Usage:
+  $script_name diff    Format the current git diff.
+  $script_name full    Format all source files.
+  $script_name check   Check the formatting of the source files.
+  $script_name (-h | --help)
+
+Options:
+  -h --help     Show this screen."
+}
+
+# Main script logic
+if [[ "$#" -eq 0 || "$1" == "-h" || "$1" == "--help" ]]; then
+  show_help
+  exit 0
+fi
+
+# Certain files have CPP annotations which cannot be parsed by fourmolu.
+# These files need to be manually formatted.
+# Moreover, we also ignore build files in dist-newstyle.
+exclude_files=(
+  "dist-newstyle"
+  "hdl-tests"
+  "src/Clash/Cores/UART.hs"
+)
+
+# Make sure it doesn't matter from where this script is executed
+DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+cd $DIR
+
+if [ $1 == "diff" ] ; then
+  src_files=$(git diff --cached --name-only --diff-filter=ACMR -- '*.hs')
+else
+  src_files=$(find -type f -name "*.hs")
+fi
+
+src_files_str=$(printf "%s\n" "${src_files[@]}" | sed 's| |\\ |g')
+exclude_files_str=$(printf "%s\n" "${exclude_files[@]}" | sed 's| |\\ |g')
+src_files=$(echo "$src_files_str" | grep -vwE  "$exclude_files_str")
+
+if [ -z "$src_files" ]; then
+  exit 0;
+fi
+
+if [[ "$1" == "diff" || "$1" == "full" ]] ; then
+  fourmolu --mode inplace $src_files
+elif [[ "$1" == "check" ]] ; then
+  fourmolu --mode check $src_files
+else
+  echo "Expected a single argument, \"full\", \"diff\", \"check\" or \"--help\"" >&2
+  exit 3
+fi

fourmolu.yaml

@@ -0,0 +1,3 @@
+indentation: 2
+column-limit: 90
+

shell.nix

@@ -10,6 +10,7 @@ pkgs.stdenv.mkDerivation {
   name = "shell";
   buildInputs = project.env.nativeBuildInputs ++ [
     haskellPackages.cabal-install
+    haskellPackages.fourmolu
     haskellPackages.haskell-language-server
   ];
   LC_ALL = "C.UTF-8";

src/Clash/Cores/Crc.hs

@@ -1,4 +1,4 @@
-{-|
+{- |
   Copyright   :  (C) 2024, Rowan Goemans <[email protected]>
   License     :  BSD2 (see the file LICENSE)
   Maintainer  :  QBayLogic B.V. <[email protected]>
@@ -75,25 +75,25 @@ indicates how many @BitVector 8@ are valid inside the @Vec@. 0 means 1 is valid.
 True
 
 Notice that the 'crcEngine' has a latency of one clock cycle.
-
 -}
+module Clash.Cores.Crc (
+  CrcParams (..),
+  KnownCrc (..),
 
-module Clash.Cores.Crc
-  ( CrcParams(..)
-  , KnownCrc(..)
   -- ** Software
-  , SoftwareCrc
-  , mkSoftwareCrc
-  , reset
-  , feed
-  , digest
-  , rawResidue
-  , residue
+  SoftwareCrc,
+  mkSoftwareCrc,
+  reset,
+  feed,
+  digest,
+  rawResidue,
+  residue,
+
   -- ** Hardware
-  , HardwareCrc
-  , deriveHardwareCrc
-  , crcEngine
-  , crcValidator
-  ) where
+  HardwareCrc,
+  deriveHardwareCrc,
+  crcEngine,
+  crcValidator,
+) where
 
 import Clash.Cores.Crc.Internal