flake.nix: add fourmolu, purge stylish-haskell

Author: geo2a

CONTRIBUTING.md

@@ -203,19 +203,19 @@ and improvements are always welcome.
 
 ## Formatting the code
 
-We use `stylish-haskell` 0.14.6.0 for Haskell code formatting.
+We use `fourmolu` 0.17.0.0 for Haskell code formatting.
 
 Either enable editor integration or call the script used by CI itself:
 
 ```bash
-./scripts/ci/run-stylish.sh
+./scripts/ci/run-fourmolu.sh
 ```
 
 When using Nix, you can use the following command, which will build and use
-the right version of `stylish-haskell`.
+the right version of `fourmolu`.
 
 ```bash
-nix develop -c ./scripts/ci/run-stylish.sh
+nix develop -c ./scripts/ci/run-fourmolu.sh
 ```
 
 # Generating documentation and setting up hoogle

docs/website/contents/for-developers/StyleGuide.md

@@ -37,8 +37,8 @@ along with its context -- eg whatever is available in the GitHub PR interface.
 As long that rendering doesn't show that the PR spoils something like
 intentional alignment for example, then the PR has no style problems.
 
-We run `stylish-haskell` as a requirement for merging. The specific
-configuration can be found [here][stylish-config].
+We run `fourmolu` as a requirement for merging. The specific
+configuration can be found [here][fourmolu-config].
 
 ## Guiding principles
 
@@ -871,8 +871,8 @@ the rules below, it is good practice to update the code's style to match them.
 
     *Why:* to avoid wasting horizontal screen space.
 
-15. __Import lists__: we use `stylish-haskell` to automatically format import
-    lists. See the [`.stylish-haskell.yaml` config][stylish-config].
+15. __Import lists__: we use `fourmolu` to automatically format import
+    lists. See the [`fourmolu.yaml` config][fourmolu-config].
 
     When importing modules from consensus and in particular modules from the
     same package, an import list and a qualifier can be omitted. For example,
@@ -882,8 +882,8 @@ the rules below, it is good practice to update the code's style to match them.
     When importing from other packages, we prefer to use either an import list
     or a qualifier.
 
-16. __Export lists__: we use `stylish-haskell` to automatically format export
-    lists. See the [`.stylish-haskell.yaml` config][stylish-config]. We format
+16. __Export lists__: we use `fourmolu` to automatically format export
+    lists. See the [`fourmolu.yaml` config][fourmolu-config]. We format
     export lists in the following way:
 
     ```haskell
@@ -917,7 +917,7 @@ the rules below, it is good practice to update the code's style to match them.
       ) where
     ```
 
-    *Why:* this is consistent with how `stylish-haskell` formats it when
+    *Why:* this is consistent with how `fourmolu` formats it when
     importing it.
 
     When intentionally hiding the constructor of a datatype or newtype, we add
@@ -978,7 +978,7 @@ the rules below, it is good practice to update the code's style to match them.
 18. __Records__:
 
     We purposefully discourage the use of `RecordWildCards`.
-    
+
     For records we often use `NamedFieldPuns` to make it convenient to extract
     fields from the record. We use the following convention when naming fields
     to avoid duplicate record fields (we do not use `DuplicateRecordFields`):
@@ -1123,10 +1123,10 @@ the rules below, it is good practice to update the code's style to match them.
     import Foo.C (fooC, ...)
 
     ```
-    
+
     *Why:* this leads to more changes to the export list, but makes it
     absolutely clear where each identifier comes from.
-    
+
 ## Guidelines
 
 There are more general guidelines on how we write and structure code.
@@ -1204,4 +1204,4 @@ There are more general guidelines on how we write and structure code.
    use that shared code in a test suite defined in another package. To avoid
    this problem, we avoid sharing source directories in `cabal` files.
 
-[stylish-config]: https://github.com/IntersectMBO/ouroboros-consensus/blob/master/.stylish-haskell.yaml
+[fourmolu-config]: https://github.com/IntersectMBO/ouroboros-consensus/blob/master/fourmolu.yaml

fourmolu.yaml

@@ -0,0 +1,6 @@
+indentation: 2
+column-limit: 100
+import-export-style: leading
+haddock-style: single-line
+single-constraint-parens: never
+single-deriving-parens: never

nix/formatting-linting.nix

@@ -25,7 +25,7 @@ let
     fi
   '';
   formattingLinting = {
-    stylish = checkFormatting pkgs.stylish-haskell ../scripts/ci/run-stylish.sh;
+    fourmolu = checkFormatting pkgs.fourmolu ../scripts/ci/run-fourmolu.sh;
     cabal-gild = checkFormatting pkgs.cabal-gild ../scripts/ci/run-cabal-gild.sh;
     nixpkgs-fmt = checkFormatting pkgs.nixpkgs-fmt ../scripts/ci/run-nixpkgs-fmt.sh;
     dos2unix = checkFormatting pkgs.dos2unix ../scripts/ci/run-dos2unix.sh;

nix/shell.nix

@@ -9,13 +9,13 @@ hsPkgs.shellFor {
     pkgs.cabal-docspec
     pkgs.fd
     pkgs.nixpkgs-fmt
-    pkgs.stylish-haskell
     pkgs.dos2unix
     pkgs.cabal-gild
     pkgs.hlint
     pkgs.cabal-hoogle
     pkgs.ghcid
     pkgs.xrefcheck
+    pkgs.fourmolu
 
     # release management
     pkgs.scriv

nix/tools.nix

@@ -31,14 +31,16 @@ in
     };
   };
 
-  stylish-haskell = tool "stylish-haskell" "0.14.6.0" { };
-
   cabal-gild = tool "cabal-gild" "1.5.0.1" { };
 
   hlint = tool "hlint" "3.8" { };
 
   xrefcheck = tool "xrefcheck" "0.3.1" { };
 
+  fourmolu = tool "fourmolu" "0.18.0.0" {
+    compiler-nix-name = "ghc98";
+  };
+
   haskellBuildUtils = prev.haskellBuildUtils.override {
     inherit (final.hsPkgs.args) compiler-nix-name;
     index-state = tool-index-state;

scripts/ci/run-stylish.sh renamed to scripts/ci/run-fourmolu.sh

@@ -3,8 +3,8 @@
 set -e
 
 echo "The custom options for formatting this repo are:"
-stylish-haskell --version
-stylish-haskell --defaults | diff - ./.stylish-haskell.yaml | grep -E "^>.*[[:alnum:]]" | grep -v "#"
+fourmolu --version
+fourmolu --print-defaults | diff - ./fourmolu.yaml | grep -E "^>.*[[:alnum:]]" | grep -v "#"
 printf "\nFormatting haskell files...\n"
 
 export LC_ALL=C.UTF-8
@@ -27,7 +27,7 @@ esac
 
 $fdcmd --full-path "$path" \
        --extension hs \
-       --exec-batch stylish-haskell -c .stylish-haskell.yaml -i
+       --exec-batch fourmolu --config fourmolu.yaml -i
 
 case "$(uname -s)" in
     MINGW*) git ls-files --eol | grep "w/crlf" | awk '{print $4}' | xargs dos2unix;;