Run fourmolu instead of stylish-haskell in Update workflow

Author: ttuegel

.github/workflows/update.yml

@@ -37,26 +37,36 @@ jobs:
           commit_message: 'Materialize Nix expressions'
           file_pattern: 'nix/ *.cabal'
 
-  stylish-haskell:
-    name: 'stylish-haskell'
+  fourmolu:
+    name: 'Style'
     runs-on: ubuntu-latest
     steps:
-      - name: Install stylish-haskell
-        run: |
-          cd $(mktemp -d)
-          wget https://github.com/jaspervdj/stylish-haskell/releases/download/v0.11.0.0/stylish-haskell-v0.11.0.0-linux-x86_64.tar.gz
-          tar xaf stylish-haskell-v0.11.0.0-linux-x86_64.tar.gz
-          sudo mv stylish-haskell-v0.11.0.0-linux-x86_64/stylish-haskell /usr/local/bin/
-          stylish-haskell --version
-
-      - uses: actions/[email protected]
+      - name: Check out code
+        uses: actions/[email protected]
         with:
           submodules: recursive
 
-      - name: Format with stylish-haskell
-        run: stylish-haskell -i -r kore
+      - name: Install Nix
+        uses: cachix/install-nix-action@v12
+        with:
+          extra_nix_config: |
+            substituters = http://cache.nixos.org https://hydra.iohk.io
+            trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=
+
+      - name: Install Cachix
+        uses: cachix/cachix-action@v8
+        with:
+          name: kore
+          signingKey: '${{ secrets.KORE_CACHIX_SIGNING_KEY }}'
+          skipPush: true
+
+      - name: Format
+        run: |
+          ./nix/fourmolu.sh
 
       - name: Commit changes
         uses: stefanzweifel/[email protected]
         with:
-          commit_message: 'Format with stylish-haskell'
+          commit_message: 'Format with fourmolu'
+          file_pattern: '*.hs'
+

nix/fourmolu.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env nix-shell
+#!nix-shell ../shell.nix -i bash
+
+fd '.*\.hs$' | xargs fourmolu -o -XTypeApplications -o -XPatternSynonyms -o -XBangPatterns -i

shell.nix

@@ -10,7 +10,7 @@ let
   pkgs = import sources."nixpkgs" {};
 
   inherit (pkgs) cabal-install ghcid stack;
-  inherit (pkgs) gnumake yq z3;
+  inherit (pkgs) fd gnumake yq z3;
 
   # Change the compiler when updating our own resolver.
   compiler-nix-name = "ghc8104";