Add caching to HLS check

.github/workflows/hls.yml

@@ -12,17 +12,29 @@ jobs:
   test-hls-works:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - name: Check out repo
+        uses: actions/checkout@v4
       - name: Install Nix with good defaults
         uses: input-output-hk/install-nix-action@v20
         with:
           extra_nix_config: |
             trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=
             substituters = https://cache.iog.io/ https://cache.nixos.org/
-          nix_path: nixpkgs=channel:nixos-unstable
-      - uses: cachix/install-nix-action@v18
+          nix_path: nixpkgs=channel:nixos-unstable 
+      - name: Cachix install Nix
+        uses: cachix/install-nix-action@v18
         with:
           nix_path: nixpkgs=channel:nixos-unstable
-      # Make the Nix environment available to next steps
-      - uses: rrbutani/use-nix-shell-action@v1
-      - run: cabal update; haskell-language-server
+      - name: Open nix environment
+        uses: rrbutani/use-nix-shell-action@v1
+      - name: Update dependencies
+        run: cabal update; cabal freeze
+      - name: Cache hie-bios folder
+        uses: actions/cache@v3
+        with:
+          path: |
+            ~/.cache/hie-bios
+          key: ${{ runner.os }}-$(ghc --version | grep -oE '[^ ]+$')-${{ hashFiles('**/*.cabal', '**/cabal.project', '**/cabal.project.freeze') }}
+          restore-key: ${{ runner.os }}-$(ghc --version | grep -oE '[^ ]+$')-
+      - name: Test HLS works
+        run: haskell-language-server