Fixed caching in ci build

Author: stickyPiston

.github/workflows/build.yml

@@ -16,29 +16,49 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - uses: actions/setup-haskell@v1
+    
+    - name: Set up GHC ${{ matrix.ghc-version }}
+      uses: haskell-actions/setup@v2
+      id: setup
       with:
         ghc-version: '9.10.1'
-        cabal-version: '3.12.1.0'
-    - name: Cache
-      uses: actions/cache@v3
+        
+    - name: Configure the build
+      run: |
+        cabal configure
+        cabal build all --dry-run
+        
+    - name: Restore cached dependencies
+      uses: actions/cache/restore@v4
+      id: cache
       env:
-        cache-name: cache-cabal
+        key: ${{ runner.os }}-ghc-${{ steps.setup.outputs.ghc-version }}-cabal-${{ steps.setup.outputs.cabal-version }}
       with:
-        path: ~/.cabal
-        key: ${{ runner.os }}-build-${{ env.cache-name }}-${{ hashFiles('**/*.cabal') }}-${{ hashFiles('**/cabal.project') }}
-        restore-keys: |
-          ${{ runner.os }}-build-${{ env.cache-name }}-
-          ${{ runner.os }}-build-
-          ${{ runner.os }}-
+        path: ${{ steps.setup.outputs.cabal-store }}
+        key: ${{ env.key }}-plan-${{ hashFiles('**/plan.json') }}
+        restore-keys: ${{ env.key }}-
+
     - name: Install dependencies
-      run: |
-        cabal update
-        cabal build --only-dependencies
+      # If we had an exact cache hit, the dependencies will be up to date.
+      if: steps.cache.outputs.cache-hit != 'true'
+      run: cabal build all --only-dependencies
+
+    # Cache dependencies already here, so that we do not have to rebuild them should the subsequent steps fail.
+    - name: Save cached dependencies
+      uses: actions/cache/save@v4
+      # If we had an exact cache hit, trying to save the cache would error because of key clash.
+      if: steps.cache.outputs.cache-hit != 'true'
+      with:
+        path: ${{ steps.setup.outputs.cabal-store }}
+        key: ${{ steps.cache.outputs.cache-primary-key }}
+        
     - name: Build hakyll project
       run: cabal build
+      
     - name: Build static website
       run: cabal exec site build
+
+    # upload-pages-artifact defaults to uploading the _site directory 
     - name: Upload artifact
       uses: actions/upload-pages-artifact@v3