Stack CI: repair cache key

Author: andreasabel

.github/workflows/stack.yml

@@ -13,8 +13,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os:      [macos-latest] # [ubuntu-latest,macos-latest,windows-latest]
-        ghc-ver: ['9.8'] # ['9.12', '9.10', '9.8', '9.6']
+        os:      [ubuntu-latest,macos-latest,windows-latest]
+        ghc-ver: ['9.12', '9.10', '9.8', '9.6']
           # Snapshots for 9.4.8, 9.2.8, 9.0.2, 8.10.7 do not have a recent enough base-compat; 0.13 is needed.
           # On ubuntu-22.04 the old versions 8.8.4, 8.6.5, 8.4.4, 8.2.2 fail due to HsOpenSSL linking errors.
           # They used to work under ubuntu-20.04, but it is not worth the trouble maintaining them.
@@ -42,12 +42,16 @@ jobs:
       with:
         ghc-version: ${{ matrix.ghc-ver }}
         enable-stack: true
+        # Andreas, 2026-04-18
+        # There have been problems with libcrypto on macOS with GHC 9.8.4 with --system-ghc
+        # so we let Stack install GHC itself.
         stack-no-global: true
 
     - name: Set up the openssl library (MacOS)
       if: runner.os == 'macOS'
+      # Already installed:
+      #         brew install openssl
       run: |
-        brew install openssl
         echo "PKG_CONFIG_PATH=${PKG_CONFIG_PATH}"
         echo "PKG_CONFIG_PATH=$(brew --prefix)/opt/openssl/lib/pkgconfig" >> "${GITHUB_ENV}"
 
@@ -71,11 +75,15 @@ jobs:
     - name: Cache dependencies (restore)
       uses: actions/cache/restore@v5
       id: cache
+      env:
+        key: ${{ runner.os }}-stack-${{ steps.setup.outputs.stack-version }}-ghc-${{ matrix.ghc-ver }}
+          # ${{ steps.setup.outputs.ghc-version }} is empty with stack-no-global
+          # so we use plain ${{ matrix.ghc-ver }}
       with:
         path: ${{ steps.setup.outputs.stack-root }}
         # Use a unique primary key (always save new cache); works if caches aren't to big or too many...
-        key:          ${{ runner.os }}-stack-${{ steps.setup.outputs.stack-version }}-ghc-${{ steps.setup.outputs.ghc-version }}-commit-${{ github.sha }}
-        restore-keys: ${{ runner.os }}-stack-${{ steps.setup.outputs.stack-version }}-ghc-${{ steps.setup.outputs.ghc-version }}-
+        key:          ${{ env.key }}-commit-${{ github.sha }}
+        restore-keys: ${{ env.key }}-
 
     - name: Install dependencies
       # if: ${{ steps.cache.outputs.cache-hit != 'true' }}