Added cache to github actions

Author: coot

.github/workflows/haskell.yml

@@ -13,6 +13,9 @@ jobs:
         os: [ubuntu-latest, macos-latest, windows-latest]
 
     steps:
+    - name: Set cache version
+      run: echo "CACHE_VERSION=pu4Aevoo" >> $GITHUB_ENV
+
     - name: "Setup haskell"
       uses: haskell/actions/setup@v1
       id: setup-haskell
@@ -27,6 +30,29 @@ jobs:
         cat ./.github/workflows/cabal.project.local > ./cabal.project.local
         cat ./cabal.project.local
 
+    - name: Record dependencies
+      id: record-deps
+      run: |
+        cabal build all --dry-run
+        cat dist-newstyle/cache/plan.json | jq -r '."install-plan"[].id' | sort | uniq > dependencies.txt
+        echo "::set-output name=weeknum::$(/bin/date -u "+%W")"
+
+    - uses: actions/cache@v3
+      name: "Cache `cabal store`"
+      with:
+        path: ${{ runner.os == 'Windows' && steps.win-setup-haskell.outputs.cabal-store || steps.setup-haskell.outputs.cabal-store }}
+        key: cache-dependencies-${{ env.CACHE_VERSION }}-${{ runner.os }}-${{ matrix.ghc }}-${{ hashFiles('dependencies.txt') }}
+        restore-keys: cache-dependencies-${{ env.CACHE_VERSION }}-${{ runner.os }}-${{ matrix.ghc }}
+
+    - uses: actions/cache@v3
+      name: "Cache `dist-newstyle`"
+      with:
+        path: |
+          dist-newstyle
+          !dist-newstyle/**/.git
+        key: cache-dist-${{ env.CACHE_VERSION }}-${{ runner.os }}-${{ matrix.ghc }}-${{ steps.record-deps.outputs.weeknum }}
+        restore-keys: cache-dist-${{ env.CACHE_VERSION }}-${{ runner.os }}-${{ matrix.ghc }}
+
     - name: Build dependencies
       run: cabal build --only-dependencies all