Merge pull request #811 from IntersectMBO/skip-hls-on-trivial-changes

Skip HLS on trivial changes

Author: palas

.github/workflows/hls.yml

@@ -21,24 +21,80 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Check if changes were trivial
+        id: check_trivial_changes
+        run: |
+          git fetch origin ${{ github.base_ref }} --unshallow
+          base_ref=origin/${{ github.base_ref }}
+          head_ref=HEAD
+          changed_files=$(git diff-tree --name-status -r "$base_ref".."$head_ref" -- | cut -f2 -d$'\t')
+          # Flag to check whether we do the rest of checks
+          exception=true
+
+          for file in $changed_files; do
+            # If changes were to a markdown file we don't mind
+            if [[ $file == *.md ]]; then
+              echo "$file: is markdown, so it doesn't matter (trivial change)"
+              continue
+            fi
+
+            # If changes were to a .cabal file, we ensure only the version changed
+            if [[ $file == *.cabal ]]; then
+              # If file doesn't exist it means it was moved or removed
+              if [ ! -f "$file" ]; then
+                echo "$file: was moved or removed and is a cabal file (non-trivial change)"
+                exception=false
+                break
+              fi
+
+              # We ensure the only change was to the version field
+              diff_version=$(git diff "$base_ref".."$head_ref" -- "$file" | perl -ne 'print if /^-(?!version:)/' | wc -l)
+              diff_no_version=$(git diff "$base_ref".."$head_ref" -- "$file" | perl -ne 'print if /^\+(?!version:)/' | wc -l)
+
+              if [ "$diff_version" -gt 1 ] || [ "$diff_no_version" -gt 1 ]; then
+                echo "$file: was modified beyond the version tag (non-trivial change)"
+                exception=false
+                break
+              fi
+              echo "In $file, at most the version field was modified"
+            else
+              # If other types of files were changed, do not skip the checks
+              echo "$file: was changed and is not a markdown nor a cabal file (non-trivial change)"
+              exception=false
+              break
+            fi
+          done
+
+          if $exception; then
+            echo "CHECK_HLS_WORKS=0" >> "$GITHUB_OUTPUT"
+            echo "All changes are trival, skipping rest of checks..."
+          else
+            echo "CHECK_HLS_WORKS=1" >> "$GITHUB_OUTPUT"
+            echo "Some changes are non-trivial. We need to do the checks!"
+          fi
       - uses: cachix/install-nix-action@v30
+        if: steps.check_trivial_changes.outputs.CHECK_HLS_WORKS > 0
         with:
           nix_path: nixpkgs=channel:nixos-unstable
           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/
 
       - uses: rrbutani/use-nix-shell-action@v1
+        if: steps.check_trivial_changes.outputs.CHECK_HLS_WORKS > 0
 
       - name: Update dependencies
+        if: steps.check_trivial_changes.outputs.CHECK_HLS_WORKS > 0
         run: cabal update; cabal freeze
 
       - name: Obtain GHC version
+        if: steps.check_trivial_changes.outputs.CHECK_HLS_WORKS > 0
         run: |
           echo "VERSION=$(ghc --numeric-version)" >> "$GITHUB_OUTPUT"
         id: ghc
 
       - name: HLS caching
+        if: steps.check_trivial_changes.outputs.CHECK_HLS_WORKS > 0
         uses: actions/cache@v4
         with:
           path: |
@@ -52,4 +108,5 @@ jobs:
             hls-cache-${{ env.HLS_CACHE_VERSION }}-${{ runner.os }}-${{ steps.ghc.outputs.VERSION }}-${{ hashFiles('**/cabal.project.freeze') }}-
 
       - name: Test HLS works
+        if: steps.check_trivial_changes.outputs.CHECK_HLS_WORKS > 0
         run: haskell-language-server