hls.yml

name: "Haskell Language Server works"
on:
  merge_group:
  pull_request:
  push:
    branches:
      - master

permissions:
  contents: read

jobs:

  test-hls-works:
    env:
      # Modify this value to "invalidate" the cache.
      HLS_CACHE_VERSION: "2024-06-25"

    runs-on: ubuntu-latest
    timeout-minutes: 60
    steps:
      - uses: actions/checkout@v6

      - name: Check if changes were trivial
        id: check_trivial_changes
        run: |
          if [ -z "${{ github.base_ref }}" ]; then
            exception=false
          else
            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
          fi

          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@v31
        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: |
            /home/runner/.cache/hie-bios
            /home/runner/.cache/ghcide
            /home/runner/.local/state/cabal
            .ghc.environment.x86_64-linux-*
            dist-newstyle
          key: hls-cache-${{ env.HLS_CACHE_VERSION }}-${{ runner.os }}-${{ steps.ghc.outputs.VERSION }}-${{ hashFiles('**/cabal.project.freeze') }}-${{ hashFiles('**/*.cabal', '**/cabal.project') }}
          restore-keys: |
            hls-cache-${{ 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