pr-closure-diff.yml

name: NixOS closure diffs

on:
  pull_request_target:
    branches:
      - main

jobs:
  closure-diffs-comment:
    runs-on: ubuntu-latest
    permissions:
      pull-requests: write
    steps:
      - name: Find potentially existing comment
        uses: peter-evans/find-comment@v3
        id: find-comment
        with:
          issue-number: ${{ github.event.pull_request.number }}
          comment-author: 'github-actions[bot]'
          body-includes: NixOS closure diffs
      - name: Set in-progress message
        uses: peter-evans/create-or-update-comment@v4
        id: create-or-update-comment
        with:
          comment-id: ${{ steps.find-comment.outputs.comment-id }}
          issue-number: ${{ github.event.pull_request.number }}
          body: |
            # NixOS closure diffs

            Just a moment...
          edit-mode: replace
      - uses: actions/checkout@v4
        with:
          path: before
          ref: ${{ github.event.pull_request.base.ref }}
      - uses: actions/checkout@v4
        with:
          path: after
          ref: ${{ github.event.pull_request.head.ref }}
      - uses: cachix/install-nix-action@v27
        with:
          extra_nix_config: |
            accept-flake-config = true
            always-allow-substitutes = true
      - run: |
          nix flake show --refresh --all-systems --json ./before |
            jq --raw-output '
              path(.. | select(.type? == "nixos-configuration")) | .[1]
            ' |
            sort > systems-before
          cat systems-before
      - run: |
          nix flake show --refresh --all-systems --json ./after |
            jq --raw-output '
              path(.. | select(.type? == "nixos-configuration")) | .[1]
            ' |
            sort > systems-after
          cat systems-after
      - run: printf '# NixOS closure diffs\n\n' > message-body
      - run: |
          printf 'Removed systems:\n```\n' >> message-body
          comm -23 systems-before systems-after >> message-body
          printf '```\n\n' >> message-body
      - run: |
          printf 'Added systems:\n```\n' >> message-body
          comm -13 systems-before systems-after >> message-body
          printf '```\n\n' >> message-body
      - run: |
          printf 'Changed systems:\n\n' >> message-body
          comm -12 systems-before systems-after |
            while read -r system; do
              printf '<details>\n<summary>%s</summary>\n\n```\n' "$system" >> message-body
              # The sed call filters out the control characters that diff-closures emits.
              # See: https://github.com/NixOS/nix/issues/4626
              nix store diff-closures --derivation \
                "./before#nixosConfigurations.\"$system\".config.system.build.toplevel" \
                "./after#nixosConfigurations.\"$system\".config.system.build.toplevel" |
                sed 's/\x1b\[[0-9;]*m//g' >> message-body
              printf '```\n</details>\n\n' >> message-body
            done
      - name: Set finished message
        uses: peter-evans/create-or-update-comment@v4
        with:
          comment-id: ${{ steps.create-or-update-comment.outputs.comment-id }}
          issue-number: ${{ github.event.pull_request.number }}
          body-path: message-body
          edit-mode: replace
      - name: Set failure message
        if: ${{ failure() }}
        uses: peter-evans/create-or-update-comment@v4
        with:
          comment-id: ${{ steps.create-or-update-comment.outputs.comment-id }}
          issue-number: ${{ github.event.pull_request.number }}
          body: |
            # NixOS closure diffs

            Something went wrong. Please check the action log.
          edit-mode: replace