nixpkgs/.github/workflows/check-by-name.yml

# Checks pkgs/by-name (see pkgs/by-name/README.md)
# using the nixpkgs-check-by-name tool (see pkgs/test/nixpkgs-check-by-name)
name: Check pkgs/by-name

# The pre-built tool is fetched from a channel,
# making it work predictable on all PRs.
on:
  # Using pull_request_target instead of pull_request avoids having to approve first time contributors
  pull_request_target

# The tool doesn't need any permissions, it only outputs success or not based on the checkout
permissions: {}

jobs:
  check:
    # This is x86_64-linux, for which the tool is always prebuilt on the nixos-* channels,
    # as specified in nixos/release-combined.nix
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          # pull_request_target checks out the base branch by default
          ref: refs/pull/${{ github.event.pull_request.number }}/merge
      - uses: cachix/install-nix-action@v23
      - name: Determining channel to use for dependencies
        run: |
          echo "Determining which channel to use for PR base branch $GITHUB_BASE_REF"
          if [[ "$GITHUB_BASE_REF" =~ ^(release|staging|staging-next)-([0-9][0-9]\.[0-9][0-9])$ ]]; then
              # Use the release channel for all PRs to release-XX.YY, staging-XX.YY and staging-next-XX.YY
              channel=nixos-${BASH_REMATCH[2]}
              echo "PR is for a release branch, using release channel $channel"
          else
              # Use the nixos-unstable channel for all other PRs
              channel=nixos-unstable
              echo "PR is for a non-release branch, using unstable channel $channel"
          fi
          echo "channel=$channel" >> "$GITHUB_ENV"
      - name: Fetching latest version of channel
        run: |
          echo "Fetching latest version of channel $channel"
          # This is probably the easiest way to get Nix to output the path to a downloaded channel!
          nixpkgs=$(nix-instantiate --find-file nixpkgs -I nixpkgs=channel:"$channel")
          # This file only exists in channels
          rev=$(<"$nixpkgs"/.git-revision)
          echo "Channel $channel is at revision $rev"
          echo "nixpkgs=$nixpkgs" >> "$GITHUB_ENV"
          echo "rev=$rev" >> "$GITHUB_ENV"
      - name: Fetching pre-built nixpkgs-check-by-name from the channel
        run: |
          echo "Fetching pre-built nixpkgs-check-by-name from channel $channel at revision $rev"
          # Passing --max-jobs 0 makes sure that we won't build anything
          nix-build "$nixpkgs" -A tests.nixpkgs-check-by-name --max-jobs 0
      - name: Running nixpkgs-check-by-name
        run: result/bin/nixpkgs-check-by-name .