How to reuse "Get changed files" in GitHub actions

[yin1999]

It's been a while since we migrated from tj-actions/changed-files to pure GitHub API calls to get changed files in PR (see mdn/translated-content#8952, mdn/content#21305...). And it works well and much more fast.

But it seems that we have made a lot copy of this part.

To improve maintainability, we'd better to make some changes to reuse this part, as mentioned by @bsmth and @nschonni.

After reading the documation. We may have two solutions:

reusable workflow

We could create reusable workflow in workflow repo. And then we could reuse this like:

jobs:
  get-changed-files:
    uses: mdn/workflows/.github/workflows/list-changed-files.yml@main
    with:
      target-repo: "mdn/translated-content"
      paths: "^files/zh-cn/"
    secrets:
      token: ${{ secrets.GITHUB_TOKEN }}

  some-job:
    runs-on: ubuntu-latest
    needs: get-changed-files
    if: ${{ needs.get-changed-files.outputs.files }}
    steps:
      # do sth.

This is a bit easy for us to create the workflow, but might be a bit difficult to use (with separated jobs).

custom action

We could create a custom action, this might be so of difficult (comparing with the reusable workflow). But we could use it like:

  steps:
    - name: Get changed files
      id: get-changed-files
      uses: mdn/list-changed-files@main
      with:
        # only list these paths
        paths: "^files/zh-cn/"
      env:
        token: ${{ secrets.GITHUB_TOKEN }}
    - name: some-step
      if: ${{ steps.get-changed-files.outputs.files }}
      run: |
        # do sth.

could be as a step within a job

We'd better to make an appropriate decision on this :)

[bsmth]

Thanks a lot for summarizing @yin1999 and getting the discussion going! 😄

This is a bit easy for us to create the workflow, but might be a bit difficult to use.

What are the difficulties of this approach? If needs: get-changed-files means it's a prerequisite step, that should be okay for us to use, is that right or what else do you see as the challenge/tricky part?

[yin1999]

What are the difficulties of this approach?

We have to create separated job for it, it's still ok for us (I think, just slightly more complicated than custom action).

If needs: get-changed-files means it's a prerequisite step

Yes, if we add this field, this job will delay until the needed job is finished.

[yin1999]

Tested as following:

• reusable workflow: ci(pr-test): use reusable workflow to get changed files yin1999/translated-content#15
• custom action: Test action yin1999/translated-content#16

The custom action is faster than reusable workflow (required to create a new VM to run the separated job). But we need to maintains a new repo.

[bsmth]

Thanks for the investigation (job example). If we need to, I think we can add it to a new repo under the MDN GitHub org. It would be good to get another opinion from the team beforehand.