Make auto-label semver action fail if there are no patchfiles

[ForestEckhardt]

The function of this task is to check if it can auto-label anything with a semver label and return the label if it can. It is run after a check to see if there are any semver labels already set and if there are not this action will run. I think that it would then follow logically that this action should fail if there are no labels to add meaning the whole check task will fail.

Checklist

• [x] I have viewed, signed, and submitted the Contributor License Agreement.
• [ ] I have linked issue(s) that this PR should close using keywords or the Github UI (See docs)
• [ ] I have added an integration test, if necessary.
• [x] I have reviewed the styleguide for guidance on my code quality.
• [x] I'm happy with the commit history on this PR (I have rebased/squashed as needed).

[robdimsdale]

For posterity:

Currently the way we use this action is as follows (edited for brevity):

jobs:
  autolabel:
    steps:
    - name: Check Minimal Semver Labels
      uses: mheap/github-action-required-labels@v3
      with:
        count: 1
        labels: semver:major, semver:minor, semver:patch
        mode: exactly

    - name: Auto-label Semver
      if: ${{ failure() }}
      uses: paketo-buildpacks/github-config/actions/pull-request/auto-semver-label@main

e.g. this workflow

So the logic here is:

• check for existing labels
  • if existing labels - exit with success
  • if no existing labels - exit with failure
• If the job fails, try to add a label. Don't worry about whether this succeeds or not

This successfully adds labels (where it can) if there weren't any, but in this case the job is always reported as failing. This is very noisy and misleading.

I think it's better to have a structure that looks more like the following:

jobs:
  autolabel:
    steps:
    - name: Check Minimal Semver Labels
      id: check
      uses: mheap/github-action-required-labels@v5
      with:
        count: 1
        labels: semver:major, semver:minor, semver:patch
        mode: exactly
        exit_type: success

    - name: Auto-label Semver
      if: ${{ steps.check.outputs.status == 'failure' }}
      uses: paketo-buildpacks/github-config/actions/pull-request/auto-semver-label@main

This structure has the following logic:

• check for existing labels
  • if existing labels - exit with success
  • if no existing labels - record that fact and continue to the next step
• If there were no labels, try to add a label. Fail the job if we can't add labels

However, that last point in bold requires a change to the action, which is this PR

[sophiewigmore]

@ForestEckhardt @robdimsdale can you explain a bit more about why we want this step to noisily fail?

[sophiewigmore]

I get the first bit, where we don't want the semver label check to fail, but still wondering why we need the next job to fail the job if we can't add labels? Won't that happen a lot, since not every file is in the patch file list?

[ForestEckhardt]

Yes it will fail but only if there is not an existing semver label and it could not apply one which is the eact scenario it should fail in because that means that the PR needs to be manually labeled. If it does not fail in this scenario the PR will pass all checks without a valid smver label attached to it.

[sophiewigmore]

Ah yea the bit about not wanting the PR checks to pass is what I wasn't considering - thank you both for explaining!