Action fails on PRs that are not backported

[mrgrain]

Using the example workflow in the readme, the action will fail when a PR is merged that does not have a backport label.
This is functionally correct, but causes confusion because the PR is now displayed with a ❌ (red x) next to it.

Do you have any suggestion how this could be avoided?
To me it feels like the Action should succeed because the PR does not have any relevant labels attached. But I am open to other suggestions.

Here is the error:

  "error": {
    "name": "BackportError",
    "errorContext": {
      "code": "no-branches-exception"
    }
  },
  "errorMessage": "There are no branches to backport to. Aborting."

Example Workflow run: https://github.com/aws/jsii-rosetta/actions/runs/9088130104/job/24977165701
Example PR: aws/jsii-rosetta#1359

[Achllle]

I agree with this. Also when the PR hasn't been merged, the check will fail, which is also not great if you're requiring all checks to have passed to allow merging. Adding a simple condition to not run in those cases should suffice, like is done in tibdex/backport.

[mrgrain]

I agree with this. Also when the PR hasn't been merged, the check will fail, which is also not great if you're requiring all checks to have passed to allow merging. Adding a simple condition to not run in those cases should suffice, like is done in tibdex/backport.

Thanks for the link! I've already had a condition:
https://github.com/aws/jsii-rosetta/blob/6d6cf286dee0d344c1a52c4c620e02f1093ed6b7/.github/workflows/backport.yml#L16

But using the github.event.label.name to check the name of the actual label is a good idea!

[Achllle]

Consider making a PR since it's a good default 😉 If not, I can make one

[mrgrain]

Finally had time to get back to this. Basically github.event.label.name doesn't work either. The issue is with the pull_request.closed event, when no matching labels are set. That always causes this action to fail.

Unfortunately there is no native to have a complex check for labels in GH Action expressions.

The simple case works:

contains(github.event.pull_request.labels.*.name, 'my-label')

But the other cases don't really

• my-label-a and my-label-b could be represented as a long chain of ORs (||), but that's annoying and will have a limit
• startsWith('my-label-') cannot be done.

tl;dr I have added a custom bash step to check labels

jobs:
  backport:
    name: Backport PR
    runs-on: ubuntu-latest
    permissions: {}
    if: github.event.pull_request.merged == true
    steps:
      - name: Check for backport labels
        id: check_labels
        run: |-
          labels='\${{ toJSON(github.event.pull_request.labels.*.name) }}'
          matched=$(echo $labels | jq '. | map(select(startswith("my-label-"))) | length')
          echo "matched=$matched"
          echo "matched=$matched" >> $GITHUB_OUTPUT
      - name: Backport Action
        if: fromJSON(steps.check_labels.outputs.matched) > 0
        uses: sqren/backport-github-action@v9.5.1

[Achllle]

@mrgrain I can confirm the fix in #133 works and didn't need any custom bash scripting, ICYMI.

[mrgrain]

@mrgrain I can confirm the fix in #133 works and didn't need any custom bash scripting, ICYMI.

What #133 changed is exactly what I had before and doesn't seem to fix it for us.

[jfagoagas]

@mrgrain I think there is a typo in your action file. There is a \ within the labels variable in the check_labels step.

This workaround works fine for me:

jobs:
  backport:
    name: Backport PR
    if: github.event.pull_request.merged == true && !(contains(github.event.pull_request.labels.*.name, 'backport'))
    runs-on: ubuntu-latest
    steps:
      # Workaround not to fail the workflow if the PR does not need a backport
      # https://github.com/sorenlouv/backport-github-action/issues/127#issuecomment-2258561266
      - name: Check for backport labels
        id: check_labels
        run: |-
          labels='${{ toJSON(github.event.pull_request.labels.*.name) }}'
          matched=$(echo "${labels}" | jq '. | map(select(startswith("backport-to-"))) | length')
          echo "matched=$matched"
          echo "matched=$matched" >> $GITHUB_OUTPUT

      - name: Backport Action
        if: fromJSON(steps.check_labels.outputs.matched) > 0
        uses: sorenlouv/backport-github-action@v9.5.1
        with:
          github_token: ${{ secrets.GITHUB_TOKEN }}
          auto_backport_label_prefix: backport-to-

      - name: Info log
        if: ${{ success() && fromJSON(steps.check_labels.outputs.matched) > 0 }} 
        run: cat ~/.backport/backport.info.log

      - name: Debug log
        if: ${{ failure() && fromJSON(steps.check_labels.outputs.matched) > 0 }}
        run: cat ~/.backport/backport.debug.log

Thank you!

[mrgrain]

Thanks for fixing the typo! Oh and I like the debug logging! @jfagoagas