Retry on mergeableState: UNKNOWN

How would you describe the issue?

We have a bot that updates dependencies once a week and it creates PRs in quick succession. Once the first PR is merged automatically, other PRs see mergeableState: UNKNOWN for a short while. Sometimes you can even observe that in the GitHub UI (the merge button is greyed out). We tried increasing the MAXIMUM_RETRIES, but it looks like the action is not retrying in this case.

How can we reproduce the issue?

I’m not sure if it can be reproduced manually without a bot. But basically create multiple PRs in quick succession. Here is an example run: https://github.com/moia-dev/scynamo/runs/1548816898#step:2:7

What are the expected results?

Retry on mergeableState: UNKNOWN according to the MAXIMUM_RETRIES setting.

What are the actual results?

AFAICT there were no retries in that run.

How much does it hurt?

Unfortunately this problem breaks our use case.

[desbo]

I’ve found that the UNKNOWN state is reported when the workflow run for a PR is in progress. As this action runs as part of a workflow run, it seems the PR will always be in this state when the automated merge is attempted. So rather than adding retry logic (which would only extend the runtime of the action), I think merges should still be attempted on state UNKNOWN.

If it helps anyone, I ended up making my own action to merge PRs that doesn’t have this issue: https://github.com/desbo/merge-pr-action

[xtazz]

@desbo I found a comment from GitHub:

The null value means that the mergeability of the pull request hasn’t been computed yet. Mergeability is computed on demand and in the background, so when you fetch a pull request for which the mergeability isn’t known – you get back a null value but also a job is kicked off to compute the mergeability. If you make another request, you should see a non-null value for the mergeable attribute.

So, sometimes it will be already calculated and present, but sometimes merge-me action will kick it off, that’s why I implemented retry logic for getting PR information.