CI_MERGE_REQUEST_REF_PATH points to non-existing reference (issue multiproject pipeline: fetch artifacts from merge request parent)

Hi,
We have a multiproject pipeline setup where child pipeline fetches artifacts from an upstream merge request pipeline. Ref to child pipeline is passed using CI_MERGE_REQUEST_REF_PATH variable. We simply use this method: Downstream pipelines | GitLab For a while everything worked fine until about month or two ago.

We are using self-hosted gitalb and now we are facing issue, where parent job is unable to find a upstream job from which it is suppose to get artifacts. I missed the moment when the problem started occurring, currently we are using 16.4.x version.

I made some investigation and I found that CI_MERGE_REQUEST_REF_PATH variable always has pattern: refs/merge_request//head
Where actual ref from upstream job sometimes has this structure: refs/merge_request//merge
Which mean that ref pointed by CI_MERGE_REQUEST_REF_PATH variable do not exist.

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I am not sure if it is some misconfiguration or this is a new issue in gitlab. I don’t see any changes regarding this functionality in manual.
The guide says to check forum first before reporting a bug, so here I am.

Also, someone else has a similar issue:

Thanks,
P

Is you parent pipeline normal Merge Request pipeline or by any chance someone switched it to Merge Result pipeline?

Yes, the checkbox was selected.
Settings → Merge Request → Merge Options → Enabled merged results pipelines. (should not be checked)

Most likely someone marked it by mistake, instead of enabling Merge checks Pipeline must succeed option.

After I disable it, a child pipelines finally is able to download artifacts from parent job.
Thanks a lot, I would never find it on myself