Merge Request Pipeline Does Not Run When Merge Request is Created

Summary

Per the documentation regarding merge request pipelines, the MR pipeline should run when the MR is created. In my experience, however, the MR pipeline does not run until a new commit is pushed to that pipeline.

Steps to reproduce

  1. Add a job in the gitlab-ci.yml to run during merge_request_events as per the merge request pipeline documentation
  2. Create an issue in a project
  3. Click the "Create merge request" button and continue to create the merge request
  4. Notice on the page the user is directed to, in the space where the MR pipeline results would normally be displayed, the user is shown a text blurb explaining "This merge request contains no changes." as the reason why no pipeline results are displayed.

Example Project

I was able to reproduce the issue in a simple project here: https://gitlab.com/zcranfill/example-mr-pipeline/-/merge_requests/1

What is the current bug behavior?

Currently, even if jobs are assigned to run during merge_request_events, the MR pipeline does not run after the MR is created.

What is the expected correct behavior?

Expected behavior is for the jobs configured to run on merge_request_events to run after the MR is created.

Output of checks

This bug happens on GitLab.com.