The behaviour of the merge request pipelines is unclear

Description

The documentation about "Pipelines for merge requests" seems to miss a few details which cause me some confusion.

Steps to reproduce

Running a job for a merge request is quite clear: add merge_requests to the "only" array.

The problem is when gitlab-ci.yml has many jobs which must run to validate any push, including a merge request.

Suppose that we have the following stages:

stages:
    - pre-flight
    - quality
    - test
    - build
    - documentation
    - deploy

pre-flight

Contains only one job which builds a dependencies cache using a "push" policy.

quality

Contains several jobs:

  • One runs some static code analysis on the changed code ("merge_request" only, since that's the only way to get the source and target branch which are required to build a proper diff).
  • A few other jobs run full static code analysis: only "master" and "develop" (not sure if I must specify "except: merge_requests"

Test

All sort of automated tests.

"merge_requests" is not specified in "except/only".

Build, Documentation, Deploy

I think their purpose is pretty clear.

"merge_requests" is not specified in "except/only".

Actual result

When I create a merge request or push changes in a branch which has a merge request, I get two pipelines, as described in the docs.

The docs also say that the detached pipeline has the precedence, but it seems that if this pipeline pass and the other one fails, the merge request will show no issues and will allow merging despite the "Pipelines must succeed" setting being checked.

Expected result

The merge request must show the failed pipeline below the description and prevent merging if any pipeline (attached or not) fails.

Further details

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