Code quality job always generates `No changes to code quality` message in the MR

Summary

This bug happens on GitLab.com and GitLab EE 12.1

When adding new code quality violation, there is no update in the Merge Request panel. I get always this message: No changes to code quality

Steps to reproduce

I create a new project with a .gitlab-ci.yml with this content: (I did it on GitLab.com and GitLab Self-Hosted 12.1.0-ee)

stages:
  - check_quality

code_quality:
  stage: check_quality
  artifacts:
    reports:
      codequality: gl-code-quality-report.json
  script: |
    cat >> gl-code-quality-report.json <<EOL
    [
      {
        "description": "👋 there is a 🐛($CI_COMMIT_SHA)",
        "fingerprint": "$CI_COMMIT_SHA",
        "location": {
          "path": "lib/index.js",
          "lines": {
            "begin": 42
          }
        }
      }
    ]
    EOL
    cat gl-code-quality-report.json

• First I commit on master branch
• Then I create a MR (a new gl-code-quality-report.json is generated)

And the message is:

With a former version of GitLab

I did the same steps on GitLab Self-Hosted 12.0.2-ee and I get this message in the MR panel:

Example Project

• Project: https://gitlab.com/tanuki-workshops/sandbox/testing-code-quality
• Merge Request sample: https://gitlab.com/tanuki-workshops/sandbox/testing-code-quality/merge_requests/2

What is the current bug behavior?

The code_quality job report is not reported in the MR panel (as if there was never a code quality violation)

What is the expected correct behavior?

Quality improvements and degradations should be displayed in the MR panel

Relevant logs and/or screenshots

See the Steps to reproduce part