Use MathJax instead of KaTeX

Release notes

LaTeX equations on markdown are properly rendered using MathJax

Problem to solve

GitLab currently uses KaTeX for rendering equations, which is lightweight but limited in features, leading to user frustration:

• #28601 (closed)
• #22590 (closed)
• #28150 (closed)
• #320956 (closed)
• #28601 (comment 589566028)

Proposal

Replace KaTeX with MathJax

• Add MathJax as dependency
• Configure to use $ for inline comments (this is disabled by default)
• Remove KaTeX related code

Intended users

Data Scientists, Machine Learning Engineers

User experience goal

The equations rendered on GitLab should match those if the notebook is opened at nbviewer.jupyter.org

For example:

Notebook: https://gitlab.com/quantumturbulence/rotating_quantum_turbulence_ufg/-/blob/branch/default/Figures/VortexLength.ipynb

Expected Output: https://nbviewer.jupyter.org/urls/gitlab.com/quantumturbulence/rotating_quantum_turbulence_ufg/-/raw/branch/default/Figures/VortexLength.ipynb#Analysis

Example:

KaTeX	MathJax

Further details

We could instead upgrade KaTeX to the latest version, which has more features but it still limited. The example above won't work for example since KaTeX doesn't support defining the command and then using it later

Usability of MathJax is a lot simpler, it works by simply adding the dependency, while KaTeX require some additional configurations.

Documentation

https://docs.gitlab.com/ee/user/markdown.html#math

Availability & Testing

This section needs to be retained and filled in during the workflow planning breakdown phase of this feature proposal, if not earlier.

What risks does this change pose to our availability? How might it affect the quality of the product? What additional test coverage or changes to tests will be needed? Will it require cross-browser testing?

Please list the test areas (unit, integration and end-to-end) that needs to be added or updated to ensure that this feature will work as intended. Please use the list below as guidance.

• Unit test changes
• Integration test changes
• End-to-end test change

See the test engineering planning process and reach out to your counterpart Software Engineer in Test for assistance: https://about.gitlab.com/handbook/engineering/quality/test-engineering/#test-planning