[hassamaslamkhan]

Description

Fixes #4123.

This PR fixes a bug in dcc.Markdown where escaped dollar signs (\$) inside inline math expressions are incorrectly interpreted by the Markdown parser, causing MathJax rendering to fail.

The fix normalizes affected inline math expressions before Markdown parsing when mathjax=True, while preserving regular Markdown behavior, including links, HTML, code blocks, and ordinary dollar signs.

The changes include:

• A normalization utility for escaped dollar signs inside inline math.
• Integration of the utility into dcc.Markdown.
• Unit tests covering escaped dollar signs, multiple expressions, Markdown links, and code blocks.
• Browser regression tests verifying correct MathJax rendering.

Contributor Checklist

• This PR targets dev (bug fix).
• I have broken down my PR scope into the following TODO tasks:
  • Identify and reproduce the escaped-dollar parsing bug.
  • Implement normalization for affected inline math expressions.
  • Preserve existing Markdown behavior for links, HTML, and code blocks.
  • Add unit and integration regression tests.
  • Run tests and code-quality checks locally.
• I have run the tests locally and they passed.
  • JavaScript unit tests: 16 passed.
  • Markdown integration tests: 24 passed.
  • Pre-commit checks: ESLint, Prettier, Pylint, Flake8, and Black passed.
• I have added tests or extended existing tests to cover the bug fixed in this PR.

Test Evidence

Screenshots attached below demonstrate:

• Passing JavaScript unit tests.

• Passing Markdown integration tests.

• The original incorrect rendering before the fix.

Optionals

• I have added an entry in CHANGELOG.md (not included in this PR).
• Documentation or community follow-up (not required for this bug fix).

[sonarqubecloud]

Quality Gate passed

Issues
4 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[AnnMarieW]

It looks like this regression is caused by upgrading remark-math from v3 to v5.

In v5 escapes inside inline math expressions are not supported:

https://www.npmjs.com/package/remark-math/v/5.1.1

👉 Note: $math$ works similar to code. That means escapes don’t work inside math but you can use more dollars around the math instead: $$\raisebox{0.25em}{$\frac a b$}$$

Rather than creating our own markdown parser, it might be better to document this change.

[hassamaslamkhan]

Thanks for pointing this out @AnnMarieW . I hadn't realized this was an intentional change in remark-math v5.

I agree that documenting the behavior and the $$...$$ workaround would be simpler than maintaining custom parsing logic.

Would you prefer that I update this PR to focus on documentation, or close it and open a separate documentation PR?

[AnnMarieW]

@hassamaslamkhan I think it would be better to document the change, but let's wait for the maintainers to chime in.

Thanks for this PR and for offering to update the docs! The Dash docs are in a private repo, so that would have to be handled seperately.