Math equations do not work when imported from another file

[ArthurFlag]

Have you read the Contributing Guidelines on issues?

• [X] I have read the Contributing Guidelines on issues.

Prerequisites

• [X] I'm using the latest version of Docusaurus.
• [X] I have tried the npm run clear or yarn clear command.
• [X] I have tried rm -rf node_modules yarn.lock package-lock.json and re-installing packages.
• [X] I have tried creating a repro with https://new.docusaurus.io.
• [X] I have read the console error message carefully (if applicable).

Description

Math equations do not get parsed/styled as they should when they are imported from another md file.

Reproducible demo

https://codesandbox.io/p/devbox/crimson-breeze-23sstv?file=%2Fdocs%2Fintro.md%3A10%2C1

Steps to reproduce

1. Create a md file in the static folder.
2. Add a math equation in it.

   ## some title
   
   some text
   
   $$ 
   2 + 4
   $$
   

3. Import that file in a docs file.

---
sidebar_position: 1
---

# Tutorial Intro

$$
{MATH} + 4
$$


import Page from "@site/static/math.md"

<Page/>

Expected behavior

I expect to see 2 equations:

• the one from my docs file.
• the one from my imported file.

Actual behavior

Only one equation is shown correctly:

Your environment

• Public source code: https://codesandbox.io/p/devbox/crimson-breeze-23sstv?file=%2Fdocs%2Fintro.md%3A10%2C1
• Public site URL:
• Docusaurus version used: 3.1.1
• Environment name and version (e.g. Chrome 89, Node.js 16.4):
• Operating system and version (e.g. Ubuntu 20.04.2 LTS):

Self-service

• [ ] I'd be willing to fix this bug myself.

[slorber]

Your codesandbox is private so I can't access it.

Currently, remark plugins (including the math plugin) are plugin-specific. They only apply to the folder of the plugin you configured them in (./docs for example).

They do not apply to the static folder, for which we do register a "fallback mdx loader" for convenience, but we don't offer a way for now to provide custom remark plugins. So it's not really easy/possible to register remark-math for mdx files outside of ./docs ./versioned_docs, ./blog or ./src/pages

Although technically you could use the plugin configureWebpack lifecycle hook to add a custom mdx-loader for that path and use custom remark plugins. But it's not super straightforward to do so, nor robust or documented.

The solution is likely to have a global siteConfig.markdown.remarkPlugins option

[LuudJanssen]

I'm running into this issue as well, where I have a monorepo and I want to reuse all of the README.md files of the packages throughout the repository, but still have them be processed with plugins.

The siteConfig.markdown.remarkPlugins option sounds like a great idea, and a nice addition to the configuration overall.

[ArthurFlag]

Sorry for the permission issue, fixed it now.

Thanks for the info about plugins work and are configured. I'll change things around but I also like your idea about a global option 👍

[Josh-Cena]

At the moment this is working as intended. The global option is tracked in https://github.com/facebook/docusaurus/issues/5999.