An error occurs with certain text when using remarkMath and rehypeKatex.

[devleejb]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and couldn’t find anything (or linked relevant results below)

Affected packages and versions

react-markdown:9.0.1

Link to runnable example

No response

Steps to reproduce

1. Implement the following code. (Node 18, npm 10)

   <Markdown
       remarkPlugins={[remarkMath]}
       rehypePlugins={[rehypeKatex]}
   >
     {`$\\begin\\ca$`}
   </Markdown>

2. Run the code.
3. Check for any errors.

Expected behavior

It should render the markdown text correctly.

Actual behavior

�Following error occurs.

Runtime

Other (please specify in steps to reproduce)

Package manager

Other (please specify in steps to reproduce)

OS

macOS

Build and bundle tools

Vite

[wooorm]

This looks like a KaTeX problem, why not raise it with KaTeX? Why raise it here? Do you think there is something to change here?

[devleejb]

@wooorm
At first, I thought that it is a KaTex problem. But, when I run the following code, it runs correctly.

const file = await unified()
  .use(remarkParse)
  .use(remarkMath)
  .use(remarkRehype)
  .use(rehypeKatex)
  .use(rehypeStringify)
  .process(`$\\begin\\ca$`)

[wooorm]

Cannot reproduce:

import {unified} from 'unified'
import remarkParse from 'remark-parse'
import remarkMath from 'remark-math'
import remarkRehype from 'remark-rehype'
import rehypeKatex from 'rehype-katex'
import rehypeStringify from 'rehype-stringify'

const file = await unified()
  .use(remarkParse)
  .use(remarkMath)
  .use(remarkRehype)
  .use(rehypeKatex)
  .use(rehypeStringify)
  .process(`$\\begin\\ca$`)

console.log(String(file))

file:///Users/tilde/Projects/oss/react-markdown/node_modules/katex/dist/katex.mjs:7482
    throw new Error("Expected node of type " + type + ", but got " + (node ? "node of type " + node.type : String(node)));
          ^

Error: Expected node of type textord, but got node of type color
    at assertNodeType (file:///Users/tilde/Projects/oss/react-markdown/node_modules/katex/dist/katex.mjs:7482:11)
    at Object.handler (file:///Users/tilde/Projects/oss/react-markdown/node_modules/katex/dist/katex.mjs:11491:18)
    at Parser.callFunction (file:///Users/tilde/Projects/oss/react-markdown/node_modules/katex/dist/katex.mjs:17637:19)
    at Parser.parseFunction (file:///Users/tilde/Projects/oss/react-markdown/node_modules/katex/dist/katex.mjs:17620:17)
    at Parser.parseGroup (file:///Users/tilde/Projects/oss/react-markdown/node_modules/katex/dist/katex.mjs:18012:21)
    at Parser.parseAtom (file:///Users/tilde/Projects/oss/react-markdown/node_modules/katex/dist/katex.mjs:17450:21)
    at Parser.parseExpression (file:///Users/tilde/Projects/oss/react-markdown/node_modules/katex/dist/katex.mjs:17312:23)
    at Parser.parse (file:///Users/tilde/Projects/oss/react-markdown/node_modules/katex/dist/katex.mjs:17244:24)
    at parseTree (file:///Users/tilde/Projects/oss/react-markdown/node_modules/katex/dist/katex.mjs:18247:21)
    at renderToDomTree (file:///Users/tilde/Projects/oss/react-markdown/node_modules/katex/dist/katex.mjs:18337:16)

As in: there’s definitely a KaTeX error, when using the latest dependencies otherwise.

Now, rehype-katex also has a problem. It should catch that error.

[devleejb]

@wooorm
Okay. Sorry, I'll check it again and raise it in KaTeX.

[wooorm]

OK, if you believe that math input to be valid for KaTeX.

I’ll also work on a fix in rehype-katex to swallow that error and display the raw input instead of crashing.

[wooorm]

In rehype-katex I am getting this error btw:

ParseError: KaTeX parse error: Undefined control sequence: \ca at position 7: \begin\̲c̲a̲
    at new ParseError (file:///Users/tilde/Projects/oss/remark-math/node_modules/katex/dist/katex.mjs:147:16)
    at Parser.parseGroup (file:///Users/tilde/Projects/oss/remark-math/node_modules/katex/dist/katex.mjs:18016:17)
    at Parser.parseAtom (file:///Users/tilde/Projects/oss/remark-math/node_modules/katex/dist/katex.mjs:17450:21)
    at Parser.parseExpression (file:///Users/tilde/Projects/oss/remark-math/node_modules/katex/dist/katex.mjs:17312:23)
    at Parser.parseArgumentGroup (file:///Users/tilde/Projects/oss/remark-math/node_modules/katex/dist/katex.mjs:17955:27)
    at Parser.parseGroupOfType (file:///Users/tilde/Projects/oss/remark-math/node_modules/katex/dist/katex.mjs:17705:21)
    at Parser.parseArguments (file:///Users/tilde/Projects/oss/remark-math/node_modules/katex/dist/katex.mjs:17670:22)
    at Parser.parseFunction (file:///Users/tilde/Projects/oss/remark-math/node_modules/katex/dist/katex.mjs:17619:14)
    at Parser.parseGroup (file:///Users/tilde/Projects/oss/remark-math/node_modules/katex/dist/katex.mjs:18012:21)
    at Parser.parseAtom (file:///Users/tilde/Projects/oss/remark-math/node_modules/katex/dist/katex.mjs:17450:21) {
  position: 6,
  length: 3,
  rawMessage: 'Undefined control sequence: \\ca'
}

So could be that that is the root problem