How should I make mdx.sync omit Frontmatter in its output using remark-frontmatter?

[ajaypillay]

Hi, so I'm trying to figure out how to use remark-frontmatter. Currently my MDX files are compiled as such:

const content = inputFile.getContentsAsString().trim()
const jsx = mdx.sync(content, {
  remarkPlugins: [[remarkFrontmatter, { type: "yaml", marker: "+" }], remarkMath, [remarkPrism, { autolinker: true }], remarkEmbedImages], rehypePlugins: [rehypeKatex, rehypeSlug, rehypeAutolinkHeadings]
})
const jsxComplete = `
import React from 'react'
import { mdx } from '@mdx-js/react'
${jsx}
  `
const output = this.babelCompiler.processOneFileForTarget(inputFile, jsxComplete)

const source = output.data
const sourceMap = JSON.stringify(output.sourceMap)
return { source, sourceMap }

However, with the following at the top of my MDX files:

+++
title = "Test title"
+++

It still gets rendered with the Frontmatter intact. From what I understand, this plugin should be generating a JSON object with the extracted Frontmatter. I'm not seeing this anywhere, and the Frontmatter is still intact in jsx.

How exactly should I be doing this? Thanks.

[ChristianMurphy]

Start by adjusting the frontmatter marker settings, you have - set as the marker

[remarkFrontmatter, { type: "yaml", marker: "-" }]

but in the mdx document, + is used

+++
title = "Test title"
+++

frontmatter will match to the marker type you set it to use, here you set it to parse - not +.

[ajaypillay]

Oh sorry, that's a mistake as I was experimenting around and copied the wrong thing over. It's the same result with no errors thrown when I use + as my marker, I tried to use both - and + as the markers, when I use - a <hr/> is rendered as it's parsed as a horizontal line.

[ChristianMurphy]

What versions of remark-frontmatter and mdx are you using?

MDX 1.x works with remark-frontmatter <=2.x
MDX 2.x works with remark-frontmatter >= 3.0

[ajaypillay]

Ah, it was a versioning issue again. mdx is at 1.6.22 and I was using remark-frontmatter at 3.0.0. I bumped it down to 2.0.0 and now it works, thank you.