How to create programatic properties via plugin

[motleydev]

• mdx-bundler version: latest
• node version: 17.x.x
• npm version:

Relevant code or config

rehypePlugins: [rehypeSlug, rehypeAutolinkHeadings, searchMeta],

What you did / Problem description:
I've written a custom plugin that extracts unique words from paragraph tags and I'd like to pass it programmatically to the output. I can add it to the vfile's data prop, but I'm not sure where this bundler is trying to pass content through to the final shape of the flattened _raw, frontmatter fields and code output.

Is there plugin I could reference for programmatic frontmatter?

[stefanprobst]

it is not possible to pass vfile.data from a unified pipeline with @mdx-js/esbuild (see mdx-js/mdx#2055). however, you could use estree-util-value-to-estree to create a named export for the data (see e.g. https://github.com/stefanprobst/rehype-extract-toc/blob/main/src/mdx.js).