Implement a codemod for syntax changes we can detect

[johno]

• <https://mdxjs.com> => [https://mdxjs.com](https://mdxjs.com)
• <3 => <3

[wooorm]

This could be done by parsing with the old remark-mdx, and compiling with the new one, although the old JSX tags would need to be parsed to the new one (or ignored and injected raw, which will then result in errors that people will manually fix, but incorrect JSX is unlikely as if it doesn’t work now then it probably didn’t work already)

var before = unified()
  .use(remarkParse)
  .use(remarkOldMdx)

var after = unified()
  .use(remarkStringify)
  .use(remarkNewMdx)
  .use(remarkNewMdxJs)

var oldTree = before.runSync(before.parse(doc))

var newTree = changeOldToNewTree(oldTree)

var output = after.stringify(after.runSync(newTree))

Finally, unified will reformat code. So alternatively, you could use the old tree to inspect if those constructs were used, and then use their positional information to replace in the document.

[wooorm]

For my last paragraph, magic-string would help with that! https://github.com/Rich-Harris/magic-string

[wooorm]

I opted not to. I’ve thought about how it’d work a couple times but it’s complex. It’d be a lot of work and wouldn’t work in some cases.
From now on though, as we do have an AST starting last RC, that includes tags and elements and expressions and all that, we can start supporting codemods for future changes.

[karlhorky]

Is there currently a codemod to convert MDX v1 code to v2? We have a lot of content written in MDX v1 and would like to avoid rewriting manually by hand if possible.

I saw https://github.com/mdx-js/codemods, but it seems a bit old...

[wooorm]

Last comment still holds. A proper code mod is really complex.
I’m not sure how much data you have.
I recommend using remark with remark-mdx on your docs folder:

remark -u remark-mdx docs/

It’ll throw errors with pretty descriptive messages. With that, and some regex kung-fu, you should be able to get far.

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Hashicorp had something somewhat working for this, but it was still missing things. Let me know if you‘re interested in getting your hands dirty and improving that project and I’ll ping folks!