Gatsby MDX reports invalid AST

[davwheat]

Preliminary Checks

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Description

When using the MDX plugin and programmatically generating pages, I get an error about invalid AST which renders MDX-generated pages unusable.

Reproduction Link

https://github.com/davwheat/gatsby-issue-reproduction-3

MDX content:

---
title: "Test?"
description: Test!
path: test
created_at: 2022-04-19T16:00Z
---

EE's innovation in RAN has found it at the bleeding edge of new 5G deployments in the UK, being the first operator to deploy 5G NR carrier
aggregation in a relatively widespread manner across many parts of the UK capital, London.

Steps to Reproduce

1. Clone repo
2. Run yarn develop

Expected Result

The pages to be built in SSG successfully.

Actual Result

SSG fails due to "invalid AST".

Environment

$ /home/david/gatsby-mdx-test/node_modules/.bin/gatsby info --clipboard

  System:
    OS: Linux 5.15 Ubuntu 22.04.1 LTS 22.04.1 LTS (Jammy Jellyfish)
    CPU: (6) x64 12th Gen Intel(R) Core(TM) i7-12700H
    Shell: 5.1.16 - /bin/bash
  Binaries:
    Node: 18.13.0 - /tmp/yarn--1674431542087-0.36198500852724314/node
    Yarn: 1.22.19 - /tmp/yarn--1674431542087-0.36198500852724314/yarn
    npm: 8.19.3 - /usr/bin/npm
  npmPackages:
    gatsby: ^5.4.2 => 5.4.2
    gatsby-plugin-mdx: ^5.4.0 => 5.4.0
    gatsby-source-filesystem: ^5.4.0 => 5.4.0


Done in 2.99s.

Config Flags

Happens with DEV SSR on (in project) and off (in reproduction).

[davwheat]

On further inspection this suggestions that Typescript is not supported with MDX? The line and position for the error shows it to be L11 C35, which is export interface IMdxPageContext {.

I don't think this is mentioned in the Gatsby docs at all.

[PaulieScanlon]

Hey @davwheat i had a look at your test.mdx file. You have a couple of unescaped characters that MDX2 will throw on. The MDX error is usually quite misleading and points to a line in the file that isn't the actual problem.

I wrote this post a while ago. Maybe try a test by removing any "special" characters. I've linked to the breaking changes in the MDX docs in the post.

https://paulie.dev/posts/2022/08/mdx-2-breaking-changes-and-gatsby-plugin-mdx-v4/

[davwheat]

Thanks for your suggestion!

I hadn't realised this, and have changed my test.mdx file accordingly to contain only a minimal example, which still results in the same error for me, unfortunately.