unist-util-visit: Cannot use 'in' operator to search for 'children' in undefined

[mark-wiemer]

Astro Info

Astro                    v5.12.9
Node                     v22.17.1
System                   Windows (x64)
Package Manager          npm
Output                   static
Adapter                  none
Integrations             @astrojs/starlight

If this issue only occurs in one browser, which browser is a problem?

No response

Describe the Bug

1. Created a new project with npm create astro@latest -- --template starlight

2. Added unist-util-visit via npm i unist-util-visit

3. Updated dependencies to latest:

   "dependencies": {
     "@astrojs/starlight": "^0.35.2",
     "astro": "^5.12.9",
     "sharp": "^0.34.3",
     "unist-util-visit": "^5.0.0"
   }
   

4. Added custom rewriteLink func to remarkPlugins:

    const rewriteLinks = (base) => {
      return (tree) => {
        visit(tree, "link", (node) => {
          if (node.url.startsWith("./") || node.url.startsWith("../")) {
            // Remove leading ./ or ../ and prepend base
            node.url = base + "/" + node.url.replace(/^(\.\/|\.\.\/)+/, "");
          }
        });
      };
    };
    const base = "/next";
    // ...
    export default defineConfig({
      // ...
      markdown: {
        remarkPlugins: [rewriteLinks(base)],
      },
    })

5. Ran npm run dev

6. Opened page and got an error:

MDXError
An error occurred.
Cannot use 'in' operator to search for 'children' in undefined

Some verbose logs:

  vite:transform 2.97ms /.astro/content-modules.mjs +16ms
  vite:load 1.60ms [fs] /src/content/docs/index.mdx?astroPropagatedAssets +6ms       
  vite:load 0.49ms [fs] src/content/docs/index.mdx +1ms
  astro:vite Error when evaluating SSR module C:/Users/markw/my-stuff/mocha-stuff/hello-astro/src/content/docs/index.mdx: Cannot use 'in' operator to search for 'children' in undefined
  astro:vite   Plugin: @mdx-js/rollup
  astro:vite   File: C:/Users/markw/my-stuff/mocha-stuff/hello-astro/src/content/docs/index.mdx:undefined:undefined
  astro:vite       at TransformPluginContext.transform (file:///C:/Users/markw/my-stuff/mocha-stuff/hello-astro/node_modules/@astrojs/mdx/dist/vite-plugin-mdx.js:62:15)  
  astro:vite       at EnvironmentPluginContainer.transform (file:///C:/Users/markw/my-stuff/mocha-stuff/hello-astro/node_modules/vite/dist/node/chunks/dep-DBxKXgDP.js:42295:19)
  astro:vite       at async loadAndTransform (file:///C:/Users/markw/my-stuff/mocha-stuff/hello-astro/node_modules/vite/dist/node/chunks/dep-DBxKXgDP.js:35735:27) +0ms   
17:54:47 [ERROR] Cannot use 'in' operator to search for 'children' in undefined      
  Location:
    C:/Users/markw/my-stuff/mocha-stuff/hello-astro/src/content/docs/index.mdx:0:0   
  Stack trace:
    at TransformPluginContext.transform (file:///C:/Users/markw/my-stuff/mocha-stuff/hello-astro/node_modules/@astrojs/mdx/dist/vite-plugin-mdx.js:62:15)
    at async loadAndTransform (file:///C:/Users/markw/my-stuff/mocha-stuff/hello-astro/node_modules/vite/dist/node/chunks/dep-DBxKXgDP.js:35735:27)
  vite:time 1997.77ms / +0ms
  vite:resolve 0.39ms /@vite/client -> C:/Users/markw/my-stuff/mocha-stuff/hello-astro/node_modules/vite/dist/client/client.mjs +64ms
  vite:load 1.43ms [fs] /@vite/client +61ms
  vite:resolve 0.12ms @vite/env -> C:/Users/markw/my-stuff/mocha-stuff/hello-astro/node_modules/vite/dist/client/env.mjs +17ms
  vite:import-analysis 1.24ms [1 imports rewritten] node_modules/vite/dist/client/client.mjs +81ms
  vite:transform 15.62ms /@vite/client +81ms
  vite:time 23.17ms /@vite/client +70ms
  vite:load 6.94ms [fs] /node_modules/vite/dist/client/env.mjs +23ms
  vite:import-analysis 0.04ms [no imports] node_modules/vite/dist/client/env.mjs +7ms
  vite:transform 0.60ms /node_modules/vite/dist/client/env.mjs +8ms
  vite:cache [304] /node_modules/vite/dist/client/env.mjs +0ms
  vite:time 0.32ms /node_modules/vite/dist/client/env.mjs +11ms

What's the expected result?

Page should load with any relative URLs rewritten. I know rewriteLinks isn't perfect but it shouldn't cause an MDXError

Link to Minimal Reproducible Example

https://github.com/mark-wiemer/hello-astro/tree/mocha-issue-5415

Participation

• I am willing to submit a pull request for this issue.

[matthewp]

Does this work in remark outside of Astro?

[mark-wiemer]

I haven't tried, I'm very new to both Astro and remark, I'm not sure how to attempt to repro this :(

[ematipico]

Can you try to reduce the reproduction even further: remove starlight and content collections, and have only one MDX page. And see if you still have the issue