Accordion component not working in `.mdx` file. Unknown element `<[object Object]>` in collection.

[uptonking]

🐛 Bug Report

• I want to render Accordion component in a .mdx file.
• for example, write documentation for Accordion in .mdx

🤔 Expected Behavior

• Accordion component in hello.mdx should be rendered in the App.

😯 Current Behavior

• simplifed demo

  • https://github.com/examples-hub/issue-react-spectrum-mdx-collection-build-error

• if Accordion in hello.mdx is commented, rendering works.

  • Button can render in both index.js and hello.mdx.
  • Accordion can render in index.js, but not in hello.mdx.

• if Accordion in hello.mdx is not commented, build fails.

error message in the console:

module.js:241 
	Uncaught Error: Unknown element <[object Object]> in collection.
    at $f8429209754fda4b9142d514065f4$export$CollectionBuilder.getFullNode (module.js:241)
    at getFullNode.next (<anonymous>)
    at $f8429209754fda4b9142d514065f4$export$CollectionBuilder.iterateCollection (module.js:177)
    at iterateCollection.next (<anonymous>)
    at Object.[Symbol.iterator] (module.js:351)
    at Generator.next (<anonymous>)
    at new $afa6f708e32ecf7f97d9a58dfd59c$export$TreeCollection (module.js:51)

💁 Possible Solution

🔦 Context

💻 Code Sample

• https://github.com/examples-hub/issue-react-spectrum-mdx-collection-build-error
• mdx is loaded with webpack and @mdx-js/loader

🌍 Your Environment

Software	Version(s)
react-spectrum	latest
Browser
Operating System

🧢 Your Company/Team

🕷 Tracking Issue (optional)

@devongovett @LFDanLu @so99ynoodles

[LFDanLu]

I tried you repo locally, looks like this is an issue with any RSP component that uses the Collection API (aka Item). Still digging to see why this is, but these components work in our docs so I'm guessing there is some extra setup that we do.