Error `TypeError: event is undefined` in manager.bundle.js after upgrade

Describe the bug After updating the vite builder (https://github.com/eirslett/storybook-builder-vite) to 0.0.6, and updating Storybook to 6.3.0-alpha.25, we are greeted by the following error in the browser console:

TypeError: event is undefined

This is the line that triggers the error, because event is undefined: https://github.com/storybookjs/storybook/blob/643e7eb011a880e2b4b8d82ad360752aa9461dd6/lib/channel-postmessage/src/index.ts#L176

And the event in question is:

"message":{
   "target":"Window",
   "isTrusted":true,
   "data":"{\"key\":\"storybook-channel\",\"refId\":\"_undefined_\"}",
   "origin":"http://localhost:3000",
   "lastEventId":"",
   "source":"Window",
   "ports":"Restricted",
   "srcElement":"Window",
   "currentTarget":"Window",
   "eventPhase":2,
   "…"
}

To Reproduce Unfortunately this isn’t really easy for me to extract from our use-case. If it turns out to be hard to reproduce, I’d try my hand on a smaller repro.

System

Environment Info:

  System:
    OS: Linux 5.11 Arch Linux
    CPU: (12) x64 Intel(R) Core(TM) i7-8850H CPU @ 2.60GHz
  Binaries:
    Node: 12.22.1 - ~/.nvm/versions/node/v12.22.1/bin/node
    Yarn: 1.22.10 - /usr/bin/yarn
    npm: 6.14.12 - ~/.nvm/versions/node/v12.22.1/bin/npm
  Browsers:
    Firefox: 87.0

Additional context Not entirely sure if this error originates in Storybook, the vite builder or the unique combination of both!

Let me know if I can help further!

[Dschungelabenteuer]

I hope I’m not completely mistaken but from what I’ve seen while taking a look at this issue, it seems like telejson’s stringify function call in @storybook/channel-postmessage’s send method does not apply properly when using the vite-builder (tested against a Vite + Vue 3 + Storybook environment). It shows no problem processing the key and refId keys. However, when processing the event key, it looks like it systematically catches a TypeError stating that isObject is not a function and returns undefined, resulting in @julrich’s error.

This happens for the following messages:

• currentStoryWasSet
• docsRendered
• storySpecified
• setStories

And this may be why:

shilman, if you see this, I plead not guilty Your Honor 😄

[julrich]

Can confirm, fixes the issue for us! Thanks a lot for the quick turnaround!