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

[julrich]

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:

storybook/lib/channel-postmessage/src/index.ts

Line 176 in 643e7eb

const eventString = Object.values(EVENTS).includes(event.type)

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 😄

[shilman]

@Dschungelabenteuer Thanks so much for tracking this down! The only thing you're guilty of is being amazing!!! ❤️

[shilman]

@ndelangen @eirslett any idea what could be going on here?

[julrich]

And let me know if I can help some way!

[ndelangen]

We should update storybook to use the new version of telejson

[shilman]

Shiver me timbers!! I just released https://github.com/storybookjs/storybook/releases/tag/v6.3.0-alpha.34 containing PR #14983 that references this issue. Upgrade today to the @next NPM tag to try it out!

npx sb upgrade --prerelease

Closing this issue. Please re-open if you think there's still more to do.

[julrich]

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