6.0.0-beta.19: Property or method "then" is not defined on the instance but referenced during render

[joelpro2]

Version

6.0.0-beta.19

Browser and OS info

Chrome 73.0.3683.103 / MacOS High Sierra

Steps to reproduce

Just load any vue app in dev mode.

What is expected?

The console should be empty.

What is actually happening?

The console is full of this kind of errors Property or method "then" is not defined on the instance but referenced during render for every component.

[DevilTea]

I found that it is caused by the fast-copy's copy method called in here

It seems like modified in commit 18397b0 and this issue existed from beta.16

The fix of #1583 isn't used in here

[DevilTea]

The warning message is triggered when copy the state at here

devtools/packages/app-backend-vue2/src/plugin.ts

Line 140 in 63f9fa1

data.state = copy(state)

Besause of the state pass to the method copy from fast-copy could possibly execute to here
https://github.com/planttheidea/fast-copy/blob/fc0c8e76fbe8b933e3574f996f666d0dd8fefa00/src/index.ts#L170

And it would trigger the vue observable get handler to print warning

In my case that I store the vue-router's Route object into store in router.beforeEach.
The Route object has a matched property that contains vue component.
That make fast-copy try to copy the vue instance and trigger the get handler to print a lot of warning.

Hope this info would help you!

[andrew-productiv]

Thanks for the quick fix to this. Any word on when you're planning to make a release that includes this fix?