storyshot/vue3 - Unable to extend vue app with plugins

[freakzlike]

Describe the bug

When running storyshot with Vue 3 I am not able to install plugins to vue app instance used on initStoryshots(). Installing the plugin in preview.js works fine in storybook and also gets called when running storyshots. But I think storyshots is using another vue app instance.

To Reproduce

1. Checkout repo: https://github.com/freakzlike/vue3-storyshot-bug
2. Install dependencies npm install
3. Run unit tests npm run test:unit

The test should fail with errors.

Expected behavior

The test should succeed without errors.

System

Environment Info:

  System:
    OS: Windows 10 10.0.19042
    CPU: (16) x64 AMD Ryzen 7 3700X 8-Core Processor
  Binaries:
    Node: 12.18.3 - F:\Program Files\nodejs\node.EXE
    Yarn: 1.22.10 - ~\AppData\Roaming\npm\yarn.CMD
    npm: 7.10.0 - F:\Program Files\nodejs\npm.CMD
  Browsers:
    Chrome: 89.0.4389.128
    Edge: Spartan (44.19041.906.0), Chromium (85.0.564.67)
  npmPackages:
    @storybook/addon-actions: ^6.3.0-alpha.11 => 6.3.0-alpha.11
    @storybook/addon-essentials: ^6.3.0-alpha.11 => 6.3.0-alpha.11
    @storybook/addon-links: ^6.3.0-alpha.11 => 6.3.0-alpha.11
    @storybook/addon-storyshots: ^6.3.0-alpha.11 => 6.3.0-alpha.11
    @storybook/vue3: ^6.3.0-alpha.11 => 6.3.0-alpha.11

Additional context

I have also tested this with Version 6.2.8

The example is running fine in storybook with the installation of the plugin in preview.js.

import { app } from '@storybook/vue3'
import plugin from '../src/plugin'

app.use(plugin)

I also tried to install the plugin within initStoryshots config without success.

initStoryshots({
  config: ({ app }) => {
    app.use(plugin)
    // ...
  }
})

The vue app instance here has already been set correctly from preview.js

[shilman]

Crikey!! I just released https://github.com/storybookjs/storybook/releases/tag/v6.4.0-beta.14 containing PR #15983 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.