6.3rc - storybook-build script hangs

[hoffination]

Describe the bug
After running the build script, the resulting script hangs and times out in our CI.

Last line before timeout:
info => Output directory: /Users/bh/Dev/<project>/storybook-dist

To Reproduce
https://github.com/hoffination/storybook-timeout-repro
Hoping to see if anyone else has come across this.
Didn't see any others recently in the issues.

System
System:
OS: macOS 11.4
CPU: (16) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
Binaries:
Node: 14.16.1 - ~/.nvm/versions/node/v14.16.1/bin/node
npm: 6.14.12 - ~/.nvm/versions/node/v14.16.1/bin/npm
Browsers:
Chrome: 91.0.4472.114
Safari: 14.1.1
npmPackages:
@storybook/addon-a11y: 6.3.0-rc.11 => 6.3.0-rc.11
@storybook/addon-actions: 6.3.0-rc.11 => 6.3.0-rc.11
@storybook/addon-essentials: 6.3.0-rc.11 => 6.3.0-rc.11
@storybook/addon-links: 6.3.0-rc.11 => 6.3.0-rc.11
@storybook/addon-storysource: 6.3.0-rc.11 => 6.3.0-rc.11
@storybook/angular: 6.3.0-rc.11 => 6.3.0-rc.11
@storybook/builder-webpack5: 6.3.0-rc.11 => 6.3.0-rc.11
@storybook/manager-webpack5: 6.3.0-rc.11 => 6.3.0-rc.11
@storybook/preset-scss: ^1.0.3 => 1.0.3 (tried with and without this)

Additional context
Same issue is present on 6.3.0-rc.0, updated in an attempt to fix.

I've tried dropping my node_modules/ and package-lock.json

[shilman]

Possible duplicate to #14405

[hoffination]

@shilman Was able to reproduce here: https://github.com/hoffination/storybook-timeout-repro

[JSMike]

I'm experiencing this issue as well, it looks to be different than #14405 in that it gets beyond 99% and gets to

<s> [webpack.Progress] 99% cache store build dependencies
<s> [webpack.Progress] 99% cache store build dependencies
<s> [webpack.Progress] 99% cache begin idle
<s> [webpack.Progress] 99% cache begin idle
<s> [webpack.Progress] 100%

info => Preview built (1.4 min)
WARN System.import() is deprecated and will be removed soon. Use import() instead.
WARN For more info visit https://webpack.js.org/guides/code-splitting/
WARN System.import() is deprecated and will be removed soon. Use import() instead.
WARN For more info visit https://webpack.js.org/guides/code-splitting/
WARN asset size limit: The following asset(s) exceed the recommended size limit (244 KiB).
WARN This can impact web performance.
WARN Assets:
WARN   448.db768870.iframe.bundle.js (3.96 MiB)
WARN entrypoint size limit: The following entrypoint(s) combined asset size exceeds the recommended limit (244 KiB). This can impact web performance.
WARN Entrypoints:
WARN   main (4.07 MiB)
WARN       runtime~main.edb3999b.iframe.bundle.js
WARN       448.db768870.iframe.bundle.js
WARN       main.4de79c35.iframe.bundle.js
WARN
info => Output directory: /path/to/build/dir

And the build dir contains a fully working storybook site that loads with no errors.

This is only happening when I add angular stories. I have some @storybook/html stories that work just fine if I exclude the angular config. Both are set up to use webpack5

Note: I'm on Windows 10, Node 14.15.0, npm 6.14.8. Storybook 6.3.0-rc.2

[meriturva]

I think it is duplicate to #15227

It is related to scss worker not correctly terminated... i presume

[JSMike]

Note, I'm also getting the following warning up above in the logs.

WARN DefinePlugin
WARN Conflicting values for 'process.env'
WARN DefinePlugin
WARN Conflicting values for 'process.env.NODE_ENV'

This is even with using the webpackDefine plugin to set a NODE_ENV the same as this previous issue: #14257 (comment)

Is something getting stuck in dev mode and listening?

[JSMike]

@meriturva That looks like it is the same root cause.

[shilman]

Closing as duplicate to #15227 & have copied repro there