[Bug]: Storybook builds twice on launch about storybook HOT 13 OPEN

@pciarach Thanks for the context. This might be a known problem with no easy fix, but I'll ask our local Webpack experts and we'll see what we can figure out. @ndelangen @valentinpalkovic @tmeasday ?

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@pciarach Can you try in 8.0.x? I have a theory about what's going wrong

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@shilman Unfortunately, the same happens on 8.0.10 :(

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@pciarach well i guess the good news is that fixing this bug might be a low-hanging optimization opportunity.

Did you encounter this problem during an upgrade from an old version that did not have this problem?

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@shilman Well, sort of. We did two upgrades recently (7.0.7 => 7.16.7 => 8.1.5) but I've just gone back in the git history and it seems that both previous versions we had were affected as well so it seems that we didn't notice that before.

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@shilman do you have a reproduction repo of this behaviour?

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@tmeasday This happens even on the clean sandbox repository (npx storybook@next sandbox with React latest + webpack 5 template). Please note that this second build I'm referring to is quite fast on this repo but [my assumption is that it] increases in proportion to number of stories.

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@pciarach I'm not sure what I am looking for. I did:

1. Create a sandbox with react-webpack/18-ts
2. Ran yarn storybook
3. It opened a browser with the welcome screen. I was watching the terminal and it didn't print anything else / there was no further activity in the browser.

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@tmeasday This is what I see in the output and in the browser:

It's less than one second there (as there are only 3 stories :D) but on the bigger repo it is almost as long as the first build:

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@pciarach OK I see what you mean. Does adding this to main.js help with the problem for you?

  webpackFinal: (config) => ({
    ...config,
    watchOptions: {
      ignored: /(node_modules|storybook-config-entry|storybook-stories)/,
    },
  }),

It feels like this is a bug in https://github.com/sysgears/webpack-virtual-modules - @ndelangen any ideas?

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@tmeasday Yes, it also helps (and it's definitely better workaround than my physical files ^^)

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@tmeasday I've been thinking of removing the need to have https://github.com/sysgears/webpack-virtual-modules for some time.

I think if we performed code injection into the html template we could likely perform the same task, but without the "magic".
Not sure how much this comment helps us, right now. But for reference, we do not have anything like virtual modules on the manager's side, because we do this:

To solve the immediately issue, we could easily add the following to the default webpack config:

  webpackFinal: (config) => ({
    ...config,
    watchOptions: {
      ignored: /(node_modules|storybook-config-entry|storybook-stories)/,
    },
  }),

That feels rather safe to me.

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@ndelangen the idea of getting rid of virtual modules seems good. But I'm not sure how it would work with Webpack's HMR?

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