feat: web worker support

[sheremet-va]

Not sure if this should be part of the core, since usual DOM APIs are enabled with envs

Maybe we can enable some kind of presets, like @vitest/frontend with happy-dom, worker by default, or just publish this as a different package

Closes #722

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[antfu]

Emmm, interesting. I think I'd prefer to have it separate from the core to avoid the complexity and also could be a playground to dogfooding out programmatic/plugin API

[sheremet-va]

Emmm, interesting. I think I'd prefer to have it separate from the core to avoid the complexity and also could be a playground to dogfooding out programmatic/plugin API

What do you think about something like this:

1. Config option addons (should not clush with plugins, the best I came up with) receives array of strings
2. These strings are paths to modules that export default a function with arguments equeal to __vitest_worker__ and config (maybe?). I wouldn't really want to expose them, but I need them to extend VitestRunner
3. Call these addons with setupFiles

We can also just expose some kind of function like defineAddon() that receives a function with the same arguments ^
This function is called right away (should be called inside setup)

[sheremet-va]

In the end I decided that using VitestRunner is quite a niche usecase, you would usually just await import something. But since I need to change the context, I decided to just use __vitest_worker__ inside web-worker.

[sheremet-va]

I also moved runner and execute to runtime, since they are run inside that context

[sheremet-va]

@poyoho I am very confused why CI is failing. It says Cannot find name '__vitest_worker__' in mocker.ts. VSCode doesn't show this error. Can you help me?

[poyoho]

yes, I'm having a problem with positioning 🙈

[poyoho]

when build the mock.ts no include worker.ts so do not had the __vitest_worker__ typescript define.

so @sheremet-va you can add this dts in src/index.ts will pass the ci.

import type { WorkerGlobalState } from './types'
declare global {
  let __vitest_worker__: WorkerGlobalState
}

[sheremet-va]

@antfu it failes on build, that's what I've been trying to tell you. It failes because I export VitestRunner that uses __vitest_worker__, but other packages don't know what it is

[sheremet-va]

@antfu CI is failing.

TBH this PR is taking so long just because of this change with global __vitest_worker__. We should either make every call to __vitest_worker__ with a wrapper with @ts-expect-error inside, or expose __vitest_worker__

[antfu]

I will handle that when we are preparing the release of v0.7