Description

Web workers are broken on legacy mode, althought caiuseit shows it can be used on legacy browsers(IE10+ supports for example non-shared web workers). Not even a warning is displayed to the user.

This could have been filed as a bug request, but I think it's better as a feature.

Suggested solution

I saw the code of the Vite worker plugin, and the initial impression is that plugin-legacy can use a regular expressions on renderChunk to find the locations the expression "new Worker" is defined, find the right worker file it reference, and transform it to legacy using Babel. But:

1. That's seems much more complicated than it needs to.
2. Does not work with worker inline import(i.e. inline as a query param in import).

Can we somehow overcome this, maybe by replace the worker constructions with some tokens on transform(), and resolves them later in the renderChunk phase?
This way:

1. Vite worker plugin will check if the current format isn't system, and only then will emit the workers assets and replace the URL/inlined-code there.
2. Vite plugin-legacy will do the same only for the system format, and will transform the worker code via Babel to support legacy.

Alternative

No response

Additional context

No response

Validations

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