Injecting polyfills for vitest browser

[edoardocavazza]

Clear and concise description of the problem

Vitest for browser ships with a polyfill-free policy, which is good. Sometimes we need to run tests across older browsers (such as Safari 14) that does not support features like BroadcastChannel.

Suggested solution

Add a sort of setup file for the runner to inject in index.html and tester.html files, in order to polyfill some features.

Alternative

No response

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[sheremet-va]

Can't you use setupFiles for this?

[edoardocavazza]

Nope, they are loaded after BroadcastChannel initialization, so the polyfill won't work.

[sheremet-va]

If BroadcastChannel channel is not supported by compatible versions (we use the same compatibility table that Vite Dev server uses) then we should rewrite it to use something else.

[sheremet-va]

As a team, we decided that the Vitest browser mode only supports browsers that implement BroadcastChannel, this is now documented.

[edoardocavazza]

It is reasonable that vitest wont support old browsers out of the box. I was just asking if you would consider to support scripts injection in order to let developers to load polyfills themselves 🙂

[sheremet-va]

We did another round of discussion and decided it would be a good idea to expose an option to inject a script into HTML. Vitest has two HTML documents, so there will be two options.

[edoardocavazza]

Thank you so much!