Define WebIDL Global to host targeted APIs targeted for testing #1534

[dontcallmedom]

A number of specs have emerged to expose e.g. fake hardware as IDL interfaces to help with testing, e.g.:

• for WebUSB
• for WebBluetooth
• for WebXR

Right now, these specs define their interfaces using WebIDL, but without qualifying the interfaces on the global on which they're exposed.

Since these interfaces are typically not exposed in a regular browsing context, I wonder if WebIDL should define a way to qualify these interfaces.

(I mistakenly originally raised this in the context of the WebDriver where some early discussion occurred)

[domenic]

I think [TestOnly, Exposed=Window] is probably better than a new global (i.e. better than [Exposed=TestOnly]). Because you want to have worker-only test-only interfaces, or window-only test-only interfaces.

Otherwise this seems pretty reasonable.

https://wicg.github.io/webusb/test/#availability has some text we might want to copy into an extended attribute definition. And the normative prose would probably be similar to https://heycam.github.io/webidl/#SecureContext. (Note that that is amenable to being refactored and deduplicated; see #883.)