Define WebIDL Global to host WebDriver targeted APIs

[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 WebDriver should define a dedicated global on which these interfaces could be exposed (e.g. with [Exposed=WebDriverGlobal] or [Exposed=TestGlobal].)

[foolip]

I think that Web IDL is not an ideal fit for this, but that we're lacking a good spec formalism that could be used instead. Shameless plug for #1510 and w3c/webdriver-bidi#21.

Web IDL converts between ECMAScript values and "IDL values", which are the implementation-internal types. For WebDriver, the conversion is rather between a JSON serialization and some internal types.

The difference sounds trivial/pedantic, but when there isn't actually a JS engine involved at all, none of the bindings-generating code that implementations have for Web IDL would be involved. And while one can squint and make it work for simple dictionaries of strings and numbers, I think it'll stop working when we sort out w3c/webdriver-bidi#16, and have a way to serialize values other than the subset of JS that can be represented as JSON.

Note that https://webbluetoothcg.github.io/web-bluetooth/tests.html is different, that's not defining a WebDriver API, but rather a test-only API which would be exposed in JavaScript like regular web APIs, just only in testing setups. There I think something like [TestOnly, Exposed=Window] could make sense.

[foolip]

Frequent Web IDL contributors @Ms2ger @domenic @TimothyGu @annevk @yasskin may have opinions about this.

[domenic]

WebUSB seems similar to WebBluetooth, in that https://wicg.github.io/webusb/test/#idl-index exposes a test attribute on the USB interface (which should presumably be [TestOnly]), which allows you to get access to a bunch of other interfaces that should probably be [TestOnly, Exposed=Window].

Actually, the same for WebXR.

I think none of the specs listed in the OP have much to do with WebDriver.

[dontcallmedom]

huh, sorry, I guess I was confused :)

So should I bring this over to the WebIDL repo then?

[domenic]

Yeah, that's probably the right place for it, although we'll want a combination of Web IDL domain experts and test-only API domain experts.

[dontcallmedom]

Raised whatwg/webidl#896 so closing this here