Introduce Messageable and Transferable for postMessage

[nikeee]

This PR addresses microsoft/TypeScript#25176

Relevant MDN pages:
https://developer.mozilla.org/en-US/docs/Web/API/BroadcastChannel/postMessage
https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage
https://developer.mozilla.org/en-US/docs/Web/API/Client/postMessage
https://developer.mozilla.org/en-US/docs/Web/API/Worker/postMessage
https://developer.mozilla.org/en-US/docs/Web/API/MessagePort/postMessage
https://developer.mozilla.org/en-US/docs/Web/API/DedicatedWorkerGlobalScope/postMessage

Map and Set do not seem to be available in dom.generated.d.ts. How would one implement the Messageable type?

[mhegazy]

Map and Set are defined in the ES6 lib file. you will need to split the declaration into two overloads, and have the Map/Set ones in dom.iterable.generated.d.ts.

[mhegazy]

@saschanaz can you please review.

[nikeee]

Map and Set are defined in the ES6 lib file. you will need to split the declaration into two overloads, and have the Map/Set ones in dom.iterable.generated.d.ts

How do I add types that sould only be included in dom.iterable.generated.d.ts.

[mhegazy]

see https://github.com/Microsoft/TSJS-lib-generator/blob/master/src/index.ts#L24

[nikeee]

I couldn't find any way to include different type defs without changing the emitter code. I removed the Messageable type def for now.

In the future, we should consider adding OffscreenCanvas to the Transferable type def since it's also Transferable according to the spec IDL. However, OffscreenCanvas is not available in lib.d.ts.

[saschanaz]

IMO okay for now, but I ultimately would prefer more automatic way as we can detect Transferable extended attribute from IDL. We may do what we are already doing for createElement.

[saschanaz]

Why transferList instead of transfer here?

[nikeee]

I named it transferList because it is landed so in the MDN docs.

https://developer.mozilla.org/en-US/docs/Web/API/Worker/postMessage

I can change it to transfer if it's preferred.

I'd prefer the automatic way as well, but for now I think this suffices.

[nikeee]

I changed it to transfer.