Design Meeting Notes, 11/30/2016

[mhegazy]

__extends and static methods / accessors

• skatejs reported issue

• Previously reported issues:

  • Why are TS get/set definedProperties in a class transpiled as enumerable/writable?

• PR from @vvakame to change __extends impementation

• the for loop is there to support browsers pre __proto__, e.g. IE8, IE9, and IE10

  • if we remove it IE10 and below will be broken

• Condition it:

  • seems like a good solution
  • proposal:

var __extendStatics = (this && this.__extendStatics) ||
    Object.setPrototypeOf || 
   ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) || 
   function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };

var __extends = (this && this.__extends) || function (d, b) {
   __extendStatics(d, b);
   function __() { this.constructor = d; }
   d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};

• What about the other side of the issue, emitting methods and accessors as enumrable: false?
  • we have to do it for --target ES5 and not --target ES3
  • if we do this we break the static inheritance for IE10,
  • concolusion:
    • wait on more feedback for this

Promise in lib.d.ts

• Issues:

  • [lib.d.ts BUG] navigator.mediaDevices.getUserMedia returns PromiseLike (actually returns a Promise)
  • Vague error message with async functions

• DOM keeps moving forward, but the lib.d.ts does not

• Resolution:

  • split the DOM into multiple definitions as well, and have the parts depend on what version they need of the library
  • this is a large effort, not clear when or how it can be done
  • No conclusion here, leave it open

Extensibility (@RyanCavanaugh)

• PR: Language service proxy
• Follow up with the experement and see what APIs are needed to be exposed

[falsandtru]

@mhegazy Where should we give feedback for __extends?

[mhegazy]

either here or at #12488

[falsandtru]

thx

[pwnall]

I just got hit by the PromiseLike issue in the WebCrypto API.

The notes above seem to state that the solution will be splitting DOM definitions into multiple libraries. As an approach, I'd suggest setting up the scaffold, and splitting out one (small) API, so the community has an example PR to look at. This way, we (the community) could help with the APIs we care about.