Re: synchronously waiting for a Promise

On Thursday, September 1, 2016 at 4:19:02 PM UTC+2, Thomas Broyer wrote:

On Thursday, September 1, 2016 at 4:10:12 PM UTC+2, Jens wrote:

var _symbol$bar = Symbol("Foo.bar");

class Foo {

  async getBar() { // Note: transformed to 'async', no 'synchronized'

    if (this[_symbol$bar] == null) {

      var realBar = …;

      this[_symbol$bar] = await realBar.get(); // transformed to await

    }

    return this[_symbol$bar];

  }

}

I think this isn't even correct, because "async getBar()" does return a promise simply because its marked async. Given that you can only call await inside async functions I think its nearly impossible to map that to a synchronous Java function while keeping the correct return type or am I missing something?

That was part of Ian's proposal (emphasis mine):

"If it makes it all the way to a function exposed with JsInterop, then that function changes signature like the rest of them to return a promise. The consumer of this function is obviously in JS and so can handle the promise fine. This would equate to translating the synchronous java calls which wait on a CompletableFuture (Promise) to return promises in JS." 

…and yes, that'd mean that one small change in one class could change the exposed API from/to a Promise "at the other end" of your project. Good luck tracking those changes and never introduce a bug because of them ;-)

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