I think you might be able to get away with Async functions something like
this:
@JsFunction
interface AsyncFunction<T> {
T execute();
}
public class Foo {
Promise<String> fetchJson() {
return Async.await(Xhr.fetch("/someJson")); // returns a
Promise<String>
}
}
public class Async {
@MustBeInlined
public static native <T> Promise<T> await(Promise<T> x) /*-{ yield x;
}-*/;
public static native void makeFooAsync(Foo f) /*-{
var old = f.@Foo::fetchJson;
f.@Foo::fetchJson = function*() { return old.apply(f, arguments); }
}-*/;
}
But I'm not sure. I prototyped a Linker approach to doing this by running
the output JS through the linker, finding all functions declared as @Async,
and adding 'async' keyword in front of them, then invoking BabelJS at the
end. I wrote about it in a G+ post and it works.
ES7 is quite a ways off so I'd probably suggest that for J2Cl this has to
be done with some kind of similar genrule to post process the JS.
It doesn't seem a stretch to imagine that Java annotations could be
harnessed to output decorators. @JsProperty is already a kind of decorator.
Personally, I think Symbols, Iterators, and Generators should be part of a
future JsInterop revision, regardless of whether Java has first class
support for them, there are always annotated or library based approaches
that can be used.
On Fri, Nov 13, 2015 at 1:51 PM, 'John Stalcup' via GWT Contributors <
[email protected]> wrote:
> Generally speaking J2CL seeks to support Java language features and in the
> process of doing so make use of modern ES6 features. When it comes to the
> separate topic of making advanced ES6 features (that don't exist in the
> Java language) available to J2CL users the path for that is via the
> JsInterop spec.
>
> To be specific:
>
> - J2CL currently outputs Closure goog.module()s instead of ES6 modules
> because no browser yet supports ES6 modules and we like having our output
> immediately runnable in the browser without a ES6to5 downsampling. When
> browsers support ES6 modules we are likely to switch.
> - When/if the Java language provides Decorators/Generators/Async
> functions we will transpile them
> - The JsInterop spec does not currently provide sugar for
> Decorators/Generators/Async
> functions but it might in a future revision
> - You can already take advantage of Generators and Async functions (but
> probably not Decorators) by using JsInterop to expose a JS library to Java
> where that JS library exposes utility functions for Generators and Async
> functions
>
>
> On Fri, Nov 13, 2015 at 1:27 PM, Paul Stockley <[email protected]>
> wrote:
>
>> Do you plan on supporting these features in j2cl in the future?
>>
>> On Friday, November 13, 2015 at 4:23:21 PM UTC-5, Ray Cromwell wrote:
>>>
>>>
>>> You could probably support Modules via a GWT linker. Generators and
>>> Async functions could be done by a GWT Generator/Linker combo + BabelJS.
>>> There's no real plans to support ES6 in GWT, but you could arrange enough
>>> hacks with Generator/Linker/Library stuff to make GWT 2.x stuff consumable
>>> from ES6 code.
>>>
>>> On Fri, Nov 13, 2015 at 1:21 PM, Paul Stockley <[email protected]>
>>> wrote:
>>>
>>>> A number of the new frameworks (Angular 2, Aurelia) are planning on
>>>> using ES6 and ES7 features such as Modules, Decorators, Generators and
>>>> Async functions etc. Are there plans to support these on the 2.x code base
>>>> or would these only be supported by j2cl in the future?
>>>>
>>>> On Friday, October 23, 2015 at 3:13:55 AM UTC-4, Goktug Gokdogan wrote:
>>>>>
>>>>> As we are getting close to 2.8 release I wrote a new document that is
>>>>> concentrating on jsinterop features to be released in 2.8:
>>>>>
>>>>> https://docs.google.com/document/d/10fmlEYIHcyead_4R1S5wKGs1t2I7Fnp_PaNaa7XTEk0/edit#
>>>>>
>>>>> Please share your feedback.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Goktug
>>>>>
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