feature request: pass arbitrary functions (not just exports) from AS to JS, or vice versa.

[trusktr]

Use case:

We want to make, for example, a requestAnimationFrame function and pass that into Wasm via the imports object.

The AssemblyScript user should be able to dynamically create and pass any callback to this function.

So on the JavaScript side, it would be something like:

const imports = {
  requestAnimationFrame(assemblyscriptFunction) {
    // call assemblyscriptFunction at some point, f.e.
    requestAnimationFrame(assemblyscriptFunction)
  }
}

Problem is, at the moment, assemblyscriptFunction is an AssemblyScript pointer number. So the above won't work.

I'm not sure how to get a function using its pointer and call it, but once we know how to do that, then we can abstract it in as-bind.

---

Similarly, although maybe less useful, we should be able to pass JS functions into an AS function going the other way.

[mathe42]

Got a similar example kind of working:

In Website:

import * as AsBind from "/node_modules/as-bind/dist/as-bind.esm.js";

const asyncTask = async () => {
  const wasm = await fetch("/build/optimized.wasm").then(v => v.arrayBuffer());

  const asBindInstance = await AsBind.instantiate(wasm);

  let e = asBindInstance.exports
  console.log(e.getA()) // logs 0
  e.call(e.change())
  console.log(e.getA()) // logs 42


};
asyncTask();

Assemblyscript:

let a: u8 = 0;

export function getA(): u8 {
  return a;
}

export function change(): () => void {
  return () => {
    a = 42;
  };
}

export function call(ptr: usize): void {
  const fn = changetype<() => void>(ptr);

  return fn();
}

For this use case we would only have to inject a call function to assemblyscript. Currently not shure with function arguments... I will test some stuff.

[mathe42]

Solution inject for each set of argumenttypes and return type.

[mathe42]

I will have a deeper look into it (with modifications to the transform) when #100 is merged. (I will also look at classes then so we can get also all of stdLib to be handled properly.