Add compute method to easily run a method in an isolate

[nioncode]

This is basically a re-post of flutter/flutter#48673, since I was advised to file this on this project instead.

It would be great if dart would offer a standard library method for simply running a method in an isolate, i.e. something along the lines of:

Future<R> run_background<R, P> (FutureOr<R> function(P argument), P argument) async {
  IsolateRunner iso = await IsolateRunner.spawn();
  try {
    return await iso.run(function, argument);
  } finally {
    await iso.close();
  }
}

Please note that this example uses IsolateRunner.run from the isolate package.

Flutter provides the compute() method for this.
However, in order to create a library that can also be run in a pure dart setting (i.e. without flutter), we need a method that behaves like compute in the dart sdk.

Is the method I showed above good enough or are there any disadvantages when using IsolateRunner.run instead of compute? For a standard library implementation, we should probably get rid of IsolateRunner though or merge it into the sdk.

One nice thing about IsolateRunner is that we can keep a long lived instance of it and dispatch methods to the isolate when needed and not incur the cost of spawning up an isolate.

[lrhn]

The dart:isolate library is a fairly low-level library with very few convenience methods, which is why the isolate package exists with a more directly usable API.
I'd just use the isolate package, that's what it's there for. I'm sure it's possible to write code that is slightly smaller and faster than the more general IsolateRunner code ... but not much faster because most of the overhead comes from creating the isolate.

[MisterJimson]

The isolate package is now discontinued. Curious how that impacts your guidance above @lrhn.

[lrhn]

I'm seriously considering adding a static run method to isolate, like

 static Future<T> run<T>(FutureOr<T> Function() computation);

which runs a function in a new (Isolate.spawn'ed) isolate.

With the improvements the VM has made on passing closures and other tricky values to other isolates, and with the Isolate.exit function to send the result back, it seems like the time is ripe for an efficient implementation.

[absar]

@lrhn was there any progress on this one, or any new recommendations?

[lrhn]

The Isolate.run method is released in Dart 2.19.

[mkustermann]

We have now a Isolate.run() method. So I think we can close this issue.