Worklet support

[hillin]

Which @angular/* package(s) are relevant/related to the feature request?

compiler

Description

The worklets are light weighted version of web workers. Currently Angular supports web workers, but not worklets, this makes us unable to make use of Angular's Typescript and bundling support when writing a worklet (i.e. we have to write the worklet in pure Javasctript, or deal with compiling and bundling ourselves).

Proposed solution

Support worklet like web workers.

Alternatives considered

For now we have come to a hacky workaround:

1. Write the worklet as if it's a web worker. This is perfecly supported by Angular. Now the problem is, to load the compiled worker script, we don't have a trivial way to get its URL.

2. Wrap the worker code like this:

if (typeof self !== "undefined") {
  postMessage(self.location.href);
} else {
  // do the worklet thing
}

When self is not undefined, we know this script is loaded as a webworker (in a worklet context it would be undefined). In this case, send the script's location by postMessage.

3. When trying to load the worklet, first load it as a web worker, wait for it to report the location, then terminate the worker and use the location to load the worklet.

E.g. load an audio worklet:

// probe worker url
const worker = new Worker(
  new URL("path/to/the/worker", import.meta.url),
);

const url = await new Promise<string>((resolve, reject) => {
  worker.onmessage = (e) => {
    resolve(e.data);
    worker.terminate();
  };

  worker.onmessageerror = reject;
});

await audioContext.audioWorklet.addModule(url);

[angular-robot]

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