Add key option to registerSharedWorker()

[codetheweb]

Motivation

We'd like to use TypeScript for shared workers.

We're currently using esbuild-register for JIT transpilation for all TS files loaded by Ava, but this doesn't work when loading shared workers. We made a small worker wrapper that allows us to load TS files as workers:
get-typescript-worker.mjs:

import "esbuild-register"
import { createRequire } from "node:module"

const require = createRequire(import.meta.url)

/**
 * This is meant to be loaded as a shared Ava worker, and allows TypeScript files to be loaded as shared workers.
 * The `initialData` payload is expected to contain a full path to the target TypeScript file as `target_worker_path`.
 */
const loadTypeScriptWorker = async ({ negotiateProtocol }) => {
  const protocol = await negotiateProtocol(["ava-4"]).ready()

  const {
    initialData: { target_worker_path },
  } = protocol

  await require(target_worker_path).default(protocol)
}

export default loadTypeScriptWorker

Problem

However, this approach means that the wrapper file is the only file ever registered with registerSharedWorker(). Since workers are currently de-duped based on the source filename, we can only load 1 TS worker in this manner.

Solution

An optional, user-specified key parameter is added to registerSharedWorker() that overrides the implicit filename key for de-duping.

After building this out, I realized that there's a second solution: when calling registerSharedWorker(), you can add a unique hash to the filename that acts as a key:
register-typescript-worker.ts:

const registerTypeScriptWorker = (worker_name: string) => {
  return registerSharedWorker<any>({
    filename: new URL(
      `file:${path.join(
        __dirname,
        "../",
        "workers",
        "get-typescript-worker.mjs"
      )}#${encodeURIComponent(worker_name)}`
    ),
    supportedProtocols: ["ava-4"],
    initialData: {
      target_worker_path: path.join(__dirname, "../", "workers", worker_name),
    },
  })
}

But this feels kinda weird and it would be nice to have an officially supported key parameter.

[novemberborn]

I chose the filename as the cache key since it's somewhat analogous to module loading: you also get the same module that was loaded previously. Within that context I think adding a hash or search parameter is a fairly decent solution that matches ES modules.

[codetheweb]

Makes sense. In that case, can I make a PR to update https://github.com/avajs/ava/blob/ae0042c95d2dbe72b4910931232ea15f6071e04e/docs/recipes/shared-workers.md with an example?

[novemberborn]

Makes sense. In that case, can I make a PR to update ae0042c/docs/recipes/shared-workers.md with an example?

Yea that'd be great!