feat: support choosing custom worker backend

createWorker.d.ts

@@ -0,0 +1 @@
+export { createWorker } from "./dist-esm/createWorker"

createWorker.js

@@ -0,0 +1 @@
+module.exports = require("./dist/createWorker")

createWorker.mjs

@@ -0,0 +1 @@
+export { createWorker } from "./dist-esm/createWorker"

docs/usage.md

@@ -166,6 +166,33 @@ const worker = await spawn(BlobWorker.fromText(MyWorker))
 
 Bundle this module and you will obtain a stand-alone bundle that has its worker inlined. This is particularly useful for libraries using threads.js.
 
+### createWorker - select worker backend
+`createWorker` allows selecting the worker backend (among web, node, and tiny), and also if you want a blob worker.
+
+The second required argument to the `createWorker` is a string that specifies `backend: 'web' | 'node' | 'tiny'`. The third optional argument is an object that can be used to specify `blob: boolean` or other `WorkerOptions`.
+
+`createWorker` uses dynamic imports to only import the needed implementation, so you can import the needed functions directly to reduce the bundle size.
+
+```js
+import { createWorker } from "threads/createWorker"
+import { spawn, Thread } from "threads"
+
+async function run() {
+  const worker = await createWorker("./worker.js", "node")
+  const add = await spawn(worker)
+  const result = await add(2, 3)
+  await Thread.terminate(add)
+  return result
+}
+
+run().then(result => {
+  console.log(`Result: ${result}`)
+}).catch(error => {
+  console.error(error)
+})
+```
+
+
 ## TypeScript
 
 ### Type-safe workers

index.d.ts

@@ -0,0 +1 @@
+export { registerSerializer, spawn, DefaultSerializer, Pool, Thread, Transfer, Worker } from "./src/index.js"

package.json

@@ -124,12 +124,12 @@
     "ts-node/register": false,
     "worker_threads": false,
     "./dist/master/implementation.js": "./dist/master/implementation.browser.js",
-    "./dist/master/implementation.node.js": false,
+    "./dist/master/implementation-node.js": false,
     "./dist/worker/implementation.js": "./dist/worker/implementation.browser.js",
     "./dist/worker/implementation.tiny-worker.js": false,
     "./dist/worker/implementation.worker_threads.js": false,
     "./dist-esm/master/implementation.js": "./dist-esm/master/implementation.browser.js",
-    "./dist-esm/master/implementation.node.js": false,
+    "./dist-esm/master/implementation-node.js": false,
     "./dist-esm/worker/implementation.js": "./dist-esm/worker/implementation.browser.js",
     "./dist-esm/worker/implementation.tiny-worker.js": false,
     "./dist-esm/worker/implementation.worker_threads.js": false
@@ -139,6 +139,7 @@
     "dist-esm/**",
     "*.js",
     "*.mjs",
-    "*.ts"
+    "*.ts",
+    "src"
   ]
 }

src/createWorker.ts

@@ -0,0 +1,35 @@
+import {
+  BlobWorker,
+  CreateWorkerOptions,
+  WorkerImplementation,
+} from "./types/master"
+
+/**
+ * async function to creat a webworker. This function uses dynamic imports to only import the required implementation
+ * @param workerPath the path or Blob to the worker code
+ * @param backend backend for the threads
+ * @param {CreateWorkerOptions} options an object that can be used to specify `blob: boolean` or other {WorkerOptions}. Defaults to `{}`.
+ * @returns A web worker, a node.js worker, or a tiny worker class.
+ */
+export async function createWorker(workerPath: string | Blob, backend: "web" | "node" | "tiny", options: CreateWorkerOptions = {}) {
+  let WorkerConstructor: typeof WorkerImplementation | typeof BlobWorker
+  if (backend === "web") {
+    const { getWorkerImplementation } = await import("./master/implementation.browser")
+    WorkerConstructor = options.blob ?
+      getWorkerImplementation().blob :
+      getWorkerImplementation().default
+  } else if (backend === "node") {
+    const { initWorkerThreadsWorker } = await import("./master/implementation-node")
+    WorkerConstructor = options.blob ?
+      initWorkerThreadsWorker().blob :
+      initWorkerThreadsWorker().default
+  } else if (backend === "tiny") {
+    const { initTinyWorker } = await import("./master/implementation-node")
+    WorkerConstructor = options.blob ?
+      initTinyWorker().blob :
+      initTinyWorker().default
+  } else {
+    throw new Error("The worker backend is not supported.")
+  }
+  return new WorkerConstructor(workerPath as string & Blob, options)
+}

src/master/implementation.node.ts → src/master/implementation-node.ts

@@ -88,7 +88,8 @@ function resolveScriptPath(scriptPath: string, baseURL?: string | undefined) {
   return workerFilePath
 }
 
-function initWorkerThreadsWorker(): ImplementationExport {
+export function initWorkerThreadsWorker(): ImplementationExport {
+  isTinyWorker = false
   // Webpack hack
   const NativeWorker = typeof __non_webpack_require__ === "function"
     ? __non_webpack_require__("worker_threads").Worker
@@ -164,7 +165,8 @@ function initWorkerThreadsWorker(): ImplementationExport {
   }
 }
 
-function initTinyWorker(): ImplementationExport {
+export function initTinyWorker(): ImplementationExport {
+  isTinyWorker = true
   const TinyWorker = require("tiny-worker")
 
   let allWorkers: Array<typeof TinyWorker> = []
@@ -248,21 +250,31 @@ function initTinyWorker(): ImplementationExport {
 let implementation: ImplementationExport
 let isTinyWorker: boolean
 
-function selectWorkerImplementation(): ImplementationExport {
-  try {
-    isTinyWorker = false
+function selectWorkerImplementation(selection?: string): ImplementationExport {
+  if (!selection) {
+
+    // automatic version based selection
+    try {
+      return initWorkerThreadsWorker()
+    } catch(error) {
+      // tslint:disable-next-line no-console
+      console.debug("Node worker_threads not available. Trying to fall back to tiny-worker polyfill...")
+      return initTinyWorker()
+    }
+
+    // manual selection
+  } else if (selection === "node") {
     return initWorkerThreadsWorker()
-  } catch(error) {
-    // tslint:disable-next-line no-console
-    console.debug("Node worker_threads not available. Trying to fall back to tiny-worker polyfill...")
-    isTinyWorker = true
+  } else if (selection === "tiny") {
     return initTinyWorker()
+  } else {
+    throw new Error("selection is not supported" + selection)
   }
 }
 
-export function getWorkerImplementation(): ImplementationExport {
+export function getWorkerImplementation(selection?: string): ImplementationExport {
   if (!implementation) {
-    implementation = selectWorkerImplementation()
+    implementation = selectWorkerImplementation(selection)
   }
   return implementation
 }

src/master/implementation.ts

@@ -5,9 +5,8 @@
 // We alias `src/master/implementation` to `src/master/implementation.browser` for web
 // browsers already in the package.json, so if get here, it's safe to pass-through the
 // node implementation
-
+import * as NodeImplementation from "./implementation-node"
 import * as BrowserImplementation from "./implementation.browser"
-import * as NodeImplementation from "./implementation.node"
 
 const runningInNode = typeof process !== 'undefined' && process.arch !== 'browser' && 'pid' in process
 const implementation = runningInNode ? NodeImplementation : BrowserImplementation

src/types/master.ts

@@ -98,6 +98,11 @@ export interface ThreadsWorkerOptions extends WorkerOptions {
   CORSWorkaround?: boolean
 }
 
+export interface CreateWorkerOptions extends ThreadsWorkerOptions {
+  /** flag to return a BlobWorker */
+  blob?: boolean
+}
+
 /** Worker implementation. Either web worker or a node.js Worker class. */
 export declare class WorkerImplementation extends EventTarget implements Worker {
   constructor(path: string, options?: ThreadsWorkerOptions)

test-tooling/rollup/app-createWorker.js

@@ -0,0 +1,17 @@
+import { createWorker } from "../../createWorker.mjs"
+import { spawn, Thread } from "../../"
+
+async function run() {
+  const add = await spawn(await createWorker("./worker.js", "node"))
+  const result = await add(2, 3)
+  await Thread.terminate(add)
+  return result
+}
+
+run().then(result => {
+  console.log(`Result: ${result}`)
+  puppet.exit(0)
+}).catch(error => {
+  console.error(error)
+  puppet.exit(1)
+})

test-tooling/rollup/rollup.test.ts

@@ -12,6 +12,11 @@ test("can be bundled using rollup", async t => {
     ...config
   })
 
+  const appCreateWorkerBundleP = rollup({
+     input: path.resolve(__dirname, "app-createWorker.js"),
+    ...config
+  })
+
   const workerBundleP = rollup({
     input: path.resolve(__dirname, "worker.js"),
     ...config
@@ -22,12 +27,17 @@ test("can be bundled using rollup", async t => {
     format: "iife"
   })
 
+  const appCreateWorkerBundleWriteP = (await appCreateWorkerBundleP).write({
+    dir: path.resolve(__dirname, "dist"),
+    format: "es"
+  })
+
   const workerBundleWriteP = (await workerBundleP).write({
     dir: path.resolve(__dirname, "dist"),
     format: "iife"
   })
 
-  await Promise.all([appBundleWriteP, workerBundleWriteP])
+  await Promise.all([appBundleWriteP, workerBundleWriteP, appCreateWorkerBundleWriteP])
 
   if (process.platform === "win32") {
     // Quick-fix for weird Windows issue in CI

test/createWorker.test.ts

@@ -0,0 +1,27 @@
+import test from "ava"
+import { createWorker } from '../src/createWorker'
+import { spawn, Thread } from "../src/index"
+
+test("createWorker web", async t => {
+  const worker = await createWorker("./workers/hello-world", "web")
+  const helloWorld = await spawn(worker)
+  t.is(await helloWorld(), "Hello World")
+  await Thread.terminate(helloWorld)
+  t.pass()
+})
+
+test("createWorker node", async t => {
+  const worker = await createWorker("./workers/hello-world", "node")
+  const helloWorld = await spawn(worker)
+  t.is(await helloWorld(), "Hello World")
+  await Thread.terminate(helloWorld)
+  t.pass()
+})
+
+test("createWorker tiny", async t => {
+  const worker = await createWorker("./workers/hello-world", "tiny")
+  const helloWorld = await spawn(worker)
+  t.is(await helloWorld(), "Hello World")
+  await Thread.terminate(helloWorld)
+  t.pass()
+})

tsconfig.json

@@ -13,6 +13,7 @@
   },
   "include": [
     "./src/index.ts",
+    "./src/createWorker.ts",
     "./src/observable.ts",
     "./src/master/*",
     "./src/worker/*",