refactor: split worker and worker host logic (#3722)

* split ops/worker.rs into ops/worker_host.rs and ops/web_worker.rs

* refactor js/workers.ts and factor out js/worker_main.ts - entry point for WebWorker runtime

* BREAKING CHANGE: remove support for blob: URL in Worker

* BREAKING CHANGE: remove Deno namespace support and noDenoNamespace option in Worker constructor

* introduce WebWorker struct which is a stripped down version of cli::Worker

cli/js/worker_main.ts

@@ -0,0 +1,98 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+/* eslint-disable @typescript-eslint/no-explicit-any */
+import { core } from "./core.ts";
+import * as dispatch from "./dispatch.ts";
+import { sendAsync, sendSync } from "./dispatch_json.ts";
+import { log } from "./util.ts";
+import { TextDecoder, TextEncoder } from "./text_encoding.ts";
+
+const encoder = new TextEncoder();
+const decoder = new TextDecoder();
+
+function encodeMessage(data: any): Uint8Array {
+  const dataJson = JSON.stringify(data);
+  return encoder.encode(dataJson);
+}
+
+function decodeMessage(dataIntArray: Uint8Array): any {
+  const dataJson = decoder.decode(dataIntArray);
+  return JSON.parse(dataJson);
+}
+
+// Stuff for workers
+export const onmessage: (e: { data: any }) => void = (): void => {};
+export const onerror: (e: { data: any }) => void = (): void => {};
+
+export function postMessage(data: any): void {
+  const dataIntArray = encodeMessage(data);
+  sendSync(dispatch.OP_WORKER_POST_MESSAGE, {}, dataIntArray);
+}
+
+export async function getMessage(): Promise<any> {
+  log("getMessage");
+  const res = await sendAsync(dispatch.OP_WORKER_GET_MESSAGE);
+  if (res.data != null) {
+    return decodeMessage(new Uint8Array(res.data));
+  } else {
+    return null;
+  }
+}
+
+export let isClosing = false;
+
+export function workerClose(): void {
+  isClosing = true;
+}
+
+export async function workerMain(): Promise<void> {
+  const ops = core.ops();
+  // TODO(bartlomieju): this is a prototype, we should come up with
+  // something a bit more sophisticated
+  for (const [name, opId] of Object.entries(ops)) {
+    const opName = `OP_${name.toUpperCase()}`;
+    // Assign op ids to actual variables
+    // TODO(ry) This type casting is gross and should be fixed.
+    ((dispatch as unknown) as { [key: string]: number })[opName] = opId;
+    core.setAsyncHandler(opId, dispatch.getAsyncHandler(opName));
+  }
+
+  log("workerMain");
+
+  while (!isClosing) {
+    const data = await getMessage();
+    if (data == null) {
+      log("workerMain got null message. quitting.");
+      break;
+    }
+
+    let result: void | Promise<void>;
+    const event = { data };
+
+    try {
+      if (!globalThis["onmessage"]) {
+        break;
+      }
+      result = globalThis.onmessage!(event);
+      if (result && "then" in result) {
+        await result;
+      }
+      if (!globalThis["onmessage"]) {
+        break;
+      }
+    } catch (e) {
+      if (globalThis["onerror"]) {
+        const result = globalThis.onerror(
+          e.message,
+          e.fileName,
+          e.lineNumber,
+          e.columnNumber,
+          e
+        );
+        if (result === true) {
+          continue;
+        }
+      }
+      throw e;
+    }
+  }
+}