worker: support MessagePort to workers data

PR-URL: https://github.com/nodejs/node/pull/32278
Fixes: https://github.com/nodejs/node/issues/32250
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>

3 files changed, 69 insertions, 1 deletions

diff --git a/doc/api/worker_threads.md b/doc/api/worker_threads.md
index 9632050b581..89caad84437 100644
--- a/doc/api/worker_threads.md
+++ b/doc/api/worker_threads.md
@@ -513,6 +513,9 @@ if (isMainThread) {
 <!-- YAML
 added: v10.5.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/32278
+    description: The `transferList` option was introduced.
   - version: v13.12.0
     pr-url: https://github.com/nodejs/node/pull/31664
     description: The `filename` parameter can be a WHATWG `URL` object using
diff --git a/lib/internal/worker.js b/lib/internal/worker.js
index 6a14d2dd56e..5f92a7898e9 100644
--- a/lib/internal/worker.js
+++ b/lib/internal/worker.js
@@ -183,6 +183,11 @@ class Worker extends EventEmitter {
     this[kParentSideStdio] = { stdin, stdout, stderr };
 
     const { port1, port2 } = new MessageChannel();
+    const transferList = [port2];
+    // If transferList is provided.
+    if (options.transferList)
+      transferList.push(...options.transferList);
+
     this[kPublicPort] = port1;
     this[kPublicPort].on('message', (message) => this.emit('message', message));
     setupPortReferencing(this[kPublicPort], this, 'message');
@@ -198,7 +203,7 @@ class Worker extends EventEmitter {
         require('internal/process/policy').src :
         null,
       hasStdin: !!options.stdin
-    }, [port2]);
+    }, transferList);
     // Actually start the new thread now that everything is in place.
     this[kHandle].startThread();
   }
diff --git a/test/parallel/test-worker-workerdata-messageport.js b/test/parallel/test-worker-workerdata-messageport.js
new file mode 100644
index 00000000000..352d0729412
--- /dev/null
+++ b/test/parallel/test-worker-workerdata-messageport.js
@@ -0,0 +1,60 @@
+'use strict';
+
+require('../common');
+const assert = require('assert');
+
+const {
+  Worker, MessageChannel
+} = require('worker_threads');
+
+const channel = new MessageChannel();
+const workerData = { mesage: channel.port1 };
+const transferList = [channel.port1];
+const meowScript = () => 'meow';
+
+{
+  // Should receive the transferList param.
+  new Worker(`${meowScript}`, { eval: true, workerData, transferList });
+}
+
+{
+  // Should work with more than one MessagePort.
+  const channel1 = new MessageChannel();
+  const channel2 = new MessageChannel();
+  const workerData = { message: channel1.port1, message2: channel2.port1 };
+  const transferList = [channel1.port1, channel2.port1];
+  new Worker(`${meowScript}`, { eval: true, workerData, transferList });
+}
+
+{
+  const uint8Array = new Uint8Array([ 1, 2, 3, 4 ]);
+  assert.deepStrictEqual(uint8Array.length, 4);
+  new Worker(`
+    const { parentPort, workerData } = require('worker_threads');
+    parentPort.postMessage(workerData);
+    `, {
+    eval: true,
+    workerData: uint8Array,
+    transferList: [uint8Array.buffer]
+  }).on(
+    'message',
+    (message) =>
+      assert.deepStrictEqual(message, Uint8Array.of(1, 2, 3, 4))
+  );
+  assert.deepStrictEqual(uint8Array.length, 0);
+}
+
+{
+  // Should throw on non valid transferList input.
+  const channel1 = new MessageChannel();
+  const channel2 = new MessageChannel();
+  const workerData = { message: channel1.port1, message2: channel2.port1 };
+  assert.throws(() => new Worker(`${meowScript}`, {
+    eval: true,
+    workerData,
+    transferList: []
+  }), {
+    code: 'ERR_MISSING_MESSAGE_PORT_IN_TRANSFER_LIST',
+    message: 'MessagePort was found in message but not listed in transferList'
+  });
+}