[major] Flip the default value of allowSynchronousEvents (#2221)

Flip the default value of the `allowSynchronousEvents` option to `true`.

Refs: #2218

doc/ws.md

@@ -76,8 +76,8 @@ This class represents a WebSocket server. It extends the `EventEmitter`.
     in response to a ping. Defaults to `true`.
   - `allowSynchronousEvents` {Boolean} Specifies whether any of the `'message'`,
     `'ping'`, and `'pong'` events can be emitted multiple times in the same
-    tick. To improve compatibility with the WHATWG standard, the default value
-    is `false`. Setting it to `true` improves performance slightly.
+    tick. Defaults to `true`. Setting it to `false` improves compatibility with
+    the WHATWG standardbut may negatively impact performance.
   - `backlog` {Number} The maximum length of the queue of pending connections.
   - `clientTracking` {Boolean} Specifies whether or not to track clients.
   - `handleProtocols` {Function} A function which can be used to handle the
@@ -302,8 +302,8 @@ This class represents a WebSocket. It extends the `EventEmitter`.
     in response to a ping. Defaults to `true`.
   - `allowSynchronousEvents` {Boolean} Specifies whether any of the `'message'`,
     `'ping'`, and `'pong'` events can be emitted multiple times in the same
-    tick. To improve compatibility with the WHATWG standard, the default value
-    is `false`. Setting it to `true` improves performance slightly.
+    tick. Defaults to `true`. Setting it to `false` improves compatibility with
+    the WHATWG standardbut may negatively impact performance.
   - `finishRequest` {Function} A function which can be used to customize the
     headers of each HTTP request before it is sent. See description below.
   - `followRedirects` {Boolean} Whether or not to follow redirects. Defaults to

lib/receiver.js

@@ -32,7 +32,7 @@ class Receiver extends Writable {
    * Creates a Receiver instance.
    *
    * @param {Object} [options] Options object
-   * @param {Boolean} [options.allowSynchronousEvents=false] Specifies whether
+   * @param {Boolean} [options.allowSynchronousEvents=true] Specifies whether
    *     any of the `'message'`, `'ping'`, and `'pong'` events can be emitted
    *     multiple times in the same tick
    * @param {String} [options.binaryType=nodebuffer] The type for binary data
@@ -47,7 +47,10 @@ class Receiver extends Writable {
   constructor(options = {}) {
     super();
 
-    this._allowSynchronousEvents = !!options.allowSynchronousEvents;
+    this._allowSynchronousEvents =
+      options.allowSynchronousEvents !== undefined
+        ? options.allowSynchronousEvents
+        : true;
     this._binaryType = options.binaryType || BINARY_TYPES[0];
     this._extensions = options.extensions || {};
     this._isServer = !!options.isServer;

lib/websocket-server.js

@@ -29,7 +29,7 @@ class WebSocketServer extends EventEmitter {
    * Create a `WebSocketServer` instance.
    *
    * @param {Object} options Configuration options
-   * @param {Boolean} [options.allowSynchronousEvents=false] Specifies whether
+   * @param {Boolean} [options.allowSynchronousEvents=true] Specifies whether
    *     any of the `'message'`, `'ping'`, and `'pong'` events can be emitted
    *     multiple times in the same tick
    * @param {Boolean} [options.autoPong=true] Specifies whether or not to
@@ -60,7 +60,7 @@ class WebSocketServer extends EventEmitter {
     super();
 
     options = {
-      allowSynchronousEvents: false,
+      allowSynchronousEvents: true,
       autoPong: true,
       maxPayload: 100 * 1024 * 1024,
       skipUTF8Validation: false,

lib/websocket.js

@@ -623,7 +623,7 @@ module.exports = WebSocket;
  * @param {(String|URL)} address The URL to which to connect
  * @param {Array} protocols The subprotocols
  * @param {Object} [options] Connection options
- * @param {Boolean} [options.allowSynchronousEvents=false] Specifies whether any
+ * @param {Boolean} [options.allowSynchronousEvents=true] Specifies whether any
  *     of the `'message'`, `'ping'`, and `'pong'` events can be emitted multiple
  *     times in the same tick
  * @param {Boolean} [options.autoPong=true] Specifies whether or not to
@@ -652,7 +652,7 @@ module.exports = WebSocket;
  */
 function initAsClient(websocket, address, protocols, options) {
   const opts = {
-    allowSynchronousEvents: false,
+    allowSynchronousEvents: true,
     autoPong: true,
     protocolVersion: protocolVersions[1],
     maxPayload: 100 * 1024 * 1024,

test/receiver.test.js

@@ -443,7 +443,7 @@ describe('Receiver', () => {
       buf[i + 1] = 0x00;
     }
 
-    const receiver = new Receiver({ allowSynchronousEvents: true });
+    const receiver = new Receiver();
     let counter = 0;
 
     receiver.on('message', (data, isBinary) => {
@@ -1085,7 +1085,7 @@ describe('Receiver', () => {
     receiver.write(Buffer.from([0x88, 0x03, 0x03, 0xe8, 0xf8]));
   });
 
-  it('emits at most one event per event loop iteration', (done) => {
+  it('honors the `allowSynchronousEvents` option', (done) => {
     const actual = [];
     const expected = [
       '1',
@@ -1121,7 +1121,7 @@ describe('Receiver', () => {
       });
     }
 
-    const receiver = new Receiver();
+    const receiver = new Receiver({ allowSynchronousEvents: false });
 
     receiver.on('message', listener);
     receiver.on('ping', listener);
@@ -1156,43 +1156,8 @@ describe('Receiver', () => {
       done();
     });
 
-    receiver.write(Buffer.from('82008200', 'hex'));
-  });
-
-  it('honors the `allowSynchronousEvents` option', (done) => {
-    const actual = [];
-    const expected = [
-      '1',
-      '2',
-      '3',
-      '4',
-      'microtask 1',
-      'microtask 2',
-      'microtask 3',
-      'microtask 4'
-    ];
-
-    function listener(data) {
-      const message = data.toString();
-      actual.push(message);
-
-      // `queueMicrotask()` is not available in Node.js < 11.
-      Promise.resolve().then(() => {
-        actual.push(`microtask ${message}`);
-
-        if (actual.length === 8) {
-          assert.deepStrictEqual(actual, expected);
-          done();
-        }
-      });
-    }
-
-    const receiver = new Receiver({ allowSynchronousEvents: true });
-
-    receiver.on('message', listener);
-    receiver.on('ping', listener);
-    receiver.on('pong', listener);
-
-    receiver.write(Buffer.from('8101318901328a0133810134', 'hex'));
+    setImmediate(() => {
+      receiver.write(Buffer.from('82008200', 'hex'));
+    });
   });
 });