Always emit error events (fixes mqttjs#1939)

src/lib/client.ts

@@ -798,16 +798,9 @@ export default class MqttClient extends TypedEventEmitter<MqttClientEventCallbac
 		}
 
 		const streamErrorHandler = (error) => {
+			// Emit all errors (see #1939)
 			this.log('streamErrorHandler :: error', error.message)
-			// error.code will only be set on NodeJS env, browser don't allow to detect errors on sockets
-			// also emitting errors on browsers seems to create issues
-			if (error.code) {
-				// handle error
-				this.log('streamErrorHandler :: emitting error')
-				this.emit('error', error)
-			} else {
-				this.noop(error)
-			}
+			this.emit('error', error)
 		}
 
 		this.log('connect :: pipe stream to writable stream')

test/abstract_client.ts

@@ -477,6 +477,15 @@ export default function abstractTest(server, config, ports) {
 			})
 		})
 
+		it('should emit error events from invalid connection options', function _test(t, done) {
+			const client = connect({ password: 'xxx' })
+
+			client.on('error', (e: any) => {
+				assert.equal(e.message, 'Username is required to use password')
+				client.end((err) => done(err))
+			})
+		})
+
 		it('should have different client ids', function _test(t, done) {
 			// bug identified in this test: the client.end callback is invoked twice, once when the `end`
 			// method completes closing the stores and invokes the callback, and another time when the