[fix] Add missing rejection handler

Use `queueMicrotask()` when available and add a rejection handler to the
shim for it.

lib/receiver.js

@@ -15,6 +15,12 @@ const { isValidStatusCode, isValidUTF8 } = require('./validation');
 const FastBuffer = Buffer[Symbol.species];
 const promise = Promise.resolve();
 
+//
+// `queueMicrotask()` is not available in Node.js < 11.
+//
+const queueTask =
+  typeof queueMicrotask === 'function' ? queueMicrotask : queueMicrotaskShim;
+
 const GET_INFO = 0;
 const GET_PAYLOAD_LENGTH_16 = 1;
 const GET_PAYLOAD_LENGTH_64 = 2;
@@ -169,11 +175,7 @@ class Receiver extends Writable {
           //
           this._loop = false;
 
-          //
-          // `queueMicrotask()` is not available in Node.js < 11 and is no
-          // better anyway.
-          //
-          promise.then(() => {
+          queueTask(() => {
             this._state = GET_INFO;
             this.startLoop(cb);
           });
@@ -646,3 +648,32 @@ function error(ErrorCtor, message, prefix, statusCode, errorCode) {
   err[kStatusCode] = statusCode;
   return err;
 }
+
+/**
+ * A shim for `queueMicrotask()`.
+ *
+ * @param {Function} cb Callback
+ */
+function queueMicrotaskShim(cb) {
+  promise.then(cb).catch(throwErrorNextTick);
+}
+
+/**
+ * Throws an error.
+ *
+ * @param {Error} err The error to throw
+ * @private
+ */
+function throwError(err) {
+  throw err;
+}
+
+/**
+ * Throws an error in the next tick.
+ *
+ * @param {Error} err The error to throw
+ * @private
+ */
+function throwErrorNextTick(err) {
+  process.nextTick(throwError, err);
+}

test/receiver.test.js

@@ -2,6 +2,7 @@
 
 const assert = require('assert');
 const crypto = require('crypto');
+const EventEmitter = require('events');
 
 const PerMessageDeflate = require('../lib/permessage-deflate');
 const Receiver = require('../lib/receiver');
@@ -1175,4 +1176,33 @@ describe('Receiver', () => {
 
     receiver.write(Buffer.from('8A01318A01328A0133', 'hex'));
   });
+
+  it('does not swallow errors thrown from event handlers', (done) => {
+    const receiver = new Receiver();
+    let count = 0;
+
+    receiver.on('message', function () {
+      if (++count === 2) {
+        throw new Error('Oops');
+      }
+    });
+
+    assert.strictEqual(
+      process.listenerCount('uncaughtException'),
+      EventEmitter.usingDomains ? 2 : 1
+    );
+
+    const listener = process.listeners('uncaughtException').pop();
+
+    process.removeListener('uncaughtException', listener);
+    process.once('uncaughtException', (err) => {
+      assert.ok(err instanceof Error);
+      assert.strictEqual(err.message, 'Oops');
+
+      process.on('uncaughtException', listener);
+      done();
+    });
+
+    receiver.write(Buffer.from('82008200', 'hex'));
+  });
 });