smtp/client: invoke callback when send is successful

allows awaiting message result when send is promisified

smtp/client.ts

@@ -63,6 +63,9 @@ export class SMTPClient {
 				}
 				this.queue.push(stack);
 				this._poll();
+				if (this.queue.every((x) => x !== stack)) {
+					callback(null, message);
+				}
 			} else {
 				callback(new Error(why), msg);
 			}

test/client.ts

@@ -4,7 +4,13 @@ import test from 'ava';
 import { simpleParser, ParsedMail } from 'mailparser';
 import { SMTPServer } from 'smtp-server';
 
-import { DEFAULT_TIMEOUT, SMTPClient, Message, MessageHeaders } from '../email';
+import {
+	DEFAULT_TIMEOUT,
+	SMTPClient,
+	Message,
+	MessageHeaders,
+	isRFC2822Date,
+} from '../email';
 
 const parseMap = new Map<string, ParsedMail>();
 const port = 3000;
@@ -309,3 +315,35 @@ test('client only responds once to greylisting', async (t) => {
 	);
 	t.is(error, "bad response on command 'RCPT': greylist");
 });
+
+test('client send can have result awaited when promisified', async (t) => {
+	// bind necessary to retain internal access to client prototype
+	const sendAsync = promisify(client.send.bind(client));
+
+	const msg = {
+		subject: 'this is a test TEXT message from emailjs',
+		from: 'piglet@gmail.com',
+		bcc: 'pooh@gmail.com',
+		text: "It is hard to be brave when you're only a Very Small Animal.",
+	};
+
+	try {
+		const message = await sendAsync(new Message(msg));
+		t.true(message instanceof Message);
+		t.like(message, {
+			alternative: null,
+			content: 'text/plain; charset=utf-8',
+			text: "It is hard to be brave when you're only a Very Small Animal.",
+			header: {
+				bcc: 'pooh@gmail.com',
+				from: 'piglet@gmail.com',
+				subject: '=?UTF-8?Q?this_is_a_test_TEXT_message_from_emailjs?=',
+			},
+		});
+		t.deepEqual(message.attachments, []);
+		t.true(isRFC2822Date(message.header.date as string));
+		t.regex(message.header['message-id'] as string, /^<.*[@]{1}.*>$/);
+	} catch (err) {
+		t.fail(err);
+	}
+});