fix(email): read the MailChannels sender through the address helper

@types/nodemailer 8 types a message's `from` as one address or a list, as
nodemailer has always accepted. The transport only knew a string or one
Address, so the list case did not type-check and, at run time, posted a
sender with no email.

The sender now goes through toMailChannelsAddresses, which already handles
all three shapes for to, cc and bcc, and the first address is the sender. A
string or a single Address comes out exactly as before.
mailchannels.test.ts sends each shape through nodemailer and reads what was
posted; against the old code the list case fails with `{}`.

Co-authored-by: Hanzo Dev <[email protected]>

packages/email/__tests__/mailchannels.test.ts

@@ -0,0 +1,54 @@
+import assert from 'node:assert';
+import { afterEach, describe, it } from 'node:test';
+
+import { createTransport } from 'nodemailer';
+import type { Options } from 'nodemailer/lib/mailer';
+
+import { MailChannelsTransport } from '../transports/mailchannels';
+
+const realFetch = globalThis.fetch;
+
+/** Sends one mail through nodemailer and returns the `from` MailChannels was posted. */
+const sendFrom = async (from: Options['from']) => {
+  const bodies: string[] = [];
+
+  globalThis.fetch = async (_input: string | URL | Request, init?: RequestInit) => {
+    bodies.push(String(init?.body));
+
+    return Promise.resolve(new Response('{}', { status: 202 }));
+  };
+
+  await createTransport(MailChannelsTransport.makeTransport({ apiKey: 'key' })).sendMail({
+    from,
+    to: '[email protected]',
+    subject: 'hi',
+    html: '<p>hi</p>',
+  });
+
+  assert.equal(bodies.length, 1);
+
+  return JSON.parse(bodies[0]).from;
+};
+
+describe('mailchannels transport', () => {
+  afterEach(() => {
+    globalThis.fetch = realFetch;
+  });
+
+  it('sends from a bare address', async () => {
+    assert.deepEqual(await sendFrom('[email protected]'), { email: '[email protected]' });
+  });
+
+  it('sends from a named address', async () => {
+    assert.deepEqual(await sendFrom({ name: 'Sign', address: '[email protected]' }), {
+      email: '[email protected]',
+      name: 'Sign',
+    });
+  });
+
+  it('sends from the first address of a list', async () => {
+    assert.deepEqual(await sendFrom(['[email protected]', '[email protected]']), {
+      email: '[email protected]',
+    });
+  });
+});

packages/email/transports/mailchannels.ts

@@ -54,13 +54,8 @@ export class MailChannelsTransport implements Transport<SentMessageInfo> {
     const mailCc = this.toMailChannelsAddresses(mail.data.cc);
     const mailBcc = this.toMailChannelsAddresses(mail.data.bcc);
 
-    const from: MailChannelsAddress =
-      typeof mail.data.from === 'string'
-        ? { email: mail.data.from }
-        : {
-            email: mail.data.from?.address,
-            name: mail.data.from?.name,
-          };
+    // nodemailer takes a list here as well as one address; a message has one sender.
+    const [from] = this.toMailChannelsAddresses(mail.data.from);
 
     const requestHeaders: Record<string, string> = {
       'Content-Type': 'application/json',