[13.x] Populate mailable recipients in mail notifications

src/Illuminate/Notifications/Channels/MailChannel.php

@@ -60,7 +60,8 @@ public function send($notifiable, Notification $notification)
         }
 
         if ($message instanceof Mailable) {
-            return $message->send($this->mailer);
+            return $this->populateMailableRecipients($message, $notifiable, $notification)
+                ->send($this->mailer);
         }
 
         return $this->mailer->mailer($message->mailer ?? null)->send(
@@ -213,7 +214,7 @@ protected function addressMessage($mailMessage, $notifiable, $notification, $mes
     {
         $this->addSender($mailMessage, $message);
 
-        $mailMessage->to($this->getRecipients($notifiable, $notification, $message));
+        $mailMessage->to($this->getRecipients($notifiable, $notification));
 
         if (! empty($message->cc)) {
             foreach ($message->cc as $cc) {
@@ -248,15 +249,35 @@ protected function addSender($mailMessage, $message)
         }
     }
 
+    /**
+     * Populate the mailable recipients using the notifiable's mail route.
+     *
+     * @param  \Illuminate\Contracts\Mail\Mailable  $mailable
+     * @param  mixed  $notifiable
+     * @param  \Illuminate\Notifications\Notification  $notification
+     * @return \Illuminate\Contracts\Mail\Mailable
+     */
+    protected function populateMailableRecipients($mailable, $notifiable, $notification)
+    {
+        if (! empty($mailable->to)) {
+            return $mailable;
+        }
+
+        if (method_exists($mailable, 'envelope') && ! empty($mailable->envelope()->to)) {
+            return $mailable;
+        }
+
+        return $mailable->to($this->getRecipients($notifiable, $notification));
+    }
+
     /**
      * Get the recipients of the given message.
      *
      * @param  mixed  $notifiable
      * @param  \Illuminate\Notifications\Notification  $notification
-     * @param  \Illuminate\Notifications\Messages\MailMessage  $message
      * @return mixed
      */
-    protected function getRecipients($notifiable, $notification, $message)
+    protected function getRecipients($notifiable, $notification)
     {
         if (is_string($recipients = $notifiable->routeNotificationFor('mail', $notification))) {
             $recipients = [$recipients];

tests/Integration/Notifications/SendingNotificationsWithLocaleTest.php

@@ -116,6 +116,38 @@ public function testMailableIsSentWithSelectedLocale()
         );
     }
 
+    public function testMailableWithoutToIsAddressedToNotifiable()
+    {
+        $user = NotifiableLocalizedUser::forceCreate([
+            'email' => 'taylor@laravel.com',
+        ]);
+
+        $user->notify(new GreetingMailNotificationWithMailableWithoutTo);
+
+        $message = app('mailer')->getSymfonyTransport()->messages()[0]->getOriginalMessage();
+
+        $this->assertSame(
+            'taylor@laravel.com',
+            $message->getTo()[0]->getAddress()
+        );
+    }
+
+    public function testMailableWithoutToIsAddressedToMultipleNotifiableRoutes()
+    {
+        $user = NotifiableLocalizedUserWithMultipleMailRoutes::forceCreate([
+            'email' => 'taylor@laravel.com',
+        ]);
+
+        $user->notify(new GreetingMailNotificationWithMailableWithoutTo);
+
+        $message = app('mailer')->getSymfonyTransport()->messages()[0]->getOriginalMessage();
+
+        $this->assertEqualsCanonicalizing(
+            ['foo_taylor@laravel.com', 'bar_taylor@laravel.com'],
+            array_map(fn ($address) => $address->getAddress(), $message->getTo())
+        );
+    }
+
     public function testMailIsSentWithLocaleUpdatedListenersCalled()
     {
         Carbon::setTestNow('2018-07-25');
@@ -247,6 +279,17 @@ public function preferredLocale()
     }
 }
 
+class NotifiableLocalizedUserWithMultipleMailRoutes extends NotifiableLocalizedUser
+{
+    public function routeNotificationForMail($notification)
+    {
+        return [
+            'foo_'.$this->email,
+            'bar_'.$this->email,
+        ];
+    }
+}
+
 class GreetingMailNotification extends Notification
 {
     public function via($notifiable)
@@ -276,6 +319,19 @@ public function toMail($notifiable)
     }
 }
 
+class GreetingMailNotificationWithMailableWithoutTo extends Notification
+{
+    public function via($notifiable)
+    {
+        return [MailChannel::class];
+    }
+
+    public function toMail($notifiable)
+    {
+        return new GreetingMailable;
+    }
+}
+
 class GreetingMailable extends Mailable
 {
     public function build()

tests/Notifications/MailChannelTest.php

@@ -0,0 +1,153 @@
+<?php
+
+namespace Illuminate\Tests\Notifications;
+
+use Illuminate\Contracts\Mail\Factory as MailFactory;
+use Illuminate\Mail\Mailable;
+use Illuminate\Mail\Markdown;
+use Illuminate\Notifications\Channels\MailChannel;
+use Illuminate\Notifications\Notification;
+use Mockery as m;
+use PHPUnit\Framework\TestCase;
+
+class MailChannelTest extends TestCase
+{
+    protected function tearDown(): void
+    {
+        m::close();
+
+        parent::tearDown();
+    }
+
+    public function testItPopulatesMailableRecipientsWhenToIsEmpty()
+    {
+        $mailable = new MailChannelTestMailable;
+
+        $mailable = $this->channel()->populateMailableRecipients(
+            $mailable,
+            new MailChannelNotifiable('taylor@laravel.com'),
+            new MailChannelTestNotification,
+        );
+
+        $this->assertSame('taylor@laravel.com', $mailable->to[0]['address']);
+    }
+
+    public function testItDoesNotOverrideExistingMailableRecipients()
+    {
+        $mailable = (new MailChannelTestMailable)->to('other@laravel.com');
+
+        $mailable = $this->channel()->populateMailableRecipients(
+            $mailable,
+            new MailChannelNotifiable('taylor@laravel.com'),
+            new MailChannelTestNotification,
+        );
+
+        $this->assertSame('other@laravel.com', $mailable->to[0]['address']);
+    }
+
+    public function testItDoesNotOverrideMailableRecipientsDefinedOnEnvelope()
+    {
+        $mailable = new MailChannelTestMailableWithEnvelopeRecipient;
+
+        $mailable = $this->channel()->populateMailableRecipients(
+            $mailable,
+            new MailChannelNotifiable('taylor@laravel.com'),
+            new MailChannelTestNotification,
+        );
+
+        $this->assertSame([], $mailable->to);
+    }
+
+    public function testItPopulatesMultipleMailableRecipientsFromRoute()
+    {
+        $mailable = new MailChannelTestMailable;
+
+        $mailable = $this->channel()->populateMailableRecipients(
+            $mailable,
+            new MailChannelNotifiableWithMultipleRoutes('taylor@laravel.com'),
+            new MailChannelTestNotification,
+        );
+
+        $this->assertEqualsCanonicalizing(
+            ['foo_taylor@laravel.com', 'bar_taylor@laravel.com'],
+            array_column($mailable->to, 'address')
+        );
+    }
+
+    protected function channel(): MailChannelForTesting
+    {
+        return new MailChannelForTesting(
+            m::mock(MailFactory::class),
+            m::mock(Markdown::class),
+        );
+    }
+}
+
+class MailChannelForTesting extends MailChannel
+{
+    public function populateMailableRecipients($mailable, $notifiable, $notification)
+    {
+        return parent::populateMailableRecipients($mailable, $notifiable, $notification);
+    }
+}
+
+class MailChannelNotifiable
+{
+    public function __construct(public string $email)
+    {
+    }
+
+    public function routeNotificationFor($driver, $notification = null)
+    {
+        return $driver === 'mail'
+            ? $this->routeNotificationForMail($notification)
+            : null;
+    }
+
+    public function routeNotificationForMail($notification)
+    {
+        return $this->email;
+    }
+}
+
+class MailChannelNotifiableWithMultipleRoutes extends MailChannelNotifiable
+{
+    public function routeNotificationForMail($notification)
+    {
+        return [
+            'foo_'.$this->email,
+            'bar_'.$this->email,
+        ];
+    }
+}
+
+class MailChannelTestMailable extends Mailable
+{
+    public function build()
+    {
+        return $this->html('Test');
+    }
+}
+
+class MailChannelTestMailableWithEnvelopeRecipient extends Mailable
+{
+    public function envelope()
+    {
+        return new \Illuminate\Mail\Mailables\Envelope(
+            to: [new \Illuminate\Mail\Mailables\Address('envelope@laravel.com')],
+            subject: 'Test',
+        );
+    }
+
+    public function content()
+    {
+        return new \Illuminate\Mail\Mailables\Content(
+            htmlString: 'Test',
+        );
+    }
+}
+
+class MailChannelTestNotification extends Notification
+{
+    //
+}