[8.x] Add Failover Swift Transport driver (#38344)

* [8.x] Add Failover Swift Transport driver

* Apply fixes from StyleCI

* formatting

Co-authored-by: Taylor Otwell <[email protected]>

Author: nerg4l

src/Illuminate/Mail/MailManager.php

@@ -18,6 +18,7 @@
 use Postmark\Transport as PostmarkTransport;
 use Psr\Log\LoggerInterface;
 use Swift_DependencyContainer;
+use Swift_FailoverTransport as FailoverTransport;
 use Swift_Mailer;
 use Swift_SendmailTransport as SendmailTransport;
 use Swift_SmtpTransport as SmtpTransport;
@@ -341,6 +342,34 @@ protected function createPostmarkTransport(array $config)
         });
     }
 
+    /**
+     * Create an instance of the Failover Swift Transport driver.
+     *
+     * @param  array  $config
+     * @return \Swift_FailoverTransport
+     */
+    protected function createFailoverTransport(array $config)
+    {
+        $transports = [];
+
+        foreach ($config['mailers'] as $name) {
+            $config = $this->getConfig($name);
+
+            if (is_null($config)) {
+                throw new InvalidArgumentException("Mailer [{$name}] is not defined.");
+            }
+
+            // Now, we will check if the "driver" key exists and if it does we will set
+            // the transport configuration parameter in order to offer compatibility
+            // with any Laravel <= 6.x application style mail configuration files.
+            $transports[] = $this->app['config']['mail.driver']
+                ? $this->createTransport(array_merge($config, ['transport' => $name]))
+                : $this->createTransport($config);
+        }
+
+        return new FailoverTransport($transports);
+    }
+
     /**
      * Create an instance of the Log Swift Transport driver.
      *

tests/Mail/MailFailoverTransportTest.php

@@ -0,0 +1,63 @@
+<?php
+
+namespace Illuminate\Tests\Mail;
+
+use Illuminate\Mail\Transport\ArrayTransport;
+use Orchestra\Testbench\TestCase;
+
+class MailFailoverTransportTest extends TestCase
+{
+    public function testGetFailoverTransportWithConfiguredTransports()
+    {
+        $this->app['config']->set('mail.default', 'failover');
+
+        $this->app['config']->set('mail.mailers', [
+            'failover' => [
+                'transport' => 'failover',
+                'mailers' => [
+                    'sendmail',
+                    'array',
+                ],
+            ],
+
+            'sendmail' => [
+                'transport' => 'sendmail',
+                'path' => '/usr/sbin/sendmail -bs',
+            ],
+
+            'array' => [
+                'transport' => 'array',
+            ],
+        ]);
+
+        $transport = app('mailer')->getSwiftMailer()->getTransport();
+        $this->assertInstanceOf(\Swift_FailoverTransport::class, $transport);
+
+        $transports = $transport->getTransports();
+        $this->assertCount(2, $transports);
+        $this->assertInstanceOf(\Swift_SendmailTransport::class, $transports[0]);
+        $this->assertEquals('/usr/sbin/sendmail -bs', $transports[0]->getCommand());
+        $this->assertInstanceOf(ArrayTransport::class, $transports[1]);
+    }
+
+    public function testGetFailoverTransportWithLaravel6StyleMailConfiguration()
+    {
+        $this->app['config']->set('mail.driver', 'failover');
+
+        $this->app['config']->set('mail.mailers', [
+            'sendmail',
+            'array',
+        ]);
+
+        $this->app['config']->set('mail.sendmail', '/usr/sbin/sendmail -bs');
+
+        $transport = app('mailer')->getSwiftMailer()->getTransport();
+        $this->assertInstanceOf(\Swift_FailoverTransport::class, $transport);
+
+        $transports = $transport->getTransports();
+        $this->assertCount(2, $transports);
+        $this->assertInstanceOf(\Swift_SendmailTransport::class, $transports[0]);
+        $this->assertEquals('/usr/sbin/sendmail -bs', $transports[0]->getCommand());
+        $this->assertInstanceOf(ArrayTransport::class, $transports[1]);
+    }
+}