[Mailer] Add support for multiple mailers

Author: fabpot

DependencyInjection/Configuration.php

@@ -1555,8 +1555,17 @@ private function addMailerSection(ArrayNodeDefinition $rootNode)
                 ->arrayNode('mailer')
                     ->info('Mailer configuration')
                     ->{!class_exists(FullStack::class) && class_exists(Mailer::class) ? 'canBeDisabled' : 'canBeEnabled'}()
+                    ->validate()
+                        ->ifTrue(function ($v) { return isset($v['dsn']) && \count($v['transports']); })
+                        ->thenInvalid('"dsn" and "transports" cannot be used together.')
+                    ->end()
+                    ->fixXmlConfig('transport')
                     ->children()
-                        ->scalarNode('dsn')->defaultValue('smtp://null')->end()
+                        ->scalarNode('dsn')->defaultNull()->end()
+                        ->arrayNode('transports')
+                            ->useAttributeAsKey('name')
+                            ->prototype('scalar')->end()
+                        ->end()
                         ->arrayNode('envelope')
                             ->info('Mailer Envelope configuration')
                             ->children()

DependencyInjection/FrameworkExtension.php

@@ -1977,7 +1977,12 @@ private function registerMailerConfiguration(array $config, ContainerBuilder $co
 
         $loader->load('mailer.xml');
         $loader->load('mailer_transports.xml');
-        $container->getDefinition('mailer.default_transport')->setArgument(0, $config['dsn']);
+        if (!\count($config['transports']) && null === $config['dsn']) {
+            $config['dsn'] = 'smtp://null';
+        }
+        $transports = $config['dsn'] ? ['main' => $config['dsn']] : $config['transports'];
+        $container->getDefinition('mailer.transports')->setArgument(0, $transports);
+        $container->getDefinition('mailer.default_transport')->setArgument(0, current($transports));
 
         $classToServices = [
             SesTransportFactory::class => 'mailer.transport_factory.amazon',

Resources/config/mailer.xml

@@ -6,13 +6,18 @@
 
     <services>
         <service id="mailer.mailer" class="Symfony\Component\Mailer\Mailer">
-            <argument type="service" id="mailer.default_transport" />
+            <argument type="service" id="mailer.transports" />
             <argument type="service" id="messenger.default_bus" on-invalid="ignore" />
             <argument type="service" id="event_dispatcher" on-invalid="ignore" />
         </service>
         <service id="mailer" alias="mailer.mailer" />
         <service id="Symfony\Component\Mailer\MailerInterface" alias="mailer.mailer" />
 
+        <service id="mailer.transports" class="Symfony\Component\Mailer\Transports">
+            <factory service="mailer.transport_factory" method="fromStrings" />
+            <argument type="collection" /> <!-- transports -->
+        </service>
+
         <service id="mailer.transport_factory" class="Symfony\Component\Mailer\Transport">
             <argument type="tagged_iterator" tag="mailer.transport_factory" />
         </service>
@@ -24,7 +29,7 @@
         <service id="Symfony\Component\Mailer\Transport\TransportInterface" alias="mailer.default_transport" />
 
         <service id="mailer.messenger.message_handler" class="Symfony\Component\Mailer\Messenger\MessageHandler">
-            <argument type="service" id="mailer.default_transport" />
+            <argument type="service" id="mailer.transports" />
             <tag name="messenger.message_handler" />
         </service>
 

Tests/DependencyInjection/ConfigurationTest.php

@@ -369,7 +369,8 @@ class_exists(SemaphoreStore::class) && SemaphoreStore::isSupported() ? 'semaphor
                 'scoped_clients' => [],
             ],
             'mailer' => [
-                'dsn' => 'smtp://null',
+                'dsn' => null,
+                'transports' => [],
                 'enabled' => !class_exists(FullStack::class) && class_exists(Mailer::class),
             ],
         ];

Tests/Functional/MailerTest.php

@@ -55,7 +55,7 @@ protected function doSend(SentMessage $message): void
             }
         };
 
-        $mailer = new Mailer($testTransport, null);
+        $mailer = new Mailer($testTransport);
 
         $message = (new Email())
             ->subject('Test subject')