From 4be991899f4b0f988ff4611b8056fa88b2a122b5 Mon Sep 17 00:00:00 2001
From: Thomas Lehmann <t.lehmann@strato.de>
Date: Tue, 29 Oct 2024 11:53:18 +0100
Subject: [PATCH] feat(Mailer): add "null" SMTP transport mode

== Goal

Allow disabling mail delivery altogether.

== Usecase

If mails ought to be send by other means than rendering messages from
templates and sending them via SMTP-like protocols.

Example: listening to specific Nextcloud events and pass parameters to
a centralized (i.e. REST-based) API that sends e-mails.

Signed-off-by: Thomas Lehmann <t.lehmann@strato.de>
---
 config/config.sample.php      |  5 ++++-
 lib/private/Mail/Mailer.php   |  4 ++++
 tests/lib/Mail/MailerTest.php | 23 ++++++++++++++++++++++-
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/config/config.sample.php b/config/config.sample.php
index b39675909f69c..c8e29ca95e9d2 100644
--- a/config/config.sample.php
+++ b/config/config.sample.php
@@ -501,7 +501,7 @@
 'mail_smtpdebug' => false,
 
 /**
- * Which mode to use for sending mail: ``sendmail``, ``smtp`` or ``qmail``.
+ * Which mode to use for sending mail: ``sendmail``, ``smtp``, ``qmail`` or ``null``.
  *
  * If you are using local or remote SMTP, set this to ``smtp``.
  *
@@ -511,6 +511,9 @@
  * For ``qmail`` the binary is /var/qmail/bin/sendmail, and it must be installed
  * on your Unix system.
  *
+ * Use the string ``null`` to send no mails (disable mail delivery). This can be
+ * useful if mails should be sent via APIs and rendering messages is not necessary.
+ *
  * Defaults to ``smtp``
  */
 'mail_smtpmode' => 'smtp',
diff --git a/lib/private/Mail/Mailer.php b/lib/private/Mail/Mailer.php
index 0a5b633c52ed1..ce219d59010e6 100644
--- a/lib/private/Mail/Mailer.php
+++ b/lib/private/Mail/Mailer.php
@@ -27,6 +27,7 @@
 use Symfony\Component\Mailer\Exception\TransportExceptionInterface;
 use Symfony\Component\Mailer\Mailer as SymfonyMailer;
 use Symfony\Component\Mailer\MailerInterface;
+use Symfony\Component\Mailer\Transport\NullTransport;
 use Symfony\Component\Mailer\Transport\SendmailTransport;
 use Symfony\Component\Mailer\Transport\Smtp\EsmtpTransport;
 use Symfony\Component\Mailer\Transport\Smtp\Stream\SocketStream;
@@ -256,6 +257,9 @@ protected function getInstance(): MailerInterface {
 		}
 
 		switch ($this->config->getSystemValueString('mail_smtpmode', 'smtp')) {
+			case 'null':
+				$transport = new NullTransport();
+				break;
 			case 'sendmail':
 				$transport = $this->getSendMailInstance();
 				break;
diff --git a/tests/lib/Mail/MailerTest.php b/tests/lib/Mail/MailerTest.php
index 2afd78eb6ff8f..d3f6adcbc971c 100644
--- a/tests/lib/Mail/MailerTest.php
+++ b/tests/lib/Mail/MailerTest.php
@@ -20,6 +20,7 @@
 use PHPUnit\Framework\MockObject\MockObject;
 use Psr\Log\LoggerInterface;
 use Symfony\Component\Mailer\Mailer as SymfonyMailer;
+use Symfony\Component\Mailer\Transport\NullTransport;
 use Symfony\Component\Mailer\Transport\SendmailTransport;
 use Symfony\Component\Mailer\Transport\Smtp\EsmtpTransport;
 use Symfony\Component\Mime\Email;
@@ -113,7 +114,27 @@ public function testGetSendmailInstanceSendMailQmail($sendmailMode, $binaryParam
 		$this->assertEquals($sendmail, self::invokePrivate($this->mailer, 'getSendMailInstance'));
 	}
 
-	public function testGetInstanceDefault() {
+	public function testEventForNullTransport(): void {
+		$this->config
+			->expects($this->exactly(1))
+			->method('getSystemValueString')
+			->with('mail_smtpmode', 'smtp')
+			->willReturn('null');
+
+		$message = $this->createMock(Message::class);
+		$message->expects($this->once())
+			->method('getSymfonyEmail')
+			->willReturn((new Email())->to("foo@bar.com")->from("bar@foo.com")->text(""));
+
+		$event = new BeforeMessageSent($message);
+		$this->dispatcher->expects($this->once())
+			->method('dispatchTyped')
+			->with($this->equalTo($event));
+
+		$this->mailer->send($message);
+	}
+
+	public function testGetInstanceDefault(): void {
 		$this->config
 			->method('getSystemValue')
 			->willReturnMap([