[9.x] Add X headers when using Mail::alwaysTo (#41101)

* add x headers when forgetting

* fqcn

* add tests back

* formatting

Co-authored-by: Taylor Otwell <taylor@laravel.com>

src/Illuminate/Mail/Mailer.php

@@ -389,6 +389,8 @@ protected function renderView($view, $data)
      */
     protected function setGlobalToAndRemoveCcAndBcc($message)
     {
+        $message->forgetTo();
+
         $message->to($this->to['address'], $this->to['name'], true);
 
         $message->forgetCc();

src/Illuminate/Mail/Message.php

@@ -105,6 +105,22 @@ public function to($address, $name = null, $override = false)
         return $this->addAddresses($address, $name, 'To');
     }
 
+    /**
+     * Remove all "to" addresses from the message.
+     *
+     * @return $this
+     */
+    public function forgetTo()
+    {
+        if ($header = $this->message->getHeaders()->get('To')) {
+            $this->addAddressDebugHeader('X-To', $this->message->getTo());
+
+            $header->setAddresses([]);
+        }
+
+        return $this;
+    }
+
     /**
      * Add a carbon copy to the message.
      *
@@ -134,6 +150,8 @@ public function cc($address, $name = null, $override = false)
     public function forgetCc()
     {
         if ($header = $this->message->getHeaders()->get('Cc')) {
+            $this->addAddressDebugHeader('X-Cc', $this->message->getCC());
+
             $header->setAddresses([]);
         }
 
@@ -169,6 +187,8 @@ public function bcc($address, $name = null, $override = false)
     public function forgetBcc()
     {
         if ($header = $this->message->getHeaders()->get('Bcc')) {
+            $this->addAddressDebugHeader('X-Bcc', $this->message->getBcc());
+
             $header->setAddresses([]);
         }
 
@@ -220,6 +240,23 @@ protected function addAddresses($address, $name, $type)
         return $this;
     }
 
+    /**
+     * Add an address debug header for a list of recipients.
+     *
+     * @param  string  $header
+     * @param  \Symfony\Component\Mime\Address[]  $addresses
+     * @return $this
+     */
+    protected function addAddressDebugHeader(string $header, array $addresses)
+    {
+        $this->message->getHeaders()->addTextHeader(
+            $header,
+            implode(', ', array_map(fn ($a) => $a->toString(), $addresses)),
+        );
+
+        return $this;
+    }
+
     /**
      * Set the subject of the message.
      *

tests/Mail/MailMailerTest.php

@@ -200,6 +200,7 @@ public function testGlobalToIsRespectedOnAllMessages()
 
         $sentMessage = $mailer->send('foo', ['data'], function (Message $message) {
             $message->from('hello@laravel.com');
+            $message->to('nuno@laravel.com');
             $message->cc('dries@laravel.com');
             $message->bcc('james@laravel.com');
         });
@@ -209,8 +210,13 @@ public function testGlobalToIsRespectedOnAllMessages()
         });
 
         $this->assertSame('taylor@laravel.com', $sentMessage->getEnvelope()->getRecipients()[0]->getAddress());
-        $this->assertStringNotContainsString('dries@laravel.com', $sentMessage->toString());
-        $this->assertStringNotContainsString('james@laravel.com', $sentMessage->toString());
+        $this->assertDoesNotMatchRegularExpression('/^To: nuno@laravel.com/m', $sentMessage->toString());
+        $this->assertDoesNotMatchRegularExpression('/^Cc: dries@laravel.com/m', $sentMessage->toString());
+        $this->assertMatchesRegularExpression('/^X-To: nuno@laravel.com/m', $sentMessage->toString());
+        $this->assertMatchesRegularExpression('/^X-Cc: dries@laravel.com/m', $sentMessage->toString());
+        $this->assertMatchesRegularExpression('/^X-Bcc: james@laravel.com/m', $sentMessage->toString());
+        $this->assertFalse($recipients->contains('nuno@laravel.com'));
+        $this->assertFalse($recipients->contains('dries@laravel.com'));
         $this->assertFalse($recipients->contains('james@laravel.com'));
     }