Add mechanism to reset an SMTP connection. (#1475)

- Potentially useful for retrying after encountering problems.

module/VuFind/src/VuFind/Mailer/Mailer.php

@@ -104,6 +104,21 @@ class Mailer implements \VuFind\I18n\Translator\TranslatorAwareInterface
         return $message;
     }
 
+    /**
+     * Reset the connection in the transport. Implements a fluent interface.
+     *
+     * @return Mailer
+     */
+    public function resetConnection()
+    {
+        // If the transport has a disconnect method, call it:
+        $transport = $this->getTransport();
+        if (is_callable([$transport, 'disconnect'])) {
+            $transport->disconnect();
+        }
+        return $this;
+    }
+
     /**
      * Set the mail transport object.
      *

module/VuFind/tests/unit-tests/src/VuFindTest/Mailer/MailerTest.php

@@ -374,6 +374,19 @@ class MailerTest extends \VuFindTest\Unit\TestCase
         $mailer = new Mailer($transport);
         $mailer->sendRecord('to@example.com', 'from@example.com', 'message', $driver, $view);
     }
+
+    /**
+     * Test connection reset
+     *
+     * @return void
+     */
+    public function testResetConnection()
+    {
+        $transport = $this->createMock(\Zend\Mail\Transport\Smtp::class);
+        $transport->expects($this->once())->method('disconnect');
+        $mailer = new Mailer($transport);
+        $mailer->resetConnection();
+    }
 }
 
 class MockEmailRenderer extends \Zend\View\Renderer\PhpRenderer