Issue #1889644 by Berdir: Convert drupal_mail_system() to a MailFactory service to allow more flexible replacements.

core/core.services.yml

@@ -487,6 +487,9 @@ services:
   flood:
     class: Drupal\Core\Flood\DatabaseBackend
     arguments: ['@database', '@request']
+  mail.factory:
+    class: Drupal\Core\Mail\MailFactory
+    arguments: ['@config.factory']
   plugin.manager.condition:
     class: Drupal\Core\Condition\ConditionManager
     arguments: ['@container.namespaces', '@cache.cache', '@language_manager', '@module_handler']

core/includes/mail.inc

@@ -200,98 +200,21 @@ function drupal_mail($module, $key, $to, $langcode, $params = array(), $from = N
 /**
  * Returns an object that implements Drupal\Core\Mail\MailInterface.
  *
- * Allows for one or more custom mail backends to format and send mail messages
+ * @param string $module
- * composed using drupal_mail().
- *
- * An implementation needs to implement the following methods:
- * - format: Allows to preprocess, format, and postprocess a mail
- *   message before it is passed to the sending system. By default, all messages
- *   may contain HTML and are converted to plain-text by the
- *   Drupal\Core\Mail\PhpMail implementation. For example, an alternative
- *   implementation could override the default implementation and additionally
- *   sanitize the HTML for usage in a MIME-encoded e-mail, but still invoking
- *   the Drupal\Core\Mail\PhpMail implementation to generate an alternate
- *   plain-text version for sending.
- * - mail: Sends a message through a custom mail sending engine.
- *   By default, all messages are sent via PHP's mail() function by the
- *   Drupal\Core\Mail\PhpMail implementation.
- *
- * The selection of a particular implementation is controlled via the config
- * 'system.mail.interface', which is a keyed array.  The default implementation
- * is the class whose name is the value of 'default' key. A more specific match
- * first to key and then to module will be used in preference to the default. To
- * specify a different class for all mail sent by one module, set the class
- * name as the value for the key corresponding to the module name. To specify
- * a class for a particular message sent by one module, set the class name as
- * the value for the array key that is the message id, which is
- * "${module}_${key}".
- *
- * For example to debug all mail sent by the user module by logging it to a
- * file, you might set the variable as something like:
- *
- * @code
- * array(
- *   'default' => 'Drupal\Core\Mail\PhpMail',
- *   'user' => 'DevelMailLog',
- * );
- * @endcode
- *
- * Finally, a different system can be specified for a specific e-mail ID (see
- * the $key param), such as one of the keys used by the contact module:
- *
- * @code
- * array(
- *   'default' => 'Drupal\Core\Mail\PhpMail',
- *   'user' => 'DevelMailLog',
- *   'contact_page_autoreply' => 'DrupalDevNullMailSend',
- * );
- * @endcode
- *
- * Other possible uses for system include a mail-sending class that actually
- * sends (or duplicates) each message to SMS, Twitter, instant message, etc, or
- * a class that queues up a large number of messages for more efficient bulk
- * sending or for sending via a remote gateway so as to reduce the load
- * on the local server.
- *
- * @param $module
  *   The module name which was used by drupal_mail() to invoke hook_mail().
- * @param $key
+ * @param string $key
  *   A key to identify the e-mail sent. The final e-mail ID for the e-mail
  *   alter hook in drupal_mail() would have been {$module}_{$key}.
  *
  * @return Drupal\Core\Mail\MailInterface
+ *   An object that implements Drupal\Core\Mail\MailInterface.
  *
  * @throws \Exception
+ *
+ * @see \Drupal\Core\Mail\MailFactory::get()
  */
 function drupal_mail_system($module, $key) {
-  $instances = &drupal_static(__FUNCTION__, array());
+  return Drupal::service('mail.factory')->get($module, $key);
-
-  $id = $module . '_' . $key;
-
-  $configuration = Drupal::config('system.mail')->get('interface');
-
-  // Look for overrides for the default class, starting from the most specific
-  // id, and falling back to the module name.
-  if (isset($configuration[$id])) {
-    $class = $configuration[$id];
-  }
-  elseif (isset($configuration[$module])) {
-    $class = $configuration[$module];
-  }
-  else {
-    $class = $configuration['default'];
-  }
-
-  if (empty($instances[$class])) {
-    $interfaces = class_implements($class);
-    if (isset($interfaces['Drupal\Core\Mail\MailInterface'])) {
-      $instances[$class] = new $class();
-    }
-    else {
-      throw new Exception(t('Class %class does not implement interface %interface', array('%class' => $class, '%interface' => 'Drupal\Core\Mail\MailInterface')));
-    }
-  }
-  return $instances[$class];
 }
 
 /**

core/lib/Drupal/Core/Mail/MailFactory.php

@@ -0,0 +1,126 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Mail\MailFactory.
+ */
+
+namespace Drupal\Core\Mail;
+
+use Drupal\Core\Config\ConfigFactory;
+use Drupal\Component\Utility\String;
+
+/**
+ * Factory for creating mail system objects.
+ */
+class MailFactory {
+
+  /**
+   * Config object for mail system configurations.
+   *
+   * @var \Drupal\Core\Config\Config
+   */
+  protected $mailConfig;
+
+  /**
+   * List of already instantiated mail system objects.
+   *
+   * @var array
+   */
+  protected $instances = array();
+
+  /**
+   * Constructs a MailFActory object.
+   *
+   * @param \Drupal\Core\Config\ConfigFactory $configFactory
+   *   The configuration factory.
+   */
+  public function __construct(ConfigFactory $configFactory) {
+    $this->mailConfig = $configFactory->get('system.mail');
+  }
+
+
+  /**
+   * Returns an object that implements \Drupal\Core\Mail\MailInterface.
+   *
+   * Allows for one or more custom mail backends to format and send mail messages
+   * composed using drupal_mail().
+   *
+   * The selection of a particular implementation is controlled via the config
+   * 'system.mail.interface', which is a keyed array.  The default
+   * implementation is the class whose name is the value of 'default' key. A
+   * more specific match first to key and then to module will be used in
+   * preference to the default. To specify a different class for all mail sent
+   * by one module, set the class name as the value for the key corresponding to
+   * the module name. To specify a class for a particular message sent by one
+   * module, set the class name as the value for the array key that is the
+   * message id, which is "${module}_${key}".
+   *
+   * For example to debug all mail sent by the user module by logging it to a
+   * file, you might set the variable as something like:
+   *
+   * @code
+   * array(
+   *   'default' => 'Drupal\Core\Mail\PhpMail',
+   *   'user' => 'DevelMailLog',
+   * );
+   * @endcode
+   *
+   * Finally, a different system can be specified for a specific e-mail ID (see
+   * the $key param), such as one of the keys used by the contact module:
+   *
+   * @code
+   * array(
+   *   'default' => 'Drupal\Core\Mail\PhpMail',
+   *   'user' => 'DevelMailLog',
+   *   'contact_page_autoreply' => 'DrupalDevNullMailSend',
+   * );
+   * @endcode
+   *
+   * Other possible uses for system include a mail-sending class that actually
+   * sends (or duplicates) each message to SMS, Twitter, instant message, etc,
+   * or a class that queues up a large number of messages for more efficient
+   * bulk sending or for sending via a remote gateway so as to reduce the load
+   * on the local server.
+   *
+   * @param string $module
+   *   The module name which was used by drupal_mail() to invoke hook_mail().
+   * @param string $key
+   *   A key to identify the e-mail sent. The final e-mail ID for the e-mail
+   *   alter hook in drupal_mail() would have been {$module}_{$key}.
+   *
+   * @return \Drupal\Core\Mail\MailInterface
+   *   An object that implements Drupal\Core\Mail\MailInterface.
+   *
+   * @throws \Exception
+   */
+  public function get($module, $key) {
+    $id = $module . '_' . $key;
+
+    $configuration = $this->mailConfig->get('interface');
+
+    // Look for overrides for the default class, starting from the most specific
+    // id, and falling back to the module name.
+    if (isset($configuration[$id])) {
+      $class = $configuration[$id];
+    }
+    elseif (isset($configuration[$module])) {
+      $class = $configuration[$module];
+    }
+    else {
+      $class = $configuration['default'];
+    }
+
+    if (empty($this->instances[$class])) {
+      $interfaces = class_implements($class);
+      if (isset($interfaces['Drupal\Core\Mail\MailInterface'])) {
+        $this->instances[$class] = new $class();
+      }
+      else {
+        throw new \Exception(String::format('Class %class does not implement interface %interface', array('%class' => $class, '%interface' => 'Drupal\Core\Mail\MailInterface')));
+      }
+    }
+    return $this->instances[$class];
+  }
+
+}

core/lib/Drupal/Core/Mail/MailInterface.php

@@ -15,6 +15,14 @@ interface MailInterface {
   /**
    * Formats a message composed by drupal_mail() prior sending.
    *
+   * Allows to preprocess, format, and postprocess a mail message before it is
+   * passed to the sending system. By default, all messages may contain HTML and
+   * are converted to plain-text by the Drupal\Core\Mail\PhpMail implementation.
+   * For example, an alternative implementation could override the default
+   * implementation and additionally sanitize the HTML for usage in a
+   * MIME-encoded e-mail, but still invoking the Drupal\Core\Mail\PhpMail
+   * implementation to generate an alternate plain-text version for sending.
+   *
    * @param array $message
    *   A message array, as described in hook_mail_alter().
    *