From 5614f82871b6daf30ebcd86cd5365c7bc6ad9f40 Mon Sep 17 00:00:00 2001
From: Alex Pott <alex.a.pott@googlemail.com>
Date: Thu, 30 May 2019 12:17:14 +0100
Subject: [PATCH] Issue #2349725 by AdamPS, alexpott, hexblot, jonathanshaw,
 Berdir, larowlan, andypost: Core Mail class prints non-overridable errors on
 the page

---
 core/lib/Drupal/Core/Mail/MailManager.php     |  9 +++++++--
 .../Drupal/Core/Mail/MailManagerInterface.php |  4 +++-
 .../tests/src/Functional/Mail/MailTest.php    | 19 +++++++++++++++++++
 3 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/core/lib/Drupal/Core/Mail/MailManager.php b/core/lib/Drupal/Core/Mail/MailManager.php
index 5cf3c9ea05b..4fd4f9ba7e6 100644
--- a/core/lib/Drupal/Core/Mail/MailManager.php
+++ b/core/lib/Drupal/Core/Mail/MailManager.php
@@ -202,7 +202,9 @@ class MailManager extends DefaultPluginManager implements MailManagerInterface {
    * @param string $langcode
    *   Language code to use to compose the email.
    * @param array $params
-   *   (optional) Parameters to build the email.
+   *   (optional) Parameters to build the email. Use the key '_error_message'
+   *   to provide translatable markup to display as a message if an error
+   *   occurs, or set this to false to disable error display.
    * @param string|null $reply
    *   Optional email address to be used to answer.
    * @param bool $send
@@ -311,7 +313,10 @@ class MailManager extends DefaultPluginManager implements MailManagerInterface {
             '%to' => $message['to'],
             '%reply' => $message['reply-to'] ? $message['reply-to'] : $this->t('not set'),
           ]);
-          $this->messenger()->addError($this->t('Unable to send email. Contact the site administrator if the problem persists.'));
+          $error_message = $params['_error_message'] ?? $this->t('Unable to send email. Contact the site administrator if the problem persists.');
+          if ($error_message) {
+            $this->messenger()->addError($error_message);
+          }
         }
       }
     }
diff --git a/core/lib/Drupal/Core/Mail/MailManagerInterface.php b/core/lib/Drupal/Core/Mail/MailManagerInterface.php
index eadba56f001..6ff083d8cbb 100644
--- a/core/lib/Drupal/Core/Mail/MailManagerInterface.php
+++ b/core/lib/Drupal/Core/Mail/MailManagerInterface.php
@@ -102,7 +102,9 @@ interface MailManagerInterface extends PluginManagerInterface {
    * @param string $langcode
    *   Language code to use to compose the email.
    * @param array $params
-   *   (optional) Parameters to build the email.
+   *   (optional) Parameters to build the email. Use the key '_error_message'
+   *   to provide translatable markup to display as a message if an error
+   *   occurs, or set this to false to disable error display.
    * @param string|null $reply
    *   Optional email address to be used to answer.
    * @param bool $send
diff --git a/core/modules/system/tests/src/Functional/Mail/MailTest.php b/core/modules/system/tests/src/Functional/Mail/MailTest.php
index ef59d0128d1..a821c686116 100644
--- a/core/modules/system/tests/src/Functional/Mail/MailTest.php
+++ b/core/modules/system/tests/src/Functional/Mail/MailTest.php
@@ -6,6 +6,7 @@ use Drupal\Component\Utility\Random;
 use Drupal\Component\Utility\Unicode;
 use Drupal\Core\Mail\MailFormatHelper;
 use Drupal\Core\Mail\Plugin\Mail\TestMailCollector;
+use Drupal\Core\Messenger\MessengerInterface;
 use Drupal\Core\Render\Markup;
 use Drupal\Core\Url;
 use Drupal\file\Entity\File;
@@ -51,6 +52,24 @@ class MailTest extends BrowserTestBase {
     $this->assertTrue($mail_backend instanceof TestMailCollector, 'Additional mail interfaces can be added.');
   }
 
+  /**
+   * Assert that the pluggable mail system is functional.
+   */
+  public function testErrorMessageDisplay() {
+    // Switch mail backends.
+    $this->config('system.mail')->set('interface.default', 'test_php_mail_failure')->save();
+
+    // Test with errors displayed to users.
+    \Drupal::service('plugin.manager.mail')->mail('default', 'default', 'test@example.com', 'en');
+    $messages = \Drupal::messenger()->messagesByType(MessengerInterface::TYPE_ERROR);
+    $this->assertEquals('Unable to send email. Contact the site administrator if the problem persists.', $messages[0]);
+    \Drupal::messenger()->deleteAll();
+
+    // Test without errors displayed to users.
+    \Drupal::service('plugin.manager.mail')->mail('default', 'default', 'test@example.com', 'en', ['_error_message' => '']);
+    $this->assertEmpty(\Drupal::messenger()->messagesByType(MessengerInterface::TYPE_ERROR));
+  }
+
   /**
    * Test that message sending may be canceled.
    *