From 15b2b5edc3d6799333da48bd3f13f946f1091fd9 Mon Sep 17 00:00:00 2001
From: Alex Pott <alex.a.pott@googlemail.com>
Date: Sat, 22 Aug 2015 17:45:12 +0100
Subject: [PATCH] Issue #2120813 by pjonckiere, mpdonadio, ursula, borisson_,
 jsbalsera: Allow several date formats with identical date format strings

---
 .../system/src/Form/DateFormatFormBase.php        |  7 +++----
 .../system/src/Tests/System/DateTimeTest.php      | 15 +++++++++++++++
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/core/modules/system/src/Form/DateFormatFormBase.php b/core/modules/system/src/Form/DateFormatFormBase.php
index b8d0e1788252..bf78cc4642de 100644
--- a/core/modules/system/src/Form/DateFormatFormBase.php
+++ b/core/modules/system/src/Form/DateFormatFormBase.php
@@ -130,12 +130,11 @@ abstract class DateFormatFormBase extends EntityForm {
     parent::validateForm($form, $form_state);
 
     // The machine name field should already check to see if the requested
-    // machine name is available. Regardless of machine_name or human readable
-    // name, check to see if the provided pattern exists.
+    // machine name is available.
     $pattern = trim($form_state->getValue('date_format_pattern'));
     foreach ($this->dateFormatStorage->loadMultiple() as $format) {
-      if ($format->getPattern() == $pattern && ($this->entity->isNew() || $format->id() != $this->entity->id())) {
-        $form_state->setErrorByName('date_format_pattern', $this->t('This format already exists. Enter a unique format string.'));
+      if ($format->getPattern() == $pattern && ($format->id() == $this->entity->id())) {
+        drupal_set_message(t('The existing format/name combination has not been altered.'));
         continue;
       }
     }
diff --git a/core/modules/system/src/Tests/System/DateTimeTest.php b/core/modules/system/src/Tests/System/DateTimeTest.php
index 88868e995525..4fdc2790fa22 100644
--- a/core/modules/system/src/Tests/System/DateTimeTest.php
+++ b/core/modules/system/src/Tests/System/DateTimeTest.php
@@ -117,6 +117,21 @@ class DateTimeTest extends WebTestBase {
     // Make sure the date does not exist in config.
     $date_format = entity_load('date_format', $date_format_id);
     $this->assertFalse($date_format);
+
+    // Add a new date format with an existing format.
+    $date_format_id = strtolower($this->randomMachineName(8));
+    $name = ucwords($date_format_id);
+    $date_format = 'Y';
+    $edit = array(
+      'id' => $date_format_id,
+      'label' => $name,
+      'date_format_pattern' => $date_format,
+    );
+    $this->drupalPostForm('admin/config/regional/date-time/formats/add', $edit, t('Add format'));
+    $this->assertUrl(\Drupal::url('entity.date_format.collection', [], ['absolute' => TRUE]), [], 'Correct page redirection.');
+    $this->assertText(t('Custom date format added.'), 'Date format added confirmation message appears.');
+    $this->assertText($name, 'Custom date format appears in the date format list.');
+    $this->assertText(t('Delete'), 'Delete link for custom date format appears.');
   }
 
   /**