commit 4780fb9873bde0006ec9d3f531a6a673071db62c
Author: Francesco Placella <plach.git@psegno.it>
Date:   Sat Dec 13 17:24:19 2014 +0100

    Fixed #137 and #138.

diff --git a/core/lib/Drupal/Core/Entity/ContentEntityForm.php b/core/lib/Drupal/Core/Entity/ContentEntityForm.php
index 181e954..5815799 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityForm.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityForm.php
@@ -51,6 +51,9 @@ public static function create(ContainerInterface $container) {
   public function form(array $form, FormStateInterface $form_state) {
     $form = parent::form($form, $form_state);
     $this->getFormDisplay($form_state)->buildForm($this->entity, $form, $form_state);
+    // There are use cases for modules to act both before and after form
+    // language being updated, thus we perform the update in an entity builder
+    // so both cases can be supported.
     $form['#entity_builders']['update_form_langcode'] = [$this, 'updateFormLangcode'];
     return $form;
   }
@@ -69,15 +72,17 @@ public function validate(array $form, FormStateInterface $form_state) {
   }
 
   /**
-   * Initialize the form state and the entity before the first form build.
+   * Initializes the form state and the entity before the first form build.
+   *
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
    */
   protected function init(FormStateInterface $form_state) {
     // Ensure we act on the translation object corresponding to the current form
     // language.
+    $this->initFormLangcodes($form_state);
     $langcode = $this->getFormLangcode($form_state);
     $this->entity = $this->entity->getTranslation($langcode);
-    // Initialize default form langcode status.
-    $this->isDefaultFormLangcode($form_state);
 
     $form_display = EntityFormDisplay::collectRenderDisplay($this->entity, $this->getOperation());
     $this->setFormDisplay($form_display, $form_state);
@@ -86,15 +91,33 @@ protected function init(FormStateInterface $form_state) {
   }
 
   /**
-   * {@inheritdoc}
+   * Initializes form language code values.
+   *
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
    */
-  public function getFormLangcode(FormStateInterface $form_state) {
+  protected function initFormLangcodes(FormStateInterface $form_state) {
+    // Store the entity default language to allow checking whether the form is
+    // dealing with the original entity or a translation.
+    if (!$form_state->has('entity_default_langcode')) {
+      $form_state->set('entity_default_langcode', $this->entity->getUntranslated()->language()->getId());
+    }
+    // This value might have been explicitly populated to work with a particular
+    // entity translation. If not we fall back to the most proper language based
+    // on contextual information.
     if (!$form_state->has('langcode')) {
       // Imply a 'view' operation to ensure users edit entities in the same
       // language they are displayed. This allows to keep contextual editing
       // working also for multilingual entities.
       $form_state->set('langcode', $this->entityManager->getTranslationFromContext($this->entity)->language()->getId());
     }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormLangcode(FormStateInterface $form_state) {
+    $this->initFormLangcodes($form_state);
     return $form_state->get('langcode');
   }
 
@@ -102,11 +125,8 @@ public function getFormLangcode(FormStateInterface $form_state) {
    * {@inheritdoc}
    */
   public function isDefaultFormLangcode(FormStateInterface $form_state) {
-    if (!$form_state->has('default_form_langcode')) {
-      $value = $this->getFormLangcode($form_state) == $this->entity->getUntranslated()->language()->getId();
-      $form_state->set('default_form_langcode', $value);
-    }
-    return $form_state->get('default_form_langcode');
+    $this->initFormLangcodes($form_state);
+    return $form_state->get('langcode') == $form_state->get('entity_default_langcode');
   }
 
   /**
diff --git a/core/modules/user/src/AccountForm.php b/core/modules/user/src/AccountForm.php
index acd8845..2ac9477 100644
--- a/core/modules/user/src/AccountForm.php
+++ b/core/modules/user/src/AccountForm.php
@@ -267,8 +267,9 @@ public function form(array $form, FormStateInterface $form_state) {
       '#languages' => LanguageInterface::STATE_CONFIGURABLE,
       '#default_value' => $user_preferred_langcode,
       '#description' => $user_language_added ? $this->t("This account's preferred language for emails and site presentation.") : $this->t("This account's preferred language for emails."),
-      // This is used to explain the user preferred language and entity language
-      // are synchronized and can be removed if a different behavior is desired.
+      // This is used to explain that user preferred language and entity
+      // language are synchronized. It can be removed if a different behavior is
+      // desired.
       '#pre_render' => ['user_langcode' => [$this, 'alterPreferredLangcodeDescription']],
     );
 
@@ -310,10 +311,10 @@ public function form(array $form, FormStateInterface $form_state) {
    * @return array
    *   The preferred language form element.
    */
-  public function alterPreferredLangcodeDescription($element) {
+  public function alterPreferredLangcodeDescription(array $element) {
     // Only add to the description if the form element has a description.
     if (isset($element['#description'])) {
-      $element['#description'] .= ' ' . t("This is also assumed to be the primary language of this account's profile information.");
+      $element['#description'] .= ' ' . $this->t("This is also assumed to be the primary language of this account's profile information.");
     }
     return $element;
   }
@@ -330,7 +331,7 @@ public function alterPreferredLangcodeDescription($element) {
    * @param \Drupal\Core\Form\FormStateInterface $form_state
    *   The current state of the form.
    */
-  public function syncUserLangcode($entity_type_id, UserInterface $user, &$form, &$form_state) {
+  public function syncUserLangcode($entity_type_id, UserInterface $user, array &$form, FormStateInterface &$form_state) {
     $user->langcode = $user->preferred_langcode;
   }