Make language fallback behavior for translated fields configurable

+1 for @getu-lar patch.
Here is another version if you want to have a different behaviour on the admin UI. Not 100% perfect but it might be useful.

Entity Translation provides a setting "Enable language fallback" (See attached screenshot) - I propose to use this value. I have attached a patch, which does this.

That way I can disable language fallback - which is the only thing I need to do :)

However, it should be noted that the language fallback logic as it is currently implemented in Entity API differs to how core determines fallback languages for field values to display them. Entity API uses only the language of the parent entity as fallback, while core tries to find data for this field from all other languages (For details see locale_field_language_fallback).

BUT, it seems as fago does not want to use field-level fallback languages as he notes in a code comment: "Note that we cannot use field_language() as we are not about to display values, but generally read/write values.". Which makes sense somehow, but then I wonder why there is this fallback logic anyhow.

Removing the unneeded tags.

Here is an alternative patch, which simply uses field_language to determine the language when reading a value.

I am testing this on an existing project which uses entity translation heavily.

In my patch from #6 I forgot another getter callback which needs to used field_language. In the entity_metadata_field_property_get function I need it too. This function is used for properties on fields (eg for the value of plain text fields).

Would be happy to see this feature soon. I've a content type with dates. The dates are different in each language or maybe there are no dates in a language. So if this is the case it should not happen that it displays the dates from the default language.

My workaround is to disable the language fallback in general. But I like the node fallback feature but not for each no-value field in a translated node.

I didn't see this and created a duplicated issue #2761319: Why always fallback to entity language when read field value?. I think patch #6 is not acceptable because it is a revert of the linked commit (http://cgit.drupalcode.org/entity/commit/modules/callbacks.inc?id=658db8...).

Setting to "needs review".

Here's a condensed excerpt of the failing test:

$body['en'][0] = array('value' => '<b>English body.</b>', 'summary' => '<b>The body.</b>');
$node = $this->drupalCreateNode(array('body' => $body, 'language' => 'en', 'type' => 'page'));
$wrapper = entity_metadata_wrapper('node', $node);
// ...
$wrapper->language('de');
// ...
$wrapper->body->set(array('value' => "<b>Der zweite Text.</b>"));
// ...
$wrapper->language(LANGUAGE_NONE);
// ...
$this->assertEqual($wrapper->body->value->value(), "<p>English body.</p>\n", 'Default language text is still there.');

@jcisio (comment 9) - the big difference between this patch and the reverse of that commit is that this only changes the fallback for getters, which were the only places that already used the contentious fallback. It mustn't change setters, I'd agree on that!

(The fallback in those getters will just change from the entity's inherent language, to whatever fallback is appropriate for the specific field in question. Given that these getters are field-specific, I believe this is the correct approach.)

I had the same issue where language fallback config and entity_metadata_wrapper getters didn't jive. In our case, we don't use fallback ever, so rather then patching, I just tweaked for our use case...

/**
 * Implements hook_entity_property_info_alter().
 *
 * Address issue where entity_metadata_wrapper get doesn't respect the
 * fallback config setting.
 *
 * @see https://www.drupal.org/project/entity/issues/2335357
 */
function et_override_entity_property_info_alter(&$info) {
  // Minimize impact of this alter.
  $bundles = [
    'dct_device',
    'dct_product',
  ];

  foreach ($info['node']['bundles'] as $bundle_name => &$bundle) {
    if (in_array($bundle_name, $bundles)) {
      foreach ($bundle['properties'] as $property_name => &$property) {
        if ($property['translatable'] && $property['getter callback'] == 'entity_metadata_field_property_get') {
          $property['getter callback'] = 'et_override_entity_metadata_field_property_get';
        }
      }
    }
  }
}

/**
 * Entity translate override version of entity_metadata_field_property_get().
 *
 * Addresses shortfall where entity_metadata_field_get_language is called
 * with language fallback hardcoded to TRUE.
 *
 * @see https://www.drupal.org/project/entity/issues/2335357
 */
function et_override_entity_metadata_field_property_get($entity, array $options, $name, $entity_type, $info) {
  $field = field_info_field($name);
  $columns = array_keys($field['columns']);
  $langcode = isset($options['language']) ? $options['language']->language : LANGUAGE_NONE;
  $langcode = entity_metadata_field_get_language($entity_type, $entity, $field, $langcode, FALSE);
  $values = array();
  if (isset($entity->{$name}[$langcode])) {
    foreach ($entity->{$name}[$langcode] as $delta => $data) {
      $values[$delta] = $data[$columns[0]];
      if ($info['type'] == 'boolean' || $info['type'] == 'list<boolean>') {
        // Ensure that we have a clean boolean data type.
        $values[$delta] = (boolean) $values[$delta];
      }
    }
  }
  // For an empty single-valued field, we have to return NULL.
  return $field['cardinality'] == 1 ? ($values ? reset($values) : NULL) : $values;
}