Problem with relation fields that have unlimited number of values (patch provided)

I have realised this fix doesn not work in PHP 5.3, though it works in PHP 5.4

Given the following code:

$a = "foo"; echo empty($a['bar']) ? 'empty' : 'full';

This will output "empty" with PHP 5.4 but "full" with PHP 5.3

The code that cleans up the input array calls node_reference_field_is_empty, which returns empty($item['nid']) - this will give a different result on PHP 5.3 than PHP 5.4 if $item is not array.

The function however is called directly from _field_invoke in /modules/field/field.attach.inc, so it is up to the function to clean up the array.

So I now see the 'add_more' field should never have made it that far. Trying to remove it at that stage is doing the work that should have been done in field_attach_submit. Relation Select needs to implement hook_field_attach_submit.

So if I understand the code well, what the relation_select module does is create the relation entity when field_insert is called. This has the disadvantage of not having the form information at the point anymore.

I have looked at the field_collection module and they do this when 'validate' is called - which means they do it when they still have the form information. However creating the entity in validate does not seem right either.

So a quick fix for my problem would be to unset add_more in relation_select_field_insert in the same way that field_default_extract_form_values does.

But a proper fix, I think, would require moving the logic of creating the relation entity and mapping the fields into hook_field_attach_submit.

Here is a stub version (all it does is remove the 'add_more' field) :

/**
 * Implements hook_field_attach_submit
 */
function relation_select_field_attach_submit($entity_type, $entity, $form, &$form_state) {
  list(, , $bundle) = entity_extract_ids($entity_type, $entity);  
  $instances = field_info_instances($entity_type, $bundle);
  foreach ($instances as $instance) {
    $field_name = $instance['field_name'];
    $field_info = field_info_field_by_id($instance['field_id']);
    if ($field_info['type'] != 'relation_select') {
      continue;
    }

    $languages = field_available_languages($entity_type, $field_info);
    foreach ($languages as $langcode) {
      if (!property_exists($entity, $field_name) || 
           empty($entity->{$field_name}[$langcode]['relation_fields'])) {
        continue;
      }
      $relation_fields = $entity->{$field_name}[$langcode]['relation_fields'];
      foreach ($relation_fields as $relation_field_name => $relation_field_items) {
        $relation_field_info = field_info_field($relation_field_name);
        $relation_field_languages = field_available_languages('relation', $relation_field_info);
        foreach ($relation_field_languages as $relation_field_langcode) {
          unset($entity->{$field_name}[$langcode]['relation_fields'][$relation_field_name][$relation_field_langcode]['add_more']);
        }
      }
    }
  }
}

@steveoliver: Thanks for you reply. From what you say, I think my suggestion above is one that would go into the normalize branch, and the main branch should keep using the current architecture until the normalize branch is ready.

In that case I'd suggest for the main branch that relation_select_field_insert should look for and unset 'add_more' when present.