Entity Reference Views Widget plus Organic Groups Nightmare

Let's suppose you are using the Entity Reference Views Widget to display items to be included in an Entity Reference field. This is actually quite a cool module while being a little awkward to use - essentially it gives you a views listing of candidate entities to add, with an AJAX-driven checkbox: click the box and the entity gets moved to the list on the left to display what's been chosen.

Which is all fine.

The project I'm currently working on uses Organic Groups to group certain users within an organisation allowing them to work on very specific types of node content. I had to create a completely new type of entity (though that's not important) for them so they could add one or more of these entities to one or more of their special content.

The new entity was made subject to the OG, and that too was fine.

So then I came to build the Entity Reference Views Widget to only display the new entities that belonged to the current user's OG.

Meltdown. Either I listed everything, or nothing. Filtering OGs is not the easiest thing in the world: You have to create an OG relationship for the entity in question (easy) and then add an argument which if it has no value (the desired state) uses the OG Context module to figure out what OGs are available.

Weird fact number #87654: The OG context module allows you to base OG on the current node and on a user currently being viewed or edited, but not on the current user. So I had to build a quick context for that:

/**
 * Implements hook_og_context_negotiation_info().
 */
function mymodule_og_context_negotiation_info() {
  return array(
    'user' => array(
      'name' => t('User'),
      'description' => t("Determine context by finding the current user's OG (if any)."),
      'callback' => 'mymodule_context_handler_user',
    ),
  );
}

/**
 * Implements hook_og_context_negotiation_info_alter().
 */
function mymodule_og_context_negotiation_info_alter(&$contexts) {
  $context['node']['menu path'][] = 'node/%/edit';
}

function mymodule_context_handler_user() {
  global $user;
  $account = clone $user;
  $contexts = _group_context_handler_entity('user', $account);
  return $contexts;
}

In fact this does two things: it expands the context checking for nodes to include nodes being edited and adds a context that looks at the current user.

Okay. Next factor: Entity Reference Views Widget has this neat facility for feeding the entity IDs of entities already selected back into the view and excluding them. This is great and it also uses an argument, which needs to be the first argument.

However, and this is the nastiness, if the ERVW argument does not exist (i.e. no entities have yet to be selected for the field) the second argument fails to fire and you see all the entities without any OG filtering.

The solution is thankfully quite simple: Edit the ERVW argument so that it has a default value of "all", this means it always exists and the second argument does fire and figure out the correct OG context puts it into the query and filtering actually works.

Obviously I went through various stages of thinking each handler was broken or that there was something weird about my newly created entity. But none of those things were true. The problem was simply one of configuration.

Hope that helps.