Improve integration with Entity API

For those who would like to access the entity being edited within their rules workflow, here is a temporary workaround:

First download and enabled Rules Data Transforms, then within the configuration for your rules form support rule do the following

Add the action: "Explode text."
Set "Input Text" = "site:current-page:path" using data selector.
Set "delimiter" = "/"
"Provided variables" should = "output_list"
Click save

Add the action: "Convert data type."
Set "target type" = "integer"
Click continue
Set "value to convert" = "output-list:1" using the data selector (This is assuming your path = node/*/edit where * = node-id. If you were editing a term, for example, you would select output-list:2 because the path for editing terms = vocabulary/taxonomy/*/edit where * = term-id)
"Provided variables" should = "conversion_results"
Click save

Now add an action "Fetch entity by id"
Select your entity type
Click continue
Set "Identifier" = "conversion-results" using the data selector
"Provided variables" should = "entity_fetched"
Click save

You have now added Entity support to you Rules Form Support rule! If you want to do anything special with the entity (such as with its fields), you will need to add conditions. In order to add conditions, you must create a "rules component" action and pass the "entity_fetched" variable into this component as a parameter variable. This component must already have been created and the "component plugin" must = "rule". Within this component you may add any conditions and actions as needed (such as the "entity has field" condition...) You can also pass back results of this rules component to the rule as "provided" variables....

Not the ideal integration that version2 may be working towards, but a workaround none the less, and is quiet flexible!

Related: #1983908: Integrate with Entityform module.

FWIW: I wanted to be able to use the conditions such as "Entity is of Type". I'm also writing some conditions which use Entity and Field Names as parameters as it's a bit more intuitive in the Rules UI to select those rather then form, form_state and form_element.

Found it easiest to use hook_rules_event_info_alter(&$events) to add the Entity object to the variables array for the rules_forms events. I'm unsure on how to make it apply only to forms which only edit entities.

function merci_rules_rules_event_info_alter(&$events) {
  $form_events = variable_get('rules_forms_event_info', array());
  foreach ($form_events as $form_id => $info) {
    $events['rules_forms_' . $form_id . '_form_validate']['variables']['entity'] = array(
      'type' => 'entity',
      'label' => 'Entity',
      'handler' => 'merci_rules_events_variable_entity_load',
    ); 
  }
}

function merci_rules_events_variable_entity_load($arguments, $variable_name, $variable_info) {
  $entity = $arguments['form_state']['values'];
  $entity_type = array_key_exists('#entity_type', $arguments['form']) ? $arguments['form']['#entity_type'] : NULL;
  if (empty($entity_type)) {
    return NULL;
  } 
  return entity_metadata_wrapper($entity_type, (object) $entity);
}