Wrong mappig in getFieldTypeMapping() for date field

Hello,

I'm creating a custom processor that adds some fields to the index. I'm using alterPropertyDefinitions(), for definition, preprocessIndexItems() for adding some fields and preIndexSave() where I use ensureField().

It works well for all fields that I'm adding except for the 'date' field type.

I don't know if the solution is to

1. Modify the getFieldTypeMapping() adding also 'date'.
   

   'date' => array(
       'datetime_iso8601',
       'timestamp',
   ),
   

   Should be

   'date' => array(
       'date',
       'datetime_iso8601',
       'timestamp',
   ),
   

2. Call ensureField() making sure that the third param is always added.
   $this->ensureField(NULL, $field_id, $field_definition['type']);

Both of them solve the issue, but I don't know about which one to use. I added a patch, just in case the first option is the right one.