Undefined function entity_token_tokens

Here is this patch.

Just faced such problem with Rules 7.x-2.9
Fatal error: Call to undefined function entity_token_tokens() in /var/www/mydom/sites/all/modules/rules/rules.module on line 1671

in my case patch resulted that any tokens (not related to entities, just primitive strings too) was not solving in rules.
This patch works better

function rules_tokens($type, $tokens, $data, $options = array()) {
  // Handle replacements of primitive variable types.
  if (substr($type, 0, 6) == 'rules_' && !empty($data[$type])) {
module_load_include('module', 'entity_token'); //++
module_load_include('inc', 'entity_token', 'entity_token.tokens'); //++
    // Leverage entity tokens token processor by passing on as struct.
    $info['property info']['value'] = array(
      'type' => substr($type, 6),
      'label' => '',
    );
    // Entity tokens uses metadata wrappers as values for 'struct' types.
    $wrapper = entity_metadata_wrapper('struct', array('value' => $data[$type]), $info);
    return entity_token_tokens('struct', $tokens, array('struct' => $wrapper), $options);
  }
}

I can see that is some very edge cases perhaps entity_token.tokens.inc is not loaded at the point when rules_tokens() is invoked. But there are easy workarounds for this if you are encountering that situation, and as the original poster points out this will not happen to most people.

The problem with the patch is that replacing the call to entity_token_tokens() with module_invoke('entity_token', 'tokens', ...) does not actually force entity_token.tokens.inc to be loaded, so it does not solve the problem. The only thing it does is to hide the error message. Essentially, module_invoke() is just calling function_exists() to check if entity_token_tokens() exists before using it. If it doesn't exist, then it's never loaded. So this patch does not fix the problem, just hides it.

I'm marking this as "won't fix" because it really doesn't affect a lot of users, and those users have an easy work-around of using module_load_include() in their own code if they want to call module_invoke('rules', 'tokens') directly. IMO the potential problems caused by changing how include files are loaded at this point in the D7 lifecycle far outweigh the benefits.

FYI: Just ran into the same issue when submitting an entity form:
Error: Call to undefined function entity_token_tokens() in rules_tokens() (Zeile 1711 von /sites/all/modules/contrib/rules/rules.module).

Using Rules 7.x-2.12

EDIT: Updating to Rules 7.x-2.13 fixed the issue!