hook_roles

I would like to propose a modification to the core Drupal system: A new hook titled
hook_roles.

hook_roles would add role IDs to the array of roles returned by the existing Drupal operation:

$user->roles

Module developers would create a function in their module titled "my_module_name_roles" and this function would return the IDs of additional roles that the module has determined the user should have at the time $user->roles is called.

So, the process would be:

1. $user->roles is called in some function somewhere.
2. Drupal checks hooks. Sample:

function mymodule_roles($user) {
  array added_roles();
  // Do whatever to determine what roles should be added to this user at this point.
  return added_roles();

3. Whatever roles are returned by the hook_roles hooks are added to the results of $user->roles.
4. Drupal processes the results of $user->roles as normal.

I have a module I developed call og_user_roles http://drupal.org/node/87679. What this module does is assign roles to OG Group Members that are specific to the group the member is in at the time the requested function is called. Right now, for this to work, I have to hack the user_access function in the user.module like this:

function user_access($string, $account = NULL) {
  global $user;
  static $perm = array();

  if (is_null($account)) {
    $account = $user;
  }

  // User #1 has all privileges:
  if ($account->uid == 1) {
    return TRUE;
  }

  // To reduce the number of SQL queries, we cache the user's permissions
  // in a static variable.
//
// Modifications
//
// We don't cache, so we don't need to check if $perm[$account->uid] is set
// We now use "user_all_roles" to bring back additional roles by group, instead of just $account->roles
//
//  if (!isset($perm[$account->uid])) {
//    $result = db_query("SELECT DISTINCT(p.perm) FROM {role} r INNER JOIN {permission} p ON p.rid = r.rid WHERE r.rid IN (%s)", implode(',', array_keys($account->roles))); // orig code
    $result = db_query("SELECT DISTINCT(p.perm) FROM {role} r INNER JOIN {permission} p ON p.rid = r.rid WHERE r.rid IN (%s)", implode(',', user_all_roles($account))); // my modification

    $perm[$account->uid] = '';
    while ($row = db_fetch_object($result)) {
      $perm[$account->uid] .= "$row->perm, ";
    }
//  }
//
// Modification
// Remove duplicates from $perm[$account->uid];
//
  	static $tempArray = array();
	static $tempArray0 = array();
  	$tempString = "";
	//
	// First covert $perm[$account->uid] to string;
	//
		$tempString = $perm[$account->uid];
	//
	// Next, convert this to an array;
	//
		$tempArray = split(',', $tempString);
	//
	// Now, make the array unique
	//
		$tempArray0 = array_unique($tempArray);
	//
	// Now copy back to $perm[$account->uid];
	//
	    $perm[$account->uid] = implode(",", $tempArray0);

  if (isset($perm[$account->uid])) {
    return strpos($perm[$account->uid], "$string, ") !== FALSE;
  }

  return FALSE;
}

This proposed hook would eliminate the need for me, or anyone else with a similar need, to hack the core module for this purpose.