Allow for shared email addresses

Some sites attract families who share an email address. Some companies have groups of workers who share a role and need a common meail address. Allow for a shared email address.

The right way would be a hook_meail_verification to let modules replace the email verification in module user. The second way is the quick modification I show in the following code. This example mod simply allows duplicate email addresses if set in the admin interface.

A preferred option would be to pass the verification to en external module through a hook. The same module would need to process the verification email and the password replacement email so that the process can allow for people with no email address who use alternative communications. The idea is discussed in http://drupal.org/node/15578. I suggest a tasty alternative communications media in http://drupal.org/node/15578#comment-1026668. SMS is another alternative to hook in through a module.

user_admin.inc function user_admin_settings() gets an extra setting:

function user_admin_settings() {
  // User registration settings.
  $form['registration'] = array('#type' => 'fieldset', '#title' => t('User registration settings'));
  $form['registration']['user_register'] = array('#type' => 'radios', '#title' => t('Public registrations'), '#default_value' => variable_get('user_register', 1), '#options' => array(t('Only site administrators can create new user accounts.'), t('Visitors can create accounts and no administrator approval is required.'), t('Visitors can create accounts but administrator approval is required.')));
  $form['registration']['user_email_verification'] = array('#type' => 'checkbox', '#title' => t('Require e-mail verification when a visitor creates an account'), '#default_value' => variable_get('user_email_verification', TRUE), '#description' => t('If this box is checked, new users will be required to validate their e-mail address prior to logging into the site, and will be assigned a system-generated password. With it unchecked, users will be logged in immediately upon registering, and may select their own passwords during registration.'));
/*
20080917 PeterMoulding.com Allow duplicate email addresses so families can share email addresses.
*/
	$form['registration']['user_email_duplication'] = array('#type' => 'checkbox',
		'#title' => t('Allow duplicate e-mail addresses when a visitor creates an account'),
		'#default_value' => variable_get('user_email_duplication', false),
		'#description' => t('If this box is checked, new users will be allowed to use e-mail addresses already registered in the database.'));
  
  $form['registration']['user_registration_help'] = array('#type' => 'textarea', '#title' => t('User registration guidelines'), '#default_value' => variable_get('user_registration_help', ''), '#description' => t('This text is displayed at the top of the user registration form and is useful for helping or instructing your users.'));

  // User e-mail settings.

user.module function _user_edit_validate() checks the setting then drops a test if true:

function _user_edit_validate($uid, &$edit) {
  $user = user_load(array('uid' => $uid));
  // Validate the username:
  if (user_access('change own username') || user_access('administer users') || !$user->uid) {
    if ($error = user_validate_name($edit['name'])) {
      form_set_error('name', $error);
    }
    else if (db_result(db_query("SELECT COUNT(*) FROM {users} WHERE uid != %d AND LOWER(name) = LOWER('%s')", $uid, $edit['name'])) > 0) {
      form_set_error('name', t('The name %name is already taken.', array('%name' => $edit['name'])));
    }
    else if (drupal_is_denied('user', $edit['name'])) {
      form_set_error('name', t('The name %name has been denied access.', array('%name' => $edit['name'])));
    }
  }

  // Validate the e-mail address:
  if ($error = user_validate_mail($edit['mail'])) {
    form_set_error('mail', $error);
  }
/*
20080917 PeterMoulding.com Allow duplicate email addresses so families can share email addresses.
  else if (db_result(db_query("SELECT COUNT(*) FROM {users} WHERE uid != %d AND LOWER(mail) = LOWER('%s')", $uid, $edit['mail'])) > 0) {
    form_set_error('mail', t('The e-mail address %email is already registered. <a href="@password">Have you forgotten your password?</a>', array('%email' => $edit['mail'], '@password' => url('user/password'))));
  }
*/
	else if (!variable_get('user_email_duplication', false)
	and db_result(db_query("SELECT COUNT(*) FROM {users} WHERE uid != %d AND LOWER(mail) = LOWER('%s')", $uid, $edit['mail'])) > 0)
		{
		form_set_error('mail', t('The e-mail address %email is already registered. <a href="@password">Have you forgotten your password?</a>',
			array('%email' => $edit['mail'], '@password' => url('user/password'))));
		}

  else if (drupal_is_denied('mail', $edit['mail'])) {
    form_set_error('mail', t('The e-mail address %email has been denied access.', array('%email' => $edit['mail'])));
  }
}