[development] Installation -- Can A Module "Refuse" To Be Installed?

[Earl Miles]

Rob Thorne wrote:
> I've started to write .install files for the modules I'm responsible 
> for.  Mostly this is pretty straightforward.  But there are a few areas 
> I'm hoping there is support for in the system:
> 
>    * UI for problems/status during install:  I've made it a practice to
>      do like merlinofchaos and put up a message to indicate I've
>      installed tables (with a call to drupal_set_message).  It's less
>      clear what's best to call if there's a problem.
>    * I've noticed that there are calls in install.inc to register
>      schema versions, but I haven't seen any examples of their being
>      used.  How *should* those functions be used?
>    * Dependencies are an issue for some of the stuff I'm installing. 
>      It would be a good thing if the .install could detect that a
>      needed module was not present, and in that case, put up an error
>      message and refuse to install.  Is there a mechanism to do this
>      currently?

cut & paste cause I lazy

/**
  * hunmonk's module dependency check: see http://drupal.org/node/54463
  */
function views_ui_form_alter($form_id, &$form) {
   if ($form_id == 'system_modules' && !$_POST) {
     views_ui_system_module_validate($form);
   }
}

/**
  * hunmonk's module dependency check: see http://drupal.org/node/54463
  */
function views_ui_system_module_validate(&$form) {
   $module = 'views_ui';
   $dependencies = array('views');
   foreach ($dependencies as $dependency) {
       if (!in_array($dependency, $form['status']['#default_value'])) {
         $missing_dependency = TRUE;
         $missing_dependency_list[] = $dependency;
       }
   }
   if (in_array($module, $form['status']['#default_value']) && 
isset($missing_dependency)) {
     db_query("UPDATE {system} SET status = 0 WHERE type = 'module' AND name = 
'%s'", $module);
     $key = array_search($module, $form['status']['#default_value']);
     unset($form['status']['#default_value'][$key]);
     drupal_set_message(t('The module %module was deactivated--it requires the 
following disabled/non-existant modules to function properly: %dependencies', 
array('%module' => $module, '%dependencies' => implode(', ', 
$missing_dependency_list))), 'error');
   }
}