Issue #2379407 by twistor, MegaChriz: Make module required if plugins are in use

feeds.module

@@ -719,6 +719,58 @@ function feeds_field_extra_fields() {
   return $extras;
 }
 
+
+/**
+ * Implements hook_system_info_alter().
+ *
+ * Goes through a list of all modules that provide Feeds plugins and makes them
+ * required if there are any importers using those plugins.
+ */
+function feeds_system_info_alter(array &$info, $file, $type) {
+  if ($type !== 'module' || !module_hook($file->name, 'feeds_plugins')) {
+    return;
+  }
+
+  // Don't make Feeds require itself, otherwise you can't disable Feeds until
+  // all importers are deleted.
+  if ($file->name === 'feeds' || !function_exists('ctools_include')) {
+    return;
+  }
+
+  // Get the plugins that belong to the current module.
+  ctools_include('plugins');
+  $module_plugins = array();
+  foreach (ctools_get_plugins('feeds', 'plugins') as $plugin_id => $plugin) {
+    if ($file->name === $plugin['module']) {
+      $module_plugins[$plugin_id] = TRUE;
+    }
+  }
+
+  // Check if any importers are using any plugins from the current module.
+  foreach (feeds_importer_load_all(TRUE) as $importer) {
+    $configuration = $importer->getConfig();
+
+    foreach (array('fetcher', 'parser', 'processor') as $plugin_type) {
+      $plugin_key = $configuration[$plugin_type]['plugin_key'];
+      if (isset($module_plugins[$plugin_key])) {
+        $info['required'] = TRUE;
+        break 2;
+      }
+    }
+  }
+
+  if (empty($info['required'])) {
+    return;
+  }
+
+  if (module_exists('feeds_ui') && user_access('administer feeds')) {
+    $info['explanation'] = t('Feeds is currently using this module for one or more <a href="@link">importers</a>.', array('@link' => url('admin/structure/feeds')));
+  }
+  else {
+    $info['explanation'] = t('Feeds is currently using this module for one or more importers.');
+  }
+}
+
 /**
  * @}
  */