MDL-33019: Check that message providers' plugins are enabled and exist

lib/messagelib.php

@@ -389,7 +389,7 @@ function message_get_providers_for_user($userid) {
 
     $systemcontext = get_context_instance(CONTEXT_SYSTEM);
 
-    $providers = $DB->get_records('message_providers', null, 'name');
+    $providers = get_message_providers();
 
     // Remove all the providers we aren't allowed to see now
     foreach ($providers as $providerid => $provider) {

message/defaultoutputs.php

@@ -34,7 +34,7 @@
 // Fetch processors
 $processors = get_message_processors(true);
 // Fetch message providers
-$providers = $DB->get_records('message_providers', null, 'name');
+$providers = get_message_providers();
 
 if (($form = data_submitted()) && confirm_sesskey()) {
     $preferences = array();

message/lib.php

@@ -2297,6 +2297,36 @@ function get_message_processors($ready = false) {
     return $processors;
 }
 
+/**
+ * Get all message providers, validate their plugin existance and
+ * system configuration
+ *
+ * @return mixed $processors array of objects containing information on message processors
+ */
+function get_message_providers() {
+    global $CFG, $DB;
+    require_once($CFG->libdir . '/pluginlib.php');
+    $pluginman = plugin_manager::instance();
+
+    $providers = $DB->get_records('message_providers', null, 'name');
+
+    // Remove all the providers whose plugins are disabled or don't exist
+    foreach ($providers as $providerid => $provider) {
+        $plugin = $pluginman->get_plugin_info($provider->component);
+        if ($plugin) {
+            if ($plugin->get_status() === plugin_manager::PLUGIN_STATUS_MISSING) {
+                unset($providers[$providerid]);   // Plugins does not exist
+                continue;
+            }
+            if ($plugin->is_enabled() === false) {
+                unset($providers[$providerid]);   // Plugin disabled
+                continue;
+            }
+        }
+    }
+    return $providers;
+}
+
 /**
  * Get an instance of the message_output class for one of the output plugins.
  * @param string $type the message output type. E.g. 'email' or 'jabber'.