[RM] Add error handling for missing plugin tags in URDF parsing (backport #2138) (#2145)

Author: mergify[bot]

hardware_interface/src/component_parser.cpp

@@ -411,6 +411,10 @@ TransmissionInfo parse_transmission_from_xml(const tinyxml2::XMLElement * transm
   // Find name, type and class of a transmission
   transmission.name = get_attribute_value(transmission_it, kNameAttribute, transmission_it->Name());
   const auto * type_it = transmission_it->FirstChildElement(kClassTypeTag);
+  if (!type_it)
+  {
+    throw std::runtime_error("Missing <plugin> tag of <transmission> element in your URDF.");
+  }
   transmission.type = get_text_for_element(type_it, kClassTypeTag);
 
   // Parse joints
@@ -515,6 +519,10 @@ HardwareInfo parse_resource_from_xml(
     if (!std::string(kHardwareTag).compare(ros2_control_child_it->Name()))
     {
       const auto * type_it = ros2_control_child_it->FirstChildElement(kClassTypeTag);
+      if (!type_it)
+      {
+        throw std::runtime_error("Missing <plugin> tag of <hardware> element in your URDF.");
+      }
       hardware.hardware_class_type =
         get_text_for_element(type_it, std::string("hardware ") + kClassTypeTag);
       const auto * params_it = ros2_control_child_it->FirstChildElement(kParamTag);