Remove mjCPlugin from xml_native_reader.

PiperOrigin-RevId: 608546883
Change-Id: Ib529c2756102e4e2185d1d8e9585187c30049011

src/user/user_api.cc

@@ -13,7 +13,10 @@
 // limitations under the License.
 
 #include "user/user_api.h"
+#include <functional>
+#include <map>
 #include <string>
+#include <utility>
 #include <vector>
 
 #include <mujoco/mujoco.h>
@@ -318,8 +321,8 @@ mjmKey* mjm_addKey(mjmModel* model) {
 mjmPlugin* mjm_addPlugin(mjmModel* model) {
   mjCModel* modelC = reinterpret_cast<mjCModel*>(model->element);
   mjCPlugin* plugin = modelC->AddPlugin();
-  plugin->plugin.instance = (mjElement)plugin;
-  return &plugin->plugin;
+  plugin->spec.instance = (mjElement)plugin;
+  return &plugin->spec;
 }
 
 
@@ -508,6 +511,16 @@ const double* mjm_getDouble(const mjDoubleVec source, int* size) {
 
 
 
+// set plugin attributes
+void mjm_setPluginAttributes(mjmPlugin* plugin, void* attributes) {
+  mjCPlugin* pluginC = reinterpret_cast<mjCPlugin*>(plugin->instance);
+  std::map<std::string, std::string, std::less<>>* config_attribs =
+      reinterpret_cast<std::map<std::string, std::string, std::less<>>*>(attributes);
+  pluginC->config_attribs = std::move(*config_attribs);
+}
+
+
+
 // compute full inertia
 const char* mjm_setFullInertia(mjmBody* bodyspec, double quat[4], double inertia[3]) {
   mjCBody* body = reinterpret_cast<mjCBody*>(bodyspec->element);