Replace mjs_detachBody and mjs_detachDefault with mjs_detach.

In a follow-up, mjs_detach will be changed to only remove without deleting an element.

PiperOrigin-RevId: 773637351
Change-Id: I9ee4d3584ba88ccc225591337cf036bab806e25c

src/user/user_api.cc

@@ -284,35 +284,18 @@ const char* mjs_getError(mjSpec* s) {
 
 
 // detach body from mjSpec, return 0 on success
-int mjs_detachBody(mjSpec* s, mjsBody* b) {
+int mjs_detach(mjSpec* s, mjsElement* element) {
   mjCModel* model = static_cast<mjCModel*>(s->element);
-  mjCBody* body = static_cast<mjCBody*>(b->element);
-  try {
-    *model -= *body;
-  } catch (mjCError& e) {
-    model->SetError(e);
+  if (!element) {
+    model->SetError(mjCError(0, "Element is null."));
     return -1;
   }
-  model->Detach(body);
-  return 0;
+  mjCError e(0, "Detach is not implemented yet.");
+  model->SetError(e);
+  return -1;
 }
 
-// detach default from mjSpec, return 0 on success
-int mjs_detachDefault(mjSpec* s, mjsDefault* def) {
-  mjCModel* modelC = static_cast<mjCModel*>(s->element);
-  if (!def) {
-    modelC->SetError(mjCError(0, "Cannot detach, default is null"));
-    return -1;
-  }
-  mjCDef* defC = static_cast<mjCDef*>(def->element);
-  try {
-    *modelC -= *defC;
-  } catch (mjCError& e) {
-    modelC->SetError(e);
-    return -1;
-  }
-  return 0;
-}
+
 
 // check if model has warnings
 int mjs_isWarning(mjSpec* s) {
@@ -372,15 +355,24 @@ int mj_copyBack(mjSpec* s, const mjModel* m) {
 
 
 // delete object, return 0 on success
-int mjs_delete(mjsElement* element) {
-  mjCModel* model;
-  if (element->elemtype == mjOBJ_DEFAULT)
-    model = static_cast<mjCDef*>(element)->model;
-  else
-    model = static_cast<mjCBase*>(element)->model;
+int mjs_delete(mjSpec* s, mjsElement* element) {
+  mjCModel* model = static_cast<mjCModel*>(s->element);
+  if (!element) {
+    model->SetError(mjCError(0, "Element is null."));
+    return -1;
+  }
   try {
-    // it will call the appropriate destructor since ~mjCBase is virtual
-    model->DeleteElement(element);
+    if (element->elemtype == mjOBJ_BODY) {
+      mjCBody* body = static_cast<mjCBody*>(element);
+      *model -= *body;
+      model->DeleteElement(body);
+    } else if (element->elemtype == mjOBJ_DEFAULT) {
+      mjCDef* def = static_cast<mjCDef*>(element);
+      *model -= *def;
+    } else {
+      // it will call the appropriate destructor since ~mjCBase is virtual
+      model->DeleteElement(element);
+    }
     return 0;
   } catch (mjCError& e) {
     model->SetError(e);
@@ -1035,7 +1027,7 @@ const char* mjs_resolveOrientation(double quat[4], mjtByte degree, const char* s
 mjsFrame* mjs_bodyToFrame(mjsBody** body) {
   mjCBody* bodyC = static_cast<mjCBody*>((*body)->element);
   mjCFrame* frameC = bodyC->ToFrame();
-  bodyC->model->Detach(bodyC);
+  bodyC->model->DeleteElement((*body)->element);
   *body = nullptr;
   return &frameC->spec;
 }

src/user/user_api.h

@@ -76,11 +76,8 @@ MJAPI int mj_copyBack(mjSpec* s, const mjModel* m);
 MJAPI mjsElement* mjs_attach(mjsElement* parent, const mjsElement* child,
                              const char* prefix, const char* suffix);
 
-// Detach body from mjSpec, remove all references and delete the body, return 0 on success.
-MJAPI int mjs_detachBody(mjSpec* s, mjsBody* b);
-
-// Detach default from mjSpec, remove all references and delete the default, return 0 on success.
-MJAPI int mjs_detachDefault(mjSpec* s, mjsDefault* d);
+// Detach but not delete object corresponding to the given element, return 0 on success.
+MJAPI int mjs_detach(mjSpec* s, mjsElement* element);
 
 //---------------------------------- Add tree elements ---------------------------------------------
 
@@ -109,7 +106,7 @@ MJAPI mjsLight* mjs_addLight(mjsBody* body, const mjsDefault* def);
 MJAPI mjsFrame* mjs_addFrame(mjsBody* body, mjsFrame* parentframe);
 
 // Delete object corresponding to the given element, return 0 on success.
-MJAPI int mjs_delete(mjsElement* element);
+MJAPI int mjs_delete(mjSpec* s, mjsElement* element);
 
 
 //---------------------------------- Add non-tree elements -----------------------------------------

src/user/user_model.cc

@@ -742,15 +742,44 @@ void deletefromlist(std::vector<T*>* list, mjsElement* element) {
 
 
 
+// recursively delete all plugins in the subtree
+static void deletesubtreeplugin(mjCBody* subtree, mjCModel* model) {
+  mjsPlugin* plugin = &(subtree->spec.plugin);
+  if (plugin->active && plugin->name->empty()) {
+    model->DeleteElement(plugin->element);
+  }
+  for (auto* body : subtree->Bodies()) {
+    deletesubtreeplugin(body, model);
+  }
+}
+
+
+
 // discard all invalid elements from all lists
 void mjCModel::DeleteElement(mjsElement* el) {
   ResetTreeLists();
 
+  if (el->elemtype != mjOBJ_DEFAULT) {
+    if (static_cast<mjCBase*>(el)->model != this) {
+      throw mjCError(nullptr, "element is not in this model");
+    }
+  } else {
+    if (static_cast<mjCDef*>(el)->model != this) {
+      throw mjCError(nullptr, "default is not in this model");
+    }
+  }
+
   switch (el->elemtype) {
     case mjOBJ_BODY:
+    {
       MakeTreeLists();  // rebuild lists that were reset at the beginning of the function
-      throw mjCError(nullptr, "bodies cannot be deleted, use detach instead");
+      mjCBody* subtree = static_cast<mjCBody*>(el);
+      if (subtree->GetRef() == 1)  {
+        deletesubtreeplugin(subtree, this);
+      }
+      subtree->Release();
       break;
+    }
 
     case mjOBJ_DEFAULT:
       MakeTreeLists();  // rebuild lists that were reset at the beginning of the function
@@ -828,29 +857,6 @@ void mjCModel::DeleteElement(mjsElement* el) {
 
 
 
-// recursively delete all plugins in the subtree
-void deletesubtreeplugin(mjCBody* subtree, mjCModel* model) {
-  mjsPlugin* plugin = &(subtree->spec.plugin);
-  if (plugin->active && plugin->name->empty()) {
-    model->DeleteElement(plugin->element);
-  }
-  for (auto* body : subtree->Bodies()) {
-    deletesubtreeplugin(body, model);
-  }
-}
-
-
-
-// deletes all plugins in the subtree and then the subtree itself
-void mjCModel::Detach(mjCBody* subtree) {
-  if (subtree->GetRef() == 1)  {
-    deletesubtreeplugin(subtree, this);
-  }
-  subtree->Release();
-}
-
-
-
 // TODO: we should not use C-type casting with multiple C++ inheritance
 void mjCModel::CreateObjectLists() {
   for (int i = 0; i < mjNOBJECT; ++i) {

src/user/user_model.h

@@ -232,9 +232,6 @@ class mjCModel : public mjCModel_, private mjSpec {
   // delete default and all descendants
   void RemoveDefault(mjCDef* def);
 
-  // detach subtree from model
-  void Detach(mjCBody* subtree);
-
   // API for access to model elements (outside tree)
   int NumObjects(mjtObj type);              // number of objects in specified list
   mjCBase* GetObject(mjtObj type, int id);  // pointer to specified object

src/xml/xml_native_reader.cc

@@ -3554,7 +3554,7 @@ void mjXReader::Body(XMLElement* section, mjsBody* body, mjsFrame* frame,
       }
 
       // delete subtree
-      if (mjs_detachBody(spec, subtree)) {
+      if (mjs_delete(spec, subtree->element)) {
         throw mjXError(elem, mjs_getError(spec));
       }
     }