add mjs_detachDefault to delete a default class from mjSpec

PiperOrigin-RevId: 738452369
Change-Id: I5a53a6dc8f89e1e8136aeefc09d7d9b7b7204e1f

doc/APIreference/functions.rst

@@ -3851,7 +3851,16 @@ Attach child frame to a parent site, return the attached frame if success or NUL
 
 .. mujoco-include:: mjs_detachBody
 
-Detach body from mjSpec, remove all references and delete the body, return 0 on success.
+Delete body and descendants from mjSpec, remove all references, return 0 on success.
+
+.. _mjs_detachDefault:
+
+`mjs_detachDefault <#mjs_detachDefault>`__
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. mujoco-include:: mjs_detachDefault
+
+Delete default class and descendants from mjSpec, remove all references, return 0 on success.
 
 .. _AddTreeElements:
 
@@ -3936,7 +3945,8 @@ Add frame to body.
 
 .. mujoco-include:: mjs_delete
 
-Delete object corresponding to the given element, return 0 on success.
+Delete object corresponding to the given element, return 0 on success. This function should only be used for element
+types that cannot have children, i.e. excluding bodies and default classes.
 
 .. _AddNonTreeElements:
 

doc/APIreference/functions_override.rst

@@ -704,3 +704,8 @@ to the inputs. Below, :math:`\bar q` denotes the pre-modified quaternion:
 
 Note that derivatives depend only on :math:`h` and :math:`v` (in fact, on :math:`s = h v`).
 All outputs are optional.
+
+.. _mjs_delete:
+
+Delete object corresponding to the given element, return 0 on success. This function should only be used for element
+types that cannot have children, i.e. excluding bodies and default classes.

doc/includes/references.h

@@ -603,7 +603,9 @@ typedef enum mjtObj_ {            // type of MujoCo object
   mjNOBJECT,                      // number of object types
 
   // meta elements, do not appear in mjModel
-  mjOBJ_FRAME         = 100       // frame
+  mjOBJ_FRAME         = 100,      // frame
+  mjOBJ_DEFAULT                   // default
+
 } mjtObj;
 typedef enum mjtConstraint_ {     // type of constraint
   mjCNSTR_EQUALITY    = 0,        // equality constraint
@@ -3612,6 +3614,7 @@ mjsBody* mjs_attachToSite(mjsSite* parent, const mjsBody* child,
 mjsFrame* mjs_attachFrameToSite(mjsSite* parent, const mjsFrame* child,
                                 const char* prefix, const char* suffix);
 int mjs_detachBody(mjSpec* s, mjsBody* b);
+int mjs_detachDefault(mjSpec* s, mjsDefault* d);
 mjsBody* mjs_addBody(mjsBody* body, const mjsDefault* def);
 mjsSite* mjs_addSite(mjsBody* body, const mjsDefault* def);
 mjsJoint* mjs_addJoint(mjsBody* body, const mjsDefault* def);
@@ -3652,7 +3655,7 @@ mjsBody* mjs_getParent(mjsElement* element);
 mjsFrame* mjs_getFrame(mjsElement* element);
 mjsFrame* mjs_findFrame(mjSpec* s, const char* name);
 mjsDefault* mjs_getDefault(mjsElement* element);
-const mjsDefault* mjs_findDefault(mjSpec* s, const char* classname);
+mjsDefault* mjs_findDefault(mjSpec* s, const char* classname);
 mjsDefault* mjs_getSpecDefault(mjSpec* s);
 int mjs_getId(mjsElement* element);
 mjsElement* mjs_firstChild(mjsBody* body, mjtObj type, int recurse);