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);

include/mujoco/mjmodel.h

@@ -268,7 +268,9 @@ 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;
 
 

include/mujoco/mujoco.h

@@ -1430,9 +1430,11 @@ MJAPI mjsBody* mjs_attachToSite(mjsSite* parent, const mjsBody* child,
 MJAPI mjsFrame* mjs_attachFrameToSite(mjsSite* parent, const mjsFrame* child,
                                       const char* prefix, const char* suffix);
 
-// 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.
 MJAPI int mjs_detachBody(mjSpec* s, mjsBody* b);
 
+// Delete default class and descendants from mjSpec, remove all references, return 0 on success.
+MJAPI int mjs_detachDefault(mjSpec* s, mjsDefault* d);
 
 //---------------------------------- Tree elements -------------------------------------------------
 
@@ -1566,7 +1568,7 @@ MJAPI mjsFrame* mjs_findFrame(mjSpec* s, const char* name);
 MJAPI mjsDefault* mjs_getDefault(mjsElement* element);
 
 // Find default in model by class name.
-MJAPI const mjsDefault* mjs_findDefault(mjSpec* s, const char* classname);
+MJAPI mjsDefault* mjs_findDefault(mjSpec* s, const char* classname);
 
 // Get global default from model.
 MJAPI mjsDefault* mjs_getSpecDefault(mjSpec* s);

python/mujoco/introspect/enums.py

@@ -287,6 +287,7 @@ ENUMS: Mapping[str, EnumDecl] = dict([
              ('mjOBJ_PLUGIN', 25),
              ('mjNOBJECT', 26),
              ('mjOBJ_FRAME', 100),
+             ('mjOBJ_DEFAULT', 101),
          ]),
      )),
     ('mjtConstraint',

python/mujoco/introspect/functions.py

@@ -9154,7 +9154,27 @@ FUNCTIONS: Mapping[str, FunctionDecl] = dict([
                  ),
              ),
          ),
-         doc='Detach body from mjSpec, remove all references and delete the body, return 0 on success.',  # pylint: disable=line-too-long
+         doc='Delete body and descendants from mjSpec, remove all references, return 0 on success.',  # pylint: disable=line-too-long
+     )),
+    ('mjs_detachDefault',
+     FunctionDecl(
+         name='mjs_detachDefault',
+         return_type=ValueType(name='int'),
+         parameters=(
+             FunctionParameterDecl(
+                 name='s',
+                 type=PointerType(
+                     inner_type=ValueType(name='mjSpec'),
+                 ),
+             ),
+             FunctionParameterDecl(
+                 name='d',
+                 type=PointerType(
+                     inner_type=ValueType(name='mjsDefault'),
+                 ),
+             ),
+         ),
+         doc='Delete default class and descendants from mjSpec, remove all references, return 0 on success.',  # pylint: disable=line-too-long
      )),
     ('mjs_addBody',
      FunctionDecl(
@@ -9954,7 +9974,7 @@ FUNCTIONS: Mapping[str, FunctionDecl] = dict([
      FunctionDecl(
          name='mjs_findDefault',
          return_type=PointerType(
-             inner_type=ValueType(name='mjsDefault', is_const=True),
+             inner_type=ValueType(name='mjsDefault'),
          ),
          parameters=(
              FunctionParameterDecl(

python/mujoco/specs.cc

@@ -448,7 +448,7 @@ PYBIND11_MODULE(_specs, m) {
       py::return_value_policy::reference_internal);
   mjSpec.def(
       "find_default",
-      [](MjSpec& self, std::string& classname) -> const raw::MjsDefault* {
+      [](MjSpec& self, std::string& classname) -> raw::MjsDefault* {
         return mjs_findDefault(self.ptr, classname.c_str());
       },
       py::return_value_policy::reference_internal);
@@ -499,6 +499,11 @@ PYBIND11_MODULE(_specs, m) {
         return mjs_addDefault(spec->ptr, classname.c_str(), parent);
       },
       py::return_value_policy::reference_internal);
+  mjSpec.def("detach_default", [](MjSpec& self, raw::MjsDefault& def) {
+    if (mjs_detachDefault(self.ptr, &def) != 0) {
+      throw pybind11::value_error(mjs_getError(self.ptr));
+    }
+  });
   mjSpec.def_property_readonly(
       "default",
       [](MjSpec& self) -> raw::MjsDefault* {

python/mujoco/specs_test.py

@@ -589,6 +589,12 @@ class SpecsTest(absltest.TestCase):
     spec.compile()
     self.assertEqual(spec.to_xml(), XML)
 
+    # test delete default
+    def1 = spec.find_default('def1')
+    spec.detach_default(def1)
+    def1 = spec.find_default('def1')
+    self.assertIsNone(def1)
+
   def test_element_list(self):
     spec = mujoco.MjSpec()
     sensor1 = spec.add_sensor()

src/engine/engine_io.c

@@ -2137,6 +2137,7 @@ static int sensorSize(mjtSensor sensor_type, int sensor_dim) {
 //   -2: invalid objtype
 static int numObjects(const mjModel* m, mjtObj objtype) {
   switch (objtype) {
+  case mjOBJ_DEFAULT:
   case mjOBJ_FRAME:
   case mjOBJ_UNKNOWN:
     return -1;

src/user/user_api.cc

@@ -227,7 +227,7 @@ const char* mjs_getError(mjSpec* s) {
 
 
 
-// Detach body from mjSpec, return 0 if success.
+// detach body from mjSpec, return 0 on success
 int mjs_detachBody(mjSpec* s, mjsBody* b) {
   mjCModel* model = static_cast<mjCModel*>(s->element);
   mjCBody* body = static_cast<mjCBody*>(b->element);
@@ -241,7 +241,22 @@ int mjs_detachBody(mjSpec* s, mjsBody* b) {
   return 0;
 }
 
-
+// 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) {
@@ -292,15 +307,19 @@ int mjs_setDeepCopy(mjSpec* s, int deepcopy) {
 
 
 
-// delete object, return 0 if success
+// delete object, return 0 on success
 int mjs_delete(mjsElement* element) {
-  mjCBase* object = static_cast<mjCBase*>(element);
+  mjCModel* model;
+  if (element->elemtype == mjOBJ_DEFAULT)
+    model = static_cast<mjCDef*>(element)->model;
+  else
+    model = static_cast<mjCBase*>(element)->model;
   try {
     // it will call the appropriate destructor since ~mjCBase is virtual
-    object->model->DeleteElement(element);
+    model->DeleteElement(element);
     return 0;
   } catch (mjCError& e) {
-    object->model->SetError(e);
+    model->SetError(e);
     return -1;
   }
 }
@@ -625,7 +644,7 @@ mjsDefault* mjs_getDefault(mjsElement* element) {
 
 
 // Find default with given name in model.
-const mjsDefault* mjs_findDefault(mjSpec* s, const char* classname) {
+mjsDefault* mjs_findDefault(mjSpec* s, const char* classname) {
   mjCModel* modelC = static_cast<mjCModel*>(s->element);
   mjCDef* cdef = modelC->FindDefault(classname);
   if (!cdef) {

src/user/user_api.h

@@ -88,6 +88,8 @@ MJAPI mjsFrame* mjs_attachFrameToSite(mjsSite* parent, const mjsFrame* child,
 // 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);
 
 //---------------------------------- Add tree elements ---------------------------------------------
 
@@ -221,7 +223,7 @@ MJAPI mjsFrame* mjs_findFrame(mjSpec* s, const char* name);
 MJAPI mjsDefault* mjs_getDefault(mjsElement* element);
 
 // Find default in model by class name.
-MJAPI const mjsDefault* mjs_findDefault(mjSpec* s, const char* classname);
+MJAPI mjsDefault* mjs_findDefault(mjSpec* s, const char* classname);
 
 // Get global default from model.
 MJAPI mjsDefault* mjs_getSpecDefault(mjSpec* s);

src/user/user_model.cc

@@ -24,6 +24,7 @@
 #include <cstdlib>
 #include <cstring>
 #include <exception>
+#include <functional>
 #include <mutex>
 #include <string>
 #include <string_view>
@@ -144,7 +145,7 @@ mjCModel::mjCModel() {
   Clear();
 
   //------------------------ master default set
-  defaults_.push_back(new mjCDef);
+  defaults_.push_back(new mjCDef(this));
   defaults_.back()->name = "main";
 
   // point to model from spec
@@ -564,6 +565,7 @@ mjCModel& mjCModel::operator-=(const mjCBody& subtree) {
 mjCModel_& mjCModel::operator+=(mjCDef& subtree) {
   defaults_.push_back(&subtree);
   def_map[subtree.name] = &subtree;
+  subtree.model = this;
 
   // set parent to the main default if this is not the only default in the model
   if (!subtree.parent && &subtree != defaults_[0]) {
@@ -579,6 +581,58 @@ mjCModel_& mjCModel::operator+=(mjCDef& subtree) {
 
 
 
+// remove default class from array
+mjCModel& mjCModel::operator-=(const mjCDef& subtree) {
+
+  // check we aren't trying to remove the 'main' default
+  if (subtree.id == 0) {
+    throw mjCError(0, "cannot remove the global default ('main')");
+  }
+
+  // remove this default from parent's child list
+  mjCDef* parent = subtree.parent;
+  if (parent) {
+    for (int i = 0; i < parent->child.size(); ++i) {
+      if (parent->child[i] == &subtree) {
+        parent->child.erase(parent->child.begin() + i);
+        break;
+      }
+    }
+  }
+
+  // traverse tree to find all descendants starting from subtree.id
+  std::vector<int> default_ids_to_remove;
+  std::vector<int> stack;
+  stack.push_back(subtree.id);
+  while (!stack.empty()) {
+    int id = stack.back();
+    stack.pop_back();
+    default_ids_to_remove.push_back(id);
+    for (int i=0; i<defaults_[id]->child.size(); i++) {
+      stack.push_back(defaults_[id]->child[i]->id);
+    }
+  }
+
+  // remove from the tree
+  std::sort(default_ids_to_remove.begin(),
+            default_ids_to_remove.end(),
+            std::greater<int>());
+
+  for (int id : default_ids_to_remove) {
+    delete defaults_[id];
+    defaults_.erase(defaults_.begin() + id);
+  }
+
+  // reset default ids
+  for (int i = 0; i < defaults_.size(); ++i) {
+    defaults_[i]->id = i;
+  }
+
+  return *this;
+}
+
+
+
 template <class T>
 void deletefromlist(std::vector<T*>* list, mjsElement* element) {
   if (!list) {
@@ -609,6 +663,10 @@ void mjCModel::DeleteElement(mjsElement* el) {
       throw mjCError(nullptr, "bodies cannot be deleted, use detach instead");
       break;
 
+    case mjOBJ_DEFAULT:
+      throw mjCError(nullptr, "defaults cannot be deleted, use detach instead");
+      break;
+
     case mjOBJ_GEOM:
     {
       mjCGeom* geom = static_cast<mjCGeom*>(el);
@@ -1180,7 +1238,7 @@ mjCDef* mjCModel::AddDefault(string name, mjCDef* parent) {
   }
 
   // create new object
-  mjCDef* def = new mjCDef;
+  mjCDef* def = new mjCDef(parent->model);
   defaults_.push_back(def);
   def->id = thisid;
 

src/user/user_model.h

@@ -183,10 +183,11 @@ class mjCModel : public mjCModel_, private mjSpec {
   void CopyFromSpec();  // copy spec to private attributes
   void PointToLocal();
 
-  mjCModel& operator=(const mjCModel& other);  // copy other into this, if they are not the same
+  mjCModel& operator=(const mjCModel& other);     // copy other into this, if they are not the same
-  mjCModel& operator+=(const mjCModel& other);  // add other into this, even if they are the same
+  mjCModel& operator+=(const mjCModel& other);    // add other into this, even if they are the same
-  mjCModel& operator-=(const mjCBody& subtree);  // remove subtree and all references from model
+  mjCModel& operator-=(const mjCBody& subtree);   // remove subtree and all references from model
-  mjCModel_& operator+=(mjCDef& subtree);  // add default tree to this model
+  mjCModel_& operator+=(mjCDef& subtree);         // add default tree to this model
+  mjCModel& operator-=(const mjCDef& subtree);    // remove default tree from this model
 
   mjSpec spec;
 
@@ -225,6 +226,9 @@ class mjCModel : public mjCModel_, private mjSpec {
   // delete object from the corresponding list
   void DeleteElement(mjsElement* el);
 
+  // delete default and all descendants
+  void RemoveDefault(mjCDef* def);
+
   // detach subtree from model
   void Detach(mjCBody* subtree);
 

src/user/user_objects.cc

@@ -536,12 +536,16 @@ int mjCBoundingVolumeHierarchy::MakeBVH(
 
 //------------------------- class mjCDef implementation --------------------------------------------
 
+
+
 // constructor
 mjCDef::mjCDef() {
   name.clear();
   id = 0;
   parent = nullptr;
+  model = 0;
   child.clear();
+  elemtype = mjOBJ_DEFAULT;
   mjs_defaultJoint(&joint_.spec);
   mjs_defaultGeom(&geom_.spec);
   mjs_defaultSite(&site_.spec);
@@ -561,6 +565,13 @@ mjCDef::mjCDef() {
 
 
 
+// constructor with model
+mjCDef::mjCDef(mjCModel* _model) : mjCDef() {
+  model = _model;
+}
+
+
+
 // copy constructor
 mjCDef::mjCDef(const mjCDef& other) {
   *this = other;

src/user/user_objects.h

@@ -1866,6 +1866,7 @@ class mjCDef : public mjsElement {
 
  public:
   mjCDef();
+  mjCDef(mjCModel*);
   mjCDef(const mjCDef& other);
   mjCDef& operator=(const mjCDef& other);
   mjCDef& operator+=(const mjCDef& other);
@@ -1898,6 +1899,7 @@ class mjCDef : public mjsElement {
   std::vector<mjCDef*> child;     // child classes
 
   mjsDefault spec;
+  mjCModel* model;                // pointer to model that owns object
 
  private:
   mjCJoint joint_;

test/user/user_api_test.cc

@@ -2544,6 +2544,91 @@ TEST_F(MujocoTest, ApplyNameSpaceToDefaults) {
   mj_deleteVFS(vfs.get());
 }
 
+TEST_F(MujocoTest, DetachDefault) {
+  static constexpr char xml_c[] = R"(
+  <mujoco>
+    <default>
+      <default class="parent">
+        <default class="child1">
+          <mesh scale="0.001 0.001 0.001"/>
+        </default>
+        <default class="child2">
+          <mesh scale="0.001 0.001 0.001"/>
+        </default>
+      </default>
+    </default>
+    <asset>
+      <mesh file="cube.obj" class="child2"/>
+    </asset>
+    <worldbody>
+      <body name="body">
+        <geom type="mesh" mesh="cube"/>
+      </body>
+    </worldbody>
+  </mujoco>)";
+
+  static constexpr char cube[] = R"(
+  v -0.500000 -0.500000  0.500000
+  v  0.500000 -0.500000  0.500000
+  v -0.500000  0.500000  0.500000
+  v  0.500000  0.500000  0.500000
+  v -0.500000  0.500000 -0.500000
+  v  0.500000  0.500000 -0.500000
+  v -0.500000 -0.500000 -0.500000
+  v  0.500000 -0.500000 -0.500000)";
+
+  auto vfs = std::make_unique<mjVFS>();
+  mj_defaultVFS(vfs.get());
+  mj_addBufferVFS(vfs.get(), "cube.obj", cube, sizeof(cube));
+
+  std::array<char, 1024> err;
+  mjSpec* spec = mj_parseXMLString(xml_c, vfs.get(), err.data(), err.size());
+  EXPECT_THAT(spec, NotNull()) << err.data();
+
+  // get default
+  mjsDefault* child = mjs_findDefault(spec, "child1");
+  EXPECT_THAT(child, NotNull());
+
+  // try using mjs_delete to remove default, should fail
+  EXPECT_EQ(mjs_delete(child->element), -1);
+
+  // detach default
+  EXPECT_EQ(mjs_detachDefault(spec, child), 0);
+  child = mjs_findDefault(spec, "child1");
+  EXPECT_THAT(child, IsNull());
+
+  // try and detach previously detached default, should fail
+  EXPECT_EQ(mjs_detachDefault(spec, child), -1);
+  child = mjs_findDefault(spec, "child1");
+  EXPECT_THAT(child, IsNull());
+  EXPECT_THAT(mjs_getError(spec),
+              HasSubstr("Cannot detach, default is null"));
+
+  // detach parent
+  mjsDefault* parent = mjs_findDefault(spec, "parent");
+  EXPECT_THAT(parent, NotNull());
+  mjs_detachDefault(spec, parent);
+
+  // both parent and remaining child should be removed
+  parent = mjs_findDefault(spec, "parent");
+  EXPECT_THAT(parent, IsNull());
+  child = mjs_findDefault(spec, "child2");
+  EXPECT_THAT(child, IsNull());
+
+  // error when trying to detach the 'main' default
+  mjsDefault* main = mjs_findDefault(spec, "main");
+  EXPECT_THAT(main, NotNull());
+  EXPECT_EQ(mjs_detachDefault(spec, main), -1);
+  EXPECT_THAT(mjs_getError(spec),
+              HasSubstr("cannot remove the global default ('main')"));
+
+  main = mjs_findDefault(spec, "main");
+  EXPECT_THAT(main, NotNull());
+
+  mj_deleteVFS(vfs.get());
+  mj_deleteSpec(spec);
+}
+
 TEST_F(MujocoTest, ErrorWhenCompilingOrphanedSpec) {
   static constexpr char xml[] = R"(
   <mujoco>

unity/Runtime/Bindings/MjBindings.cs

@@ -319,6 +319,7 @@ public enum mjtObj : int{
   mjOBJ_PLUGIN = 25,
   mjNOBJECT = 26,
   mjOBJ_FRAME = 100,
+  mjOBJ_DEFAULT = 101,
 }
 public enum mjtConstraint : int{
   mjCNSTR_EQUALITY = 0,