Do not delete attached specs after compilation.

Also, copy them when copying the spec.

PiperOrigin-RevId: 688998464
Change-Id: I7229fd8032eafede582194ccf73ab4160fe06768

doc/APIreference/functions.rst

@@ -4139,6 +4139,15 @@ mjs_getSpec
 
 Get spec from body.
 
+.. _mjs_findSpec:
+
+mjs_findSpec
+~~~~~~~~~~~~
+
+.. mujoco-include:: mjs_findSpec
+
+Find spec (model asset) by name.
+
 .. _mjs_findBody:
 
 mjs_findBody

doc/includes/references.h

@@ -3600,6 +3600,7 @@ mjsSkin* mjs_addSkin(mjSpec* s);
 mjsTexture* mjs_addTexture(mjSpec* s);
 mjsMaterial* mjs_addMaterial(mjSpec* s, mjsDefault* def);
 mjSpec* mjs_getSpec(mjsElement* element);
+mjSpec* mjs_findSpec(mjSpec* spec, const char* name);
 mjsBody* mjs_findBody(mjSpec* s, const char* name);
 mjsElement* mjs_findElement(mjSpec* s, mjtObj type, const char* name);
 mjsBody* mjs_findChild(mjsBody* body, const char* name);

include/mujoco/mujoco.h

@@ -1534,6 +1534,9 @@ MJAPI mjsMaterial* mjs_addMaterial(mjSpec* s, mjsDefault* def);
 // Get spec from body.
 MJAPI mjSpec* mjs_getSpec(mjsElement* element);
 
+// Find spec (model asset) by name.
+MJAPI mjSpec* mjs_findSpec(mjSpec* spec, const char* name);
+
 // Find body in spec by name.
 MJAPI mjsBody* mjs_findBody(mjSpec* s, const char* name);
 

introspect/functions.py

@@ -9742,6 +9742,28 @@ FUNCTIONS: Mapping[str, FunctionDecl] = dict([
          ),
          doc='Get spec from body.',
      )),
+    ('mjs_findSpec',
+     FunctionDecl(
+         name='mjs_findSpec',
+         return_type=PointerType(
+             inner_type=ValueType(name='mjSpec'),
+         ),
+         parameters=(
+             FunctionParameterDecl(
+                 name='spec',
+                 type=PointerType(
+                     inner_type=ValueType(name='mjSpec'),
+                 ),
+             ),
+             FunctionParameterDecl(
+                 name='name',
+                 type=PointerType(
+                     inner_type=ValueType(name='char', is_const=True),
+                 ),
+             ),
+         ),
+         doc='Find spec (model asset) by name.',
+     )),
     ('mjs_findBody',
      FunctionDecl(
          name='mjs_findBody',

src/user/user_model.cc

@@ -388,6 +388,9 @@ mjCModel& mjCModel::operator+=(const mjCModel& other) {
     }
     CopyList(numerics_, other.numerics_);
     CopyList(texts_, other.texts_);
+    for (const auto* s : other.specs_) {
+      specs_.push_back(mj_copySpec(s));
+    }
   }
   CopyList(flexes_, other.flexes_);
   CopyList(pairs_, other.pairs_);
@@ -3648,12 +3651,6 @@ mjModel* mjCModel::Compile(const mjVFS* vfs, mjModel** m) {
     return nullptr;
   }
 
-  // destroy attached specs
-  for (auto spec : specs_) {
-    mj_deleteSpec(spec);
-  }
-  specs_.clear();
-
   // restore error handler, mark as compiled, return mjModel
   _mjPRIVATE__set_tls_error_fn(save_error);
   _mjPRIVATE__set_tls_warning_fn(save_warning);

src/xml/xml.cc

@@ -387,11 +387,11 @@ mjSpec* ParseXML(const char* filename, const mjVFS* vfs,
   return spec;
 }
 
-mjSpec* ParseSpecFromString(std::string_view xml, char* error, int nerror) {
+mjSpec* ParseSpecFromString(std::string_view xml, const mjVFS* vfs, char* error, int nerror) {
   RegisterResourceProvider();
   std::string xml2 = {xml.begin(), xml.end()};
   std::string str = "LoadModelFromString:" +  xml2;
-  return ParseXML(str.c_str(), nullptr, error, nerror);
+  return ParseXML(str.c_str(), vfs, error, nerror);
 }
 
 // Main writer function - calls mjXWrite

src/xml/xml.h

@@ -26,7 +26,8 @@ mjSpec* ParseXML(const char* filename, const mjVFS* vfs, char* error, int nerror
 
 // Returns a newly-allocated mjSpec, loaded from the contents of xml.
 // On failure returns nullptr and populates the error array if present.
-mjSpec* ParseSpecFromString(std::string_view xml, char* error = nullptr, int nerror = 0);
+mjSpec* ParseSpecFromString(std::string_view xml, const mjVFS* vfs = nullptr,
+                            char* error = nullptr, int nerror = 0);
 
 // Main writer function
 std::string WriteXML(const mjModel* m, const mjSpec* spec, char* error, int nerror);

src/xml/xml_api.cc

@@ -221,7 +221,7 @@ mjSpec* mj_parseXML(const char* filename, const mjVFS* vfs, char* error, int err
 
 // parse spec from string
 mjSpec* mj_parseXMLString(const char* xml, const mjVFS* vfs, char* error, int error_sz) {
-  return ParseSpecFromString(xml, error, error_sz);
+  return ParseSpecFromString(xml, vfs, error, error_sz);
 }
 
 

test/user/user_api_test.cc

@@ -1849,5 +1849,57 @@ TEST_F(MujocoTest, DifferentUnitsNotAllowed) {
   mj_deleteSpec(spec_2);
 }
 
+TEST_F(MujocoTest, CopyAttachedSpec) {
+  static constexpr char xml_parent[] = R"(
+  <mujoco>
+    <asset>
+      <model name="child" file="xml_child.xml"/>
+    </asset>
+    <worldbody>
+      <body name="parent">
+        <geom name="geom" size="2"/>
+        <attach model="child" body="body" prefix="other"/>
+      </body>
+    </worldbody>
+  </mujoco>
+  )";
+
+  static constexpr char xml_child[] = R"(
+  <mujoco>
+    <worldbody>
+      <body name="body">
+        <geom name="geom" size="1" pos="2 0 0"/>
+      </body>
+    </worldbody>
+  </mujoco>
+  )";
+
+  auto vfs = std::make_unique<mjVFS>();
+  mj_defaultVFS(vfs.get());
+  mj_addBufferVFS(vfs.get(), "xml_child.xml", xml_child, sizeof(xml_child));
+
+  std::array<char, 1024> er;
+  mjSpec* spec = mj_parseXMLString(xml_parent, vfs.get(), er.data(), er.size());
+  EXPECT_THAT(spec, NotNull()) << er.data();
+
+  mjModel* model = mj_compile(spec, vfs.get());
+  EXPECT_THAT(model, NotNull()) << er.data();
+
+  mjSpec* child = mjs_findSpec(spec, "child");
+  EXPECT_THAT(child, NotNull());
+
+  mjSpec* copy = mj_copySpec(spec);
+  EXPECT_THAT(copy, NotNull());
+
+  mjSpec* child_copy = mjs_findSpec(copy, "child");
+  EXPECT_THAT(child_copy, NotNull());
+  EXPECT_NE(child_copy, child);
+
+  mj_deleteSpec(spec);
+  mj_deleteSpec(copy);
+  mj_deleteModel(model);
+  mj_deleteVFS(vfs.get());
+}
+
 }  // namespace
 }  // namespace mujoco