Add urdf file extension case to mj_parse.

fixes #3004

PiperOrigin-RevId: 855249634
Change-Id: I6c21d0ada4fe482059f64e96d413796f5c1c66ce

python/mujoco/specs_test.py

@@ -479,6 +479,14 @@ class SpecsTest(absltest.TestCase):
     # Check that the state is the same.
     np.testing.assert_array_equal(state1, state2)
 
+  def test_parses_urdf(self):
+    file_path = epath.resource_path("mujoco") / "testdata" / "model.urdf"
+    filename = file_path.as_posix()
+
+    # Load from file.
+    spec1 = mujoco.MjSpec.from_file(filename)
+    self.assertIsNotNone(spec1)
+
   def test_make_mesh(self):
     spec = mujoco.MjSpec()
 

python/mujoco/testdata/model.urdf

@@ -0,0 +1,4 @@
+<?xml version="1.0" ?>
+<robot name="tool">
+  <link name="tool"/>
+</robot>

python/pyproject.toml

@@ -58,6 +58,7 @@ mujoco = [
     "testdata/*.msh",
     "testdata/*.usda",
     "testdata/*.zip",
+    "testdata/*.urdf",
 ]
 
 [project.optional-dependencies]

src/user/user_api.cc

@@ -72,7 +72,9 @@ mjSpec* mj_parse(const char* filename, const char* content_type,
 
   // early exit for existing XML workflow
   auto filepath = mujoco::user::FilePath(filename);
-  if (filepath.Ext() == ".xml" || (content_type && std::strcmp(content_type, "text/xml") == 0)) {
+  if (filepath.Ext() == ".xml" ||
+      filepath.Ext() == ".urdf" ||
+      (content_type && std::strcmp(content_type, "text/xml") == 0)) {
     return mj_parseXML(filename, vfs, error, error_sz);
   }