Raise appropriate errors for mj_addBufferVFS in Python bindings.

When loading models in the XML bindings, different issues with the asset dictionary were all reported as "assets dict is too big".

PiperOrigin-RevId: 670960339
Change-Id: I2e47d91a6b433fd90ebdf9960a9b5b47413af410

python/mujoco/bindings_test.py

@@ -128,6 +128,14 @@ class MuJoCoBindingsTest(parameterized.TestCase):
     self.assertEqual(
         mujoco.mj_name2id(model, mujoco.mjtObj.mjOBJ_GEOM, 'ball'), 2)
 
+  def test_load_xml_repeated_asset_name(self):
+    # Assets aren't allowed to have the same filename (even if they have
+    # different paths).
+    with self.assertRaisesRegex(ValueError, r'Repeated.*'):
+      mujoco.MjModel.from_xml_string(
+          '<mujoco/>', {'asset.xml': b'asset1', 'path/asset.xml': b'asset2'}
+      )
+
   def test_can_read_array(self):
     np.testing.assert_array_equal(
         self.model.body_pos,
@@ -766,7 +774,6 @@ class MuJoCoBindingsTest(parameterized.TestCase):
     np.testing.assert_array_equal(qvel, self.data.qvel)
     np.testing.assert_array_equal(act, self.data.act)
 
-
   def test_mj_angmomMat(self):  # pylint: disable=invalid-name
     self.data.qvel = np.ones(self.model.nv, np.float64)
     mujoco.mj_forward(self.model, self.data)

python/mujoco/structs.cc

@@ -345,7 +345,13 @@ static raw::MjModel* LoadModelFileImpl(
       const int vfs_error = InterceptMjErrors(mj_addBufferVFS)(
           vfs_ptr, buffer_name.c_str(), asset.content, asset.content_size);
       if (vfs_error) {
-        throw py::value_error("assets dict is too big");
+        mj_deleteVFS(vfs_ptr);
+        if (vfs_error == 2) {
+          throw py::value_error("Repeated file name in assets dict: " +
+                                buffer_name);
+        } else {
+          throw py::value_error("Asset failed to load: " + buffer_name);
+        }
       }
     }
   }