Raise error if trying to bind with a spec with an empty name.

PiperOrigin-RevId: 731360983
Change-Id: I00365d158c1cae1cd912962ef453f43e93701080

mjx/mujoco/mjx/_src/support.py

@@ -295,7 +295,9 @@ class BindModel(object):
     self.prefix = ''
     ids = []
     for spec in specs:
-      if isinstance(spec, mujoco.MjsBody):
+      if not spec.name:
+        raise KeyError(f'cannot bind spec with empty name')
+      elif isinstance(spec, mujoco.MjsBody):
         self.prefix = 'body_'
         idx = name2id(model, mujoco.mjtObj.mjOBJ_BODY, spec.name)
       elif isinstance(spec, mujoco.MjsJoint):
@@ -400,7 +402,9 @@ class BindData(object):
     self.prefix = ''
     ids = []
     for spec in specs:
-      if isinstance(spec, mujoco.MjsBody):
+      if not spec.name:
+        raise KeyError(f'cannot bind spec with empty name')
+      elif isinstance(spec, mujoco.MjsBody):
         idx = name2id(model, mujoco.mjtObj.mjOBJ_BODY, spec.name)
       elif isinstance(spec, mujoco.MjsJoint):
         self.prefix = 'jnt_'

mjx/mujoco/mjx/_src/support_test.py

@@ -333,6 +333,13 @@ class SupportTest(parameterized.TestCase):
           vdx.bind(mx, s.bodies[i]).xpos, [d.xpos[i, :]] * batch_size
       )
 
+    # test emtpy name
+    s.worldbody.add_body()
+    m = s.compile()
+    mx = mjx.put_model(m)
+    with self.assertRaises(KeyError, msg='cannot bind spec with empty name'):
+      mx.bind(s.bodies)
+
   _CONTACTS = """
     <mujoco>
       <worldbody>