MJCF Parsing Error - Identifier Containing Separator

[peterdavidfagan]

I really like using MJCF for configuring my robots and environments. Recently I tried to upgrade one of my packages to the robot_descriptions package which references the mujoco_menagerie robot models.

When making this transition I encountered parsing errors related to the latest robot models in mujoco_menagerie containing separators, which is raised as an error in the following section of the dm_control code.

The error can be reproduced with the latest versions of mujoco, robot_descriptions and mujoco_menagerie

import os 

from dm_control import mjcf
from robot_descriptions import panda_mj_description

PANDA_MJCF_PATH = os.path.join(panda_mj_description.PACKAGE_PATH, 'panda_nohand.xml')

franka_mjcf = mjcf.from_path(PANDA_MJCF_PATH)

Error:

raceback (most recent call last):
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/element.py", line 205, in __init__
    self._attributes[attribute_spec.name] = attribute_spec.type(
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/attribute.py", line 59, in __init__
    self._check_and_assign(value)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/attribute.py", line 65, in _check_and_assign
    self._assign_from_string(new_value)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/attribute.py", line 106, in _assign_from_string
    self._assign(string)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/attribute.py", line 256, in _assign
    raise ValueError(
ValueError: An identifier cannot contain a '/', as this is reserved for scoping purposes: got 'panda/visual'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/parser.py", line 210, in _parse_children
    mjcf_child = mjcf_element.add(xml_child.tag, **attributes)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/element.py", line 630, in add
    return self.insert(element_name, position=None, **kwargs)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/element.py", line 655, in insert
    new_element = _make_element(child_spec, self, attributes=kwargs)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/element.py", line 124, in _make_element
    return _DefaultElement(spec, parent, attributes)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/element.py", line 217, in __init__
    raise err_type(  # pylint: disable=raise-missing-from
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/element.py", line 205, in __init__
    self._attributes[attribute_spec.name] = attribute_spec.type(
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/attribute.py", line 59, in __init__
    self._check_and_assign(value)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/attribute.py", line 65, in _check_and_assign
    self._assign_from_string(new_value)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/attribute.py", line 106, in _assign_from_string
    self._assign(string)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/attribute.py", line 256, in _assign
    raise ValueError(
ValueError: during initialization of attribute 'class' of element <default>: An identifier cannot contain a '/', as this is reserved for scoping purposes: got 'panda/visual'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/parser.py", line 104, in from_path
    return _parse(xml_root, escape_separators,
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/parser.py", line 169, in _parse
    _parse_children(xml_root, mjcf_root, escape_separators)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/parser.py", line 219, in _parse_children
    _parse_children(xml_child, mjcf_child, escape_separators)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/parser.py", line 219, in _parse_children
    _parse_children(xml_child, mjcf_child, escape_separators)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/parser.py", line 216, in _parse_children
    raise err_type(
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/parser.py", line 210, in _parse_children
    mjcf_child = mjcf_element.add(xml_child.tag, **attributes)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/element.py", line 630, in add
    return self.insert(element_name, position=None, **kwargs)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/element.py", line 655, in insert
    new_element = _make_element(child_spec, self, attributes=kwargs)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/element.py", line 124, in _make_element
    return _DefaultElement(spec, parent, attributes)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/element.py", line 217, in __init__
    raise err_type(  # pylint: disable=raise-missing-from
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/element.py", line 205, in __init__
    self._attributes[attribute_spec.name] = attribute_spec.type(
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/attribute.py", line 59, in __init__
    self._check_and_assign(value)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/attribute.py", line 65, in _check_and_assign
    self._assign_from_string(new_value)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/attribute.py", line 106, in _assign_from_string
    self._assign(string)
  File "/Users/peterfagan/Library/Caches/pypoetry/virtualenvs/mujoco-robot-environments-_OvGmQF9-py3.10/lib/python3.10/site-packages/dm_control/mjcf/attribute.py", line 256, in _assign
    raise ValueError(
ValueError: Line 15: error while parsing element <default>: during initialization of attribute 'class' of element <default>: An identifier cannot contain a '/', as this is reserved for scoping purposes: got 'panda/visual'

[peterdavidfagan]

Update: for now I am moving to using the panda.xml model and removing the hand via the dm_control.mjcf API. I opened the above pr to update the official panda_nohand.xml model such that it is compatible with the dm_control.mjcf API.

[yuvaltassa]

I think @erez-tom just dealt with a similar issue?

[kevinzakka]

Can you try using escape_separators please?

[peterdavidfagan]

Can you try using escape_separators please?

Ah my bad on this, I don't know how I managed to miss the escape_serparators function argument. Thanks for the responses, hopefully it helps someone else who also managed to miss this argument.