xacro doesn't support property names starting with double underscore __

[Brennand Pierce]

Hello,

The current head of ros2 is broken, 2.0.7. When I try and use the UR_description that has been running for the last couple of months I now get errors. It will no longer convert these degrees to anything and I get an error. It might be due to commit 4f3bc78:

joint_limits:
  shoulder_pan:
    # acceleration limits are not publicly available
    has_acceleration_limits: false
    has_effort_limits: true
    has_position_limits: true
    has_velocity_limits: true
    max_effort: 150.0
    max_position: !degrees  180.0
    max_velocity: !degrees  180.0
    min_position: !degrees -180.0

The error:

Use of invalid name(s): __limits when evaluating expression '__limits['shoulder_pan']['min_position']'

The urdf:

` <xacro:property name="__joint_limit_parameters" value="${load_yaml(joint_limits_parameters_file)}"/>
<xacro:property name="__kinematics_parameters" value="${load_yaml(kinematics_parameters_file)}"/>
<xacro:property name="__physical_parameters" value="${load_yaml(physical_parameters_file)}"/>
<xacro:property name="__visual_parameters" value="${load_yaml(visual_parameters_file)}"/>

<!-- Extract subsections from yaml dictionaries -->
<xacro:property name="__limits" value="${__joint_limit_parameters['joint_limits']}"/>
<xacro:property name="__dh_parameters" value="${__physical_parameters['dh_parameters']}"/>
<xacro:property name="__offsets" value="${__physical_parameters['offsets']}"/>
<xacro:property name="__inertia_parameters" value="${__physical_parameters['inertia_parameters']}" />
<xacro:property name="__mesh_files" value="${__visual_parameters['mesh_files']}" />
<xacro:property name="__kinematics" value="${__kinematics_parameters['kinematics']}" />

<!-- JOINTS LIMIT PARAMETERS -->
<xacro:property name="shoulder_pan_lower_limit" value="${__limits['shoulder_pan']['min_position']}" scope="parent"/>`

When I switch the branch to this: 5671b7d (2.0.7) it all works fine.

[Robert Haschke]

Since 2.0.7 xacro forbids the use of double-underscore names for security reasons.
See ros-industrial/universal_robot#579 for a fix of your issue.

[G.A. vd. Hoorn]

Just to clarify: the ROS 2 version of ur_description is somewhat decoupled from ros-industrial/universal_robot.

The issue was fixed there in UniversalRobots/Universal_Robots_ROS2_Driver#166.