Derive Messages from Base Classes

[InvincibleRMC]

Description

Having messages inherit from a common base class will make it so Client/Service/ActionClient/ActionServer can automatically infer the generic types they are using. Currently they need to be manually specified.

Based on the original issue but the base classes in rosidl_pycommon.
Builds off ros2/rosidl#887

Fixes #215

Is this user-facing behavior change?

It would allow users to isinstance check to determine if an object is a message.

Did you use Generative AI?

Additional Information

[fujitatomoya]

this makes sense to me.
this PR upgrades the inheritance of the generated metaclass to use ROS-specific metaclass logic, improving support for endpoint types and their associated messages in ROS 2 Python code generation.

i would like to have another approval before merge.

[christophebedard]

I have a minor comment in the other PR, otherwise LGTM

[christophebedard]

Pulls: #230, ros2/rosidl#887
Gist: https://gist.githubusercontent.com/christophebedard/eed622fd1da65170263b1734edfe11de/raw/b75cc11d0a0989e0916903b5dc6e8064be274b42/ros2.repos
BUILD args: --packages-above-and-dependencies rosidl_pycommon rosidl_generator_py
TEST args: --packages-above rosidl_pycommon rosidl_generator_py
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/16931

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[christophebedard]

@InvincibleRMC it looks like there's a real test failure in rosidl_generator_py/test/test_interfaces.py's test_strings

[InvincibleRMC]

Ok I found the bug not having __slots__ in the base class was allowing dynamic attributes. It originated in the rosidl pr. It should be good now.

[christophebedard]

Pulls: #230, ros2/rosidl#887
Gist: https://gist.githubusercontent.com/christophebedard/e44c47ef2dc14944e3f6dc0a1ce87cea/raw/1bd32654fcd99a86f61159ce9523b75466bf24c8/ros2.repos
BUILD args: --packages-above-and-dependencies rosidl_pycommon rosidl_generator_py
TEST args: --packages-above rosidl_pycommon rosidl_generator_py
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/17020

• Linux
• Linux-aarch64
• Linux-rhel
• Windows