Buffer and BufferClient do not the same function signatures

[christian-rauch]

The abstract method lookup_transform, as implemented by tf2_ros.buffer.Buffer and tf2_ros.buffer_client.BufferClient, is using different types for time.

Bug report

Required Info:

• Operating System:
  • Ubuntu 20.04
• Installation type:
  • binaries
• Version or commit hash:
  • foxy
• Client library (if applicable):
  • rclpy

Steps to reproduce issue

1. Instantiate a tf2_ros.buffer.Buffer and call lookup_transform with time from the header.stamp (type: builtin_interfaces.msg.Time). This will pass.
2. Instantiate a tf2_ros.buffer_client.BufferClient and call the same function with the same time type. This will fail with AttributeError: 'Time' object has no attribute 'to_msg'.

Expected behavior

Since both classes inherit from tf2_ros.BufferInterface the function signatures should be the same and the actual implementation should be interchangeable.

Actual behavior

BufferClient uses a different type for the time than the Buffer as BufferClient tries to convert the time message of type builtin_interfaces.msg.Time again via to_msg().

[christian-rauch]

I see that this is fixed in humble:

geometry2/tf2_ros_py/tf2_ros/buffer_interface.py

Line 145 in d508d9c

time: Time,

where the rclpy.time.Time type is used for all implementations.

Could this (and other fixes to the BufferClient) be backported to foxy?

[clalancette]

Could this (and other fixes to the BufferClient) be backported to foxy?

They can be backported if they don't change API or ABI. If they do change either of those, then another solution has to be found.

I'll also point out that Foxy goes End-of-Life in one month, so it may not be worth the effort.