String formatting for ros2 topic echo

Bug report

Required Info:

• Operating System:
  • Ubuntu 18.04
• Installation type:
  • Binaries & Source
• Version or commit hash:
  • 72961082678fa3491b2cf778dc004bf820cd4c7c
• DDS implementation:
  • Default
• Client library (if applicable):
  • N/A

Steps to reproduce issue

Talker:

#!/usr/bin/env python3

import rclpy
import rclpy.node
import std_msgs.msg as std_msgs

class Talker(rclpy.node.Node):

    def __init__(self):
        super().__init__('talker')
        self.pub = self.create_publisher(std_msgs.String, 'chatter')
        timer_period = 1.0
        self.tmr = self.create_timer(timer_period, self.timer_callback)
        self.toggle = False
        self.msg_with_newlines = std_msgs.String(
            data="Dude\nand\nDudettes"
        )
        self.msg_with_escape_sequences = std_msgs.String(
            data="\x1b[34mDude\x1b[0m\nand\nDudettes"
        )

    def timer_callback(self):
        msg = std_msgs.String()
        if self.toggle:
            msg = self.msg_with_escape_sequences
        else:
            msg = self.msg_with_newlines
        self.toggle = not self.toggle
        print("-----------\n{}".format(msg.data))
        self.pub.publish(msg)

if __name__ == '__main__':
    rclpy.init()
    node = Talker()
    try:
        rclpy.spin(node)
    except KeyboardInterrupt:
        pass
    node.destroy_node()
    rclpy.shutdown()

Execution:

# In a first shell
$ ./talker
# in a second shell
$ ros2 topic echo /chatter
data: 'Dude

  and

  Dudettes'
data: "\e[34mDude\e[0m\nand\nDudettes"

Expected behavior

String formatting that pays attention to newlines, tabs, console sequences etc (as per ROS1).

Actual behavior

No string formatting at all.

Additional information

This is especially useful in publishers of the std_msgs.msg.String variety which exist to describe the runtime system or to provide introspective data about a module formatted in some clean, easy to read way.

Start by locating the implementation behind the ros2 topic echo command and reproduce the issue with the provided Python talker. Compare its current output with the expected ROS1-style rendering, then verify handling of newlines, tabs, and console escape sequences.