Install colcon via 'rosdep install'

edit

I'm still on ROS1K (about to EoL). Only occasionally trying newer stuff.

If I want to reference colcon as a dependency in rosdep-sphere, what's the right way to do assuming doing so is NOT out of the range of ROS2 and/or colcon framework?

A bit of motivation for me is to allow developers to specify build-tool/system and use package.xml for that so that you don't need to specify required/preferred build-tool/system separately (hope I'm interpreting the intent of buildtool_depend right).

Trying to find existing references,

• in rclcpp (that appeared at the top on github.com/ros2 org at the time I went there, so I assumed it's up-to-date to the status of ROS2 framework) it still? uses ament in buildtool_depend. I couldn't find any pkg that refers to colcon in buildtool_depend.
• docs.ros.org/en/foxy/Tutorials/Creating-Your-First-ROS2-Package shows ament for buildtool_depend.

So far I've tried: - Add ros.org to apt source. - Add python3-colcon-common-extensions (took it from installation section in colcon.readthedocs.io) and a few others in <buildtool_depend>.

If it's simply that rosdep keys for colcon-related packages are missing, that's easy. But I'm just not sure if that's the plan.

$ docker run -it ros:melodic-ros-base

# cat src/tester_colcon_dep/package.xml
<?xml version="1.0"?>
<package format="3">
  <name>tester_colcon_dep</name>
  <version>0.0.0</version>
  <description>The tester package</description>
  <maintainer email="root@todo.todo">root</maintainer>
  <license>TODO</license>
<!--  <buildtool_depend>colcon</buildtool_depend> -->
<!--  <buildtool_depend>colcon-ros</buildtool_depend> -->
  <buildtool_depend>python3-colcon-common-extensions</buildtool_depend>
<!--  <buildtool_depend>python3-colcon</buildtool_depend> -->
</package>

# rosdep install -y --from-paths src --ignore-src
:
tester_colcon_dep: Cannot locate rosdep definition for [colcon]

root@46d1b53edc16:/cws# rosdep install -y --from-paths src --ignore-src
:
tester_colcon_dep: Cannot locate rosdep definition for [python3-colcon-common-extensions]

# apt install python3-colcon-common-extensions
:
The following additional packages will be installed:
  javascript-common libjs-jquery libjs-jquery-hotkeys libjs-jquery-isonscreen libjs-jquery-metadata libjs-jquery-tablesorter    libjs-jquery-throttle-debounce libwebpdemux2 libwebpmux3 notification-daemon python3-argcomplete python3-attr python3-catkin-pkg-modules      python3-colcon-argcomplete python3-colcon-bash python3-colcon-cd python3-colcon-cmake python3-colcon-core python3-colcon-defaults      python3-colcon-devtools python3-colcon-library-path python3-colcon-metadata python3-colcon-notification python3-colcon-output
:
(Manually terminated)

root@46d1b53edc16:/cws# more /etc/apt/sources.list.d/ros1-latest.list 
deb http://packages.ros.org/ros/ubuntu bionic main


# apt-cache policy python3-colcon-* | ack -A 1 -i installed
  Installed: (none)
  Candidate: 0.2.5-1
--                  
  Installed: (none)
  Candidate: 0.2.1-1
--                  
  Installed: (none)     
  Candidate: 0.1.0-1
--
  Installed: (none)
  Candidate: 0.2.10-1
--
  Installed: (none)
  Candidate: 0.0.8-1
--
  Installed: (none)
  Candidate: 0.1.1-1
--
  Installed: (none)
  Candidate: 0.1.2-1
--
  Installed: (none)
  Candidate: 0.2.26-1
--
  Installed: (none)
  Candidate: 0.2.7-1
--
  Installed: (none)
  Candidate: 0.5.0-1
--
  Installed: (none)
  Candidate: 0.2.4-1
--
  Installed: (none)
  Candidate: 0.2.13-1
--
  Installed: (none)
  Candidate: 0.2.12-1
--
  Installed: (none)
  Candidate: 0.3.8-1
--
  Installed: (none)
  Candidate: 0.2.1-1
--
  Installed: (none)
  Candidate: 0.2.1-1
--
  Installed: (none)
  Candidate: 0.3.21-1
--
  Installed: (none)
  Candidate: 0.3.3-1
--
  Installed: (none)
  Candidate: 0.3.6-1
--
  Installed: (none)
  Candidate: 0.2.0-1
--
  Installed: (none)
  Candidate: 0.1.0-1
--
  Installed: (none)
  Candidate: 0.4.2-1
--
  Installed: (none)
  Candidate: 0.6.1-1
--
  Installed: (none)
  Candidate: 0.2.2-1 ...