Error when building the package using Colcon (mixin)

[axelssons]

While precisely following the installation and build instructions in the README-file of this repository, I get an error while running:
colcon build --mixin release --packages-up-to motoros2_client_interface_dependencies

The error is:
colcon: error: Mixin 'release' is not available for 'build'

Why do I get this and is this troubling? When running just colcon build it works fine. Will it work this way or do I have to build it with the --mixin and --packages-up-to flags?

[gavanderhoorn]

The error is: colcon: error: Mixin 'release' is not available for 'build'

it looks like you don't have colcon_mixin installed.

The ROS 2 Docker images (ie: ros:humble, etc) come with that installed by default, which is perhaps why our tests didn't show that as missing.

Why do I get this [..]? When running just colcon build it works fine. Will it work this way or do I have to build it with the --mixin and --packages-up-to flags?

The main difference would be:

• all packages in your workspace get built, instead of just motoros2_client_interface_dependencies and its dependencies, and
• your packages are built with Debug build type, instead of the Release build type, meaning no compiler optimisation will be enabled

and is this troubling

it isn't really problematic, if that's what you're asking.

Building with Release build type enabled will typically make binaries more performant.

In most cases however, you'll not notice it (your HW is likely 'fast enough' to compensate).

[gavanderhoorn]

If you have ROS already installed (and thus the package repositories enabled), you could install python3-colcon-mixin and then you should be able to build using --mixin release.

Note that --packages-up-to is basic Colcon functionality and is not related to colcon_mixin.

[axelssons]

Thank you!

Apparently, colcon_mixin was already installed. However, I needed to register the colcon mixin repository with:
colcon mixin add default https://raw.githubusercontent.com/colcon/colcon-mixin-repository/master/index.yaml
followed by colcon mixin update default.