Vcstool and rosinstall file

In ROS, it’s common to have the list of repositories listed in a rosinstall file. These files are read by Vcstool to import the specified repositories.

In the snapcraft.yaml, writing multiple parts in order to cover multiple git repositories might not be necessary. Instead, a rosinstall file could be used.

Snapcraft support various source-type but rosinstall is not part of the default implementation. Fortunately, we can still leverage the features of Vcstool within snapcraft by the means of the overrides part steps feature.

Overrides part steps

Snapcraft provides plugins that ease the build steps of our parts. It automatises everything based on the most common way to use a tool.

Obviously, sometimes we might need to do things slightly differently. And that is why snapcraft has an overrides part steps feature. This feature allows overriding and customising steps of a part’s lifecycle (pull, build, stage, and prime). Also, we can still call the default step action within our script. As an example, we display a message at the end of our build with:

parts:
   foo:
    plugin: colcon
    # ...
    override-build: |
      craftctl build
      echo “Everything built!”

That is exactly what we need for our rosinstall case.

Using Vcstool

With a rosinstall file call my_robot.rosinstall placed at the root of our repository, we could simply call Vcstool manually. Also, we should make sure that python3-vcstool is listed in our build-packages as we will need it at build-time.

parts:
  workspace:
    plugin: colcon # or catkin
    source: . # import our rosinstall file
    build-packages: [python3-vcstool, git]
    override-pull: |
      craftctl default # or snapcraftctl pull
      # Here we are going to use the local .rosinstall file
      vcs import --input my_robot.rosinstall

As we can see apart from the rosinstall specificity, building a whole robot stack inside a robot is actually as simple as building a basic talker-listener example.