add dependency on cmake in Debian package

[mikaelarguedas]

After installing colcon-core from apt, I am unable to build a CMake package despite having colcon-cmake installed. For convenience it would be good to have an explicit dependency on cmake for the debs of colcon-cmake

[dirk-thomas]

The Ubuntu package cmake has recommended dependencies on gcc and make. I am not sure pulling those in by default is a good choice.

E.g. in ROS packages we commonly do not declare a dependency on cmake or build-essential. Instead we let the user install what he wants in order to be able to build a package (independent of the build tool).

[mikaelarguedas]

E.g. in ROS packages we commonly do not declare a dependency on cmake or build-essential. Instead we let the user install what he wants in order to be able to build a package (independent of the build tool).

This is fair in the context of packages that don't need CMake at runtime. However I don't think this should apply to packages that invoke the cmake executable directly and cannot run without it (from my understanding). These packages do require cmake. It seems more conventional to always install the required packages and to let user opt out of the recommended packages if they want to (which can be easily done using the --no-install-recommends apt flag).

The fact that cmake recommends gcc and make in Ubuntu is something one can't control, but it seems unconventional to decide not to declare a required dependency based on that information.

[mjcarroll]

I think that it makes sense that colcon-cmake depends on cmake, and the exclusion with --no-install-recommends would prevent from getting other things installed.

My only reservation here is that it if this is done consistently across colcon packages (eg should colcon-zsh depend on zsh? should colcon-bazel depend on bazel?) it will make colcon-common-extensions quite large.

[mikaelarguedas]

From my perspective these are slightly different scenarios:

• colcon-zsh generates zsh files but doesnt need zsh to be installed to do so, so it is not a required dependency (same would apply to other shells)
• colcon-bazel would not be able to run without bazel installed, so bazel is a required dep (though is not part of colcon-common-extensions)

it will make colcon-common-extensions quite large.

A closer look at which packages in colcon-common-extensions would bring in extra dependencies is needed to answer that. At a glance apart from colcon-cmake the other packages seem to already bring in their dependencies (e.g. colcon-ros brings in catkin_pkg etc)

[mjcarroll]

That's fair, for some reason I thought that colcon-bazel was in the common extensions, but it looks like I was mistaken. In that case, I think that this change makes sense (along with a corresponding change in colcon-bazel).

I also agree with your logic around zsh/powershell/etc

[dirk-thomas]

Ok, sounds good to me then.

along with a corresponding change in colcon-bazel

It would be great if you could create a corresponding pull request for colcon-bazel then.

[mikaelarguedas]

It would be great if you could create a corresponding pull request for colcon-bazel then.

I can't find bazel in the official ubuntu repositories. Maybe it's only available via ppa

[mjcarroll]

Maybe it's only available via ppa

That is exactly the case as of bionic: https://docs.bazel.build/versions/master/install-ubuntu.html