build: allow for building of cmake projects which do not have package.xml

[wjwwood]

The idea is that you can have a folder of plain CMake projects, which will all get built first, in parallel and in no particular order before trying to build any catkin packages. This allows you to easily build CMake projects as part of your workspace without creating package.xml's for them.

[NikolausDemmel]

+1

Just to mention this here, without a package.xml there is no good way for tools like rosdep to detect their precense in the workspace and therefore also for your packages to to depend on these cmake packages, but it seems to have vaild use cases none the less.

Also, didn't someone mention that this might not work well with the devel space? Is that issue any different from plain cmake projects with added package.xml?

[jbohren]

Also, didn't someone mention that this might not work well with the devel space? Is that issue any different from plain cmake projects with added package.xml?

That's not changed when you add a package.xml. They'll still only work out of the install-space.

[NikolausDemmel]

Also, didn't someone mention that this might not work well with the devel space? Is that issue any different from plain cmake projects with added package.xml?

That's not changed when you add a package.xml. They'll still only work out of the install-space.

As a slightly OT question related to this purley for my understanding: How come I can build desktop_full from scratch with catkin build (no install) even though some of the catkin packages depend on some of the cmake only packages (e.g. opencv)?

[jbohren]

Also, didn't someone mention that this might not work well with the devel space? Is that issue any different from plain cmake projects with added package.xml?

That's not changed when you add a package.xml. They'll still only work out of the install-space.

As a slightly OT question related to this purley for my understanding: How come I can build desktop_full from scratch with catkin build (no install) even though some of the catkin packages depend on some of the cmake only packages (e.g. opencv)?

I'm not sure that's guaranteed to work. Are you actually linking against that version of opencv and are there opencv-related products in your devel-space?

[NikolausDemmel]

@jbohren: I moved this to a new issue: #69

[dirk-thomas]

For pure CMake packages catkin_make_isolated as well as catkin build just install the package into the devel space (when no --install is requested) since that is the only way for pure CMake packages.

[wjwwood]

@dirk-thomas is right, when no --install is requested then the plain cmake packages are make install'ed into the devel space.

[NikolausDemmel]

Thanks for the clarification. To sum up, for the interaction with the devel space the existance of a package.xml for pure cmake packages makes no difference. The difference is only the build order and the ability to depend in it.

Is there special handling of the pure cmake packages for --isolate-install and --isolate-devel? For the package.xml-less packages there should be an implicit dependency from all other packages in order for them to be useful?

[wjwwood]

We would probably not allow these ad-hoc cmake packages to have an isolated install folder, but in stead we would build them all, install them all somewhere, and source that implicitly before all package.xml builds, regardless of their isolated/merged devel/install spaces.

[NikolausDemmel]

@dirk-thomas is right, when no --install is requested then the plain cmake packages are make install'ed into the devel space.

Is this actually supposed to still work? It seems for me it does not (i.e. the package is built but not installed into the devel space, using the latest binary release and tested with all 3 devel space options). I will do more testing and open another issue, but I was just wondering if people are using this feature.

cc @mikepurvis, @wjwwood