Generate GTSAM_UNSTABLE CMake exports

[varunagrawal]

Fixes #881

This will require a user to now do find_package(GTSAM_UNSTABLE) if they wish to use GTSAM_UNSTABLE features.

[varunagrawal]

@berndpfrommer any news on this?

[berndpfrommer]

Funny, I was just typing as I just completed the following test:

• Merge Generate GTSAM_UNSTABLE CMake exports #906 with the packaging branch and build the package, works.
• Packages install just gtsam-dev + libgtsam (no unstable), and compile my code (tagslam) against it, works. This would have been a failure mode before, I just never discovered the failure since I always installed both libraries (stable and unstable).
  Let me also test that I can use and compile against the unstable API. I was just working on that.

[varunagrawal]

Amazing!!

[berndpfrommer]

Almost, almost. Here's a gotcha.
The cmake config files are all in the libgtsam-dev package, including the ones for libgtsam-unstable.

dpkg -c ./libgtsam-dev_4.1.0-1ubuntu2~389.gbpb9908d_amd64.deb | grep -i cmake
drwxr-xr-x root/root         0 2021-10-08 23:09 ./usr/lib/cmake/
drwxr-xr-x root/root         0 2021-10-08 23:09 ./usr/lib/cmake/GTSAM/
-rw-r--r-- root/root       859 2021-10-08 23:09 ./usr/lib/cmake/GTSAM/GTSAM-exports-relwithdebinfo.cmake
-rw-r--r-- root/root      4451 2021-10-08 23:09 ./usr/lib/cmake/GTSAM/GTSAM-exports.cmake
-rw-r--r-- root/root      1203 2021-10-08 23:09 ./usr/lib/cmake/GTSAM/GTSAMConfig.cmake
-rw-r--r-- root/root      1722 2021-10-08 23:09 ./usr/lib/cmake/GTSAM/GTSAMConfigVersion.cmake
-rw-r--r-- root/root       309 2021-10-08 23:09 ./usr/lib/cmake/GTSAM/gtsam_extra.cmake
drwxr-xr-x root/root         0 2021-10-08 23:09 ./usr/lib/cmake/GTSAMCMakeTools/
-rw-r--r-- root/root      1235 2021-10-08 23:09 ./usr/lib/cmake/GTSAMCMakeTools/Config.cmake.in
-rw-r--r-- root/root      4306 2021-10-08 23:09 ./usr/lib/cmake/GTSAMCMakeTools/FindNumPy.cmake
-rw-r--r-- root/root       212 2021-10-08 23:09 ./usr/lib/cmake/GTSAMCMakeTools/GTSAMCMakeToolsConfig.cmake
-rw-r--r-- root/root     15511 2021-10-08 23:09 ./usr/lib/cmake/GTSAMCMakeTools/GtsamBuildTypes.cmake
-rw-r--r-- root/root      2240 2021-10-08 23:09 ./usr/lib/cmake/GTSAMCMakeTools/GtsamMakeConfigFile.cmake
-rw-r--r-- root/root      2452 2021-10-08 23:09 ./usr/lib/cmake/GTSAMCMakeTools/GtsamPrinting.cmake
-rw-r--r-- root/root     12246 2021-10-08 23:09 ./usr/lib/cmake/GTSAMCMakeTools/GtsamTesting.cmake
-rw-r--r-- root/root      5704 2021-10-08 23:09 ./usr/lib/cmake/GTSAMCMakeTools/README.html
-rw-r--r-- root/root      1856 2021-10-08 23:09 ./usr/lib/cmake/GTSAMCMakeTools/dllexport.h.in
drwxr-xr-x root/root         0 2021-10-08 23:09 ./usr/lib/cmake/GTSAM_UNSTABLE/
-rw-r--r-- root/root       931 2021-10-08 23:09 ./usr/lib/cmake/GTSAM_UNSTABLE/GTSAM_UNSTABLE-exports-relwithdebinfo.cmake
-rw-r--r-- root/root      4562 2021-10-08 23:09 ./usr/lib/cmake/GTSAM_UNSTABLE/GTSAM_UNSTABLE-exports.cmake
-rw-r--r-- root/root      1257 2021-10-08 23:09 ./usr/lib/cmake/GTSAM_UNSTABLE/GTSAM_UNSTABLEConfig.cmake
-rw-r--r-- root/root      1722 2021-10-08 23:09 ./usr/lib/cmake/GTSAM_UNSTABLE/GTSAM_UNSTABLEConfigVersion.cmake
-rw-r--r-- root/root       309 2021-10-08 23:09 ./usr/lib/cmake/GTSAM_UNSTABLE/gtsam_extra.cmake

But libgtsam-unstable-dev does not have any cmake config files:

dpkg -c ./libgtsam-unstable-dev_4.1.0-1ubuntu2~389.gbpb9908d_amd64.deb | grep -i cmake                                                                                              

I suspect that the problem is with the CMakeLists.txt files: the libgtsam-dev target installs also the cmake config files for the libgtsam-unstable-dev target.
Need to look into this some more.

[berndpfrommer]

nope, not a CMakeLists.txt error, but actually a bug in my packaging files

[berndpfrommer]

Fixed the packaging and everything is working. Without a find_package(GTSAM_UNSTABLE), the old-style INCLUDE_DIR variable is empty:

GTSAM_INCLUDE_DIR: /usr/lib/cmake/GTSAM/../../../include
GTSAM_UNSTABLE_INCLUDE_DIR: 

And the target include properties also don't have "unstable" in them. The build of the user executable fails as it should because it can't find the unstable library.

Adding the find_package(UNSTABLE) leads to successful compilation.

OK, from my end this commit is good to go. Once this has been merged into devel I will fix the packaging bug as well.

[ProfFan]

LGTM :) Thanks Varun!