How to check that message exists with catkin for conditional compilation (sensor_msgs/BatteryState)

edit

This is tricky, because there are not a lot of good ways to do it.

Old versions of rosmsg show does not return an error code if the message does not exist, so that probably isn't the best choice.

The python messages aren't generated until the build step, so they may not exist at configure time, which means that a python script which tries to import messages will always fail the first time, even if the package contains the messages you're looking for.

I think the best way to do this would be to check which version of sensor_msgs you're building against from cmake, and use that as the conditional in your build. You can do this with the VERSION_GREATER or VERSION_LESS comparisons:

# cmake
find_package(catkin REQUIRED COMPONENTS
    sensor_msgs 
    # etc
)

if( ${sensor_msgs_VERSION} VERSION_LESS 2.42.3 ) # substitute the version you care about
    message("sensor_msgs too old; won't build foo")
else()
    # build cool new things
endif()

(This SHOULD work; but I haven't tested it. May need a little tweaking)