Wrong condition on the number of arguments for mux

[cedricpradalier]

Between humble and kilted, the condition for the number of argument in topic_tools/mux has been reversed.

Before, it was: if >= 3 {use parameters}. Now it fails if the number of argument is smaller than 3, which is normal when one uses the input and output parameters in a launch file, as referenced in the documentation.

topic_tools/topic_tools/src/mux.cpp

Line 27 in c6c6ef6

if (args.size() < 3) {

For now, it is possible to come back to arguments in the launch file, but it was more "rossy" to use parameters. Can we bring back the previous functionality, which is consistent with the documentaton ?

Thanks

[christophebedard]

I think this was changed in #106 (ad48bc0#diff-cfd39f8d6f91b1d92530de23788a2b0ccce27e18e148bb7d492e2380373ea4e1) while porting demux, because that's how it worked in ROS 1 (and is simpler for the CLI): https://wiki.ros.org/topic_tools/mux. If we want to change this, we should do it for everything in topic_tools. In any case, the documentation should correctly reflect the current behaviour.

You could also use the mux node (MuxNode) directly as a ComposableNode in your launch file and provide your parameters to that, although that's probably more complex than your current setup.