Confusing and misleading `rosidl_write_generator_arguments` error

[GuillaumeDua]

Description

In cmake/rosidl_generate_interfaces.cmake, the directive if(rosidl_adapter_FOUND) results in rosidl_write_generator_arguments being called with an empty rosidl_generate_interfaces_IDL_TUPLES when false,
producing the following error:

[cmake] CMake Error at /opt/ros/jazzy/share/rosidl_cmake/cmake/rosidl_write_generator_arguments.cmake:66 (message):
[cmake]   rosidl_write_generator_arguments() must be invoked with at least one of the
[cmake]   IDL_TUPLES;NON_IDL_TUPLES;ROS_INTERFACE_FILES arguments

While making a generator available fix it:

find_package(rosidl_default_generators REQUIRED)

Suggested solution

• Consider adding a else() clause which warns the user about missing rosidl_adapter

[fujitatomoya]

@GuillaumeDua can you take a look at #886 to see if that is what you suggested here?

[GuillaumeDua]

@fujitatomoya Thanks for the contribution, LGTM 👍