It appears this behavior is by design, as explained nicely over here.
What you'll need to do in this case is not have Group::Constants
extend from ActiveSupport::Concern
since that will block its implementation from being shared with other ActiveSupport::Concern
extending modules (although it will be ultimately shared in a class that includes the second module):
module A
TEST_A = 'foo'
end
module B
extend ActiveSupport::Concern
TEST_B = 'bar'
end
module C
extend ActiveSupport::Concern
include A
include B
end
C::TEST_A
=> 'foo'
C::TEST_B
=> uninitialized constant C::TEST_B
class D
include C
end
D::TEST_A
=> 'foo'
D::TEST_B
=> 'bar'
In short, you'll need to make Group::Constants
a standard module and then all will be well.