Feature #11927
Updated by sawa (Tsuyoshi Sawada) over 3 years ago
Currently, `Module#include` and `Module#prepend` return the receiver, regardless of whether the ancestor chain has been modified. It is not straightforward to know whether it actually had effect. ~~~ruby module A; end module B; end A.include B # => A A.ancestors # => [A, B] A.prepend B # => A A.ancestors # => [A, B] ~~~ I propose that, when `Module#include` and `Module#prepend` have no effect, they should either: (1) return `nil` (2) return `false`, or (3) raise an exception This is similar to `Kernel#require`, which returns `false` when it has no effect. To make it parallel with `Kernel#require`, it might be even better to return `true` when `Module#include` and `Module#prepend` have effect, and `false` otherwise. It makes no not sense to return the receiver because that is known. Some relevant cases with expectations are: * prepend after include ~~~ruby module A; end module B; end A.include B # => A/true A.prepend B # => nil/false/exception ~~~ * include after prepend ~~~ruby module A; end module B; end A.include B # => A/true A.prepend B # => nil/false/exception ~~~ * include/prepend after include/include at superclass ~~~ruby class A; end module B; end A.include M # => A/true class B < A; end B.include M # => nil/false/exception ~~~