I’m working on a large codebase in ruby 1.8.7 and I’m encountering a
weird error regarding method delegation.
This is the expected behaviour and a reproduction of the issue:
module DiscountSupport
def attach_coupon
:in_discount_support
end
end
class Loan
include DiscountSupport
end
module LoanTest
def attach_coupon
:in_loan_test
end
end
include LoanTest # some file in the test suite does this great thing,
which includes a lot of test helper methods in Object
puts Loan.new.attach_coupon #.should eq :in_discount_support
Because include works with “append_features”, if a method already exists
on an object, it will not be overridden by an include. This was always
working, until in one of my tests a loan object started getting
dispatched to the LoanTest method. I’m attaching a coupon twice, with
the first time working as expected, and only the second time I’m getting
dispatched to the LoanTest method.
I’ve tried to debug this. I thought first, attach_coupon does not exist
anymore on loan?
loan.method(:attach_coupon)
=> #<Method: Loan(LoanDiscountSupport)#attach_coupon> (the expected and
correct location for loan.attach_coupon())
loan.method(:attach_coupon).arity
-2 (which tells us that attach_coupon() is variadic function, with at
least one argument, as opposed to the one from the test suite which
doesn’t have any required arguments).
So ruby still thinks that attach_coupon exists on loan and it’s defined
in LoanDiscountSupport, but when we call the method, we are not hitting
it.
This is the backtrace, where you can see that instead of being
dispatched to loan_discount_support, we are getting dispatched to a the
method in the test suite.
begin; loan.attach_coupon; rescue Exception => @e; end
[“gems/activerecord-1.15.6/lib/active_record/base.rb:1863:in
method_missing'", "lib/rails/models/loan.rb:2900:inmethod_missing’”,
“gems/activerecord-1.15.6/lib/active_record/associations/association_proxy.rb:123:in
send'", "gems/activerecord-1.15.6/lib/active_record/associations/association_proxy.rb:123:inmethod_missing’”,
“suite/lib/helpers/portal_helpers.rb:243:in attach_coupon'", "(pry):9:inattach_coupon’”,
Can anyone help out with some more debugging ideas on this issue?