Add option to make predicates return `false`

[avdi]

Presently all generated predicate methods (methods ending in ?) return the same default value as any other method: either nil or self, depending on the configuration. It might be nice to have an option to automatically define predicates to return false instead, to better comply with legacy code expectations. This is particularly important for black hole objects, since self is truthy for the purpose of if statements etc.

[guillec]

@avdi would something like this do the trick? Or by option do you mean make this configurable? If so I can submit a pull request.

def stub_method_returning_self(subject, name)
   subject.module_eval do
    define_method(name) do |*args|  
       if args[0] && args[0].match(/(.*)\?/)
         return false
       else
         return self
       end
     end
   end
 end

[fcofdez]

I think that this is correct, but making it configurable adds flexibility. On the other hand, Allowing all objects to use this options also add flexibility.

[avdi]

I'd like it to be a separate builder method - predicates_return(false) or something along those lines.

[guillec]

Great thanks for the clarification. Tied up with some work right now, will work on this later today. Thanks!

[avdi]

To be least-surprising, this will have to work in several contexts:

• On a "normal" method_missing nullobj (maybe rewrite method_missing to look at the method name?)
• On a black hole nullobj (same as above)
• On mimic/impersonate nullobjs (implementation possibility: in a defer block, go through all the instance_methods currently defined on subject, and rewrite each one that ends in '?'.)

Bonus points for doing this completely in a command object without putting any new logic in NullClassBuilder!

[mdespuits]

Bonus points for doing this completely in a command object without putting any new logic in NullClassBuilder!

[avdi]

Sorry, I really wanted to get this in so I went ahead and wrote it. I didn't quite qualify for bonus points, although I managed to do it with minimal changes to the NullClassBuilder.