@enebo this is still an issue even in 9.1.5.0

@PetrKaleta That is a good question. I know we fixed a number of proc passing bugs since then and I also know recently there was some activity with CI and 9.1.5.0 + warden. I would be inclined to think it has been fixed but I am not sure how to test this. I cannot run your snippets can I? Any way for you to retest?

@enebo sure you can, its a fully working example. Means just copy & paste it, no other dependency needed

@enebo and I don't think it's an issue related to proc passing. It looks like issue of inconsistent define_method behaviour. As you can see SessionSerializer already has serialize method, but it's redefined to serialize method withou argument. But JRuby 1.7.x and MRI keeps the original...

@PetrKaleta ah I was confused by the working subset comment. I thought it still required warden and was an example. So ok I have more info. I would say your understanding is not quite right but I am unclear on what is happening. Check out this snippet:

class SessionSerializer
  def serialize(obj)
    puts "HELL YES: #{obj}"
  end
end

class Manager
  def self.serialize_into_session(&block)
    SessionSerializer.send :define_method, :serialize, &block
  end
end

def frogger
  puts "HOH"
end
public :frogger

Manager.serialize_into_session(&:frogger) # => :serialize
SessionSerializer.new.serialize(1) # ArgumentError: wrong number of arguments (1 for 0)

If I run this in MRI I get "HOH" printed out so it seems to definitely be calling the new method and not the original one. If I add a param to frogger then MRI stops working with an argument error...

@enebo ah pardon, here is the point

class SessionSerializer
  def serialize(obj)
    obj.to_s
  end
end

class Manager
  def self.serialize_into_session(&block)
    SessionSerializer.send :define_method, :serialize, &block
  end
end

SessionSerializer.new.serialize(1) # => "1"

So there's some SessionSerializer with a default method serialize that takes an object and stringify it. But user can define its own serializer by, like this:

Manager.serialize_into_session { |obj| "Custom serialization of: #{obj}" }

So now when you call the serialize method:

SessionSerializer.new.serialize(1)  # => "Custom serialization of: 1"

But JRuby 9.x.x fails on that block passing, you were right :)

Reduced case (bottom one):

# Ruby proc with -1 arity works
s = proc { |*a| a.first.to_s }
define_method :serialize, s
p s.arity
p serialize(0)

# Symbol.to_proc generated method does not work
s = :to_s.to_proc
define_method :serialize, s
p s.arity
p serialize(1)

So Symbol.to_proc proc claims to have -1 arity like first working example but we stumble over argument error to seemingly not having a negative arity (I would bet on 0).