add_method_tracer modifies object arguments

[dipth]

add_method_tracer causes object arguments to be cloned.

Description

When tracing a method that takes an object argument that is supposed to be mutated during the execution of that method, the tracing causes the passed argument to be a clone of the object, meaning that any mutations are lost to outside references to the same object.

Expected Behavior

No cloning of arguments should happen and the passed object should be included in the call to the method as is.

Steps to Reproduce

class Demonstration
  include ::NewRelic::Agent::MethodTracer

  def call
    (1..10).each_with_object({}) do |i, hash|
      process(i, hash)
    end
  end

  def process(i, hash)
    hash[i] = i * 2
  end

  add_method_tracer :process, 'Demonstration/process'
end

Demonstration.new.call
#=> {}

Expected result:

Demonstration.new.call
=> {1=>2, 2=>4, 3=>6, 4=>8, 5=>10, 6=>12, 7=>14, 8=>16, 9=>18, 10=>20}

Your Environment

ruby 2.7.1p83 (2020-03-31 revision a0c7c23c9c) [x86_64-darwin19]

Additional context

It seems like this is not an issue in Ruby 2.6

[tannalynn]

Hello @dipth. We will take a closer look at this.
Thank you for bringing this to our attention.

[mwlang]

This should be solved by this PR: #422