Question

Is there a way to get the list (array) of all the constants (including modules and classes) and their methods and class or instance variables that are added or redefined upon loading an external ruby file?

Answer 1

This should do the trick:

def all_constants_with_methods
  constants = Object.constants.map { |sym| Object.const_get sym }
  Hash[constants.map { |constant| [constant, (constant.instance_methods rescue [])] }]
end

before = all_constants_with_methods
load foo.rb
after = all_constants_with_methods

constants_added = after.keys - before.keys
methods_added = Hash[after.keys.map do |c|
                       [c, after[c] - (before[c] || [])]
                     end.reject do |_, v|
                       v.empty?
                     end]

There’s no way that I know of to know if a method was redefined, though. You can easily expand this to class variables (using class_variables) and class instance variables (using instance_variables).