rails--rails/activesupport/lib/active_support/deprecation/reporting.rb

module ActiveSupport
  module Deprecation
    class << self
      attr_accessor :silenced

      def warn(message = nil, callstack = caller)
        return if silenced
        deprecation_message(callstack, message).tap do |m|
          behavior.each { |b| b.call(m, callstack) }
        end
      end

      # Silence deprecation warnings within the block.
      def silence
        old_silenced, @silenced = @silenced, true
        yield
      ensure
        @silenced = old_silenced
      end

      def deprecated_method_warning(method_name, message = nil)
        warning = "#{method_name} is deprecated and will be removed from Rails #{deprecation_horizon}"
        case message
          when Symbol then "#{warning} (use #{message} instead)"
          when String then "#{warning} (#{message})"
          else warning
        end
      end

      private
        def deprecation_message(callstack, message = nil)
          message ||= "You are using deprecated behavior which will be removed from the next major or minor release."
          message += '.' unless message =~ /\.$/
          "DEPRECATION WARNING: #{message} #{deprecation_caller_message(callstack)}"
        end

        def deprecation_caller_message(callstack)
          file, line, method = extract_callstack(callstack)
          if file
            if line && method
              "(called from #{method} at #{file}:#{line})"
            else
              "(called from #{file}:#{line})"
            end
          end
        end

        def extract_callstack(callstack)
          if md = callstack.first.match(/^(.+?):(\d+)(?::in `(.*?)')?/)
            md.captures
          else
            callstack.first
          end
        end
    end
  end
end