Change ActiveSupport::Deprecation to class.

ActiveSupport::Deprecation is now a class rather than a module. You can
get instance of ActiveSupport::Deprecation calling #instance method.

  ActiveSupport::Deprecation.instance

But when you need to get new object od ActiveSupport::Deprecation you
need to just call #new.

  @instance = ActiveSupport::Deprecation.new

Since you can create a new object, you can change the version and the
name of the library where the deprecator concerned.

  ActiveSupport::Deprecation.new('2.0', 'MyGem')

If you need use another deprecator instance you can select it in the
options of deprecate method.

  deprecate :method, :deprecator => deprecator_instance

Documentation has been updated.

9 files changed, 405 insertions, 221 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 3914f4dc4c..6dff6de83a 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,5 +1,37 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   ActiveSupport::Deprecation is now a class. It is possible to create an instance
+    of deprecator. Backwards compatibility has been preserved.
+
+    You can choose which instance of the deprecator will be used.
+
+      deprecate :method_name, :deprecator => deprecator_instance
+
+    You can use ActiveSupport::Deprecation in your gem.
+
+      require 'active_support/deprecation'
+      require 'active_support/core_ext/module/deprecation'
+
+      class MyGem
+        def old_method
+        end
+        deprecate :old_method => :new_method, :deprecator => deprecator
+
+        def new_method
+        end
+
+        def self.deprecator
+          ActiveSupport::Deprecation.new('2.0', 'MyGem')
+        end
+      end
+
+      MyGem.new.old_method
+
+      DEPRECATION WARNING: old_method is deprecated and will be removed from MyGem 2.0
+      (use new_method instead). (called from <main> at file.rb:18)
+
+    *Piotr Niełacny & Robert Pankowecki*
+
 *   `ERB::Util.html_escape` encodes single quote as `#39`. Decimal form has better support in old browsers. *Kalys Osmonov*
 
 *   `ActiveSupport::Callbacks`: deprecate monkey patch of object callbacks.
diff --git a/activesupport/lib/active_support/core_ext/module/deprecation.rb b/activesupport/lib/active_support/core_ext/module/deprecation.rb
index 9e77ac3c45..9affd38baa 100644
--- a/activesupport/lib/active_support/core_ext/module/deprecation.rb
+++ b/activesupport/lib/active_support/core_ext/module/deprecation.rb
@@ -1,10 +1,42 @@
 require 'active_support/deprecation/method_wrappers'
 
 class Module
-  # Declare that a method has been deprecated.
   #   deprecate :foo
   #   deprecate :bar => 'message'
   #   deprecate :foo, :bar, :baz => 'warning!', :qux => 'gone!'
+  #
+  # You can use custom deprecator instance
+  #   deprecate :foo, :deprecator => MyLib::Deprecator.new
+  #   deprecate :foo, :bar => "warning!", :deprecator => MyLib::Deprecator.new
+  #
+  # \Custom deprecators must respond to one method
+  # [deprecation_warning(deprecated_method_name, message, caller_backtrace)] will be called with the deprecated
+  #                                                                          method name, the message it was declared
+  #                                                                          with and caller_backtrace. Implement
+  #                                                                          whatever warning behavior you like here.
+  #
+  # Example
+  #    class MyLib::Deprecator
+  #
+  #      def deprecation_warning(deprecated_method_name, message, caller_backtrace)
+  #         message = "#{method_name} is deprecated and will be removed from MyLibrary | #{message}"
+  #         Kernel.warn message
+  #      end
+  #
+  #    end
+  #
+  #    module MyLib
+  #      mattr_accessor :deprecator
+  #      self.deprecator = Deprecator.new
+  #    end
+  #
+  # When we deprecate method
+  #    class MyLib::Bar
+  #      deprecate :foo => "this is very old method", :deprecator => MyLib.deprecator
+  #    end
+  #
+  # It will build deprecation message and invoke deprecator warning by calling
+  #   MyLib.deprecator.deprecation_warning(:foo, "this is a very old method", caller)
   def deprecate(*method_names)
     ActiveSupport::Deprecation.deprecate_methods(self, *method_names)
   end
diff --git a/activesupport/lib/active_support/deprecation.rb b/activesupport/lib/active_support/deprecation.rb
index 968ee1eaf8..678cbbcbf2 100644
--- a/activesupport/lib/active_support/deprecation.rb
+++ b/activesupport/lib/active_support/deprecation.rb
@@ -1,19 +1,40 @@
 require 'active_support/core_ext/module/deprecation'
+require 'active_support/deprecation/instance_delegator'
 require 'active_support/deprecation/behaviors'
 require 'active_support/deprecation/reporting'
 require 'active_support/deprecation/method_wrappers'
 require 'active_support/deprecation/proxy_wrappers'
+require 'singleton'
 
 module ActiveSupport
-  module Deprecation
-    class << self
-      # The version the deprecated behavior will be removed, by default.
-      attr_accessor :deprecation_horizon
-    end
-    self.deprecation_horizon = '4.1'
+  # \Deprecation specifies the API used by Rails to deprecate
+  # methods, instance variables, objects and constants.
+  # The API depends on four methods:
+  #
+  # * +initialize+ which expects two parameters
+  #   described below;
+  class Deprecation
+    include Singleton
+    include InstanceDelegator
+    include Behavior
+    include Reporting
+    include MethodWrapper
+
+    # The version the deprecated behavior will be removed, by default.
+    attr_accessor :deprecation_horizon
 
-    # By default, warnings are not silenced and debugging is off.
-    self.silenced = false
-    self.debug = false
+    # It accepts two parameters on initialization. The first is an version of library
+    # and the second is an library name
+    #
+    # == Example
+    #
+    #   ActiveSupport::Deprecation.new('2.0', 'MyLibrary')
+    def initialize(deprecation_horizon = '4.1', gem_name = 'Rails')
+      self.gem_name = gem_name
+      self.deprecation_horizon = deprecation_horizon
+      # By default, warnings are not silenced and debugging is off.
+      self.silenced = false
+      self.debug = false
+    end
   end
 end
diff --git a/activesupport/lib/active_support/deprecation/behaviors.rb b/activesupport/lib/active_support/deprecation/behaviors.rb
index c956560a99..b4c8a0e92d 100644
--- a/activesupport/lib/active_support/deprecation/behaviors.rb
+++ b/activesupport/lib/active_support/deprecation/behaviors.rb
@@ -1,39 +1,7 @@
 require "active_support/notifications"
 
 module ActiveSupport
-  module Deprecation
-    # Whether to print a backtrace along with the warning.
-    attr_accessor :debug
-
-    # Returns the current behavior or if one isn't set, defaults to +:stderr+
-    def behavior
-      @behavior ||= [DEFAULT_BEHAVIORS[:stderr]]
-    end
-
-    # Sets the behavior to the specified value. Can be a single value, array, or
-    # an object that responds to +call+.
-    #
-    # Available behaviors:
-    #
-    # [+stderr+]  Log all deprecation warnings to +$stderr+.
-    # [+log+]     Log all deprecation warnings to +Rails.logger+.
-    # [+notify]   Use +ActiveSupport::Notifications+ to notify +deprecation.rails+.
-    # [+silence+] Do nothing.
-    #
-    # Setting behaviors only affects deprecations that happen after boot time.
-    # Deprecation warnings raised by gems are not affected by this setting because
-    # they happen before Rails boots up.
-    #
-    #   ActiveSupport::Deprecation.behavior = :stderr
-    #   ActiveSupport::Deprecation.behavior = [:stderr, :log]
-    #   ActiveSupport::Deprecation.behavior = MyCustomHandler
-    #   ActiveSupport::Deprecation.behavior = proc { |message, callstack|
-    #     # custom stuff
-    #   }
-    def behavior=(behavior)
-      @behavior = Array(behavior).map { |b| DEFAULT_BEHAVIORS[b] || b }
-    end
-
+  class Deprecation
     # Default warning behaviors per Rails.env.
     DEFAULT_BEHAVIORS = {
       :stderr => Proc.new { |message, callstack|
@@ -41,21 +9,55 @@ module ActiveSupport
         $stderr.puts callstack.join("\n  ") if debug
       },
       :log => Proc.new { |message, callstack|
-         logger =
-           if defined?(Rails) && Rails.logger
-             Rails.logger
-           else
-             require 'active_support/logger'
-             ActiveSupport::Logger.new($stderr)
-           end
-         logger.warn message
-         logger.debug callstack.join("\n  ") if debug
-       },
-       :notify => Proc.new { |message, callstack|
-          ActiveSupport::Notifications.instrument("deprecation.rails",
-          :message => message, :callstack => callstack)
-       },
-       :silence => Proc.new { |message, callstack| }
+        logger =
+            if defined?(Rails) && Rails.logger
+              Rails.logger
+            else
+              require 'active_support/logger'
+              ActiveSupport::Logger.new($stderr)
+            end
+        logger.warn message
+        logger.debug callstack.join("\n  ") if debug
+      },
+      :notify => Proc.new { |message, callstack|
+        ActiveSupport::Notifications.instrument("deprecation.rails",
+                                                :message => message, :callstack => callstack)
+      },
+      :silence => Proc.new { |message, callstack| }
     }
+
+    module Behavior
+      # Whether to print a backtrace along with the warning.
+      attr_accessor :debug
+
+      # Returns the current behavior or if one isn't set, defaults to +:stderr+
+      def behavior
+        @behavior ||= [DEFAULT_BEHAVIORS[:stderr]]
+      end
+
+      # Sets the behavior to the specified value. Can be a single value, array, or
+      # an object that responds to +call+.
+      #
+      # Available behaviors:
+      #
+      # [+stderr+]  Log all deprecation warnings to +$stderr+.
+      # [+log+]     Log all deprecation warnings to +Rails.logger+.
+      # [+notify+]  Use +ActiveSupport::Notifications+ to notify +deprecation.rails+.
+      # [+silence+] Do nothing.
+      #
+      # Setting behaviors only affects deprecations that happen after boot time.
+      # Deprecation warnings raised by gems are not affected by this setting because
+      # they happen before Rails boots up.
+      #
+      #   ActiveSupport::Deprecation.behavior = :stderr
+      #   ActiveSupport::Deprecation.behavior = [:stderr, :log]
+      #   ActiveSupport::Deprecation.behavior = MyCustomHandler
+      #   ActiveSupport::Deprecation.behavior = proc { |message, callstack|
+      #     # custom stuff
+      #   }
+      def behavior=(behavior)
+        @behavior = Array(behavior).map { |b| DEFAULT_BEHAVIORS[b] || b }
+      end
+    end
   end
 end
diff --git a/activesupport/lib/active_support/deprecation/instance_delegator.rb b/activesupport/lib/active_support/deprecation/instance_delegator.rb
new file mode 100644
index 0000000000..ff240cb887
--- /dev/null
+++ b/activesupport/lib/active_support/deprecation/instance_delegator.rb
@@ -0,0 +1,24 @@
+require 'active_support/core_ext/kernel/singleton_class'
+require 'active_support/core_ext/module/delegation'
+
+module ActiveSupport
+  class Deprecation
+    module InstanceDelegator
+      def self.included(base)
+        base.extend(ClassMethods)
+        base.public_class_method :new
+      end
+
+      module ClassMethods
+        def include(included_module)
+          included_module.instance_methods.each { |m| method_added(m) }
+          super
+        end
+
+        def method_added(method_name)
+          singleton_class.delegate(method_name, to: :instance)
+        end
+      end
+    end
+  end
+end
\ No newline at end of file
diff --git a/activesupport/lib/active_support/deprecation/method_wrappers.rb b/activesupport/lib/active_support/deprecation/method_wrappers.rb
index f4ad15cc63..d3907b03e5 100644
--- a/activesupport/lib/active_support/deprecation/method_wrappers.rb
+++ b/activesupport/lib/active_support/deprecation/method_wrappers.rb
@@ -2,46 +2,41 @@ require 'active_support/core_ext/module/aliasing'
 require 'active_support/core_ext/array/extract_options'
 
 module ActiveSupport
-  module Deprecation
-    # Declare that a method has been deprecated.
-    #
-    #   module Fred
-    #     extend self
-    #
-    #     def foo; end
-    #     def bar; end
-    #     def baz; end
-    #   end
-    #
-    #   ActiveSupport::Deprecation.deprecate_methods(Fred, :foo, bar: :qux, baz: 'use Bar#baz instead')
-    #   # => [:foo, :bar, :baz]
-    #
-    #   Fred.foo
-    #   # => "DEPRECATION WARNING: foo is deprecated and will be removed from Rails 4.1."
-    #
-    #   Fred.bar
-    #   # => "DEPRECATION WARNING: bar is deprecated and will be removed from Rails 4.1 (use qux instead)."
-    #
-    #   Fred.baz
-    #   # => "DEPRECATION WARNING: baz is deprecated and will be removed from Rails 4.1 (use Bar#baz instead)."
-    def self.deprecate_methods(target_module, *method_names)
-      options = method_names.extract_options!
-      method_names += options.keys
+  class Deprecation
+    module MethodWrapper
+      # Declare that a method has been deprecated.
+      #
+      #   module Fred
+      #     extend self
+      #
+      #     def foo; end
+      #     def bar; end
+      #     def baz; end
+      #   end
+      #
+      #   ActiveSupport::Deprecation.deprecate_methods(Fred, :foo, bar: :qux, baz: 'use Bar#baz instead')
+      #   # => [:foo, :bar, :baz]
+      #
+      #   Fred.foo
+      #   # => "DEPRECATION WARNING: foo is deprecated and will be removed from Rails 4.1."
+      #
+      #   Fred.bar
+      #   # => "DEPRECATION WARNING: bar is deprecated and will be removed from Rails 4.1 (use qux instead)."
+      #
+      #   Fred.baz
+      #   # => "DEPRECATION WARNING: baz is deprecated and will be removed from Rails 4.1 (use Bar#baz instead)."
+      def deprecate_methods(target_module, *method_names)
+        options = method_names.extract_options!
+        deprecator = options.delete(:deprecator) || ActiveSupport::Deprecation.instance
+        method_names += options.keys
 
-      method_names.each do |method_name|
-        target_module.alias_method_chain(method_name, :deprecation) do |target, punctuation|
-          target_module.module_eval(<<-end_eval, __FILE__, __LINE__ + 1)
-            def #{target}_with_deprecation#{punctuation}(*args, &block)
-              deprecator = respond_to?(:deprecator) ? deprecator() : ActiveSupport::Deprecation
-              deprecator.warn(
-                deprecator.deprecated_method_warning(
-                  :#{method_name},
-                  #{options[method_name].inspect}),
-                caller
-              )
-              send(:#{target}_without_deprecation#{punctuation}, *args, &block)
+        method_names.each do |method_name|
+          target_module.alias_method_chain(method_name, :deprecation) do |target, punctuation|
+            target_module.send(:define_method, "#{target}_with_deprecation#{punctuation}") do |*args, &block|
+              deprecator.deprecation_warning(method_name, options[method_name], caller)
+              send(:"#{target}_without_deprecation#{punctuation}", *args, &block)
             end
-          end_eval
+          end
         end
       end
     end
diff --git a/activesupport/lib/active_support/deprecation/proxy_wrappers.rb b/activesupport/lib/active_support/deprecation/proxy_wrappers.rb
index 382f2e88f0..2b8282c34e 100644
--- a/activesupport/lib/active_support/deprecation/proxy_wrappers.rb
+++ b/activesupport/lib/active_support/deprecation/proxy_wrappers.rb
@@ -1,7 +1,7 @@
 require 'active_support/inflector/methods'
 
 module ActiveSupport
-  module Deprecation
+  class Deprecation
     class DeprecationProxy #:nodoc:
       def self.new(*args, &block)
         object = args.first
@@ -25,8 +25,18 @@ module ActiveSupport
         end
     end
 
-    class DeprecatedObjectProxy < DeprecationProxy #:nodoc:
-      def initialize(object, message, deprecator = ActiveSupport::Deprecation)
+    # This DeprecatedObjectProxy transforms object to depracated object.
+    #
+    # Example
+    #   @old_object = DeprecatedObjectProxy.new(Object.new, "Don't use this object anymore!")
+    # Example with custom deprecator
+    #   @old_object = DeprecatedObjectProxy.new(Object.new, "Don't use this object anymore!", deprecator_instance)
+    #
+    # When someone execute any method expect +inspect+ on proxy object this will trigger +warn+ method on +deprecator_instance+
+    #
+    # Default deprecator is ActiveSupport::Deprecation
+    class DeprecatedObjectProxy < DeprecationProxy
+      def initialize(object, message, deprecator = ActiveSupport::Deprecation.instance)
         @object = object
         @message = message
         @deprecator = deprecator
@@ -42,14 +52,34 @@ module ActiveSupport
         end
     end
 
-    # Stand-in for <tt>@request</tt>, <tt>@attributes</tt>, <tt>@params</tt>, etc.
-    # which emits deprecation warnings on any method call (except +inspect+).
-    class DeprecatedInstanceVariableProxy < DeprecationProxy #:nodoc:
-      def initialize(instance, method, var = :"@#{method}", deprecator = nil)
+    # This DeprecatedInstanceVariableProxy transforms instance variable to depracated instance variable.
+    #
+    # Example
+    #  class Example
+    #    def initialize(deprecator)
+    #      @request = ActiveSupport::Deprecation::DeprecatedInstanceVariableProxy.new(self, :request, :@request, deprecator)
+    #      @_request = :a_request
+    #    end
+    #
+    #    def request
+    #       @_request
+    #     end
+    #
+    #    def old_request
+    #       @request
+    #    end
+    #  end
+    #
+    # When someone execute any method on @request variable this will trigger +warn+ method on +deprecator_instance+
+    # and will fetch @_request variable via +request+ method and execute the same method on non-proxy instance variable.
+    #
+    # Default deprecator is ActiveSupport::Deprecation
+    class DeprecatedInstanceVariableProxy < DeprecationProxy
+      def initialize(instance, method, var = "@#{method}", deprecator = ActiveSupport::Deprecation.instance)
         @instance = instance
         @method = method
         @var = var
-        @deprecator = deprecator || (@instance.respond_to?(:deprecator) ? @instance.deprecator : ActiveSupport::Deprecation)
+        @deprecator = deprecator
       end
 
       private
@@ -62,8 +92,17 @@ module ActiveSupport
         end
     end
 
-    class DeprecatedConstantProxy < DeprecationProxy #:nodoc:all
-      def initialize(old_const, new_const, deprecator = ActiveSupport::Deprecation)
+    # This DeprecatedConstantProxy transforms constant to depracated constant.
+    #
+    # Example
+    #   OLD_CONST = ActiveSupport::Deprecation::DeprecatedConstantProxy.new('OLD_CONST', 'NEW_CONST')
+    # Example with custom deprecator
+    #   OLD_CONST = ActiveSupport::Deprecation::DeprecatedConstantProxy.new('OLD_CONST', 'NEW_CONST', deprecator_instance)
+    # When someone use old constant this will trigger +warn+ method on +deprecator_instance+
+    #
+    # Default deprecator is ActiveSupport::Deprecation
+    class DeprecatedConstantProxy < DeprecationProxy
+      def initialize(old_const, new_const, deprecator = ActiveSupport::Deprecation.instance)
         @old_const = old_const
         @new_const = new_const
         @deprecator = deprecator
diff --git a/activesupport/lib/active_support/deprecation/reporting.rb b/activesupport/lib/active_support/deprecation/reporting.rb
index 69de79b93c..cf91ca1acb 100644
--- a/activesupport/lib/active_support/deprecation/reporting.rb
+++ b/activesupport/lib/active_support/deprecation/reporting.rb
@@ -1,73 +1,90 @@
 module ActiveSupport
-  module Deprecation
-    attr_accessor :silenced
+  class Deprecation
+    module Reporting
+      # Whether to print a message (silent mode)
+      attr_accessor :silenced
+      # Name of gem where method is deprecated
+      attr_accessor :gem_name
 
-    # Outputs a deprecation warning to the output configured by
-    # <tt>ActiveSupport::Deprecation.behavior</tt>.
-    #
-    #   ActiveSupport::Deprecation.warn("something broke!")
-    #   # => "DEPRECATION WARNING: something broke! (called from your_code.rb:1)"
-    def warn(message = nil, callstack = caller)
-      return if silenced
-      deprecation_message(callstack, message).tap do |m|
-        behavior.each { |b| b.call(m, callstack) }
+      # Outputs a deprecation warning to the output configured by
+      # <tt>ActiveSupport::Deprecation.behavior</tt>.
+      #
+      #   ActiveSupport::Deprecation.warn("something broke!")
+      #   # => "DEPRECATION WARNING: something broke! (called from your_code.rb:1)"
+      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
-    end
 
-    # Silence deprecation warnings within the block.
-    #
-    #   ActiveSupport::Deprecation.warn("something broke!")
-    #   # => "DEPRECATION WARNING: something broke! (called from your_code.rb:1)"
-    #
-    #   ActiveSupport::Deprecation.silence do
-    #     ActiveSupport::Deprecation.warn("something broke!")
-    #   end
-    #   # => nil
-    def silence
-      old_silenced, @silenced = @silenced, true
-      yield
-    ensure
-      @silenced = old_silenced
-    end
+      # Silence deprecation warnings within the block.
+      #
+      #   ActiveSupport::Deprecation.warn("something broke!")
+      #   # => "DEPRECATION WARNING: something broke! (called from your_code.rb:1)"
+      #
+      #   ActiveSupport::Deprecation.silence do
+      #     ActiveSupport::Deprecation.warn("something broke!")
+      #   end
+      #   # => nil
+      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})"
+      def deprecation_warning(deprecated_method_name, message = nil, caller_backtrace = caller)
+        deprecated_method_warning(deprecated_method_name, message).tap do |message|
+          warn(message, caller_backtrace)
+        end
       end
-      warning
-    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
+      private
+        # Outputs a deprecation warning message
+        #   ActiveSupport::Deprecation.deprecated_method_warning(:method_name)
+        #   # => "method_name is deprecated and will be removed from Rails #{deprecation_horizon}"
+        #   ActiveSupport::Deprecation.deprecated_method_warning(:method_name, :another_method)
+        #   # => "method_name is deprecated and will be removed from Rails #{deprecation_horizon} (use another_method instead)"
+        #   ActiveSupport::Deprecation.deprecated_method_warning(:method_name, "Optional message")
+        #   # => "method_name is deprecated and will be removed from Rails #{deprecation_horizon} (Optional message)"
+        def deprecated_method_warning(method_name, message = nil)
+          warning = "#{method_name} is deprecated and will be removed from #{gem_name} #{deprecation_horizon}"
+          case message
+            when Symbol then "#{warning} (use #{message} instead)"
+            when String then "#{warning} (#{message})"
+            else warning
+          end
+        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})"
+        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
-      end
-    end
 
-    def extract_callstack(callstack)
-      rails_gem_root = File.expand_path("../../../../..", __FILE__) + "/"
-      offending_line = callstack.find { |line| !line.start_with?(rails_gem_root) } || callstack.first
-      if offending_line
-        if md = offending_line.match(/^(.+?):(\d+)(?::in `(.*?)')?/)
-          md.captures
-        else
-          offending_line
+        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)
+          rails_gem_root = File.expand_path("../../../../..", __FILE__) + "/"
+          offending_line = callstack.find { |line| !line.start_with?(rails_gem_root) } || callstack.first
+          if offending_line
+            if md = offending_line.match(/^(.+?):(\d+)(?::in `(.*?)')?/)
+              md.captures
+            else
+              offending_line
+            end
+          end
         end
-      end
     end
   end
 end
diff --git a/activesupport/test/deprecation_test.rb b/activesupport/test/deprecation_test.rb
index 308c7c3fe7..c081103cc7 100644
--- a/activesupport/test/deprecation_test.rb
+++ b/activesupport/test/deprecation_test.rb
@@ -104,6 +104,17 @@ class DeprecationTest < ActiveSupport::TestCase
     assert_match(/call stack!/, content)
   end
 
+  def test_default_stderr_behavior_with_warn_method
+    ActiveSupport::Deprecation.behavior = :stderr
+
+    content = capture(:stderr) {
+      ActiveSupport::Deprecation.warn('Instance error!', ['instance call stack!'])
+    }
+
+    assert_match(/Instance error!/, content)
+    assert_match(/instance call stack!/, content)
+  end
+
   def test_default_silence_behavior
     ActiveSupport::Deprecation.behavior = :silence
     behavior = ActiveSupport::Deprecation.behavior.first
@@ -187,39 +198,57 @@ class DeprecationTest < ActiveSupport::TestCase
     assert_deprecated(/you now need to do something extra for this one/) { @dtc.d }
   end
 
-  def test_deprecation_in_other_module_does_not_interfere
+  def test_deprecation_in_other_object
     messages = []
 
-    m = Module.new
-    m.extend ActiveSupport::Deprecation
-    m.behavior = Proc.new{|message, callstack| messages << message}
-    assert_not_deprecated do # not globally
-      assert_difference("messages.size") do # but locally
-        m.warn("warning")
-      end
+    klass = Class.new do
+      delegate :warn, :behavior=, to: ActiveSupport::Deprecation
+    end
+
+    o = klass.new
+    o.behavior = Proc.new { |message, callstack| messages << message }
+    assert_difference("messages.size") do
+      o.warn("warning")
     end
   end
 
-  def test_deprecated_method_with_deprecator_implemented
+  def test_deprecated_method_with_custom_method_warning
     deprecator = deprecator_with_messages
-    def deprecator.deprecated_method_warning(method, *params)
-      "deprecator.deprecated_method_warning.#{method}"
+
+    class << deprecator
+      private
+        def deprecated_method_warning(method, message)
+          "deprecator.deprecated_method_warning.#{method}"
+        end
     end
 
-    deprecatee = Class.new() do
+    deprecatee = Class.new do
       def method
       end
-      deprecate :method
-      define_method(:deprecator){ deprecator }
+      deprecate :method, deprecator: deprecator
     end
 
     deprecatee.new.method
     assert deprecator.messages.first.match("DEPRECATION WARNING: deprecator.deprecated_method_warning.method")
   end
 
+  def test_deprecate_with_custom_deprecator
+    custom_deprecator = mock('Deprecator') do
+      expects(:deprecation_warning)
+    end
+
+    klass = Class.new do
+      def method
+      end
+      deprecate :method, deprecator: custom_deprecator
+    end
+
+    klass.new.method
+  end
+
   def test_deprecated_constant_with_deprecator_given
     deprecator = deprecator_with_messages
-    klass = Class.new()
+    klass = Class.new
     klass.const_set(:OLD, ActiveSupport::Deprecation::DeprecatedConstantProxy.new('klass::OLD', 'Object', deprecator) )
     assert_difference("deprecator.messages.size") do
       klass::OLD.to_s
@@ -230,23 +259,21 @@ class DeprecationTest < ActiveSupport::TestCase
     deprecator = deprecator_with_messages
     
     klass = Class.new() do
-      def initialize
-        @request = ActiveSupport::Deprecation::DeprecatedInstanceVariableProxy.new(self, :request)
+      def initialize(deprecator)
+        @request = ActiveSupport::Deprecation::DeprecatedInstanceVariableProxy.new(self, :request, :@request, deprecator)
         @_request = :a_request
       end
       def request; @_request end
       def old_request; @request end
-      define_method(:deprecator) { deprecator }
     end
 
-    assert_difference("deprecator.messages.size") { klass.new.old_request.to_s }
-    
+    assert_difference("deprecator.messages.size") { klass.new(deprecator).old_request.to_s }
   end
 
   def test_deprecated_instance_variable_with_given_deprecator
     deprecator = deprecator_with_messages
 
-    klass = Class.new() do
+    klass = Class.new do
       define_method(:initialize) do
         @request = ActiveSupport::Deprecation::DeprecatedInstanceVariableProxy.new(self, :request, :@request, deprecator)
         @_request = :a_request
@@ -258,23 +285,23 @@ class DeprecationTest < ActiveSupport::TestCase
     assert_difference("deprecator.messages.size") { klass.new.old_request.to_s }
   end
 
-  def test_included_deprecation_module
-    klass = Class.new() do
+  def test_delegate_deprecator_instance
+    klass = Class.new do
       attr_reader :last_message
-      include ActiveSupport::Deprecation
+      delegate :warn, :behavior=, to: ActiveSupport::Deprecation
+
+      def initialize
+        self.behavior = [Proc.new { |message| @last_message = message }]
+      end
+
       def deprecated_method
         warn(deprecated_method_warning(:deprecated_method, "You are calling deprecated method"))
       end
 
       private
-
-      def deprecated_method_warning(method_name, message = nil)
-        message || "#{method_name} is deprecated and will be removed from This Library"
-      end
-
-      def behavior
-        @behavior ||= [Proc.new { |message| @last_message = message }]
-      end
+        def deprecated_method_warning(method_name, message = nil)
+          message || "#{method_name} is deprecated and will be removed from This Library"
+        end
     end
 
     object = klass.new
@@ -282,35 +309,30 @@ class DeprecationTest < ActiveSupport::TestCase
     assert_match(/You are calling deprecated method/, object.last_message)
   end
 
-  unless defined?(::MiniTest)
-    def test_assertion_failed_error_doesnt_spout_deprecation_warnings
-      error_class = Class.new(StandardError) do
-        def message
-          ActiveSupport::Deprecation.warn 'warning in error message'
-          super
-        end
-      end
-
-      raise error_class.new('hmm')
+  def test_default_gem_name
+    deprecator = ActiveSupport::Deprecation.new
 
-    rescue => e
-      error = Test::Unit::Error.new('testing ur doodz', e)
-      assert_not_deprecated { error.message }
-      assert_nil @last_message
+    deprecator.send(:deprecated_method_warning, :deprecated_method, "You are calling deprecated method").tap do |message|
+      assert_match(/is deprecated and will be removed from Rails/, message)
     end
   end
 
+  def test_custom_gem_name
+    deprecator = ActiveSupport::Deprecation.new('2.0', 'Custom')
 
-  private
-
-
-  def deprecator_with_messages
-    deprecator = Object.new
-    deprecator.extend(ActiveSupport::Deprecation)
-    deprecator.behavior = Proc.new{|message, callstack| deprecator.messages << message}
-    def deprecator.messages
-      @messages ||= []
+    deprecator.send(:deprecated_method_warning, :deprecated_method, "You are calling deprecated method").tap do |message|
+      assert_match(/is deprecated and will be removed from Custom/, message)
     end
-    deprecator
   end
+
+  private
+    def deprecator_with_messages
+      klass = Class.new(ActiveSupport::Deprecation)
+      deprecator = klass.new
+      deprecator.behavior = Proc.new{|message, callstack| deprecator.messages << message}
+      def deprecator.messages
+        @messages ||= []
+      end
+      deprecator
+    end
 end