Merge pull request #8312 from senny/make_active_model_parts_individually_loadable

make sure that individual parts `ActiveModel` can be required by itself

activemodel/CHANGELOG.md

 ## Rails 4.0.0 (unreleased) ##
 
+*   Removed dispensable `require` statements. Make sure to require `active_model` before requiring
+    individual parts of the framework.
+
+    *Yves Senn*
+
 *   Use BCrypt's MIN_COST in the test environment for speedier tests when using `has_secure_pasword`.
 
     *Brian Cardarella + Jeremy Kemper + Trevor Turk*

activemodel/lib/active_model/attribute_methods.rb

@@ -8,7 +8,7 @@ module ActiveModel
   #
   #   user = User.first
   #   user.pets.select(:id).first.user_id
-  #   # => ActiveModel::MissingAttributeError: missing attribute: user_id
+  #   # => ActiveModel::MissingAttributeError: missing attribute: user_id
   class MissingAttributeError < NoMethodError
   end
   # == Active \Model Attribute Methods
@@ -202,7 +202,7 @@ def attribute_method_affix(*affixes)
       #   person.name            # => "Bob"
       #   person.nickname        # => "Bob"
       #   person.name_short?     # => true
-      #   person.nickname_short? # => true
+      #   person.nickname_short? # => true
       def alias_attribute(new_name, old_name)
         self.attribute_aliases = attribute_aliases.merge(new_name.to_s => old_name.to_s)
         attribute_method_matchers.each do |matcher|

activemodel/lib/active_model/callbacks.rb

-require 'active_support/callbacks'
-
 module ActiveModel
   # == Active \Model \Callbacks
   #

activemodel/lib/active_model/conversion.rb

-require 'active_support/inflector'
-
 module ActiveModel
   # == Active \Model Conversions
   #

activemodel/lib/active_model/dirty.rb

-require 'active_model/attribute_methods'
 require 'active_support/hash_with_indifferent_access'
 require 'active_support/core_ext/object/duplicable'
 

activemodel/lib/active_model/naming.rb

-require 'active_support/inflector'
 require 'active_support/core_ext/hash/except'
 require 'active_support/core_ext/module/introspection'
 
@@ -56,8 +55,8 @@ class Name
     #   end
     #
     #   BlogPost.model_name <=> 'BlogPost'  # => 0
-    #   BlogPost.model_name <=> 'Blog'      # => 1
-    #   BlogPost.model_name <=> 'BlogPosts' # => -1
+    #   BlogPost.model_name <=> 'Blog'      # => 1
+    #   BlogPost.model_name <=> 'BlogPosts' # => -1
 
     ##
     # :method: =~

activemodel/lib/active_model/observing.rb

@@ -5,7 +5,6 @@
 require 'active_support/core_ext/string/inflections'
 require 'active_support/core_ext/enumerable'
 require 'active_support/core_ext/object/try'
-require 'active_support/descendants_tracker'
 
 module ActiveModel
   # == Active \Model Observers Activation
@@ -49,7 +48,7 @@ def observers=(*values)
       #   end
       #
       #   ORM.observers = :cacher, :garbage_collector
-      #   ORM.observers       # => [:cacher, :garbage_collector]
+      #   ORM.observers       # => [:cacher, :garbage_collector]
       #   ORM.observers.class # => ActiveModel::ObserverArray
       def observers
         @observers ||= ObserverArray.new(self)
@@ -328,8 +327,8 @@ def observed_classes
       # Returns the class observed by default. It's inferred from the observer's
       # class name.
       #
-      #   PersonObserver.observed_class  # => Person
-      #   AccountObserver.observed_class # => Account
+      #   PersonObserver.observed_class  # => Person
+      #   AccountObserver.observed_class # => Account
       def observed_class
         name[/(.*)Observer/, 1].try :constantize
       end

activemodel/lib/active_model/validations.rb

 require 'active_support/core_ext/array/extract_options'
 require 'active_support/core_ext/hash/keys'
 require 'active_support/core_ext/hash/except'
-require 'active_model/errors'
-require 'active_model/validations/callbacks'
-require 'active_model/validator'
 
 module ActiveModel
 

activemodel/lib/active_model/validations/callbacks.rb

-require 'active_support/callbacks'
-
 module ActiveModel
   module Validations
     # == Active \Model Validation Callbacks
@@ -85,8 +83,8 @@ def before_validation(*args, &block)
         #   person = Person.new
         #   person.name = ''
         #   person.valid? # => false
-        #   person.status # => false
-        #   person.name = 'bob'
+        #   person.status # => false
+        #   person.name = 'bob'
         #   person.valid? # => true
         #   person.status # => true
         def after_validation(*args, &block)