Optionally disable duplicate assignment of attributes in initialize_with

By setting:

    FactoryGirl.duplicate_attribute_assignment_from_initialize_with =
false

This turns off duplicate assignment of attributes accessed from
initialize_with. This means any attributes accessed from the factory and
assigned in the initialize_with block won't be subsequently set after
the object has been instantiated.

This will be the default functionality in 4.0.

Closes #345

GETTING_STARTED.md

@@ -771,6 +771,15 @@ FactoryGirl.define do
 end
 ```
 
+When using `initialize_with`, attributes accessed from the `initialize_with`
+block are assigned a second time to the instance. Duplicate assignment can be
+disabled by configuring FactoryGirl as such:
+
+    FactoryGirl.duplicate_attribute_assignment_from_initialize_with = false
+
+This would allow for attributes declared as ignored to not be ignored, since
+it won't assign them for a second time.
+
 Custom Strategies
 -----------------
 

lib/factory_girl.rb

@@ -37,6 +37,9 @@
 require 'factory_girl/syntax_runner'
 require 'factory_girl/find_definitions'
 require 'factory_girl/reload'
+require 'factory_girl/decorator'
+require 'factory_girl/decorator/invocation_tracker'
+require 'factory_girl/decorator/invocation_ignorer'
 require 'factory_girl/version'
 
 module FactoryGirl
@@ -50,7 +53,8 @@ def self.reset_configuration
 
   class << self
     delegate :factories, :sequences, :traits, :strategies, :callback_names,
-      :to_create, :skip_create, :initialize_with, :constructor, to: :configuration
+      :to_create, :skip_create, :initialize_with, :constructor, :duplicate_attribute_assignment_from_initialize_with,
+      :duplicate_attribute_assignment_from_initialize_with=, to: :configuration
   end
 
   def self.register_factory(factory)

lib/factory_girl/attribute_assigner.rb

@@ -30,8 +30,28 @@ def hash
 
     private
 
+    def method_tracking_evaluator
+      @method_tracking_evaluator ||= invocation_decorator.new(@evaluator)
+    end
+
+    def invocation_decorator
+      if FactoryGirl.duplicate_attribute_assignment_from_initialize_with
+        Decorator::InvocationIgnorer
+      else
+        Decorator::InvocationTracker
+      end
+    end
+
+    def methods_invoked_on_evaluator
+      @method_tracking_evaluator.__invoked_methods__
+    end
+
     def build_class_instance
-      @build_class_instance ||= @evaluator.instance_exec(&@instance_builder)
+      @build_class_instance ||= method_tracking_evaluator.instance_exec(&@instance_builder).tap do
+        if @instance_builder != FactoryGirl.constructor && FactoryGirl.duplicate_attribute_assignment_from_initialize_with
+          ActiveSupport::Deprecation.warn 'Accessing attributes from initialize_with when duplicate assignment is enabled is deprecated; use FactoryGirl.duplicate_attribute_assignment_from_initialize_with = false.', caller
+        end
+      end
     end
 
     def build_hash
@@ -43,7 +63,7 @@ def get(attribute_name)
     end
 
     def attributes_to_set_on_instance
-      (attribute_names_to_assign - @attribute_names_assigned).uniq
+      (attribute_names_to_assign - @attribute_names_assigned - methods_invoked_on_evaluator).uniq
     end
 
     def attributes_to_set_on_hash

lib/factory_girl/configuration.rb

@@ -3,6 +3,8 @@ module FactoryGirl
   class Configuration
     attr_reader :factories, :sequences, :traits, :strategies, :callback_names
 
+    attr_accessor :duplicate_attribute_assignment_from_initialize_with
+
     def initialize
       @factories      = DisallowsDuplicatesRegistry.new(Registry.new('Factory'))
       @sequences      = DisallowsDuplicatesRegistry.new(Registry.new('Sequence'))
@@ -11,6 +13,8 @@ def initialize
       @callback_names = Set.new
       @definition     = Definition.new
 
+      @duplicate_attribute_assignment_from_initialize_with = true
+
       to_create {|instance| instance.save! }
       initialize_with { new }
     end

lib/factory_girl/decorator.rb

@@ -0,0 +1,17 @@
+module FactoryGirl
+  class Decorator < BasicObject
+    undef_method :==
+
+    def initialize(component)
+      @component = component
+    end
+
+    def method_missing(name, *args, &block)
+      @component.send(name, *args, &block)
+    end
+
+    def send(symbol, *args)
+      __send__(symbol, *args)
+    end
+  end
+end

lib/factory_girl/decorator/invocation_ignorer.rb

@@ -0,0 +1,9 @@
+module FactoryGirl
+  class Decorator
+    class InvocationIgnorer < Decorator
+      def __invoked_methods__
+        []
+      end
+    end
+  end
+end

lib/factory_girl/decorator/invocation_tracker.rb

@@ -0,0 +1,19 @@
+module FactoryGirl
+  class Decorator
+    class InvocationTracker < Decorator
+      def initialize(component)
+        super
+        @invoked_methods = []
+      end
+
+      def method_missing(name, *args, &block)
+        @invoked_methods << name
+        super
+      end
+
+      def __invoked_methods__
+        @invoked_methods.uniq
+      end
+    end
+  end
+end

spec/acceptance/global_initialize_with_spec.rb

@@ -2,6 +2,8 @@
 
 describe 'global initialize_with' do
   before do
+    ActiveSupport::Deprecation.silenced = true
+
     define_class('User') do
       attr_accessor:name
 

spec/acceptance/initialize_with_spec.rb

@@ -4,6 +4,8 @@
   include FactoryGirl::Syntax::Methods
 
   before do
+    ActiveSupport::Deprecation.silenced = true
+
     define_model("User", name: :string, age: :integer) do
       def self.construct(name, age)
         new(name: name, age: age)
@@ -26,6 +28,8 @@ def self.construct(name, age)
   include FactoryGirl::Syntax::Methods
 
   before do
+    ActiveSupport::Deprecation.silenced = true
+
     define_model("User", name: :string) do
       def self.construct(name)
         new(name: "#{name} from .construct")
@@ -51,6 +55,8 @@ def self.construct(name)
   include FactoryGirl::Syntax::Methods
 
   before do
+    ActiveSupport::Deprecation.silenced = true
+
     define_model("User", name: :string) do
       def self.construct(name)
         new(name: "#{name} from .construct")
@@ -75,6 +81,8 @@ def self.construct(name)
   include FactoryGirl::Syntax::Methods
 
   before do
+    ActiveSupport::Deprecation.silenced = true
+
     define_class("ReportGenerator") do
       attr_reader :name, :data
 
@@ -108,6 +116,8 @@ def initialize(name, data)
 
 describe "initialize_with parent and child factories" do
   before do
+    ActiveSupport::Deprecation.silenced = true
+
     define_class("Awesome") do
       attr_reader :name
 
@@ -148,6 +158,8 @@ def initialize(name)
 
 describe "initialize_with implicit constructor" do
   before do
+    ActiveSupport::Deprecation.silenced = true
+
     define_class("Awesome") do
       attr_reader :name
 
@@ -171,3 +183,38 @@ def initialize(name)
     FactoryGirl.build(:awesome, name: "Awesome name").name.should == "Awesome name"
   end
 end
+
+describe "initialize_with doesn't duplicate assignment on attributes accessed from initialize_with" do
+  before do
+    ActiveSupport::Deprecation.silenced = true
+
+    define_class("User") do
+      attr_reader :name
+      attr_accessor :email
+
+      def initialize(name)
+        @name = name
+      end
+    end
+
+    FactoryGirl.define do
+      sequence(:email) {|n| "person#{n}@example.com" }
+
+      factory :user do
+        email
+
+        name { email.gsub(/\@.+/, "") }
+
+        initialize_with { new(name) }
+      end
+    end
+  end
+
+  it "instantiates the correct object" do
+    FactoryGirl.duplicate_attribute_assignment_from_initialize_with = false
+
+    built_user = FactoryGirl.build(:user)
+    built_user.name.should == "person1"
+    built_user.email.should == "person1@example.com"
+  end
+end

spec/acceptance/traits_spec.rb

@@ -490,6 +490,8 @@
 
 describe "traits with initialize_with" do
   before do
+    ActiveSupport::Deprecation.silenced = true
+
     define_class("User") do
       attr_reader :name