Add use_parent_strategy option for building associations (#961)

This change means that:

1. The option is turned on, and
2. A Post has a User (for example), and
3. We build an association
4. Then the User is built too.

With the flag off, the User would be created, which matches current
behaviour.

See: https://github.com/thoughtbot/factory_girl/pull/749

lib/factory_girl.rb

@@ -68,10 +68,23 @@ module FactoryGirl
   end
 
   class << self
-    delegate :factories, :sequences, :traits, :callbacks, :strategies, :callback_names,
-      :to_create, :skip_create, :initialize_with, :constructor,
-      :duplicate_attribute_assignment_from_initialize_with, :duplicate_attribute_assignment_from_initialize_with=,
-      :allow_class_lookup, :allow_class_lookup=, to: :configuration
+    delegate :factories,
+             :sequences,
+             :traits,
+             :callbacks,
+             :strategies,
+             :callback_names,
+             :to_create,
+             :skip_create,
+             :initialize_with,
+             :constructor,
+             :duplicate_attribute_assignment_from_initialize_with,
+             :duplicate_attribute_assignment_from_initialize_with=,
+             :allow_class_lookup,
+             :allow_class_lookup=,
+             :use_parent_strategy,
+             :use_parent_strategy=,
+             to: :configuration
   end
 
   def self.register_factory(factory)

lib/factory_girl/configuration.rb

@@ -3,7 +3,7 @@ module FactoryGirl
   class Configuration
     attr_reader :factories, :sequences, :traits, :strategies, :callback_names
 
-    attr_accessor :allow_class_lookup
+    attr_accessor :allow_class_lookup, :use_parent_strategy
 
     def initialize
       @factories      = Decorator::DisallowsDuplicatesRegistry.new(Registry.new('Factory'))

lib/factory_girl/evaluator.rb

@@ -23,7 +23,9 @@ module FactoryGirl
 
     def association(factory_name, *traits_and_overrides)
       overrides = traits_and_overrides.extract_options!
-      strategy_override = overrides.fetch(:strategy) { :create }
+      strategy_override = overrides.fetch(:strategy) do
+        FactoryGirl.use_parent_strategy ? @build_strategy.class : :create
+      end
 
       traits_and_overrides += [overrides.except(:strategy)]
 

spec/acceptance/build_spec.rb

@@ -23,13 +23,33 @@ describe "a built instance" do
 
   it { should be_new_record }
 
-  it "assigns and saves associations" do
+  context "when the :use_parent_strategy config option has not been set" do
+    before { FactoryGirl.use_parent_strategy = nil }
+
+    it "assigns and saves associations" do
+      expect(subject.user).to be_kind_of(User)
+      expect(subject.user).not_to be_new_record
+    end
+  end
+
+  context "when the :use_parent_strategy config option has been enabled" do
+    before { FactoryGirl.use_parent_strategy = true }
+
+    it "assigns but does not save associations" do
+      expect(subject.user).to be_kind_of(User)
+      expect(subject.user).to be_new_record
+    end
+  end
+
+  it "assigns but does not save associations when using parent strategy" do
+    FactoryGirl.use_parent_strategy = true
+
     expect(subject.user).to be_kind_of(User)
-    expect(subject.user).not_to be_new_record
+    expect(subject.user).to be_new_record
   end
 end
 
-describe "a built instance with strategy: :build" do
+describe "a built instance with strategy: :create" do
   include FactoryGirl::Syntax::Methods
 
   before do
@@ -43,7 +63,7 @@ describe "a built instance with strategy: :build" do
       factory :user
 
       factory :post do
-        association(:user, strategy: :build)
+        association(:user, strategy: :create)
       end
     end
   end
@@ -52,9 +72,9 @@ describe "a built instance with strategy: :build" do
 
   it { should be_new_record }
 
-  it "assigns but does not save associations" do
+  it "assigns and saves associations" do
     expect(subject.user).to be_kind_of(User)
-    expect(subject.user).to be_new_record
+    expect(subject.user).not_to be_new_record
   end
 end
 

spec/acceptance/build_stubbed_spec.rb

@@ -35,7 +35,7 @@ describe "a generated stub instance" do
   end
 
   it "assigns associations" do
-    expect(subject.user).not_to be_nil
+    expect(subject.user).to be_kind_of(User)
   end
 
   it "has an id" do
@@ -51,6 +51,10 @@ describe "a generated stub instance" do
     expect(subject).not_to be_new_record
   end
 
+  it "assigns associations that aren't new records" do
+    expect(subject.user).not_to be_new_record
+  end
+
   it "isn't changed" do
     expect(subject).not_to be_changed
   end

spec/acceptance/register_strategies_spec.rb

@@ -100,10 +100,26 @@ describe "associations without overriding :strategy" do
     end
   end
 
-  it "uses the overridden create strategy to create the association" do
-    FactoryGirl.register_strategy(:create, custom_strategy)
-    post = FactoryGirl.build(:post)
-    expect(post.user.name).to eq "Custom strategy"
+  context "when the :use_parent_strategy config option has not been enabled" do
+    before { FactoryGirl.use_parent_strategy = nil }
+
+    it "uses the overridden strategy on the association" do
+      FactoryGirl.register_strategy(:create, custom_strategy)
+
+      post = FactoryGirl.build(:post)
+      expect(post.user.name).to eq "Custom strategy"
+    end
+  end
+
+  context "when the :use_parent_strategy config option has been enabled" do
+    before { FactoryGirl.use_parent_strategy = true }
+
+    it "uses the parent strategy on the association" do
+      FactoryGirl.register_strategy(:create, custom_strategy)
+
+      post = FactoryGirl.build(:post)
+      expect(post.user.name).to eq "John Doe"
+    end
   end
 end