BugFix: Ensure callbacks only run once per instance.

lib/factory_bot/callbacks_observer.rb

@@ -4,11 +4,15 @@ class CallbacksObserver
     def initialize(callbacks, evaluator)
       @callbacks = callbacks
       @evaluator = evaluator
+      @completed = []
     end
 
     def update(name, result_instance)
       callbacks_by_name(name).each do |callback|
-        callback.run(result_instance, @evaluator)
+        if !completed?(result_instance, callback)
+          callback.run(result_instance, @evaluator)
+          record_completion!(result_instance, callback)
+        end
       end
     end
 
@@ -17,5 +21,19 @@ def update(name, result_instance)
     def callbacks_by_name(name)
       @callbacks.select { |callback| callback.name == name }
     end
+
+    def completed?(instance, callback)
+      key = completion_key_for(instance, callback)
+      @completed.include?(key)
+    end
+
+    def record_completion!(instance, callback)
+      key = completion_key_for(instance, callback)
+      @completed << key
+    end
+
+    def completion_key_for(instance, callback)
+      "#{instance.object_id}-#{callback.object_id}"
+    end
   end
 end

spec/acceptance/callbacks_spec.rb

@@ -13,6 +13,15 @@
         after(:stub) { |user| user.last_name = "Double-Stubby" }
         after(:build) { |user| user.first_name = "Child-Buildy" }
       end
+
+      factory :user_with_multi_called_callbacks, class: :user do
+        first_name { "Jane" }
+        trait :alias_2 do alias_1 end
+        trait :alias_1 do surname end
+        trait :surname do
+          after(:build) { |user| user.first_name += " Doe" }
+        end
+      end
     end
   end
 
@@ -42,6 +51,15 @@
     user = FactoryBot.build(:user_with_inherited_callbacks)
     expect(user.first_name).to eq "Child-Buildy"
   end
+
+  it "only runs each callback once per instance" do
+    user_1 = FactoryBot.build(:user_with_multi_called_callbacks, :surname, :alias_1, :alias_2)
+    user_2 = FactoryBot.build(:user_with_multi_called_callbacks, :alias_1, :alias_2, :surname)
+    user_3 = FactoryBot.build(:user_with_multi_called_callbacks, :alias_2, :surname, :alias_1)
+    expect(user_1.first_name).to eq "Jane Doe"
+    expect(user_2.first_name).to eq "Jane Doe"
+    expect(user_3.first_name).to eq "Jane Doe"
+  end
 end
 
 describe "callbacks using Symbol#to_proc" do