Initialization block is a part of build_record

Should be done before `before_add` callbacks.

activerecord/lib/active_record/associations/association.rb

@@ -275,6 +275,7 @@ module ActiveRecord
         def build_record(attributes)
           reflection.build_association(attributes) do |record|
             initialize_attributes(record, attributes)
+            yield(record) if block_given?
           end
         end
 

activerecord/lib/active_record/associations/collection_association.rb

@@ -105,9 +105,7 @@ module ActiveRecord
         if attributes.is_a?(Array)
           attributes.collect { |attr| build(attr, &block) }
         else
-          add_to_target(build_record(attributes)) do |record|
+          add_to_target(build_record(attributes, &block))
-            yield(record) if block_given?
-          end
         end
       end
 
@@ -361,8 +359,7 @@ module ActiveRecord
             attributes.collect { |attr| _create_record(attr, raise, &block) }
           else
             transaction do
-              add_to_target(build_record(attributes)) do |record|
+              add_to_target(build_record(attributes, &block)) do |record|
-                yield(record) if block_given?
                 insert_record(record, true, raise) {
                   @_was_loaded = loaded?
                   @association_ids = nil

activerecord/lib/active_record/associations/has_many_through_association.rb

@@ -90,7 +90,7 @@ module ActiveRecord
         def build_record(attributes)
           ensure_not_nested
 
-          record = super(attributes)
+          record = super
 
           inverse = source_reflection.inverse_of
           if inverse

activerecord/lib/active_record/associations/has_one_association.rb

@@ -106,7 +106,7 @@ module ActiveRecord
           end
         end
 
-        def _create_record(attributes, raise_error = false)
+        def _create_record(attributes, raise_error = false, &block)
           unless owner.persisted?
             raise ActiveRecord::RecordNotSaved, "You cannot call create unless the parent is saved"
           end

activerecord/lib/active_record/associations/singular_association.rb

@@ -17,9 +17,8 @@ module ActiveRecord
         replace(record)
       end
 
-      def build(attributes = {})
+      def build(attributes = {}, &block)
-        record = build_record(attributes)
+        record = build_record(attributes, &block)
-        yield(record) if block_given?
         set_new_record(record)
         record
       end
@@ -62,9 +61,8 @@ module ActiveRecord
           replace(record)
         end
 
-        def _create_record(attributes, raise_error = false)
+        def _create_record(attributes, raise_error = false, &block)
-          record = build_record(attributes)
+          record = build_record(attributes, &block)
-          yield(record) if block_given?
           saved = record.save
           set_new_record(record)
           raise RecordInvalid.new(record) if !saved && raise_error

activerecord/lib/active_record/associations/through_association.rb

@@ -114,7 +114,7 @@ module ActiveRecord
             attributes[inverse.foreign_key] = target.id
           end
 
-          super(attributes)
+          super
         end
     end
   end

activerecord/test/cases/associations/has_many_through_associations_test.rb

@@ -737,6 +737,18 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
       [:added, :before, "Roger"],
       [:added, :after, "Roger"]
     ], log.last(4)
+
+    post.people_with_callbacks.build { |person| person.first_name = "Ted" }
+    assert_equal [
+      [:added, :before, "Ted"],
+      [:added, :after, "Ted"]
+    ], log.last(2)
+
+    post.people_with_callbacks.create { |person| person.first_name = "Sam" }
+    assert_equal [
+      [:added, :before, "Sam"],
+      [:added, :after, "Sam"]
+    ], log.last(2)
   end
 
   def test_dynamic_find_should_respect_association_include