Move pk initialization logic onto `AttributeSet`

Better encapsulates its internals from `ActiveRecord::Base`.

2 files changed, 7 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/attribute_set.rb b/activerecord/lib/active_record/attribute_set.rb
index 8a964fb03c..2889d59328 100644
--- a/activerecord/lib/active_record/attribute_set.rb
+++ b/activerecord/lib/active_record/attribute_set.rb
@@ -52,6 +52,12 @@ module ActiveRecord
       super
     end
 
+    def ensure_initialized(key)
+      unless self[key].initialized?
+        write_from_database(key, nil)
+      end
+    end
+
     protected
 
     attr_reader :attributes
diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 224112b559..8be5b340de 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -515,10 +515,7 @@ module ActiveRecord
     end
 
     def init_internals
-      pk = self.class.primary_key
-      if pk && !@attributes.include?(pk)
-        @attributes.write_from_database(pk, nil)
-      end
+      @attributes.ensure_initialized(self.class.primary_key)
 
       @aggregation_cache        = {}
       @association_cache        = {}