Persist default values for Rails 6.1

This extends the fix from 1f150f6
to Rails 6.1, and adds test coverage.  Specifically, it adds a record
reload to the "stores the default on creation" test to ensure that the
postcondition holds.  Without the reload, the "stores the default on
creation" test would pass even before
1f150f6.

This commit also adds a test for when the record is partially loaded,
and changes some Rails private API calls to equivalent public API calls.

Author: jonathanhefner

lib/active_record/typed_store/behavior.rb

@@ -74,20 +74,29 @@ def attribute?(attr_name)
 
     private
 
-    def attribute_names_for_partial_inserts
-      # Contrary to all vanilla Rails types, typedstore attribute have an inherent default
-      # value that doesn't match the database column default.
-      # As such we need to insert them on partial inserts even if they weren't changed.
-      super | self.class.typed_stores.keys.map(&:to_s)
-    end
+    if ActiveRecord.version.segments.first >= 7
+      def attribute_names_for_partial_inserts
+        # Contrary to all vanilla Rails types, typedstore attribute have an inherent default
+        # value that doesn't match the database column default.
+        # As such we need to insert them on partial inserts even if they weren't changed.
+        super | self.class.typed_stores.keys.map(&:to_s)
+      end
 
-    def attribute_names_for_partial_updates
-      # On partial updates we shouldn't need to force stores to be persisted. However since
-      # we weren't persisting them for a while on insertion, we now need to gracefully deal
-      # with existing records that may have been persisted with a `NULL` store
-      # We use `blank?` as an heuristic to detect these.
-      super | self.class.typed_stores.keys.map(&:to_s).select do |store|
-        @attributes.key?(store) && @attributes[store].value_before_type_cast.blank?
+      def attribute_names_for_partial_updates
+        # On partial updates we shouldn't need to force stores to be persisted. However since
+        # we weren't persisting them for a while on insertion, we now need to gracefully deal
+        # with existing records that may have been persisted with a `NULL` store
+        # We use `blank?` as an heuristic to detect these.
+        super | self.class.typed_stores.keys.map(&:to_s).select do |store|
+          has_attribute?(store) && read_attribute_before_type_cast(store).blank?
+        end
+      end
+    else
+      # Rails 6.1 capability
+      def attribute_names_for_partial_writes
+        super | self.class.typed_stores.keys.map(&:to_s).select do |store|
+          has_attribute?(store) && read_attribute_before_type_cast(store).blank?
+        end
       end
     end
   end

spec/active_record/typed_store_spec.rb

@@ -958,6 +958,7 @@
 describe DirtyTrackingModel do
   it 'stores the default on creation' do
     model = DirtyTrackingModel.create!
+    model = DirtyTrackingModel.find(model.id)
     expect(model.settings_before_type_cast).to_not be_blank
   end
 
@@ -973,4 +974,13 @@
     expect(model.settings_changed?).to be false
     expect(model.changes).to be_empty
   end
+
+  it 'does not update missing attributes in partially loaded records' do
+    model = DirtyTrackingModel.create!(active: true)
+    model = DirtyTrackingModel.select(:id, :title).find(model.id)
+    model.update!(title: "Hello")
+
+    model = DirtyTrackingModel.find(model.id)
+    expect(model.active).to be true
+  end
 end

spec/support/models.rb

@@ -190,7 +190,7 @@ class MarshalTypedStoreModel < ActiveRecord::Base
 ]
 
 class DirtyTrackingModel < ActiveRecord::Base
-  after_update :read_active
+  after_update :read_active, if: -> { has_attribute?(:settings) }
 
   typed_store(:settings) do |f|
     f.boolean :active, default: false, null: false