Make serialization_modification_detection plugin work correctly with …

…new objects and after saving existing objects (Fixes jeremyevans#432)

Previously, the plugin only really worked correctly on existing objects
loaded from the database before saving.  That's generally the main use
case, but other cases should be handled as well.  Unfortunately, to
handle the other cases, on new object creation and after saving, you
need to serialize and deserialize all of the deserialized columns to
get clean copies.

CHANGELOG

@@ -1,5 +1,7 @@
 === HEAD
 
+* Make serialization_modification_detection plugin work correctly with new objects and after saving existing objects (jeremyevans) (#432)
+
 * Make refreshes after model creation clear the deserialized values in the serialization plugin (jeremyevans)
 
 * Add Dataset#update_ignore on MySQL, for using UPDATE IGNORE in queries (danielb2) (#429)

lib/sequel/plugins/serialization_modification_detection.rb

@@ -25,6 +25,13 @@ def self.apply(model)
       end
 
       module InstanceMethods
+        # Clear the cache of original deserialized values after saving so that it doesn't
+        # show the column is modified after saving.
+        def after_save
+          super
+          copy_deserialized_values
+        end
+
         # Detect which serialized columns have changed.
         def changed_columns
           cc = super
@@ -34,11 +41,16 @@ def changed_columns
 
         private
 
-        # Clear the cache of original deserialized values after saving so that it doesn't
-        # show the column is modified after saving.
-        def after_save
+        # For new objects, populate the original deserialized value so that we know it hasn't
+        # changed since initialization.
+        def initialize_set(values)
           super
-          @original_deserialized_values.clear if @original_deserialized_values
+          copy_deserialized_values
+        end
+
+        def copy_deserialized_values
+          @original_deserialized_values = h = {}
+          @deserialized_values.each{|k, v| h[k] = deserialize_value(k, serialize_value(k, v))}
         end
 
         # Return the original deserialized value of the column, caching it to improve performance.

spec/extensions/serialization_modification_detection_spec.rb

@@ -9,12 +9,20 @@
       plugin :serialization, :yaml, :h
       plugin :serialization_modification_detection
     end
-    @o1 = @c.new
+    @o1 = @c.new(:h=>{})
     @o2 = @c.load(:id=>1, :h=>"--- {}\n\n")
+    @o3 = @c.new
+    @o4 = @c.load(:id=>1, :h=>nil)
     MODEL_DB.reset
   end
 
   it "should not detect columns that haven't been changed" do
+    @o1.changed_columns.should == []
+    @o1.h.should == {}
+    @o1.h[1] = 2
+    @o1.h.clear
+    @o1.changed_columns.should == []
+
     @o2.changed_columns.should == []
     @o2.h.should == {}
     @o2.h[1] = 2
@@ -23,15 +31,42 @@
   end
 
   it "should detect columns that have been changed" do
+    @o1.changed_columns.should == []
+    @o1.h.should == {}
+    @o1.h[1] = 2
+    @o1.changed_columns.should == [:h]
+
     @o2.changed_columns.should == []
     @o2.h.should == {}
     @o2.h[1] = 2
     @o2.changed_columns.should == [:h]
+
+    @o3.changed_columns.should == []
+    @o3.h.should == nil
+    @o3.h = {}
+    @o3.changed_columns.should == [:h]
+
+    @o4.changed_columns.should == []
+    @o4.h.should == nil
+    @o4.h = {}
+    @o4.changed_columns.should == [:h]
   end
 
   it "should report correct changed_columns after saving" do
+    @o1.h[1] = 2
+    @o1.save
+    @o1.changed_columns.should == []
+
     @o2.h[1] = 2
     @o2.save_changes
     @o2.changed_columns.should == []
+
+    @o3.h = {1=>2}
+    @o3.save
+    @o3.changed_columns.should == []
+
+    @o4.h = {1=>2}
+    @o4.save
+    @o4.changed_columns.should == []
   end
 end