Inherit DB field type from superclass

Problem: All custom DataMapper::Properties (e.g. in dm-types) have database field types based upon their Ruby primitives. Especially Properties inheriting from DataMapper::Property::Text like DataMapper::Property::JSON have some problems with that behavior (since they will result in VARCARs instead of LOBs).

This commit adds logic to try to find a database field type based upon the superclasses of the (custom) property. Only if no superclass has a direkt mapping from `property.class` to field type the fallback to the Ruby primitive (returned by `dump_as`) will take place.

lib/dm-migrations/adapters/dm-do-adapter.rb

@@ -196,9 +196,9 @@ def create_unique_index_statements(model)
         # @api private
         def property_schema_hash(property)
           dump_class = property.dump_class
-          type_map   = self.class.type_map
+          type_by_property_class = self.class.type_by_property_class(property.class)
 
-          schema = (type_map[property.class] || type_map[dump_class]).merge(:name => property.field)
+          schema = (type_by_property_class || self.class.type_map[dump_class]).merge(:name => property.field)
 
           schema_primitive = schema[:primitive]
 
@@ -293,6 +293,17 @@ def type_map
             Property::Text   => { :primitive => 'TEXT'                                              },
           }.freeze
         end
+
+        # Finds a type for a given property.
+        #
+        # @return [Hash | nil] type matching the given property or one of the properties ancestors
+        #
+        # @api private
+        def type_by_property_class(property_class)
+          return nil unless property_class < DataMapper::Property
+
+          type_map[property_class] || type_by_property_class(property_class.superclass)
+        end
       end
     end
 

lib/dm-migrations/sql/table_creator.rb

@@ -82,14 +82,13 @@ def build_type(type_class)
         if type_class.kind_of?(String)
           schema[:primitive] = type_class
         else
-          type_map  = @adapter.class.type_map
           primitive = type_class.respond_to?(:dump_as) ? type_class.dump_as : type_class
-          options   = (type_map[type_class] || type_map[primitive])
+          options   = @adapter.class.type_by_property_class(type_class) || @adapter.class.type_map[primitive]
 
           schema.update(type_class.options) if type_class.respond_to?(:options)
           schema.update(options)
 
-          schema.delete(:length) if type_class == DataMapper::Property::Text
+          schema.delete(:length) if type_class <= DataMapper::Property::Text
         end
 
         schema.update(@opts)

spec/unit/sql/table_creator_spec.rb

@@ -63,6 +63,7 @@
 
         @adapter.stub!(:quote_column_name).and_return(%{'id'})
         @adapter.class.stub!(:type_map).and_return(Integer => {:type => 'int'})
+        @adapter.class.stub!(:type_by_property_class).and_return(Integer => {:type => 'int'})
         @adapter.stub!(:property_schema_statement).and_return("SOME SQL")
         @adapter.stub!(:with_connection).and_yield(connection)
         @c = SQL::TableCreator::Column.new(@adapter, 'id', Integer, :serial => true)