Don't type cast the default on the column

If we want to have type decorators mess with the attribute, but not the
column, we need to stop type casting on the column. Where possible, we
changed the tests to test the value of `column_defaults`, which is
public API. `Column#default` is not.

4 files changed, 25 insertions, 19 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
index 5a0efe49c7..9bd0401e40 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb
@@ -23,7 +23,8 @@ module ActiveRecord
         spec[:precision] = column.precision.inspect if column.precision
         spec[:scale]     = column.scale.inspect if column.scale
         spec[:null]      = 'false' unless column.null
-        spec[:default]   = column.type_cast_for_schema(column.default) if column.has_default?
+        spec[:default]   = schema_default(column) if column.has_default?
+        spec.delete(:default) if spec[:default].nil?
         spec
       end
 
@@ -31,6 +32,15 @@ module ActiveRecord
       def migration_keys
         [:name, :limit, :precision, :scale, :default, :null]
       end
+
+      private
+
+      def schema_default(column)
+        default = column.type_cast_from_database(column.default)
+        unless default.nil?
+          column.type_cast_for_schema(default)
+        end
+      end
     end
   end
 end
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index a9b97d5919..3ef8878ad1 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -62,15 +62,14 @@ module ActiveRecord
           @extra     = extra
           super(name, default, cast_type, sql_type, null)
           assert_valid_default(default)
+          extract_default
         end
 
-        def default
-          @default ||= if blob_or_text_column?
-            null || strict ? nil : ''
-          elsif missing_default_forged_as_empty_string?(@original_default)
-            nil
-          else
-            super
+        def extract_default
+          if blob_or_text_column?
+            @default = null || strict ? nil : ''
+          elsif missing_default_forged_as_empty_string?(@default)
+            @default = nil
           end
         end
 
diff --git a/activerecord/lib/active_record/connection_adapters/column.rb b/activerecord/lib/active_record/connection_adapters/column.rb
index d629fca911..8be4678ace 100644
--- a/activerecord/lib/active_record/connection_adapters/column.rb
+++ b/activerecord/lib/active_record/connection_adapters/column.rb
@@ -13,7 +13,7 @@ module ActiveRecord
         ISO_DATETIME = /\A(\d{4})-(\d\d)-(\d\d) (\d\d):(\d\d):(\d\d)(\.\d+)?\z/
       end
 
-      attr_reader :name, :cast_type, :null, :sql_type, :default_function
+      attr_reader :name, :cast_type, :null, :sql_type, :default, :default_function
 
       delegate :type, :precision, :scale, :limit, :klass, :accessor,
         :text?, :number?, :binary?, :changed?,
@@ -35,7 +35,7 @@ module ActiveRecord
         @cast_type        = cast_type
         @sql_type         = sql_type
         @null             = null
-        @original_default = default
+        @default          = default
         @default_function = nil
       end
 
@@ -51,13 +51,8 @@ module ActiveRecord
         Base.human_attribute_name(@name)
       end
 
-      def default
-        @default ||= type_cast_from_database(@original_default)
-      end
-
       def with_type(type)
         dup.tap do |clone|
-          clone.instance_variable_set('@default', nil)
           clone.instance_variable_set('@cast_type', type)
         end
       end
diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index b9558b0752..fad7eae461 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -230,14 +230,16 @@ module ActiveRecord
       # Returns a hash where the keys are column names and the values are
       # default values when instantiating the AR object for this table.
       def column_defaults
-        @column_defaults ||= Hash[columns.map { |c| [c.name, c.default] }]
+        @column_defaults ||= Hash[columns_hash.map { |name, column|
+          [name, column.type_cast_from_database(column.default)]
+        }]
       end
 
       # Returns a hash where the keys are the column names and the values
       # are the default values suitable for use in `@raw_attriubtes`
       def raw_column_defaults # :nodoc:
-        @raw_column_defauts ||= Hash[column_defaults.map { |name, default|
-          [name, columns_hash[name].type_cast_for_database(default)]
+        @raw_column_defaults ||= Hash[columns_hash.map { |name, column|
+          [name, column.default]
         }]
       end
 
@@ -285,7 +287,7 @@ module ActiveRecord
 
         @arel_engine             = nil
         @column_defaults         = nil
-        @raw_column_defauts      = nil
+        @raw_column_defaults     = nil
         @column_names            = nil
         @column_types            = nil
         @content_columns         = nil