refactor, introduce `Type#type_cast_for_schema` to cast for schema.rb

This removes the case statement in `SchemaDumper` and gives every `Type`
the possibility to control the SchemaDumper default value output.

/cc @sgrif

activerecord/lib/active_record/connection_adapters/abstract/schema_dumper.rb

@@ -25,7 +25,7 @@ def prepare_column_options(column, types)
         spec[:precision] = column.precision.inspect if column.precision
         spec[:scale]     = column.scale.inspect if column.scale
         spec[:null]      = 'false' unless column.null
-        spec[:default]   = default_string(column.default) if column.has_default?
+        spec[:default]   = column.type_cast_for_schema(column.default) if column.has_default?
         spec
       end
 
@@ -33,31 +33,6 @@ def prepare_column_options(column, types)
       def migration_keys
         [:name, :limit, :precision, :scale, :default, :null]
       end
-
-      private
-
-        def default_string(value)
-          case value
-          when BigDecimal
-            value.to_s
-          when Date, DateTime, Time
-            "'#{value.to_s(:db)}'"
-          when Range
-            # infinity dumps as Infinity, which causes uninitialized constant error
-            value.inspect.gsub('Infinity', '::Float::INFINITY')
-          when IPAddr
-            subnet_mask = value.instance_variable_get(:@mask_addr)
-
-            # If the subnet mask is equal to /32, don't output it
-            if subnet_mask == (2**32 - 1)
-              "\"#{value.to_s}\""
-            else
-              "\"#{value.to_s}/#{subnet_mask.to_s(2).count('1')}\""
-            end
-          else
-            value.inspect
-          end
-        end
     end
   end
 end

activerecord/lib/active_record/connection_adapters/column.rb

@@ -18,6 +18,7 @@ module Format
       delegate :type, :precision, :scale, :limit, :klass, :accessor,
         :text?, :number?, :binary?, :serialized?,
         :type_cast, :type_cast_for_write, :raw_type_cast_for_write, :type_cast_for_database,
+        :type_cast_for_schema,
         to: :cast_type
 
       # Instantiates a new column in the table.

activerecord/lib/active_record/connection_adapters/postgresql/oid/cidr.rb

@@ -7,6 +7,17 @@ def type
             :cidr
           end
 
+          def type_cast_for_schema(value)
+            subnet_mask = value.instance_variable_get(:@mask_addr)
+
+            # If the subnet mask is equal to /32, don't output it
+            if subnet_mask == (2**32 - 1)
+              "\"#{value.to_s}\""
+            else
+              "\"#{value.to_s}/#{subnet_mask.to_s(2).count('1')}\""
+            end
+          end
+
           def cast_value(value)
             ConnectionAdapters::PostgreSQLColumn.string_to_cidr value
           end

activerecord/lib/active_record/connection_adapters/postgresql/oid/range.rb

@@ -24,6 +24,10 @@ def infinity?(value)
             value.respond_to?(:infinite?) && value.infinite?
           end
 
+          def type_cast_for_schema(value)
+            value.inspect.gsub('Infinity', '::Float::INFINITY')
+          end
+
           def type_cast_single(value)
             infinity?(value) ? value : @subtype.type_cast(value)
           end

activerecord/lib/active_record/type/date.rb

@@ -9,6 +9,10 @@ def klass
         ::Date
       end
 
+      def type_cast_for_schema(value)
+        "'#{value.to_s(:db)}'"
+      end
+
       private
 
       def cast_value(value)

activerecord/lib/active_record/type/decimal.rb

@@ -11,6 +11,10 @@ def klass
         ::BigDecimal
       end
 
+      def type_cast_for_schema(value)
+        value.to_s
+      end
+
       private
 
       def cast_value(value)

activerecord/lib/active_record/type/time_value.rb

@@ -5,6 +5,10 @@ def klass
         ::Time
       end
 
+      def type_cast_for_schema(value)
+        "'#{value.to_s(:db)}'"
+      end
+
       private
 
       def new_time(year, mon, mday, hour, min, sec, microsec, offset = nil)

activerecord/lib/active_record/type/value.rb

@@ -27,6 +27,10 @@ def type_cast_for_database(value)
         type_cast_for_write(value)
       end
 
+      def type_cast_for_schema(value)
+        value.inspect
+      end
+
       def text?
         false
       end