Refactor microsecond precision to be database agnostic

The various databases don't actually need significantly different
handling for this behavior, and they can achieve it without knowing
about the type of the object.

The old implementation was returning a string, which will cause problems
such as breaking TZ aware attributes, and making it impossible for the
adapters to supply their logic for time objects.

1 files changed, 9 insertions, 14 deletions

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 c29692d6ca..054c59ef5c 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -712,11 +712,6 @@ module ActiveRecord
         m.alias_type %r(year)i,          'integer'
         m.alias_type %r(bit)i,           'binary'
 
-        m.register_type(%r(datetime)i) do |sql_type|
-          precision = extract_precision(sql_type)
-          MysqlDateTime.new(precision: precision)
-        end
-
         m.register_type(%r(enum)i) do |sql_type|
           limit = sql_type[/^enum\((.+)\)/i, 1]
             .split(',').map{|enum| enum.strip.length - 2}.max
@@ -734,6 +729,14 @@ module ActiveRecord
         end
       end
 
+      def extract_precision(sql_type)
+        if /datetime/ === sql_type
+          super || 0
+        else
+          super
+        end
+      end
+
       def fetch_type_metadata(sql_type, collation = "", extra = "")
         MysqlTypeMetadata.new(super(sql_type), collation: collation, extra: extra, strict: strict_mode?)
       end
@@ -916,14 +919,6 @@ module ActiveRecord
         TableDefinition.new(native_database_types, name, temporary, options, as)
       end
 
-      class MysqlDateTime < Type::DateTime # :nodoc:
-        private
-
-        def has_precision?
-          precision || 0
-        end
-      end
-
       class MysqlString < Type::String # :nodoc:
         def type_cast_for_database(value)
           case value
@@ -945,7 +940,7 @@ module ActiveRecord
       end
 
       def type_classes_with_standard_constructor
-        super.merge(string: MysqlString, date_time: MysqlDateTime)
+        super.merge(string: MysqlString)
       end
     end
   end