Fix infinite loop and lookup miss when `SET` type includes other types

This commit fixes the following problems:

* cause infinit type lookup loop when SET includes aliased types
 * For example:
   when SET('set') includes aliased type `set`,
   then aliased `varchar('set')` by type lookup,
   but type lookup infinit matching same rule.
* cause type lookup miss when SET includes registered types
 * For example:
   when SET('time') includes registered type `time`,
   then aliased `varchar('time')` by type lookup,
   then matching `time` type.

1 files changed, 6 insertions, 1 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 00e3d2965b..7e3a705449 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -789,7 +789,6 @@ module ActiveRecord
         register_integer_type m, %r(^tinyint)i,   limit: 1
 
         m.alias_type %r(tinyint\(1\))i,  'boolean' if emulate_booleans
-        m.alias_type %r(set)i,           'varchar'
         m.alias_type %r(year)i,          'integer'
         m.alias_type %r(bit)i,           'binary'
 
@@ -798,6 +797,12 @@ module ActiveRecord
             .split(',').map{|enum| enum.strip.length - 2}.max
           MysqlString.new(limit: limit)
         end
+
+        m.register_type(%r(^set)i) do |sql_type|
+          limit = sql_type[/^set\((.+)\)/i, 1]
+            .split(',').map{|set| set.strip.length - 1}.sum - 1
+          MysqlString.new(limit: limit)
+        end
       end
 
       def register_integer_type(mapping, key, options) # :nodoc: