update_column take ruby-land input, not database-land input

In the case of serialized columns, we would expect the unserialized
value as input, not the serialized value. The original issue which made
this distinction, #14163, introduced a bug. If you passed serialized
input to the method, it would double serialize when it was sent to the
database. You would see the wrong input upon reloading, or get an error
if you had a specific type on the serialized column.

To put it another way, `update_column` is a special case of
`update_all`, which would take `['a']` and not `['a'].to_yaml`, but you
would not pass data from `params` to it.

Fixes #18037

activerecord/lib/active_record/attribute.rb

@@ -9,6 +9,10 @@ def from_user(name, value, type)
         FromUser.new(name, value, type)
       end
 
+      def with_cast_value(name, value, type)
+        WithCastValue.new(name, value, type)
+      end
+
       def null(name)
         Null.new(name)
       end
@@ -58,6 +62,10 @@ def with_value_from_database(value)
       self.class.from_database(name, value, type)
     end
 
+    def with_cast_value(value)
+      self.class.with_cast_value(name, value, type)
+    end
+
     def type_cast(*)
       raise NotImplementedError
     end
@@ -93,6 +101,16 @@ def type_cast(value)
       end
     end
 
+    class WithCastValue < Attribute # :nodoc:
+      def type_cast(value)
+        value
+      end
+
+      def changed_in_place_from?(old_value)
+        false
+      end
+    end
+
     class Null < Attribute # :nodoc:
       def initialize(name)
         super(name, nil, Type::Value.new)

activerecord/lib/active_record/attribute_methods/write.rb

@@ -73,7 +73,7 @@ def write_attribute_with_type_cast(attr_name, value, should_type_cast)
         if should_type_cast
           @attributes.write_from_user(attr_name, value)
         else
-          @attributes.write_from_database(attr_name, value)
+          @attributes.write_cast_value(attr_name, value)
         end
 
         value

activerecord/lib/active_record/attribute_set.rb

@@ -39,6 +39,10 @@ def write_from_user(name, value)
       attributes[name] = self[name].with_value_from_user(value)
     end
 
+    def write_cast_value(name, value)
+      attributes[name] = self[name].with_cast_value(value)
+    end
+
     def freeze
       @attributes.freeze
       super

activerecord/test/cases/serialized_attribute_test.rb

@@ -243,8 +243,9 @@ def test_serialized_column_should_unserialize_after_update_column
     t = Topic.create(content: "first")
     assert_equal("first", t.content)
 
-    t.update_column(:content, Topic.type_for_attribute('content').type_cast_for_database("second"))
-    assert_equal("second", t.content)
+    t.update_column(:content, ["second"])
+    assert_equal(["second"], t.content)
+    assert_equal(["second"], t.reload.content)
   end
 
   def test_serialized_column_should_unserialize_after_update_attribute
@@ -253,5 +254,6 @@ def test_serialized_column_should_unserialize_after_update_attribute
 
     t.update_attribute(:content, "second")
     assert_equal("second", t.content)
+    assert_equal("second", t.reload.content)
   end
 end