Ensure numericality validations work with mutation

The detection of in-place changes caused a weird unexpected issue with
numericality validations. That validator (out of necessity) works on the
`_before_type_cast` version of the attribute, since on an `:integer`
type column, a non-numeric string would type cast to 0.

However, strings are mutable, and we changed strings to ensure that the
post type cast version of the attribute was a different instance than
the before type cast version (so the mutation detection can work
properly).

Even though strings are the only mutable type for which a numericality
validation makes sense, special casing strings would feel like a strange
change to make here. Instead, we can make the assumption that for all
mutable types, we should work on the post-type-cast version of the
attribute, since all cases which would return 0 for non-numeric strings
are immutable.

Fixes #17852

1 files changed, 11 insertions, 0 deletions

diff --git a/activemodel/lib/active_model/validations/numericality.rb b/activemodel/lib/active_model/validations/numericality.rb
index 13d6a966c0..4ba4e3e8f7 100644
--- a/activemodel/lib/active_model/validations/numericality.rb
+++ b/activemodel/lib/active_model/validations/numericality.rb
@@ -23,6 +23,10 @@ module ActiveModel
         raw_value = record.send(before_type_cast) if record.respond_to?(before_type_cast)
         raw_value ||= value
 
+        if record_attribute_changed_in_place?(record, attr_name)
+          raw_value = value
+        end
+
         return if options[:allow_nil] && raw_value.nil?
 
         unless value = parse_raw_value_as_a_number(raw_value)
@@ -86,6 +90,13 @@ module ActiveModel
           options[:only_integer]
         end
       end
+
+      private
+
+      def record_attribute_changed_in_place?(record, attr_name)
+        record.respond_to?(:attribute_changed_in_place?) &&
+          record.attribute_changed_in_place?(attr_name.to_s)
+      end
     end
 
     module HelperMethods