AR absence validator respects `marked_for_destruction?`. Closes #20449.

Associated objects that were marked for destruction are considered absent.

2 files changed, 25 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/validations.rb b/activerecord/lib/active_record/validations.rb
index e227212827..34d96b19fe 100644
--- a/activerecord/lib/active_record/validations.rb
+++ b/activerecord/lib/active_record/validations.rb
@@ -76,4 +76,5 @@ end
 require "active_record/validations/associated"
 require "active_record/validations/uniqueness"
 require "active_record/validations/presence"
+require "active_record/validations/absence"
 require "active_record/validations/length"
diff --git a/activerecord/lib/active_record/validations/absence.rb b/activerecord/lib/active_record/validations/absence.rb
new file mode 100644
index 0000000000..2e19e6dc5c
--- /dev/null
+++ b/activerecord/lib/active_record/validations/absence.rb
@@ -0,0 +1,24 @@
+module ActiveRecord
+  module Validations
+    class AbsenceValidator < ActiveModel::Validations::AbsenceValidator # :nodoc:
+      def validate_each(record, attribute, association_or_value)
+        return unless should_validate?(record)
+        if record.class._reflect_on_association(attribute)
+          association_or_value = Array.wrap(association_or_value).reject(&:marked_for_destruction?)
+        end
+        super
+      end
+    end
+
+    module ClassMethods
+      # Validates that the specified attributes are not present (as defined by
+      # Object#present?). If the attribute is an association, the associated object
+      # is considered absent if it was marked for destruction.
+      #
+      # See ActiveModel::Validations::HelperMethods.validates_absence_of for more information.
+      def validates_absence_of(*attr_names)
+        validates_with AbsenceValidator, _merge_attributes(attr_names)
+      end
+    end
+  end
+end