Follow-up to #10776

The name `ActiveModel::AttributeAssignment::UnknownAttributeError` is
too implementation specific so let's move the constant directly under
the ActiveModel namespace.

Also since this constant used to be under the ActiveRecord namespace, to
make the upgrade path easier, let's avoid raising the former constant
when we deal with this error on the Active Record side.

2 files changed, 9 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/attribute_assignment.rb b/activerecord/lib/active_record/attribute_assignment.rb
index 483d4200bd..cc265e2af6 100644
--- a/activerecord/lib/active_record/attribute_assignment.rb
+++ b/activerecord/lib/active_record/attribute_assignment.rb
@@ -29,6 +29,13 @@ module ActiveRecord
       assign_multiparameter_attributes(multi_parameter_attributes) unless multi_parameter_attributes.empty?
     end
 
+    # Re-raise with the ActiveRecord constant in case of an error
+    def _assign_attribute(k, v) # :nodoc:
+      super
+    rescue ActiveModel::UnknownAttributeError
+      raise UnknownAttributeError.new(self, k)
+    end
+
     # Assign any deferred nested attributes after the base attributes have been set.
     def assign_nested_parameter_attributes(pairs)
       pairs.each { |k, v| _assign_attribute(k, v) }
diff --git a/activerecord/lib/active_record/errors.rb b/activerecord/lib/active_record/errors.rb
index d710d96a9a..98aee77557 100644
--- a/activerecord/lib/active_record/errors.rb
+++ b/activerecord/lib/active_record/errors.rb
@@ -178,10 +178,8 @@ module ActiveRecord
   class DangerousAttributeError < ActiveRecordError
   end
 
-  UnknownAttributeError = ActiveSupport::Deprecation::DeprecatedConstantProxy.new( # :nodoc:
-    'ActiveRecord::UnknownAttributeError', 
-    'ActiveModel::AttributeAssignment::UnknownAttributeError'
-  )
+  # Raised when unknown attributes are supplied via mass assignment.
+  UnknownAttributeError = ActiveModel::UnknownAttributeError
 
   # Raised when an error occurred while doing a mass assignment to an attribute through the
   # +attributes=+ method. The exception has an +attribute+ property that is the name of the