Mutation tracker should be cleared before continuing around callbacks

[ypresto]

Summary

changes_applied should be called before continuing around callback chain. Otherwise the mutation tracker returns old value for methods like changed? or id_in_database in around callbacks. Also methods depend on id_in_database, like update_column, are not working in around_create callbacks.

class Foo < ActiveRecord::Base
  around_create :around_create_callback

  def around_create_callback
    ...
    yield
    p id_in_database # => nil
    update_column(:generated_column, generate_value) # silently fails
  end

  ...
end

Other Information

We found this issue with update_column called from around_create in our code (our generated value contains id, so we should generate after actual save of record).
It was working in Rails 5.1 and not in Rails 5.2.
The bug of update_column seems to be emerged by 41484eb, which changes method to fetch primary key from id to id_in_database.

Thanks for debugging this issue: @kimihito @elim

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[kamipo]

I'm prefer not to care about what kind of value is returned in this module.
Can you use ensure instead?

diff --git a/activerecord/lib/active_record/attribute_methods/dirty.rb b/activerecord/lib/active_record/attribute_methods/dirty.rb
index 233ee29fac..58613f5e88 100644
--- a/activerecord/lib/active_record/attribute_methods/dirty.rb
+++ b/activerecord/lib/active_record/attribute_methods/dirty.rb
@@ -169,10 +169,14 @@ def write_attribute_without_type_cast(attr_name, _)

         def _update_record(*)
           partial_writes? ? super(keys_for_partial_write) : super
+        ensure
+          changes_applied
         end

         def _create_record(*)
           partial_writes? ? super(keys_for_partial_write) : super
+        ensure
+          changes_applied
         end

         def keys_for_partial_write

[kamipo]

hm... I've confirmed using ensure would change current behavior if any exception is raised from database.
We should not use ensure at least in this point.

[kamipo]

Thank you, and congratulations on your first PR contribution to Rails 🎉

[bogdanvlviv]

@kamipo Should we backport it to 5-2-stable?

[kamipo]

Yeah, backported in bd6ac44.

[sgrif]

This is a change in behavior that will cause breakage in apps. We need to go through a deprecation cycle for this the same way we did for after_* callbacks

[sgrif]

Scratch that, I see it was a change in behavior between 5.1 and 5.2