after_save callbacks are called before dirty tracking is updated

No, does not answer my question. The question is when should @previously_changed be populated and changes be cleared? It appears that it is populated AFTER the after_save, after_create, etc. callbacks are called. In the 2.3 branch, the changes were cleared before the after_save callbacks. The behavior has changed. Is this intentional (if so, it doesn't seem right to me and certainly does not appear to be documented) or is this a bug? It seems like a bug to me.

I see what you are saying. I will try to get some info on this.

Yes, this seems to be a bug. Maybe the order of callbacks is reversed? In other words:

after_save :a after_save :b

Should first execute :a and then :b. This may cause the callback that cleans up dirty attributes to come last.

Neeraj, I think we had a ticket about this, right? Wasn't it fixed? Ari, in which Rails version have you tested?

Ari said:

In the 2.3 branch, the changes were cleared before the after_save callbacks.

I tested with Rails 2.3.10 and this is what I found.

class User < ActiveRecord::Base
  after_save :show_previous_changes

  def show_previous_changes
    #puts "Previous changes: #{self.previous_changes}"
    puts "Changes: #{self.changes.inspect}"
  end  
end

u = Useree-1.8.7-2010.02 > u = User.first
  User Load (0.6ms)   SELECT * FROM "users" LIMIT 1
 => #<User id: 1, name: "john", created_at: "2010-11-26 09:31:07", updated_at: "2010-11-26 09:42:53"> 
ree-1.8.7-2010.02 > u.name = 'john2'
ree-1.8.7-2010.02 > u.save
Changes: {"name"=>["john", "john2"], "updated_at"=>[Fri Nov 26 09:42:53 UTC 2010, Fri, 26 Nov 2010 09:43:21 UTC +00:00]}
ree-1.8.7-2010.02 > u.show_previous_changes
Changes: {}

As you can see after_save callback in Rails 2.3.10 has changes NOT cleared.

If I run the same code with rails edge this is what I get

class User < ActiveRecord::Base
  after_save :show_previous_changes

  def show_previous_changes
    puts "Previous changes: #{self.previous_changes}"
    puts "Changes: #{self.changes.inspect}"
  end
end

ree-1.8.7-2010.02 > u = User.first
  User Load (0.8ms)  SELECT "users".* FROM "users" LIMIT 1
 => #<User id: 1, name: "john", created_at: "2010-11-26 09:33:47", updated_at: "2010-11-26 09:43:07"> 
ree-1.8.7-2010.02 > u.name='john2'
ree-1.8.7-2010.02 > u.save
Previous changes: 
Changes: {"name"=>["john", "john2"], "updated_at"=>[Fri, 26 Nov 2010 09:43:07 UTC +00:00, Fri, 26 Nov 2010 09:43:54 UTC +00:00]}
ree-1.8.7-2010.02 > u.show_previous_changes
Previous changes: namejohnjohn2updated_at2010-11-26 09:43:07 UTC2010-11-26 09:43:54 UTC
Changes: {}

It seems to me that both Rails edge and Rails 2.3.10 after_save callbacks keep the value of changes intact and there does not seem to be any discrepancy.

It's 5 in the morning so I am sure I am missing something. :-)

Hmm... when I did my initial coding on an application where this matters, I could swear that changes got reset before after_save callbacks, but I'm finding this isn't the case with 2.3.5 or subsequent branches. So I guess this is not a bug if it's the intended behavior. Just want to make sure it's not going to change.