rails: save (ActiveRecord::Persistence) can return true even when the model is not saved, and seems to break the principle of "least surprise"

Imported from Lighthouse. Original ticket at: http://rails.lighthouseapp.com/projects/8994/tickets/6666 Created by Alexey Muranov - 2011-04-04 19:14:57 UTC

These two examples illustrate the unexpected (to me) behavior of save method in ActiveRecord::Persistence for a sample application created with

$ rails new test_app
$ cd test_app
$ rails generate model Person name:string
$ rake db:migrate

First example. In console:

p = Person.create(:name=>'Bill')
p.destroy
p.name  # => "Bill"
p.save  # => true

Despite the true returned by save, the database is empty in the end.

Second example. In console:

p = Person.create(:name=>'Bill')
Person.find(p.id).destroy
p.persisted?     # => true
p.destroyed?     # => false
p.name = "John"  # => "John"
p.save           # => true

Again, despite the true returned by save, the database is empty in the end.

This problem was discussed by me and others here: http://www.ruby-forum.com/topic/1386349

I saw other tickets about unexpected behavior of save, but didn’t find an exact match to this problem.