Restore ActiveRecord states after a rollback for models w/o callbacks

This fixes a regression (#13744) that was caused by 67d8bb9.

In 67d8bb9, we introduced lazy rollback for records, such that the
record's internal states and attributes are not restored immediately
after a transaction rollback, but deferred until they are first
accessed.

This optimization is only performed when the model does not have any
transactional callbacks (e.g. `after_commit` and `after_create`).

Unfortunately, the models used to test the affected codepaths all
comes with some sort of transactional callbacks. Therefore this
codepath remains largely untested until now and as a result there are
a few issues in the implementation that remains hidden until now.

First, the `sync_with_transaction_state` (or more accurately,
`update_attributes_from_transaction_state`) would perform the
synchronization prematurely before a transaction is finalized (i.e.
comitted or rolled back). As a result, when the actuall rollback
happens, the record will incorrectly assumes that its internal states
match the transaction state, and neglect to perform the restore.

Second, `update_attributes_from_transaction_state` calls `committed!`
in some cases. This in turns checks for the `destroyed?` state which
also requires synchronization with the transaction stae, which causes
an infnite recurrsion.

This fix works by deferring the synchronization until the transaction
has been finalized (addressing the first point), and also unrolled
the `committed!` and `rolledback!` logic in-place (addressing the
second point).

It should be noted that the primary purpose of the `committed!` and
`rolledback!` methods are to trigger the relevant transactional
callbacks. Since this code path is only entered when there are no
transactional callbacks on the model, this shouldn't be necessary. By
unrolling the method calls, the intention here (to restore the states
when necessary) becomes more clear.

1 files changed, 11 insertions, 0 deletions

diff --git a/activerecord/test/cases/transactions_test.rb b/activerecord/test/cases/transactions_test.rb
index 89dab16975..1664f1a096 100644
--- a/activerecord/test/cases/transactions_test.rb
+++ b/activerecord/test/cases/transactions_test.rb
@@ -430,17 +430,26 @@ class TransactionTest < ActiveRecord::TestCase
   end
 
   def test_restore_active_record_state_for_all_records_in_a_transaction
+    topic_without_callbacks = Class.new(ActiveRecord::Base) do
+      self.table_name = 'topics'
+    end
+
     topic_1 = Topic.new(:title => 'test_1')
     topic_2 = Topic.new(:title => 'test_2')
+    topic_3 = topic_without_callbacks.new(:title => 'test_3')
+
     Topic.transaction do
       assert topic_1.save
       assert topic_2.save
+      assert topic_3.save
       @first.save
       @second.destroy
       assert topic_1.persisted?, 'persisted'
       assert_not_nil topic_1.id
       assert topic_2.persisted?, 'persisted'
       assert_not_nil topic_2.id
+      assert topic_3.persisted?, 'persisted'
+      assert_not_nil topic_3.id
       assert @first.persisted?, 'persisted'
       assert_not_nil @first.id
       assert @second.destroyed?, 'destroyed'
@@ -451,6 +460,8 @@ class TransactionTest < ActiveRecord::TestCase
     assert_nil topic_1.id
     assert !topic_2.persisted?, 'not persisted'
     assert_nil topic_2.id
+    assert !topic_3.persisted?, 'not persisted'
+    assert_nil topic_3.id
     assert @first.persisted?, 'persisted'
     assert_not_nil @first.id
     assert !@second.destroyed?, 'not destroyed'