Apply record state based on parent transaction state

Let's say you have a nested transaction and both records are saved.
Before the outer transaction closes, a rollback is performed. Previously
the record in the outer transaction would get marked as not persisted
but the inner transaction would get persisted.

```ruby
Post.transaction do
  post_one.save # will get rolled back

  Post.transaction(requires_new: true) do
    post_two.save # incorrectly remains marked as persisted
  end

  raise ActiveRecord::Rollback
end
```

To fix this the PR changes transaction handling to have the child
transaction ask the parent how the records should be marked. When
there are child transactions, it will always be a SavpointTransaction
because the stack isn't empty. From there we pass the parent_transaction
to the child SavepointTransaction where we add the children to the parent
so the parent can mark the inner transaction as rolledback and thus mark
the record as not persisted.

`update_attributes_from_transaction_state` uses the `completed?` check to
correctly mark all the transactions as rolledback and the inner record as
not persisted.

```ruby
Post.transaction do
  post_one.save # will get rolled back

  Post.transaction(requires_new: true) do
    post_two.save # with new behavior, correctly marked as not persisted
    on rollback
  end

  raise ActiveRecord::Rollback
end
```

Fixes #29320

activerecord/CHANGELOG.md

+*   Fix transactions to apply state to child transactions
+
+    Previously if you had a nested transaction and the outer transaction was rolledback the record from the
+    inner transaction would still be marked as persisted.
+
+    This change fixes that by applying the state of the parent transaction to the child transaction when the
+    parent transaction is rolledback. This will correctly mark records from the inner transaction as not persisted.
+
+    *Eileen M. Uchitelle*, *Aaron Patterson*
+
 *   Deprecate `set_state` method in `TransactionState`
 
     Deprecated the `set_state` method in favor of setting the state via specific methods. If you need to mark the

activerecord/lib/active_record/connection_adapters/abstract/transaction.rb

@@ -3,6 +3,11 @@ module ConnectionAdapters
     class TransactionState
       def initialize(state = nil)
         @state = state
+        @children = []
+      end
+
+      def add_child(state)
+        @children << state
       end
 
       def finalized?
@@ -17,6 +22,10 @@ def rolledback?
         @state == :rolledback
       end
 
+      def fully_completed?
+        completed?
+      end
+
       def completed?
         committed? || rolledback?
       end
@@ -40,6 +49,7 @@ def set_state(state)
       end
 
       def rollback!
+        @children.each { |c| c.rollback! }
         @state = :rolledback
       end
 
@@ -121,8 +131,11 @@ def open?; !closed?; end
     end
 
     class SavepointTransaction < Transaction
-      def initialize(connection, savepoint_name, options, *args)
+      def initialize(connection, savepoint_name, parent_transaction, options, *args)
         super(connection, options, *args)
+
+        parent_transaction.state.add_child(@state)
+
         if options[:isolation]
           raise ActiveRecord::TransactionIsolationError, "cannot set transaction isolation in a nested transaction"
         end
@@ -176,7 +189,7 @@ def begin_transaction(options = {})
             if @stack.empty?
               RealTransaction.new(@connection, options, run_commit_callbacks: run_commit_callbacks)
             else
-              SavepointTransaction.new(@connection, "active_record_#{@stack.size}", options,
+              SavepointTransaction.new(@connection, "active_record_#{@stack.size}", @stack.last, options,
                                        run_commit_callbacks: run_commit_callbacks)
             end
 

activerecord/lib/active_record/transactions.rb

@@ -490,7 +490,7 @@ def sync_with_transaction_state
       def update_attributes_from_transaction_state(transaction_state)
         if transaction_state && transaction_state.finalized?
           restore_transaction_record_state if transaction_state.rolledback?
-          clear_transaction_record_state
+          clear_transaction_record_state if transaction_state.fully_completed?
         end
       end
   end

activerecord/test/cases/transactions_test.rb

@@ -304,6 +304,76 @@ def test_nested_explicit_transactions
     assert !Topic.find(2).approved?, "Second should have been unapproved"
   end
 
+  def test_nested_transaction_with_new_transaction_applies_parent_state_on_rollback
+    topic_one = Topic.new(title: "A new topic")
+    topic_two = Topic.new(title: "Another new topic")
+
+    Topic.transaction do
+      topic_one.save
+
+      Topic.transaction(requires_new: true) do
+        topic_two.save
+
+        assert_predicate topic_one, :persisted?
+        assert_predicate topic_two, :persisted?
+      end
+
+      raise ActiveRecord::Rollback
+    end
+
+    refute_predicate topic_one, :persisted?
+    refute_predicate topic_two, :persisted?
+  end
+
+  def test_nested_transaction_without_new_transaction_applies_parent_state_on_rollback
+    topic_one = Topic.new(title: "A new topic")
+    topic_two = Topic.new(title: "Another new topic")
+
+    Topic.transaction do
+      topic_one.save
+
+      Topic.transaction do
+        topic_two.save
+
+        assert_predicate topic_one, :persisted?
+        assert_predicate topic_two, :persisted?
+      end
+
+      raise ActiveRecord::Rollback
+    end
+
+    refute_predicate topic_one, :persisted?
+    refute_predicate topic_two, :persisted?
+  end
+
+  def test_double_nested_transaction_applies_parent_state_on_rollback
+    topic_one = Topic.new(title: "A new topic")
+    topic_two = Topic.new(title: "Another new topic")
+    topic_three = Topic.new(title: "Another new topic of course")
+
+    Topic.transaction do
+      topic_one.save
+
+      Topic.transaction do
+        topic_two.save
+
+        Topic.transaction do
+          topic_three.save
+        end
+      end
+
+      assert_predicate topic_one, :persisted?
+      assert_predicate topic_two, :persisted?
+      assert_predicate topic_three, :persisted?
+
+      raise ActiveRecord::Rollback
+    end
+
+    refute_predicate topic_one, :persisted?
+    refute_predicate topic_two, :persisted?
+    refute_predicate topic_three, :persisted?
+  end
+
   def test_manually_rolling_back_a_transaction
     Topic.transaction do
       @first.approved  = true