Rollback the transaction when a before_* callback returns false.

Previously this would have committed the transaction but not carried out save or destroy operation.

[#891 state:committed]
Signed-off-by: NMichael Koziarski <michael@koziarski.com>

activerecord/CHANGELOG

 *Edge*
 
+* before_save, before_validation and before_destroy callbacks that return false will now ROLLBACK the transaction.  Previously this would have been committed before the processing was aborted. #891 [Xavier Noria]
+
 * Transactional migrations for databases which support them.  #834 [divoxx, Adam Wiggins, Tarmo Tänav]
 
 * Set config.active_record.timestamped_migrations = false to have migrations with numeric prefix instead of UTC timestamp. #446. [Andrew Stone, Nik Wakelin]

activerecord/lib/active_record/callbacks.rb

@@ -169,6 +169,18 @@ module ActiveRecord
   # If a <tt>before_*</tt> callback returns +false+, all the later callbacks and the associated action are cancelled. If an <tt>after_*</tt> callback returns
   # +false+, all the later callbacks are cancelled. Callbacks are generally run in the order they are defined, with the exception of callbacks
   # defined as methods on the model, which are called last.
+  #
+  # == Transactions
+  #
+  # The entire callback chain of a +save+, <tt>save!</tt>, or +destroy+ call runs
+  # within a transaction. That includes <tt>after_*</tt> hooks. If everything
+  # goes fine a COMMIT is executed once the chain has been completed.
+  #
+  # If a <tt>before_*</tt> callback cancels the action a ROLLBACK is issued. You
+  # can also trigger a ROLLBACK raising an exception in any of the callbacks,
+  # including <tt>after_*</tt> hooks. Note, however, that in that case the client
+  # needs to be aware of it because an ordinary +save+ will raise such exception
+  # instead of quietly returning +false+.
   module Callbacks
     CALLBACKS = %w(
       after_find after_initialize before_save after_save before_create after_create before_update after_update before_validation

activerecord/lib/active_record/transactions.rb

@@ -91,11 +91,11 @@ def transaction(&block)
     end
 
     def destroy_with_transactions #:nodoc:
-      transaction { destroy_without_transactions }
+      with_transaction_returning_status(:destroy_without_transactions)
     end
 
     def save_with_transactions(perform_validation = true) #:nodoc:
-      rollback_active_record_state! { transaction { save_without_transactions(perform_validation) } }
+      rollback_active_record_state! { with_transaction_returning_status(:save_without_transactions, perform_validation) }
     end
 
     def save_with_transactions! #:nodoc:
@@ -118,5 +118,17 @@ def rollback_active_record_state!
       end
       raise
     end
+
+    # Executes +method+ within a transaction and captures its return value as a
+    # status flag. If the status is true the transaction is committed, otherwise
+    # a ROLLBACK is issued. In any case the status flag is returned.
+    def with_transaction_returning_status(method, *args)
+      status = nil
+      transaction do
+        status = send(method, *args)
+        raise ActiveRecord::Rollback unless status
+      end
+      status
+    end
   end
 end

activerecord/test/cases/transactions_test.rb

@@ -2,6 +2,7 @@
 require 'models/topic'
 require 'models/reply'
 require 'models/developer'
+require 'models/book'
 
 class TransactionTest < ActiveRecord::TestCase
   self.use_transactional_fixtures = false
@@ -86,8 +87,7 @@ def test_failing_on_exception
     assert Topic.find(2).approved?, "Second should still be approved"
   end
 
-
-  def test_callback_rollback_in_save
+  def test_raising_exception_in_callback_rollbacks_in_save
     add_exception_raising_after_save_callback_to_topic
 
     begin
@@ -102,6 +102,54 @@ def test_callback_rollback_in_save
     end
   end
 
+  def test_cancellation_from_before_destroy_rollbacks_in_destroy
+    add_cancelling_before_destroy_with_db_side_effect_to_topic
+    begin
+      nbooks_before_destroy = Book.count
+      status = @first.destroy
+      assert !status
+      assert_nothing_raised(ActiveRecord::RecordNotFound) { @first.reload }
+      assert_equal nbooks_before_destroy, Book.count
+    ensure
+      remove_cancelling_before_destroy_with_db_side_effect_to_topic
+    end
+  end
+
+  def test_cancellation_from_before_filters_rollbacks_in_save
+    %w(validation save).each do |filter|
+      send("add_cancelling_before_#{filter}_with_db_side_effect_to_topic")
+      begin
+        nbooks_before_save = Book.count
+        original_author_name = @first.author_name
+        @first.author_name += '_this_should_not_end_up_in_the_db'
+        status = @first.save
+        assert !status
+        assert_equal original_author_name, @first.reload.author_name
+        assert_equal nbooks_before_save, Book.count
+      ensure
+        send("remove_cancelling_before_#{filter}_with_db_side_effect_to_topic")
+      end
+    end
+  end
+
+  def test_cancellation_from_before_filters_rollbacks_in_save!
+    %w(validation save).each do |filter|
+      send("add_cancelling_before_#{filter}_with_db_side_effect_to_topic")
+      begin
+        nbooks_before_save = Book.count
+        original_author_name = @first.author_name
+        @first.author_name += '_this_should_not_end_up_in_the_db'
+        @first.save!
+        flunk
+      rescue => e
+        assert_equal original_author_name, @first.reload.author_name
+        assert_equal nbooks_before_save, Book.count
+      ensure
+        send("remove_cancelling_before_#{filter}_with_db_side_effect_to_topic")
+      end
+    end
+  end
+
   def test_callback_rollback_in_create
     new_topic = Topic.new(
       :title => "A new topic",
@@ -221,6 +269,16 @@ def add_exception_raising_after_create_callback_to_topic
     def remove_exception_raising_after_create_callback_to_topic
       Topic.class_eval { remove_method :after_create }
     end
+
+    %w(validation save destroy).each do |filter|
+      define_method("add_cancelling_before_#{filter}_with_db_side_effect_to_topic") do
+        Topic.class_eval "def before_#{filter}() Book.create; false end"
+      end
+
+      define_method("remove_cancelling_before_#{filter}_with_db_side_effect_to_topic") do
+        Topic.class_eval "remove_method :before_#{filter}"
+      end
+    end
 end
 
 if current_adapter?(:PostgreSQLAdapter)