Added database connection as a yield parameter to...

Added database connection as a yield parameter to ActiveRecord::Base.transaction so you can manually rollback [DHH]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@6196 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

 *SVN*
 
+* Added database connection as a yield parameter to ActiveRecord::Base.transaction so you can manually rollback [DHH]. Example:
+
+    transaction do |transaction|
+      david.withdrawal(100)
+      mary.deposit(100)
+      transaction.rollback! # rolls back the transaction that was otherwise going to be successful
+    end
+
 * Made increment_counter/decrement_counter play nicely with optimistic locking, and added a more general update_counters method [Jamis Buck]
 
 * Reworked David's query cache to be available as Model.cache {...}. For the duration of the block no select query should be run more then once. Any inserts/deletes/executes will flush the whole cache however [Tobias Luetke]

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

@@ -56,7 +56,7 @@ def transaction(start_db_transaction = true)
               begin_db_transaction 
               transaction_open = true
             end
-            yield
+            yield self
           end
         rescue Exception => database_transaction_rollback
           if transaction_open
@@ -79,6 +79,11 @@ def commit_db_transaction()   end
       # done if the transaction block raises an exception or returns false.
       def rollback_db_transaction() end
 
+      # Alias for rollback_db_transaction to be used when yielding the transaction
+      def rollback!
+        rollback_db_transaction
+      end
+
       # Alias for #add_limit_offset!.
       def add_limit!(sql, options)
         add_limit_offset!(sql, options) if options

activerecord/lib/active_record/transactions.rb

@@ -32,6 +32,17 @@ def self.included(base)
     # Exceptions will force a ROLLBACK that returns the database to the state before the transaction was begun. Be aware, though,
     # that the objects by default will _not_ have their instance data returned to their pre-transactional state.
     #
+    # == Rolling back a transaction manually
+    #
+    # Instead of relying on exceptions to rollback your transactions, you can also do so manually from within the scope
+    # of the transaction by accepting a yield parameter and calling rollback! on it. Example:
+    #
+    #   transaction do |transaction|
+    #     david.withdrawal(100)
+    #     mary.deposit(100)
+    #     transaction.rollback! # rolls back the transaction that was otherwise going to be successful
+    #   end
+    #
     # == Transactions are not distributed across database connections
     #
     # A transaction acts on a single database connection.  If you have

activerecord/test/transactions_test.rb

@@ -88,7 +88,7 @@ def test_failing_on_exception
   
   def test_failing_with_object_rollback
     assert !@first.approved?, "First should be unapproved initially"
-
+  
     begin
       assert_deprecated /Object transactions/ do
         Topic.transaction(@first, @second) do
@@ -168,6 +168,24 @@ def test_nested_explicit_transactions
     assert !Topic.find(2).approved?, "Second should have been unapproved"
   end
 
+  def test_manually_rolling_back_a_transaction
+    Topic.transaction do |transaction|
+      @first.approved  = true
+      @second.approved = false
+      @first.save
+      @second.save
+      
+      transaction.rollback!
+    end
+
+    assert @first.approved?, "First should still be changed in the objects"
+    assert !@second.approved?, "Second should still be changed in the objects"
+    
+    assert !Topic.find(1).approved?, "First shouldn't have been approved"
+    assert Topic.find(2).approved?, "Second should still be approved"
+  end
+
+
   private
     def add_exception_raising_after_save_callback_to_topic
       Topic.class_eval { def after_save() raise "Make the transaction rollback" end }