From ab3c8bdfc00ef61da8a2d4856329c61a2cf26d25 Mon Sep 17 00:00:00 2001
From: Curtis Hawthorne <curtis@curtis.hawthorne.name>
Date: Fri, 13 Feb 2009 22:20:45 -0500
Subject: [PATCH] destroy now respects optimistic locking

---
 .../lib/active_record/locking/optimistic.rb        |   33 ++++++++++++++++++++
 activerecord/test/cases/locking_test.rb            |   18 +++++++++++
 2 files changed, 51 insertions(+), 0 deletions(-)

diff --git a/activerecord/lib/active_record/locking/optimistic.rb b/activerecord/lib/active_record/locking/optimistic.rb
index ff9899d..5030c6b 100644
--- a/activerecord/lib/active_record/locking/optimistic.rb
+++ b/activerecord/lib/active_record/locking/optimistic.rb
@@ -23,6 +23,16 @@ module ActiveRecord
     #   p2.first_name = "should fail"
     #   p2.save # Raises a ActiveRecord::StaleObjectError
     #
+    # Optimistic locking will also check for stale data when objects are destroyed.  Example:
+    #
+    #   p1 = Person.find(1)
+    #   p2 = Person.find(1)
+    #
+    #   p1.first_name = "Michael"
+    #   p1.save
+    #
+    #   p2.destroy # Raises a ActiveRecord::StaleObjectError
+    #
     # You're then responsible for dealing with the conflict by rescuing the exception and either rolling back, merging,
     # or otherwise apply the business logic needed to resolve the conflict.
     #
@@ -39,6 +49,7 @@ module ActiveRecord
         base.lock_optimistically = true
 
         base.alias_method_chain :update, :lock
+        base.alias_method_chain :destroy, :lock
         base.alias_method_chain :attributes_from_column_definition, :lock
 
         class << base
@@ -98,6 +109,28 @@ module ActiveRecord
           end
         end
 
+	def destroy_with_lock #:nodoc:
+	  return destroy_without_lock unless locking_enabled?
+
+	  unless new_record?
+	    lock_col = self.class.locking_column
+	    previous_value = send(lock_col).to_i
+
+	    affected_rows = connection.delete(
+	      "DELETE FROM #{self.class.quoted_table_name} " +
+	      "WHERE #{connection.quote_column_name(self.class.primary_key)} = #{quoted_id} " +
+              "AND #{self.class.quoted_locking_column} = #{quote_value(previous_value)}",
+	      "#{self.class.name} Destroy"
+	    )
+
+            unless affected_rows == 1
+              raise ActiveRecord::StaleObjectError, "Attempted to delete a stale object"
+            end
+	  end
+
+	  freeze
+	end
+
       module ClassMethods
         DEFAULT_LOCKING_COLUMN = 'lock_version'
 
diff --git a/activerecord/test/cases/locking_test.rb b/activerecord/test/cases/locking_test.rb
index 077cac7..c6dbd49 100644
--- a/activerecord/test/cases/locking_test.rb
+++ b/activerecord/test/cases/locking_test.rb
@@ -38,6 +38,24 @@ class OptimisticLockingTest < ActiveRecord::TestCase
     assert_raises(ActiveRecord::StaleObjectError) { p2.save! }
   end
 
+  def test_lock_destroy
+    p1 = Person.find(1)
+    p2 = Person.find(1)
+    assert_equal 0, p1.lock_version
+    assert_equal 0, p2.lock_version
+
+    p1.first_name = 'stu'
+    p1.save!
+    assert_equal 1, p1.lock_version
+    assert_equal 0, p2.lock_version
+
+    assert_raises(ActiveRecord::StaleObjectError) { p2.destroy }
+
+    assert p1.destroy
+    assert_equal true, p1.frozen?
+    assert_raises(ActiveRecord::RecordNotFound) { Person.find(1) }
+  end
+
   def test_lock_repeating
     p1 = Person.find(1)
     p2 = Person.find(1)
-- 
1.5.6.3