Destroy association habtm record before destroying the record itself. Fixes issue #402.

4 files changed, 29 insertions, 12 deletions

diff --git a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
index d7632b2ea9..30fc44b4c2 100644
--- a/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
+++ b/activerecord/lib/active_record/associations/builder/has_and_belongs_to_many.rb
@@ -7,24 +7,22 @@ module ActiveRecord::Associations::Builder
     def build
       reflection = super
       check_validity(reflection)
-      define_after_destroy_method
+      define_destroy_hook
       reflection
     end
 
     private
 
-      def define_after_destroy_method
+      def define_destroy_hook
         name = self.name
-        model.send(:class_eval, <<-eoruby, __FILE__, __LINE__ + 1)
-          def #{after_destroy_method_name}
-            association(#{name.to_sym.inspect}).delete_all
-          end
-        eoruby
-        model.after_destroy after_destroy_method_name
-      end
-
-      def after_destroy_method_name
-        "has_and_belongs_to_many_after_destroy_for_#{name}"
+        model.send(:include, Module.new {
+          class_eval <<-RUBY, __FILE__, __LINE__ + 1
+            def destroy_associations
+              association(#{name.to_sym.inspect}).delete_all
+              super
+            end
+          RUBY
+        })
       end
 
       # TODO: These checks should probably be moved into the Reflection, and we should not be
diff --git a/activerecord/lib/active_record/persistence.rb b/activerecord/lib/active_record/persistence.rb
index f425118f59..d9cd7987b0 100644
--- a/activerecord/lib/active_record/persistence.rb
+++ b/activerecord/lib/active_record/persistence.rb
@@ -79,6 +79,8 @@ module ActiveRecord
     # Deletes the record in the database and freezes this instance to reflect
     # that no changes should be made (since they can't be persisted).
     def destroy
+      destroy_associations
+
       if persisted?
         IdentityMap.remove(self) if IdentityMap.enabled?
         pk         = self.class.primary_key
@@ -284,6 +286,11 @@ module ActiveRecord
     end
 
   private
+
+    # A hook to be overriden by association modules.
+    def destroy_associations
+    end
+
     def create_or_update
       raise ReadOnlyRecord if readonly?
       result = new_record? ? create : update
diff --git a/activerecord/test/cases/habtm_destroy_order_test.rb b/activerecord/test/cases/habtm_destroy_order_test.rb
index f2b91d977e..2ce0de360e 100644
--- a/activerecord/test/cases/habtm_destroy_order_test.rb
+++ b/activerecord/test/cases/habtm_destroy_order_test.rb
@@ -16,6 +16,16 @@ class HabtmDestroyOrderTest < ActiveRecord::TestCase
     assert !sicp.destroyed?
   end
 
+  test 'should not raise error if have foreign key in the join table' do
+    student = Student.new(:name => "Ben Bitdiddle")
+    lesson = Lesson.new(:name => "SICP")
+    lesson.students << student
+    lesson.save!
+    assert_nothing_raised do
+      student.destroy
+    end
+  end
+
   test "not destroying a student with lessons leaves student<=>lesson association intact" do
     # test a normal before_destroy doesn't destroy the habtm joins
     begin
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 4fe311b441..fd2ee23dd5 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -719,6 +719,8 @@ ActiveRecord::Schema.define do
     end
 
     execute "ALTER TABLE fk_test_has_fk ADD CONSTRAINT fk_name FOREIGN KEY (#{quote_column_name 'fk_id'}) REFERENCES #{quote_table_name 'fk_test_has_pk'} (#{quote_column_name 'id'})"
+
+    execute "ALTER TABLE lessons_students ADD CONSTRAINT student_id_fk FOREIGN KEY (#{quote_column_name 'student_id'}) REFERENCES #{quote_table_name 'students'} (#{quote_column_name 'id'})"
   end
 end