Handle enabling/disabling observers at different levels of the class hierarchy.

Last call wins.

3 files changed, 75 insertions, 3 deletions

diff --git a/activemodel/lib/active_model/observer_array.rb b/activemodel/lib/active_model/observer_array.rb
index b8aa9cc1e2..f3b5811b81 100644
--- a/activemodel/lib/active_model/observer_array.rb
+++ b/activemodel/lib/active_model/observer_array.rb
@@ -48,7 +48,7 @@ module ActiveModel
       set_enablement(true, observers, &block)
     end
 
-    private
+    protected
 
       def observer_class_for(observer)
         return observer if observer.is_a?(Class)
@@ -61,13 +61,37 @@ module ActiveModel
         end
       end
 
+      def start_transaction
+        disabled_observer_stack.push(disabled_observers.dup)
+        each_subclass_array do |array|
+          array.start_transaction
+        end
+      end
+
+      def disabled_observer_stack
+        @disabled_observer_stack ||= []
+      end
+
+      def end_transaction
+        @disabled_observers = disabled_observer_stack.pop
+        each_subclass_array do |array|
+          array.end_transaction
+        end
+      end
+
       def transaction
-        orig_disabled_observers = disabled_observers.dup
+        start_transaction
 
         begin
           yield
         ensure
-          @disabled_observers = orig_disabled_observers
+          end_transaction
+        end
+      end
+
+      def each_subclass_array
+        model_class.subclasses.each do |subclass|
+          yield self.class.for(subclass)
         end
       end
 
@@ -92,6 +116,10 @@ module ActiveModel
               disabled_observers << klass
             end
           end
+
+          each_subclass_array do |array|
+            array.set_enablement(enabled, observers)
+          end
         end
       end
   end
diff --git a/activemodel/lib/active_model/observing.rb b/activemodel/lib/active_model/observing.rb
index e1a2ce218d..ba6be46670 100644
--- a/activemodel/lib/active_model/observing.rb
+++ b/activemodel/lib/active_model/observing.rb
@@ -70,6 +70,10 @@ module ActiveModel
         observer_instances.size
       end
 
+      def subclasses
+        @subclasses ||= []
+      end
+
       protected
         def instantiate_observer(observer) #:nodoc:
           # string/symbol
@@ -89,6 +93,7 @@ module ActiveModel
         # Notify observers when the observed class is subclassed.
         def inherited(subclass)
           super
+          subclasses << subclass
           notify_observers :observed_class_inherited, subclass
         end
     end
diff --git a/activemodel/test/cases/observer_array_test.rb b/activemodel/test/cases/observer_array_test.rb
index 215ca80bb4..38e4fd59fc 100644
--- a/activemodel/test/cases/observer_array_test.rb
+++ b/activemodel/test/cases/observer_array_test.rb
@@ -118,5 +118,44 @@ class ObserverArrayTest < ActiveModel::TestCase
       ORM.observers.disable Widget
     end
   end
+
+  test "allows #enable at the superclass level to override #disable at the subclass level when called last" do
+    Widget.observers.disable :all
+    ORM.observers.enable :all
+
+    assert_observer_notified Widget, WidgetObserver
+    assert_observer_notified Budget, BudgetObserver
+    assert_observer_notified Widget, AuditTrail
+    assert_observer_notified Budget, AuditTrail
+  end
+
+  test "allows #disable at the superclass level to override #enable at the subclass level when called last" do
+    Budget.observers.enable :audit_trail
+    ORM.observers.disable :audit_trail
+
+    assert_observer_notified     Widget, WidgetObserver
+    assert_observer_notified     Budget, BudgetObserver
+    assert_observer_not_notified Widget, AuditTrail
+    assert_observer_not_notified Budget, AuditTrail
+  end
+
+  test "can use the block form at different levels of the hierarchy" do
+    yielded = false
+    Widget.observers.disable :all
+
+    ORM.observers.enable :all do
+      yielded = true
+      assert_observer_notified Widget, WidgetObserver
+      assert_observer_notified Budget, BudgetObserver
+      assert_observer_notified Widget, AuditTrail
+      assert_observer_notified Budget, AuditTrail
+    end
+
+    assert yielded
+    assert_observer_not_notified Widget, WidgetObserver
+    assert_observer_notified     Budget, BudgetObserver
+    assert_observer_not_notified Widget, AuditTrail
+    assert_observer_notified     Budget, AuditTrail
+  end
 end