observe via tags and register notifiers with metadata

traitlets/tests/test_traitlets.py

@@ -418,10 +418,10 @@ class A(HasTraits):
         a.on_trait_change(callback4, 'a')
         a.a = 100000
         self.assertEqual(self.cb,('a',10000,100000,a))
-        self.assertEqual(len(a._trait_notifiers['a']['change']), 1)
+        self.assertEqual(len(a.trait_notifiers('a')), 1)
         a.on_trait_change(callback4, 'a', remove=True)
 
-        self.assertEqual(len(a._trait_notifiers['a']['change']), 0)
+        self.assertEqual(len(a.trait_notifiers('a')), 0)
 
     def test_notify_only_once(self):
 
@@ -614,10 +614,10 @@ class A(HasTraits):
         a.a = 100
         change = change_dict('a', 10, 100, a, 'change')
         self.assertEqual(self.cb, change)
-        self.assertEqual(len(a._trait_notifiers['a']['change']), 1)
+        self.assertEqual(len(a.trait_notifiers('a')), 1)
         a.unobserve(callback1, 'a')
 
-        self.assertEqual(len(a._trait_notifiers['a']['change']), 0)
+        self.assertEqual(len(a.trait_notifiers('a')), 0)
 
     def test_notify_only_once(self):
 
@@ -658,6 +658,70 @@ def _a_changed(self, change):
         self.assertEqual(b.b, b.c)
         self.assertEqual(b.b, b.d)
 
+    def test_unobserve_with_bound_method_raises(self):
+        class A(HasTraits):
+            i = Int()
+
+            @observe('i')
+            def _observer(self, change): pass
+
+        a = A()
+        self.assertRaises(TraitError, a.unobserve, a._observer)
+
+    def test_unobserve_with_trait_notifiers(self):
+        class A(HasTraits):
+            i = Int()
+
+            @observe('i')
+            def _observer(self, change): pass
+
+        a = A()
+        n_list = a.trait_notifiers('i')
+        self.assertEqual(len(n_list), 1)
+
+        a.unobserve(n_list[0])
+        n_list = a.trait_notifiers('i')
+        self.assertEqual(len(n_list), 0)
+
+    def test_observe_decorator_via_tags(self):
+        class A(HasTraits):
+            foo = Int()
+            bar = Int().tag(test=True)
+
+            @observe(tags={'test':True})
+            def _test_observer(self, change):
+                self.foo = change['new']
+
+        a = A()
+        a.bar = 1
+        self.assertEqual(a.foo, a.bar)
+
+        a.add_traits(baz=Int().tag(test=True))
+        a.baz = 2
+        self.assertEqual(a.foo, a.baz)
+
+    def test_observe_via_tags(self):
+
+        class A(HasTraits):
+            foo = Int()
+            bar = Int().tag(test=True)
+
+        a = A()
+
+        def _test_observer(change):
+            a.foo = change['new']
+
+        a.observe(_test_observer, tags={'test':True})
+        a.bar = 1
+        self.assertEqual(a.foo, a.bar)
+
+        a.add_traits(baz=Int().tag(test=True))
+        a.baz = 2
+        self.assertEqual(a.foo, a.baz)
+
+        a.unobserve(_test_observer)
+        a.bar = 3
+        self.assertNotEqual(a.bar, a.baz)
 
 class TestHasTraits(TestCase):