Correctly register empty sources (#1806)

holoviews/streams.py

@@ -184,7 +184,7 @@ def __init__(self, rename={}, source=None, subscribers=[], linked=False,
         self._metadata = {}
 
         super(Stream, self).__init__(**params)
-        if source:
+        if source is not None:
             self.registry[id(source)].append(self)
 
 

tests/teststreams.py

@@ -1,7 +1,10 @@
 """
 Unit test of the streams system
 """
+from collections import defaultdict
+
 import param
+from holoviews.element import Points
 from holoviews.element.comparison import ComparisonTestCase
 from holoviews.streams import * # noqa (Test all available streams)
 
@@ -226,6 +229,22 @@ def test_batch_subscribers(self):
         self.assertEqual(subscriber2.call_count, 1)
 
 
+class TestStreamSource(ComparisonTestCase):
+
+    def tearDown(self):
+        Stream.registry = defaultdict(list)
+
+    def test_source_registry(self):
+        points = Points([(0, 0)])
+        positionX = PointerX(source=points)
+        self.assertIn(id(points), Stream.registry)
+
+    def test_source_registry_empty_element(self):
+        points = Points([])
+        positionX = PointerX(source=points)
+        self.assertIn(id(points), Stream.registry)
+
+
 class TestParameterRenaming(ComparisonTestCase):
 
     def test_simple_rename_constructor(self):