From d7f2e60293dac7895689af6272d3b177574b33fc Mon Sep 17 00:00:00 2001
From: Philipp Rudiger <philippjfr@continuum.io>
Date: Tue, 15 Aug 2017 13:27:07 +0100
Subject: [PATCH] Correctly register empty sources (#1806)

---
 holoviews/streams.py |  2 +-
 tests/teststreams.py | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/holoviews/streams.py b/holoviews/streams.py
index 8978d6886c..86a86372d3 100644
--- a/holoviews/streams.py
+++ b/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)
 
 
diff --git a/tests/teststreams.py b/tests/teststreams.py
index 90068cfc1d..a907d1f50e 100644
--- a/tests/teststreams.py
+++ b/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):