Ensure that widget passed as apply kwarg is treated as dynamic input (#…

…4156)

holoviews/core/accessors.py

@@ -3,11 +3,14 @@
 """
 from __future__ import absolute_import, unicode_literals
 
+import copy
+import sys
+
 from collections import OrderedDict
 from types import FunctionType
-import copy
 
 import param
+
 from param.parameterized import add_metaclass
 
 from . import util
@@ -156,6 +159,11 @@ def function(object, **kwargs):
                                          method_name)
                 return method(*args, **kwargs)
 
+        if 'panel' in sys.modules:
+            from panel.widgets.base import Widget
+            kwargs = {k: v.param.value if isinstance(v, Widget) else v
+                      for k, v in kwargs.items()}
+
         applies = isinstance(self._obj, ViewableElement)
         params = {p: val for p, val in kwargs.items()
                   if isinstance(val, param.Parameter)

holoviews/tests/core/testapply.py

@@ -1,6 +1,8 @@
 import numpy as np
 import param
 
+from panel.widgets import TextInput
+
 from holoviews.core.spaces import DynamicMap, HoloMap
 from holoviews.element import Image, Curve
 from holoviews.element.comparison import ComparisonTestCase
@@ -57,6 +59,14 @@ def test_element_apply_dynamic(self):
         self.assertEqual(len(applied.streams), 0)
         self.assertEqual(applied[()], self.element.relabel('Test'))
 
+    def test_element_apply_dynamic_with_widget_kwarg(self):
+        text = TextInput()
+        applied = self.element.apply(lambda x, label: x.relabel(label), label=text)
+        self.assertEqual(len(applied.streams), 1)
+        self.assertEqual(applied[()].label, '')
+        text.value = 'Test'
+        self.assertEqual(applied[()].label, 'Test')
+
     def test_element_apply_dynamic_with_kwarg(self):
         applied = self.element.apply(lambda x, label: x.relabel(label), dynamic=True, label='Test')
         self.assertEqual(len(applied.streams), 0)