fix: handle value=None in DateRangeSlider._sync_values

panel/tests/widgets/test_slider.py

@@ -409,6 +409,41 @@ def test_datetime_range_slider(document, comm):
         assert widget.value == (1613088000000, 1620777600000)
 
 
+def test_date_range_slider_value_none():
+    date_slider = DateRangeSlider(
+        start=date(2020, 1, 1),
+        end=date(2020, 1, 5),
+    )
+    assert date_slider.value == (date(2020, 1, 1), date(2020, 1, 5))
+    assert date_slider.value_start == date(2020, 1, 1)
+    assert date_slider.value_end == date(2020, 1, 5)
+
+    date_slider.value = None
+    assert date_slider.value is None
+    assert date_slider.value_start is None
+    assert date_slider.value_end is None
+
+    date_slider.value = (date(2020, 1, 2), date(2020, 1, 4))
+    assert date_slider.value == (date(2020, 1, 2), date(2020, 1, 4))
+    assert date_slider.value_start == date(2020, 1, 2)
+    assert date_slider.value_end == date(2020, 1, 4)
+
+
+def test_datetime_range_slider_value_none():
+    dt_slider = DatetimeRangeSlider(
+        start=datetime(2020, 1, 1),
+        end=datetime(2020, 1, 5),
+    )
+    assert dt_slider.value == (datetime(2020, 1, 1), datetime(2020, 1, 5))
+    assert dt_slider.value_start == datetime(2020, 1, 1)
+    assert dt_slider.value_end == datetime(2020, 1, 5)
+
+    dt_slider.value = None
+    assert dt_slider.value is None
+    assert dt_slider.value_start is None
+    assert dt_slider.value_end is None
+
+
 def test_discrete_slider(document, comm):
     discrete_slider = DiscreteSlider(label='DiscreteSlider', value=1,
                                      options=[0.1, 1, 10, 100])

panel/widgets/slider.py

@@ -718,8 +718,7 @@ class DateRangeSlider(_SliderBase):
     ... )
     """
 
-    value = param.DateRange(default=None, allow_None=False,  # type: ignore[call-overload]
-        doc="""
+    value = param.DateRange(default=None, doc="""
         The selected range as a tuple of values. Updated when one of the handles is
         dragged. Supports datetime.datetime, datetime.date, and np.datetime64 ranges.""")
 
@@ -782,7 +781,10 @@ def __init__(self, **params):
 
     @param.depends('value', watch=True)
     def _sync_values(self):
-        vs, ve = self.value
+        if self.value is None:
+            vs, ve = None, None
+        else:
+            vs, ve = self.value
         with edit_readonly(self):
             self.param.update(value_start=vs, value_end=ve)