Add DateRangePicker

[MarcSkovMadsen]

Panel has a DatetimeRangePicker. But not DataRangePicker.

I need it to work with param.CalenderDate parameters.

I cannot use the DatetimeRangePicker because 1) the formatting will always show time (format parameter not supported) and 2) the widget will return datetime tuples. Not date tuples.

import panel as pn
import param
from datetime import date

class Model(param.Parameterized):
    period = param.CalendarDateRange(default=(date(2022,1,1), date(2022,1,3)), bounds=(date(2022,1,1), date(2022,1,5)))

model = Model()

widget = pn.widgets.DatetimeRangePicker.from_param(model.param.period, enable_time=False)

def out(value):
    return str(value)

pn.Column(
    widget, pn.bind(out, model.param.period)
).servable()

When I change the selection I get.

 File "/home/jovyan/repos/private/panel/panel/param.py", line 513, in link_widget
    self.object.param.update(**{p_name: change.new})
  File "/home/jovyan/repos/private/panel/.venv/lib/python3.10/site-packages/param/parameterized.py", line 2282, in update
    restore = self_._update(*args, **kwargs)
  File "/home/jovyan/repos/private/panel/.venv/lib/python3.10/site-packages/param/parameterized.py", line 2315, in _update
    setattr(self_or_cls, k, v)
  File "/home/jovyan/repos/private/panel/.venv/lib/python3.10/site-packages/param/parameterized.py", line 525, in _f
    instance_param.__set__(obj, val)
  File "/home/jovyan/repos/private/panel/.venv/lib/python3.10/site-packages/param/parameterized.py", line 527, in _f
    return f(self, obj, val)
  File "/home/jovyan/repos/private/panel/.venv/lib/python3.10/site-packages/param/parameterized.py", line 1490, in __set__
    self._validate(val)
  File "/home/jovyan/repos/private/panel/.venv/lib/python3.10/site-packages/param/parameters.py", line 1274, in _validate
    self._validate_bounds(val, self.bounds, self.inclusive_bounds, 'bound')
  File "/home/jovyan/repos/private/panel/.venv/lib/python3.10/site-packages/param/parameters.py", line 1330, in _validate_bounds
    too_low = (vmin is not None) and (v < vmin if incmin else v <= vmin)
TypeError: can't compare datetime.datetime to datetime.date

There is an old, open PR to implement this in #2804

[TheoMathurin]

I also need this widget in multiple apps.

Now that it's implemented in bokeh I think there's a pretty straightforward process to include it in Panel but I don't have the details. I'm willing to do it if I have the necessary info.

[TheoMathurin]

In fact it seems like we're waiting for something to be fixed upstream. See #3789 (comment)

[hoxbro]

I don't think DateRangePicker is affected by the problem; only Datetime pickers are.

You should be able to add something like this to Panel by copying DatePicker, and replacing the _widget_type with DateRangePicker. Could be the case that you will need to update the msg in self._process_property_change and _process_param_change.

panel/panel/widgets/input.py

Line 287 in 5d6017f

class DatePicker(Widget):