Inconsistent handling of (start, end, value) in DatetimeRangeSlider and DatetimeRangePicker widget

[rhambach]

ALL software version info

Software Version Info

panel  1.4.5
param 2.1.1

Description of expected behavior and the observed behavior

• DatetimeRangePicker should allow changing start and end without raising out-of-bound exception
• value of DatetimeRange* widgets is always between start and end parameter or an Exception is raised
• same behavior of DatetimeRangeSlider and DatetimeRangePicker widget on this issue

Complete, minimal, self-contained example code that reproduces the issue

import panel as pn
import datetime as dt
dtmin = dt.datetime(1000, 1, 1)
dtlow = dt.datetime(2000, 1, 1)
dtmax = dt.datetime(3000, 1, 1)

# increasing (start, end) and set value=(start, end) SHOULD WORK !
sel_dtrange = pn.widgets.DatetimeRangeSlider(start=dtmin, end=dtlow, value=(dtmin, dtlow))
sel_dtrange.param.update(start=dtmin, end=dtmax, value=(dtmin, dtmax))  # OK

sel_dtrange = pn.widgets.DatetimeRangePicker(start=dtmin, end=dtlow, value=(dtmin, dtlow))
sel_dtrange.param.update(start=dtmin, end=dtmax, value=(dtmin, dtmax))  # ERROR
sel_dtrange.param.update(start=dtmin, end=dtmax)  # increasing (start, end) without setting value works

Stack traceback and/or browser JavaScript console output

---> [12] sel_dtrange.param.update(start=dtmin, end=dtmax, value=(dtmin, dtmax))  # ERROR

ValueError: DateRange parameter 'DatetimeRangePicker.value' upper bound must be in range [1000-01-01 00:00:00, 2000-01-01 00:00:00], not 3000-01-01 00:00:00.

Additional Info

On the contrary, the DatetimeRangeSlider does not raise an exception although value is out of bounds, which might also not be expected by the user.

import panel as pn
import datetime as dt
dtmin = dt.datetime(1000, 1, 1)
dtlow = dt.datetime(2000, 1, 1)
dtmax = dt.datetime(3000, 1, 1)

# reducing (start, end) without correcting out-of-range value SHOULD FAIL !
sel_dtrange = pn.widgets.DatetimeRangeSlider(start=dtmin, end=dtmax, value=(dtmin, dtmax))
sel_dtrange.param.update(start=dtmin, end=dtlow)   # ERROR as value is out of bounds and should raise


sel_dtrange = pn.widgets.DatetimeRangePicker(start=dtmin, end=dtmax, value=(dtmin, dtmax))
#sel_dtrange.param.update(start=dtmin, end=dtlow)   # OK, fails as value is out of bounds
sel_dtrange.param.update(start=dtmin, end=dtlow, value=(dtmin, dtlow))  # OK, setting value to reduced bounds works