Add option to produce duration_string without days

[Claude Paroz]

I have a form with a custom field (inheriting from Django's DurationField) allowing to input duration in the form "hh:mm".

However, when user inputs durations > "23:59", re-displaying those durations is kind of broken ("1 ..."). Customizing prepare_value is rather straightforward, however I'd like to avoid rewriting the whole django.utils.duration.duration_string. If that function would accept a use_days argument, it would be a lot easier to achieve my use case.

[Mariusz Felisiak]

Thanks for this ticket, however duration_string is a private undocumented API and I don't think that adding a new option is justified here. You can also re-use _get_duration_components to simplify your implementation, e.g.:

def custom_duration_string(duration):
    days, hours, minutes, seconds, microseconds = _get_duration_components(duration)
    if days:
        hours += days * 24
    string = '{:02d}:{:02d}:{:02d}'.format(hours, minutes, seconds)
    if microseconds:
        string += '.{:06d}'.format(microseconds)
    return string

[Claude Paroz]

OK, thanks for the code proposal.

[Claude Paroz]

For my use case, I think the shorter would be:

    def prepare_value(self, value):
        if isinstance(value, datetime.timedelta):
            seconds = value.days * 24 * 3600 + value.seconds
            hours = seconds // 3600
            minutes = seconds % 3600 // 60
            value = '{:02d}:{:02d}'.format(hours, minutes)
        return value