DurationField with default='1 00:00' triggers validation on otherwise empty inline formsets

[Michael Angeletti]

When I reported #24391 I should have had the sense to check DurationField, but I didn't. Note, this isn't caused by a callable default argument, rather a string.

My initial thought is that this has something to do with the conversion process of a given string value into a timedelta, etc., but I haven't had a chance to really dig in, yet. I just barely finished work and I have to run a bunch of errands, or I'd dive straight into the code. However, I wanted to at least get the bug report in here right away.

[Michael Angeletti]

I've set the severity to release blocker, since this is essentially the same regression (thought via different means) as #24391. I've looked through the code a bit and can't find anything obvious that could be causing this issue. I'm going to look some more tomorrow night.

[Claude Paroz]

In fact, you'll find the exact same behavior with current date-based fields. If you provide an initial or default value, you should provide a date/datetime Python value, not a string representation. By analogy, you should provide a timedelta value for your DurationField default value.

We *could* change that, other opinions welcome.

[Tim Graham]

I don't see a need to complicate things by allowing differing types for defaults. Maybe there's an opportunity to use the checks framework to validate defaults are the proper type, but I'll leave that for a new ticket if someone wants to try implementing it.

[Michael Angeletti]

@claudep @timgraham timedelta is obviously the right thing to use here, and I'm not sure what in the world I was thinking when I used a string. I think it was because I was getting so used to typing the string value into the admin, and just totally spaced it. I'm sorry for wasting a ticket and your time before simply taking 30 seconds to RTFM @ ​https://docs.djangoproject.com/en/1.8/ref/models/fields/#durationfield