Prepopulate modeladmin forms datetime fields using querystrings

[aleray]

Hi,

I wanted to prepopulate admin form datetime fields using querystrings like this:

http://localhost:8000/admin/app/model/add/?start=2013-06-01T20:00:00

But django wasn't really happy with me trying to pass a unicode object where it was expecting a datetime object:

AttributeError at /admin/app/model/add/
'unicode' object has no attribute 'date'

I came to editing contrib/admin/options.py, adding a special case for datetimefield. Attached is a very simple patch, let me know what you think...

Thanks,

Alex

[Florian Apolloner]

Makes sense to me since we have explicit support for M2M field too, so why not DatetimeFields. Using dateutil is not an option though since we don't want a hard dependency there.

[pyriku]

Implementation without using dateutil and using DATETIME_INPUT_FORMATS submitted on this pull request: ​https://github.com/django/django/pull/589

[Preston Holmes]

I'd make the comment that because the querystring is presumably being generated by some code, and not a locale-based human form, that we simplify this by just using a standardized ISO format.

But a broader and stickier question is how and where would you document this? This is adding API, and I would argue adding partial API probably to the wrong place.

We have a rich system for the POST side of things when something is submitted, where you can provide your own ModelForm and all its associated validation.

We have a special case for M2M on the GET/form-creation side because of #7738, but that doesn't mean we should have a public way of handling ModelForm initial data from a querystring generally, should we support all field types?

The current, not super friendly, way of handling this would be to preprocess the initial values inside your ModelForm's init - perhaps using the formfield's widget's _format_value method, which is what ModelForms do for POST values.

I'm just not sure this kind of value prep work belongs in ModelAdmin.add_view

[pyriku]

Just updated the pull request using ISO format instead: ​https://github.com/django/django/pull/589

I can see your point ptone, but I think that adding those extra checks into the current logic (inside ModelAdmin.add_view) makes sense, even if we move the entire chunk of logic for prepopulate fields somewhere else eventually. Also, as I said on the PR, I'm not really sure where to add the documentation for this.

[Tim Graham]

Duplicate of #9739