HTML5 required validation for SelectDateWidget doesn't work if the attribute is added by JavaScript

[Vlastimil Zíma]

SelectDateWidget uses 0 as a empty value. When the field uses HTML5 required attribute to make browser check the input, it does not work. Browsers (tested with Firefox 52.5 and Chromium 62) consider selected 0 as filled, thus required check incorrectly passes.

I suggest to use empty string as a value for SelectDateWidget.none_value.

[Israel Saeta Pérez]

Hi Vlastimil!

I've tried to reproduce the issue you mention but it's not possible, since when the form field is required the empty label option is not rendered. From the documentation ​https://docs.djangoproject.com/en/2.0/ref/forms/widgets/#django.forms.SelectDateWidget:

If the DateField is not required, SelectDateWidget will have an empty choice at the top of the list

You can see this in the code as well:
​https://github.com/django/django/blob/47d238b69602711c06c369a5555bb554a4b3f7fb/django/forms/widgets.py#L955-L995

Therefore what you mention can never happen I believe. Can you provide a code sample where you can reproduce the issue? Otherwise I'm in favor of marking this as invalid.

[Vlastimil Zíma]

Hi Israel,

we have a slightly more complicated use case, in which required attribute is added by JavaScript depending on other values in the form. Having 0 as a default value, makes things more complicated for us.

More cases might emerge based on browsers' behavior, which considers 0 as selected.

Also looking around for HTML5 specification, it looks like hiding the empty label for required select is not valid. According to ​https://www.w3.org/TR/html5/sec-forms.html#placeholder-label-option the empty labels must be present for selects with required attributes.

Based on Tims' closure, should I open a new ticket for that?

[Tim Graham]

I guess fixing the use case you mentioned might be feasible. I've attached an initial patch. More changes are required, for example SelectDateWidget.date_re must be adapted. Someone else can continue the work.

As for "hiding the empty label for required select is not valid", I'm not sure what exactly the spec is saying. For example, what's a "placeholder label option"? But yes, that seems like it would be a separate ticket, although it couldn't be addressed until this one is fixed, I think.

[Vlastimil Zíma]

Thanks for reopening. I've split the invalid HTML into a separate #29056.

[Vlastimil Zíma]

PR submitted ​https://github.com/django/django/pull/9632

Instead of changing the date_re, I kept the pseudo-ISO format with zeros for the invalid dates. I consider it easier to debug in case an error should occur.

[Carlton Gibson]

This looks good to me.

I think leaving the date_re using 0 for invalid values makes sense.

[Tim Graham <timograham@…>]

In fbc3c29:

Fixed #29036 -- Fixed HTML5 required validation on SelectDateWidget if the attribute is added by JavaScript.

Thanks Tim Graham for the initial patch.