Client side validation classes for forms

[karthikabinav]

Having client side javascript validation for forms having common fields like username having only alphanumerics or password and Confirm password fields matching by providing a validation class.

For example a user should be able to do something like :

forms.TextField(validators ="usernameValidation")

And automatically a javascript validation for this form field should be in place.

One way to do it could be using HTML5 attributes like ticket #16304.

[karthikabinav]

Supply accepted characters as a regular expression in CharField forms. Uses HTML5 attribute 'pattern' to provide the client side validation.

[Łukasz Rekucki]

Per discussion on django-developers, I think we can accept this on principal (not the patch itself, as it doesn't have tests or docs). IMHO, best approach would be to use HTML5 features + provide some simple JavaScript fallback for not widely supported features.

[Marcelo Galigniana]

​PR was created.

[Marcelo Galigniana]

The HTML5 pattern attribute does a re.fullmatch behind the scenes and our RegexValidator does a re.search instead.

Should I create a new Validator?

Thanks!

[Carlton Gibson]

Hi Marcelo. Thanks for the input on this old-one. Mariusz and I have been discussing it intermittently… hence the slow follow-up.

In conclusion, I just can't see that the functionality here justifies the additional passthrough kwarg on the CharField.
We can already specify pattern via the widget attributes, and a validator if desired.
I'd much rather we used that API, than add an extra code path for the same here.
In a project subclassing CharField to wrap your own options is likely.

As such I'm going to close this as wontfix. In the 10 years since this was opened things have progressed — as you said on the PR, we don't need the fallback — I think it was that which may have justified the ticket, but I don't think ever in that time there's been a stable enough JS option that we'd have wanted to include... — hence it sitting here I guess.

Even if we're not merging your fix, getting it to a conclusion is a good step forwards, so thanks! 🎁

I hope that makes sense. C.

[Marcelo Galigniana]

Of course Carlton, totally makes sense! I'm happy to see another old one closed!

Thanks you for the detailed answer!

🤗