Documentation

Is the given input valid?

Is the given input once normalized valid?

Are all inputs in a form valid according to their rules?

Are all inputs in a form valid according to their rules, once normalized?

Describe why a form input is invalid, or return the empty string.

Describe why an input, once normalized, is invalid? Or returns empty string.

Implicitly tweak the input to make it more likely to be valid.

Implicitly tweak all of a form's inputs to make them more likely to be valid.