Form validation is one of those problems we keep solving, and somehow it keeps being annoying.

We mix business rules with UI state, validate things the user hasn't touched yet, and rerun work we already did because one value changed.

But what if the validation framework remembered what happened before?

Vest 6 keeps validation state between runs. Change one field and previous results that are still useful can stay exactly where they are. Change something another field depends on and Vest can tell that the old result may no longer be trustworthy. Start two async validations and it can tell which answer belongs to the current version of the form.

I'll live code a form with Vest 6 and gradually make it more troublesome. Along the way we'll deal with retained validation state, relationships between fields, selective execution and async race conditions.

Basically, time travel.

Unfortunately, only for forms.

Live coding presentation; needs a wearable lavalier or headset mic, not handheld. Talk is new in English; an early version was presented once at a local Hebrew React meetup in Israel.