Wrong TS typing of input.value when using parseValue/formatValue that convert types

Are you submitting a bug report or a feature request?

A bug report I think

What is the current behavior?

So if I make a simple field that stores values of type A and uses some input that accepts values of type B, I get a weird type mismatch. For example, I have a field of type Date that uses a simple html select as input (please see a sandbox link below). I add parseValue that gets string from select and returns Date to store, and I add formatValue which does the opposite. In this case I would expect the input.value of FieldRenderProps to be a string but typescript infers its type as Date (in fact it’s a string). So I see a TS error.

What is the expected behavior?

I would expect the input.value of FieldRenderProps to be a string.

Sandbox Link

https://codesandbox.io/s/strongly-typed-form-values-with-react-final-form-forked-nfmmq?file=/src/index.tsx

What’s your environment?

react-final-form: 6.3.5 final-form: 4.20.1 typescript: 4.3.2

Other information

Maybe I’m doing something wrong. Would appreciate if anyone could help me to figure the things out.

[erikras]

Published fix in v6.5.4.

[mmoo]

@callmeberzerker I think that UX considerations stand apart from the issue I described. Yes, your example makes sense but I’ve had a couple of real life form fields that could win from such type conversion without harming the UX. For example I use a custom DatePicker component that accepts and returns Dates but I need to submit date-only formatted strings to server. And I prefer submitting form state unchanged without running it through some pre-submit converter. This is the case where type conversion through parse/format could help.

@mrfratello wow thanks! Your PR really fixes the thing for me 😍 Too bad it is unlikely to be merged. The repo looks abandoned.