Validate on field registration

[andyrichardson]

🚀 Feature request

Current Behavior

The following events do not cause validation to occur:

• Adding a field (useField first call i.e. registerField)
• Change to field level validation (useField validate argument change)
• Removal of a field (useField remove call i.e. unregisterField)

Desired Behavior

The following would occur on addition/change:

• Trigger changed/added field-level validation
• Update formik-wide valid state

The following would occur on removal:

• Update formik-wide valid state

Suggested Solution

Add an effect to the useField hook to trigger a validation call when triggered/removed

OR

Add validateForm call to register/unregister field functions.

Who does this impact? Who is this for?

• Anyone using field level validation

Describe alternatives you've considered

Proxying useField hook to do this manually - currently having to use this solution.

export const makeUseField = <S extends Record<string, any>>() => <
  K extends keyof S & string = Exclude<keyof S, number | symbol>
>(
  { name, validate }: UseFieldArgs<K>
) => {
  const { validateForm, isValid } = useFormikContext<any>();

  const formikUseFieldArgs = useMemo(
    () => ({ name, validate }),
    [validate],
  );

  useEffect(() => {
    validateForm();
    return () => validateForm();
  }, [validate, validateForm]);

  return useField(formikUseFieldArgs) as [FieldInputProps<S[K]>, FieldMetaProps<S[K]>];
};

[jaredpalmer]

Seems legit.