Improve isEmpty check of validateField function

[rvetere]

TLDR;

By increasing the priority of inputValue in the isEmpty check, we can have working validation with fields that only update the state (but not the DOM). PR

Background

First of all, this project is absolutely amazing! It's simply the best form library i ever worked with!

I've debugged the validateField method a lot now and I think the line "isEmpty" could be improved.

We are implementing a multi-select field with downshift.js and there we are creating custom onChange events that are correctly updating the internal form state of react-hook-form - everything great so far.

The problem is, we don't have a native select element in the DOM, representing a correct value in a classic way.

This makes react-hook-form think the field is empty.

In that case, we have a value that is an array, and - as you can see, the field would have a valid value indeed - but still, react-hook-form thinks its empty.

This is because the "ref" is not having a value in plain HTML:

But, the last part where it checks that the value also could be an Array, is not failing:

This forces us to do a very ugly workaround in our implementation:

This "hack" is fixing the is-empty-check, but nobody in our company is going to understand why our MultiSelectDropdown must have this value on the "ToggleButton" ^^

It is just to suppress the ref-check.

I've created a PR that would (hopefully) improve this check: #11179

[bluebill1049]

Thanks very much for the PR! what's your validateField function looks like? or are you refer to the required prop?

[rvetere]

Hi @bluebill1049 - i have created a codesandbox to show our case with downshift.js ;-) https://codesandbox.io/s/sharp-brahmagupta-4s8h6x?file=/src/index.js

In this sandbox, it creates the exact same state as we have it -> the form state is updated correctly, but the referenced DOM element has no value attribute:

[bluebill1049]

thanks @rvetere will check it later. I think for custom-required checks, validate function is ideal for such, but I will verify the use case.

[bluebill1049]

parking in the todo column for now.

[rvetere]

Sorry i was in vacation the past 4 weeks - my colleagues have rewritten our "custom field implementation" in the meantime and we are not facing this issue anymore :)

[bluebill1049]

kk good to hear ad thanks for let us know. 🙏