issue: useFieldArray cut off null values from array and cause broken indexing next entities

[dzwiedziu-nkg]

Version Number

7.52.1

Codesandbox/Expo snack

https://codesandbox.io/s/react-hook-form-usefieldarray-nested-arrays-forked-6jn6cm?file=/src/index.js

Steps to reproduce

I add null values to array in defaultValues. useFieldArray cut off null values from array. So indexing of is invalid. We get only two array elements with broken index.

Its happen because you wrap by compact function in this:

react-hook-form/src/logic/createFormControl.ts

Line 539 in ee7b588

compact(

Expected behaviour

When you change react-hook-form version to 7.12.2 in packages.json this example works good. We get all array elements with correct index.

What browsers are you seeing the problem on?

Chrome

Relevant log output

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[dzwiedziu-nkg]

I agree if it's marked as a duplicate of #12053. The cause of the error is the same. The example is different because I am using complex nested fields instead of an array of strings.

[bluebill1049]

would you like to send a PR with this?

[MathurAditya724]

I can create PR if no one else is working on this

[bluebill1049]

I can create PR if no one else is working on this

Yes, please would be great to attach some tests with it as well.

[bluebill1049]

but why we have null in the default values? field array doesn't support flat array.

Does not support flat field array.

https://react-hook-form.com/docs/usefieldarray

[ErBlack]

field array doesn't support flat array.

Why?