Problem

Fixes #12815

Fields with null values are not submitted when using useForm({ values }) since v7.55.0.

Before:

const { control, handleSubmit } = useForm({ values: { views: null } });

On submit: {} (null value is omitted)

Expected:
On submit: { views: null }

Root Cause:
In src/logic/getDirtyFields.ts, the markFieldsDirty function used !isNullOrUndefined(data[key]) which excluded null values from being marked as dirty, causing them to be omitted during form submission.

Solution

Changed the condition to only exclude undefined values:

} else if (!isUndefined(data[key])) {
  fields[key] = true;
}

This allows null to be treated as a valid field value while still excluding undefined fields.

Testing

Added 8 tests:

• 2 unit tests in src/__tests__/logic/getDirtyFields.test.ts
• 6 integration tests in src/__tests__/useForm/useFormWithNullValues.test.tsx

All 968 tests pass.

Changes

• src/logic/getDirtyFields.ts: Changed condition in markFieldsDirty
• src/__tests__/logic/getDirtyFields.test.ts: Added unit tests
• src/__tests__/useForm/useFormWithNullValues.test.tsx: Added integration tests

Backward compatible, no breaking changes.