isDirty is not reset when defaultValues is filled

Describe the bug When useForm is called without defaultValues, the formState.isDirty works as expected: when a form value is changed, isDirty=true, and when this form value is emptied, isDirty=false. However, if some defaultValues is provided: when a form value is changed, isDirty=true, and when this form value is set back to its initial value, there is still isDirty=true.

Codesandbox link https://codesandbox.io/s/react-hook-form-formstate-dirty-touched-submitted-forked-jnkvl?file=/src/index.js:196-205

1. Set a in the Mobile number field => you will see that isDirty=true and dirtyFields will contain Mobile number
2. Empty the Mobile number field => you will see that isDirty=true and dirtyFields will be empty

It works correctly when no default values are provided: https://codesandbox.io/s/7o2wrp86k6?file=/src/index.js

Expected behavior The isDirty behavior should be consistent whether some defaultValues are provided or not.

[kidroca]

It seems like a bug to me - isDirty is true but dirtyFields is empty {}

[lilyannh]

@bluebill1049 Just piggybacking onto this discussion since my problem is similar.

The deep compare causes false positives in isDirty if the defaultValues object is not “perfect.” In these situations isDirty will be set to true as soon as you change focus on the form, and dirtyFields is still empty.

In my case, I initialize defaultValues with a “row” from the database. For example:

{
  id: 1,
  first_name: "Bart",
  last_name: "Simpson",
  note: null
}

In a form with the fields for First Name, Last Name, and Note, isDirty will be true without changing anything because:

• note was null in defaultValues, but (I think) it gets compared to an empty string from the form
• id exists in defaultValues, but does not exist in the form

I understand the reasoning behind the deep compare, but you can see from the example here that it is also causing some real usability issues.