Be able to set null for date input

[locopati]

Describe the bug
I want to clear the date that was set on a field

Steps to reproduce the behavior

1. Create a type with a date field that is not required
2. Create an instance of the type with a value in the date field and save it
3. Edit the instance and clear the date field
4. It cannot be cleared
5. Make a GraphQL request to clear the field
6. The request errors

Expected behavior
You can clear the field in the UI
The GraphQL mutation works

Code snippets

mutation UnsetDate($id: ID!) {
  updateYourType(input:{
    where:{
      id: $id
    },
    data: {
      date_field: null
    }
  }) {
    your_type { 
      id
      date_field
    }
  }
}

This returns "message": "Expected type Date, found \"\"; Date cannot represent an invalid date-string ."

System

• Node.js version: 13.7
• Yarn version: 1.22
• Strapi version: 3b19.5
• Database: Mongo 4.2.5
• Operating system: Arch Linux 4.19-97

Additional context
Add any other context about the problem here.

[derrickmehaffy]

Node.js version: 13.7

You are on an unsupported node version, please test on node 12/10.

[lauriejim]

Thank you @locopati for reporting this issue.
This is due to the format validation. Can you please investigate it and submit a PR to allow null
Thank you.

[richardgrey]

I think this works now, so the issue could be closed. At least I was not able to reproduce it.

[lauriejim]

This error still exist with MongDB.

[weidox]

Just encountered same issue, don't know if that's DB related though we're using MongoDB. Trying to unset date field via admin UI, finding no way.

[luisjuniorj]

This error still exist with PostgreSQL.