I am implementing a Terraform provider using the Terraform Plugin Framewok.

I have this resource main_resource, that can be linked to another resource sub_resource. On API side, a sub_resource can only be deleted if it as been unlinked from any resources.

Let’s say we have the current tfstate :

resource "main_resource" "dummy" {
  sub_resource_id = sub_resource.dummy.id 
}

resource "sub_resource" "dummy" {}

And then we try to apply this plan :

resource "main_resource" "dummy" {}

Here is what I would like Terraform to do :

1. Update of main_resource.dummy (where sub_resource.dummy gets unlinked)
2. Delete of sub_resource.dummy

And here is what Terraform does :

1. Delete of sub_resource.dummy (Fails because the sub_resource is still linked to another resource)
2. Update of main_resource.dummy (We never reach this)

How can I make Terraform run this sequence in the wanted order on provider side ?