code: func resourceVSphereDatastoreClusterVMAntiAffinityRuleValidateRuleVMCount(d *schema.ResourceData) error {
  	if d.Get("virtual_machine_ids").(*schema.Set).Len() < 2 {
  		return errors.New("length of virtual_machine_ids must be 2 or more")
  	}
  	return nil
  }
docs: // resourceVSphereDatastoreClusterVMAntiAffinityRuleValidateRuleVMCount ensures
  // that the VM count in the anti-affinity rule at any point in time before it's
  // created or updated is a length of at least 2.
  //
  // This validation is necessary as a rule of only 1 VM here is a no-op and
  // ultimately will result in a broken resource (the rule will not exist after
  // creation, or example). Unfortunately, this needs to happen at apply time
  // right now due to issues with TF core and how it processes lists when values
  // are computed. Once these issues are fixed with TF core, the validation here
  // should be removed and moved to schema.