Attribute with nested Set is marked as changed even if values was not touched

[oliver-schoenherr]

SDK version

latest Plugin SDK version in master

Relevant SDK source code

resource_data.go takes not in consideration that the special case of comparing Set can happen not only on the first level but even deeper in the resource attribute tree.

func (d *ResourceData) HasChange(key string) bool {
	o, n := d.GetChange(key)
        
        // If the type implements the Equal interface, then call that
	// instead of just doing a reflect.DeepEqual. An example where this is
	// needed is *Set
	if eq, ok := o.(Equal); ok {
		return !eq.Equal(n)
	}

	return !reflect.DeepEqual(o, n)
}

Terraform Configuration Files

AWS ECS Service resource use such kind of schema:

resource "aws_ecs_service" "default" {
  ....
  network_configuration {
    security_groups = [
    aws_security_group.default.id]
    subnets          = var.subnet_ids
    assign_public_ip = false
  }
}

Expected Behavior

If network_configuration has no change, Terraform should not try to update the AWS ECS service.

Actual Behavior

Terraform tries to update the AWS ECS service always, even without any change in the network_configuration.

Steps to Reproduce

PR which enhance the resource_data_test.go test cases to reproduce the behaviour: https://github.com/oliver-schoenherr/terraform-plugin-sdk/pull/1/files

References

hashicorp/terraform-provider-aws#14711
hashicorp/terraform-provider-aws#13658

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