# Rock and a Hard Place: lookup()

**URL:** <https://discuss.hashicorp.com/t/rock-and-a-hard-place-lookup/15703>\
**Category:** Terraform\
**Created:** [October 14, 2020, 6:57pm UTC](https://discuss.hashicorp.com/t/rock-and-a-hard-place-lookup/15703 "2020-10-14T18:57:26Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![grimm26](https://sea2.discourse-cdn.com/hashicorp/user_avatar/discuss.hashicorp.com/grimm26/32/1623_2.png) [@grimm26](https://discuss.hashicorp.com/u/grimm26)\
**Post date:** [October 14, 2020, 6:57pm UTC](https://discuss.hashicorp.com/t/rock-and-a-hard-place-lookup/15703/1 "2020-10-14T18:57:26Z")

</div>

```
Error: Incorrect attribute value type

  on .terraform/modules/scry_integration/main.tf line 27, in resource "aws_apigatewayv2_route" "r":
  27: authorization_scopes = lookup(each.value, "authorization_scopes", null)
    |----------------
    | each.value is map of string with 1 element

Inappropriate value for attribute "authorization_scopes": set of string
required.

```

OK fine, I’ll make the default an empty list.

```
Error: Invalid function argument

  on .terraform/modules/scry_integration/main.tf line 27, in resource "aws_apigatewayv2_route" "r":
  27: authorization_scopes = lookup(each.value, "authorization_scopes", [])

Invalid value for "default" parameter: the default value must have the same
type as the map elements.

```

Noooo!!! So, what contortions do I have to do to make this work?

---

<div class="post-metadata">

**Author:** ![apparentlymart](https://sea2.discourse-cdn.com/hashicorp/user_avatar/discuss.hashicorp.com/apparentlymart/32/702_2.png) [@apparentlymart](https://discuss.hashicorp.com/u/apparentlymart)\
**Post date:** [October 14, 2020, 10:22pm UTC](https://discuss.hashicorp.com/t/rock-and-a-hard-place-lookup/15703/2 "2020-10-14T22:22:33Z")

</div>

Hi @grimm26,

I’m not sure that the first error is caused by the type of that second argument, because the error seems to be talking about `authorization_scopes`'s own type constraint. Specifically, the error message says that `each.value` is a map of string and therefore `each.value["authorization_scopes"]` would be a string, and that doesn’t meet the “set of string” type constraint.

I’m not sure what to suggest without seeing more context, but if you can make that expression produce something that can convert automatically to a set of string, such as a single-element list, I think `null` should then work just fine as a fallback.

---

<div class="post-metadata">

**Author:** ![grimm26](https://sea2.discourse-cdn.com/hashicorp/user_avatar/discuss.hashicorp.com/grimm26/32/1623_2.png) [@grimm26](https://discuss.hashicorp.com/u/grimm26)\
**Post date:** [October 14, 2020, 11:21pm UTC](https://discuss.hashicorp.com/t/rock-and-a-hard-place-lookup/15703/3 "2020-10-14T23:21:55Z")

</div>

so, each.key is a map. It has no key for `authorization_scopes` because I am testing defaults. The first error is indeed because `aws_apigatewayv2_route.authorization_scopes` expects a list of strings and I gave it a `null`. But when I set the default value for the lookup to return an empty list, then lookup complains. For that plan, each.key is a map that has only one key and its value is a string, so I assume that that’s what is making lookup think that all values of that map need to be strings.

That led me to have to define the variable feeding the for\_each of that resource to be  
type = list(  
object(  
{  
authorization\_scopes = list(string)  
authorization\_type = string  
authorizer\_id = string  
route\_key = string  
}  
)  
)

Which means that the consumer always has to fill out all of the null or empty values because it is not possible to define an object type with optional pieces.