How to assign default values to map(object()) input in Terraform?

Question

When defining a complex input variable:

variable "s3_shares" {
  type = map(object({
    s3_bucket_arn         = string
    client_list           = list(string)
    read_only             = bool
    default_storage_class = string
  }))
}

How can one deal with read_only and default_storage_class being mutually exclusive? In other words, when using the module and defining an s3_share with read_only = true the default_storage_class could be omitted.

Will · Accepted Answer · 2022-06-06 08:36:09Z

3

Using validation{} block and alltrue() function :

variable "s3_shares" {
  type = map(object({
    s3_bucket_arn         = string
    client_list           = list(string)
    read_only             = bool
    default_storage_class = string
  }))
default = {
  "one" = {
    s3_bucket_arn         = "foo"
    client_list           = ["foo","bar"]
    read_only             = false
    default_storage_class = "bar" # IS OK
}
  "two" = {
    s3_bucket_arn         = "foo"
    client_list           = ["foo","bar"]
    read_only             = false
    default_storage_class = "" # IS OK
}}
  "three" = {
    s3_bucket_arn         = "foo"
    client_list           = ["foo","bar"]
    read_only             = true
    default_storage_class = "" # IS OK
}}
  "four" = {
    s3_bucket_arn         = "foo"
    client_list           = ["foo","bar"]
    read_only             = true
    default_storage_class = "bar" # IS KO
}}

validation {
  condition = alltrue([
     for o in var.s3_shares : !(o.read_only && length(o.default_storage_class) > 0)])
     error_message = "Read_only and default_storage_class are exclusive."     
   }
}

Mind the use case "two" where read_only is set to false and default_storage_class is empty : this will return true. This might not be the behavior you are looking for.

edited Jun 6, 2022 at 8:36

answered Jun 6, 2022 at 7:48

Will

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4 Comments

Martin Schulze Over a year ago

Thank you! I wasn't aware of the validation block before. Could this though also be used with the map wrapped around the object?

Will Over a year ago

No worries. I think that would still works, but I struggle to understand why you need a map there. Would you mind explaining me the usecase ?

Martin Schulze Over a year ago

Of course, I don't mind, :) I'm deploying the AWS Storage Gateway and one gateway will have multiple file shares. The object describes the individual share, and the map brings all shares together that belong to the gateway. I will give the solution a try and mark it working later :)

Will Over a year ago

I've updated my answer. It works like a charm on my side ;)

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