Conversion of map to object

[aniketpant1]

Terraform Version

Terraform v1.10.1

Affected Pages

https://developer.hashicorp.com/terraform/language/expressions/type-constraints#conversion-of-complex-types

What is the docs issue?

Mentioning in the documentation map -> object map conversions can be lossy.

Proposal

It is a confusing as i haven't find any example on the internet and on the documentation where map to object conversion can be failed or lossy. Even though we should have a object function where it can convert map to object. If we have simple example on this . It would be easier for the users also.

References

No response

[crw]

Thanks for this request.

[aniketpant1]

May i know the dates ? Or anyone who can help me by giving example in this thread

[liamcervante]

Hi @aniketpant1, here's a potential example of a lossy conversion from map to object.

# ./main.tf

variable "map" {
    type = map(string)
    default = {
        a = "a"
        b = "b"
        c = "c"
    }
}

module "mod" {
    source = "./module"

    object = var.map
}

output "map" {
    value = var.map
}

output "object" {
    value = module.mod.object
}

# ./module/main.tf

variable "object" {
  type = object({
    a = string
    b = string
  })
}

output "object" {
  value = var.object
}

If you execute the above Terraform files, you can see from the outputs that the c value from the map has been automatically stripped from the returned object. This is the conversion being lossy - as values from the map have been silently removed in order to make the type match the type required by the object variable.

map = tomap({
  "a" = "a"
  "b" = "b"
  "c" = "c"
})
object = {
  "a" = "a"
  "b" = "b"
}

Hope this helps!

[aniketpant1]

Thank You @liamcervante .