Convert: variables / locals / referenced maps need to use accessor syntax

[DanielMSchmidt]

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cdktf & Language Versions

Affected Resource(s)

Summary

Converting this example leads to an invalid access to the project key in the map, where a Fn.lookup call would have been necessary

variable "default_tags" {
  type        = map(string)
  description = "Map of default tags to apply to resources"
  default = {
    project = "Learning Live with AWS & HashiCorp"
  }
}

resource "aws_eip" "nat" {
  vpc = true
  tags = {
    "Name" = "${var.default_tags.project}-nat-eip"
  }
}

[ansgarm]

While this might not be that much better than Fn.lookup – we might think about exposing the PropertyAccess expression. The good thing about that way, would be that it supports a path, which might be more readable for nested access:

Fn.Lookup(Fn.Lookup(Fn.Lookup(mapRef, "c"), "b"), "a")
// vs.
Todo.propertyAccess(mapRef, ["a", "b", "c"])

(Sidenote: I left out the defaultValue param for lookup for simplicity, as that one is actually still optional but discouraged since TF 0.7; docs)

[ansgarm]

We might even expose this via TF functions 🤔 Maybe Fn.property(mapRef, ["a", "b", "c"]) (like lodash) or some better wording. Another idea would be to do the following:

Fn.lookup(ref, property, defaultValue) // => lookup() TF call
Fn.lookup(ref, property) // => ref[property] TF expression
Fn.lookupNested(ref, [propertyA, propertyB]) // => ref[propertyA][propertyB] TF expression

What do you think? 🤔

[DanielMSchmidt]

I think that's a good idea

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