Terraform tuple to map with removing empty objects?

Question

I'm trying to create local variable for for_each loop in other resource, but can't make a local map as expected.

The following is what I tried. (Terraform 0.12)

Expected map to loop

temple_list = { "test2-role" = "test-test2-role", ... }

main.tf

locals {
  tmpl_list = flatten([ 
    for role in keys(var.roles) : {
      for tmpl_vars in values(var.roles[role].tmpl_vars) : 
        role => "test-${role}" if tmpl_vars == "SECRET"
    }
  ])
}

output "tmpl_list" {
  value = local.tmpl_list
}

variable "roles" {
    type = map(object({
        tmpl_vars = map(string)
        tags = map(string)
    }))
    
    default = {
        "test-role" = {
            tmpl_vars = {test = "y"}
            tags = { test = "xxx"}
        }
            "test2-role" = {
            tmpl_vars = { token = "SECRET" }
            tags = {}
        }
        "test3-role" = {
            tmpl_vars = {test = "x"}
            tags = {}
        }
    }
}

Error comes from merge

    | var.roles is map of object with 3 elements

Call to function "merge" failed: arguments must be maps or objects, got
"tuple".

Without merge

locals {
  tmpl_list = flatten([ 
    for role in keys(var.roles) : {
      for tmpl_vars in values(var.roles[role].tmpl_vars) : 
        role => "test-${role}" if tmpl_vars == "SECRET"
    }
  ])
}

output "tmpl_list" {
  value = local.tmpl_list
}

variable "roles" {
    type = map(object({
        tmpl_vars = map(string)
        tags = map(string)
    }))
    
    default = {
        "test-role" = {
            tmpl_vars = {test = "y"}
            tags = { test = "xxx"}
        }
            "test2-role" = {
            tmpl_vars = { token = "SECRET" }
            tags = {}
        }
        "test3-role" = {
            tmpl_vars = {test = "x"}
            tags = {}
        }
    }
}

Result of no merge

tmpl_list = [
  {},
  {
    "test2-role" = "test-test2-role"
  },
  {},
]

I tried other functions like tomap(), but it seems not working for me. (Also I'm not sure why empty ones are created.)

How can I convert this tuple to a map without empty ones?

rkm · Accepted Answer · 2020-09-03 18:33:42Z

7

You can do it in two steps:

Convert it to the filtered list of objects:

locals {  
  result = flatten([
    for role, role_value in var.roles: [
      for tmpl_vars in role_value.tmpl_vars: {
        key = role
        value = "test-${role}"
      } if tmpl_vars == "SECRET"
    ]
  ])
}

local.result would have following value:

[
  {
    "key" = "test2-role"
    "value" = "test-test2-role"
  },
]

Then it's easy to convert it into the map with for:

my_map = { for item in local.result: item.key => item.value }

which gives:

{
  "test2-role" = "test-test2-role"
}

answered Sep 3, 2020 at 18:33

rkm

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