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fix: Change count for for_each on ram_principal_association due resource recreation #95

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fix: Change count for for_each on ram_principal_association due resource recreation #95

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f4660da
fix: change count for for_each into ram_principal_association resourc…
Dec 23, 2022
ea24b35
fix: create a local value in order to avoid failure on for_each by co…
Feb 12, 2023
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7 changes: 5 additions & 2 deletions main.tf
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Original file line number Diff line number Diff line change
@@ -1,4 +1,7 @@
locals {
# Store the list of principals and convert to set
ram_principals = var.create_tgw && var.share_tgw ? toset(var.ram_principals) : []
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simply moving this logic to a local does not correct its flaws

again, lets look at the conditional where its generally of the format conditional ? true case : false case

  • When the conditional is true, the type is of toset()
  • When the conditional is false, the type is of list since its just empty brackets

This is an issue because the types are now mis-matched (toset() vs list).

In addition, because you are using toset() on a list, any of the values in that list cannot be computed or else you will face the well known issue of not being able to use for_each on a value that is not yet known.

Lastly, changing from count to for_each is a breaking change

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I guess what @bryantbiggs is trying to say is since the left side of the conditional is a set you need the right one to be set too, i.e. toset([]) instead of [] which is of type list.

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simply moving this logic to a local does not correct its flaws

again, lets look at the conditional where its generally of the format conditional ? true case : false case

  • When the conditional is true, the type is of toset()
  • When the conditional is false, the type is of list since its just empty brackets

This is an issue because the types are now mis-matched (toset() vs list).

In addition, because you are using toset() on a list, any of the values in that list cannot be computed or else you will face the well known issue of not being able to use for_each on a value that is not yet known.

Lastly, changing from count to for_each is a breaking change

Sorry, Bryan!

I thought you were asking to use tolist() function insted toset() 😅

There was a misunderstanding on my part and now I got it!

Indeed, for_each cannot predict these values (when computed) while using toset() function , neather iterate over a list.

I agree with u, it’s a breaking change and maybe it’s better keep this code as is, right?

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I guess what @bryantbiggs is trying to say is since the left side of the conditional is a set you need the right one to be set too, i.e. toset([]) instead of [] which is of type list.

Exactly, Igor! Thanks 🙇

However, even solving this part (making the sides equal) we will face that for_each known issue mentioned by Bryan... 😢

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I was take a looking on main.tf again and currently it uses count on length(var.ram_principals) here:

terraform-aws-transit-gateway/main.tf

Line 165 in f4db667

count = var.create_tgw && var.share_tgw ? length(var.ram_principals) : 0

How count will know the length of the list for computed values? In this case we wil face the same problem (unknown value), right?


# List of maps with key and route values
vpc_attachments_with_routes = chunklist(flatten([
for k, v in var.vpc_attachments : setproduct([{ key = k }], v.tgw_routes) if var.create_tgw && can(v.tgw_routes)
Expand Down Expand Up @@ -161,9 +164,9 @@ resource "aws_ram_resource_association" "this" {
}

resource "aws_ram_principal_association" "this" {
count = var.create_tgw && var.share_tgw ? length(var.ram_principals) : 0
for_each = local.ram_principals

principal = var.ram_principals[count.index]
principal = each.value
resource_share_arn = aws_ram_resource_share.this[0].arn
}

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2 changes: 1 addition & 1 deletion outputs.tf
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Expand Up @@ -96,5 +96,5 @@ output "ram_resource_share_id" {

output "ram_principal_association_id" {
description = "The Amazon Resource Name (ARN) of the Resource Share and the principal, separated by a comma"
value = try(aws_ram_principal_association.this[0].id, "")
value = [for k, v in aws_ram_principal_association.this : v.id]
}