data source aws_route_tables returns list of strings

[yongzhang]

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Terraform CLI and Terraform AWS Provider Version

Terraform version: v1.1.7
AWS Provider version: 4.3.0

Affected Resource(s)

• data source: aws_route_tables

Terraform Configuration Files

Please include all Terraform configurations required to reproduce the bug. Bug reports without a functional reproduction may be closed without investigation.

data "aws_route_tables" "non_main" {
  vpc_id = data.aws_vpc.current.id

  filter {
    name   = "association.main"
    values = ["false"]
  }
}

resource "aws_route" "routes_to_devops" {
  for_each = var.environment != "devops" ? data.aws_route_tables.non_main.ids : []

  route_table_id         = each.value
  destination_cidr_block = var.vpc_cidr["devops"]
  transit_gateway_id     = data.aws_ec2_transit_gateway.parent.id

  depends_on = [aws_ec2_transit_gateway_route.route_to_vpc]
}

Debug Output

No.

Panic Output

Expected Behavior

Actual Behavior

Steps to Reproduce

1. terraform apply

│ Error: Invalid for_each argument
│
│   on vpc.tf line 38, in resource "aws_route" "routes_to_devops":
│   38:   for_each = var.environment != "devops" ? data.aws_route_tables.non_main.ids : []
│     ├────────────────
│     │ data.aws_route_tables.non_main.ids is list of string with 6 elements
│     │ var.environment is "dev"
│
│ The given "for_each" argument value is unsuitable: the "for_each" argument must be a map, or set of strings, and you have provided a value of type list of string.

[mattburgess]

As the error suggests, you need to provide a set, not a list to for_each. You can use the toset() function to do this as per https://www.terraform.io/language/functions/toset.

[yongzhang]

As the error suggests, you need to provide a set, not a list to for_each. You can use the toset() function to do this as per https://www.terraform.io/language/functions/toset.

yes we could do this, but if we look into the docs, data.aws_route_tables.non_main.ids should return the set not list of strings, and I can confirm it works very well in version 3.74.x.

[justinretzolk]

Hey @yongzhang 👋 The incorrect documentation was caught be another community member, and a PR has been merged to change set in the documentation to list (#23474). The documentation will be updated as soon as the next release goes out (a process that has actually already started at time of writing!).

Given that information, we'll close this one for now. If you feel we've done this in error, please do let us know.

[yongzhang]

@justinretzolk I checked into the source code here: https://github.com/hashicorp/terraform-provider-aws/blob/v3.74.3/internal/service/ec2/route_tables_data_source.go#L29, in v3.74.x, it was TypeSet, so is it by intention to fallback to TypeList in v4.x?

[justinretzolk]

Hey @yongzhang -- that's correct, this was an intentional change from TypeSet to TypeList that happened during the v4 upgrade. The CHANGELOG mentions for 4.0.0 mentioned this here:

data-source/aws_route_tables: The type of the ids attribute has changed from Set to List. If no route tables match the specified criteria an empty list is returned (previously an error was raised) (#21219)

[yongzhang]

Hey @yongzhang -- that's correct, this was an intentional change from TypeSet to TypeList that happened during the v4 upgrade. The CHANGELOG mentions for 4.0.0 mentioned this here:

data-source/aws_route_tables: The type of the ids attribute has changed from Set to List. If no route tables match the specified criteria an empty list is returned (previously an error was raised) (#21219)

ahh, didn't notice this one, thanks

[github-actions]

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