"Error in function call" when using neither private subnets nor NAT #944
Description
Description
TF errors out when trying to create a VPC with database subnets but no private subnets and no NAT gateways:
Call to function "coalescelist" failed: no non-null arguments.
It seems that the aws_route_table.private isn't created in this case (per count condition), but it is apparently meant to be referenced in aws_route_table_association.database.
- ✋ I have searched the open/closed issues and my issue is not listed.
Versions
-
Module version [Required]: 5.0.0
-
Terraform version: 1.4.6
-
Provider version(s): 5.0.1
Reproduction Code [Required]
module "vpc" {
source = "github.com/terraform-aws-modules/terraform-aws-vpc?ref=v5.0.0"
name = "foo"
cidr = "10.0.0.0/16"
azs = ["eu-central-1a", "eu-central-1b"]
enable_dns_hostnames = true
enable_dns_support = true
enable_nat_gateway = false
enable_ipv6 = false
public_subnets = [ "10.0.0.0/24", "10.0.1.0/24" ]
database_subnets = [ "10.0.10.0/24", "10.0.11.0/24" ]
#private_subnets = [ "10.0.20.0/24", "10.0.21.0/24" ]
}
Expected behavior
No error.
Actual behavior
Error in function call (see below).
Terminal Output Screenshot(s)
│ Error: Error in function call
│
│ on .terraform/modules/vpc/main.tf line 410, in resource "aws_route_table_association" "database":
│ 410: coalescelist(aws_route_table.database[*].id, aws_route_table.private[*].id),
│ ├────────────────
│ │ while calling coalescelist(vals...)
│ │ aws_route_table.database is empty tuple
│ │ aws_route_table.private is empty tuple
│
│ Call to function "coalescelist" failed: no non-null arguments.
Additional context
This configuration worked fine with old version v3.2.0.
When patching the module's main.tf like this ...
# There are as many routing tables as the number of NAT gateways
resource "aws_route_table" "private" {
- count = local.create_private_subnets && local.max_subnet_length > 0 ? local.nat_gateway_count : 0
+ count = local.create_private_subnets || local.max_subnet_length > 0 ? local.nat_gateway_count : 0
... it works correctly. I would submit a PR, but I don't understand the logic / intention well enough to be certain that this is a proper fix for all valid configuration options.