Graph not resolving correctly using modules

[jjshoe]

I've bumped into a situation where the graph doesn't seem to depend on a module correctly. I've boiled it down to a simple test case:

The main terraform file:

variable "aws_region" {}
variable "aws_access_key" {}
variable "aws_secret_key" {}

provider "aws" {
    access_key = "${var.aws_access_key}"
    secret_key = "${var.aws_secret_key}"
    region = "${var.aws_region}"
}

resource "aws_vpc" "env_vpc" {
    cidr_block = "10.1.0.0/16"

    tags {
        Name = "test-vpc"
    }
}

resource "aws_subnet" "env_subnet" {
    vpc_id = "${aws_vpc.env_vpc.id}"
    cidr_block = "10.2.0.0/20"
    availability_zone = "us-east-1a"
    map_public_ip_on_launch = true

    tags {
        Name = "test-subnet"
    }
}

module "accounts" {
    source = "../modules/test_app"

    service_subnets = "${join(",", aws_subnet.env_subnet.*.id)}"
}

The module:

variable "service_subnets" {}

output "test" {
    value = "${var.service_subnets}"
}

Expected:
A list of subnets made

Received:

• Resource 'aws_subnet.env_subnet' does not have attribute 'id' for variable 'aws_subnet.env_subnet.*.id'

Graph:

[jjshoe]

Workaround:

variable "aws_region" {}
variable "aws_access_key" {}
variable "aws_secret_key" {}

provider "aws" {
    access_key = "${var.aws_access_key}"
    secret_key = "${var.aws_secret_key}"
    region = "${var.aws_region}"
}

resource "aws_vpc" "env_vpc" {
    cidr_block = "10.1.0.0/16"

    tags {
        Name = "test-vpc"
    }
}

resource "aws_subnet" "env_subnet" {
    vpc_id = "${aws_vpc.env_vpc.id}"
    cidr_block = "10.2.0.0/20"
    availability_zone = "us-east-1a"
    map_public_ip_on_launch = true

    tags {
        Name = "test-subnet"
    }
}

resource "template_file" "workaround" {
    filename = "./terraform/templates/workaround.tpl"

    vars {
        subnets = "${join(",", aws_subnet.env_subnet.*.id)}"
    }
}

module "accounts" {
    source = "../modules/test_app"

    service_subnets = "${template_file.workaround.vars.subnets}"
}

[ghost]

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