Running an empty destroy with an interpolated output in module fails

[Denis Vishniakov]

Seems like another scenario when TF fail to run destroy. Reproducible on empty setup even without creating resources.
Since it's reproducible without provider credentials, is it possible to add tests?
#17768 fixed code but didn't add any tests

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Note: this block was copy-pasted from terraform-provider-aws

Terraform Version

Affected: 
0.11.4, 0.11.5
0.11.6, 0.11.7 (output differs a little bit from 0.11.4, 0.11.5)

Terraform Configuration Files

main.tf

provider "aws" {
  region  = "us-east-1"
  version = "~> 1.14"
}
terraform {
  required_version = ">= 0.11.0"
}
module "cluster" {
  source = "./cluster"
}
output "main_cluster_output" {
  value = "${module.cluster.cluster_output}" # produces an error
}
output "main_app_output" {
  value = "${module.cluster.app_output}"
}

# The same, below - works

resource "aws_ecs_cluster" "default_cluster" {
  name = "cluster_name"
}
output "cluster_output" {
  value = {
    "cluster_id"   = "${aws_ecs_cluster.default_cluster.id}"
    "cluster_name" = "${aws_ecs_cluster.default_cluster.name}"
  }
}

cluster/cluster-main.tf

resource "aws_ecs_cluster" "default_cluster" {
  name = "cluster_name"
}
resource "aws_ecr_repository" "default_ecr" {
  name = "test-bug"
}
output "cluster_output" {
  value = {
    "cluster_id" = "${aws_ecs_cluster.default_cluster.id}"

    # "repository_url" = "${aws_ecr_repository.default_ecr.repository_url}" # if you uncomment this line, error from it hides default_cluster errors
    "cluster_name" = "${aws_ecs_cluster.default_cluster.name}"
  }
}
output "app_output" {
  value = {
    "repository_url" = "${aws_ecr_repository.default_ecr.repository_url}"
  }
}

Debug Output

https://gist.github.com/dvishniakov/58ab1fef3126665d85c63f13803b3b05

Expected Behavior

No error output, successful output, exit with code 0

Actual Behavior

Error: Error applying plan:

TF 0.11.4, 0.11.5,

3 error(s) occurred:

• module.cluster.output.cluster_output: variable "default_cluster" is nil, but no error was reported
• output.cluster_output: variable "default_cluster" is nil, but no error was reported
• module.cluster.output.app_output: variable "default_ecr" is nil, but no error was reported

TF 0.11.6, 0.11.7

2 error(s) occurred:

• module.cluster.output.cluster_output: variable "default_cluster" is nil, but no error was reported
• module.cluster.output.app_output: variable "default_ecr" is nil, but no error was reported

Steps to Reproduce

1. terraform init
2. terraform plan -input=false --destroy -out=terraform.plan
3. terraform apply -input=false terraform.plan

References

#17691, probably partially fixed by @jbardin in #17768

[Denis Vishniakov]

@apparentlymart FYI

[Alex Emelyanov]

Have the same issue on v0.11.5:

resource "aws_subnet" "mysubnet" {
  vpc_id     = "${var.vpc_id}"
  cidr_block = "10.43.${var.cidr_range}.0/24"

  tags = {
    Name = "${var.tag}"
  }
}

output "subnet_id" {
  value = "${aws_subnet.mysubnet.id}"
}

Error occurs during destroy If apply was failed.
Does anyone have a workaround, I tried this:

output "subnet_id" {
  value = "${aws_subnet.mysubnet ? aws_subnet.mysubnet.id : ""}"
}

but it doesn't work with Error reading config for output subnet_id: aws_subnet.mysubnet: resource variables must be three parts: TYPE.NAME.ATTR in

[Alex Emelyanov]

Cool, after couple of hours I found the workaround:

Inspired by #16681 (comment)

We don't need several aws_subnet objects, but we can interpret it as an array with one element!

So it works:

resource "aws_subnet" "mysubnet" {
  count      = 1
  vpc_id     = "${var.vpc_id}"
  cidr_block = "10.43.${var.cidr_range}.0/24"

  tags = {
    Name = "${var.tag}"
  }
}

output "subnet_id" {
  value = "${element(concat(aws_instance.mysubnet.*.public_ip, list("")), 0)}"
}

Don't forget to fix references to this resources in another places in my case from "${aws_subnet. mysubnet.id}" to "${aws_subnet.mysubnet.0.id}"

[Jason Antman]

I'm seeing this as well on 0.11.7 with:

* provider.archive: version = "~> 1.0"
* provider.aws: version = "~> 1.28"
* provider.consul: version = "~> 2.1"
* provider.datadog: version = "~> 1.0"
* provider.null: version = "~> 1.0"
* provider.template: version = "~> 1.0"

In my case the initial destroy failed after actually deleting everything; I'm left with an empty state file but every destroy fails with these errors for interpolated outputs:

* module.bento-githook-proxy.output.hook_url: Resource 'aws_api_gateway_rest_api.rest_api' does not have attribute 'id' for variable 'aws_api_gateway_rest_api.rest_api.id'
* module.bento_iam_role.output.ip_arn: variable "bento" is nil, but no error was reported
* module.bento_iam_role.output.arn: variable "bento" is nil, but no error was reported

[Denis Vishniakov]

@jantman have you tried TF_WARN_OUTPUT_ERRORS=1 terraform destroy?

[Hamish Durkin]

+1 for fixing this issue. If a single issue occurs during our delete process our environment is left in a half destroyed yet undestroyable state. The TF_WARN_OUTPUT_ERRORS=1 fix works, but I feel it is a hack masking the underlying problem

[sulabhk]

The TF_WARN_OUTPUT_ERRORS variable does not see to work with 0.11.8 on Linux 64 bit Please refer this link as well https://github.com/hashicorp/terraform/pull/17768#issuecomment-417281234

[Dee Kryvenko]

I just found another use case related to that:

provider "random" {
  version = "= 2.0.0"
}

resource "random_id" "test_suffix" {
  byte_length = 2
}

module "some_awesome_module" {
  source = "../.."

  foo = "bar-${random_id.test_suffix.hex}"
}

I'm getting:

       * module.some_awesome_module.var.foo: variable "test_suffix" is nil, but no error was reported

TF_WARN_OUTPUT_ERRORS obviously not going to make any difference as in this case it has nothing to do with the output. Same applies to random_string. It is reproducible on both 0.11.8 and 0.11.3.

The issue was there for a while preventing implementing integration testing with kitchen-terraform and inspec, even for some basic stuff such as simple use case using random provider. cc @ncs-alane - maybe there some workaround can be done on the kitchen side?

[Aaron Lane]

Hey @llibicpep,

If you would like to open an issue against Kitchen-Terraform, we may be able to identity a workflow or configuration to avoid your particular problem.

[Dee Kryvenko]

Created newcontext-oss/kitchen-terraform#271

[hpuc]

We have the same problem with Terraform v0.11.8 on Linux 64bit. The output looks a little bit different:

• module.compute.output.service_endpoint: Resource 'aws_lb.ext-alb' does not have attribute 'dns_name' for variable 'aws_lb.ext-alb.dns_name'
• module.compute.output.bastion_host_public_ip: Resource 'aws_instance.bastion_host' does not have attribute 'public_ip' for variable 'aws_instance.bastion_host.public_ip'

With TF_WARN_OUTPUT_ERRORS=1, the problem disappears but it should not happen in the first place IMHO.

[Vlad Dinulescu]

Hello,

Any updates on this bug? It's quite a problem to not be able to destroy resources

[Miguel Bernadin]

This is still a problem with variables:

$ TF_WARN_OUTPUT_ERRORS=1 terraform destroy --auto-approve

Error: Error applying plan:

1 error(s) occurred:

* module.dcos.local.cluster_name: local.cluster_name: variable "id" is nil, but no error was reported

[Marques Johansson]

@bernadinm I overcame a very similar sounding problem in 0.11 using this approach:

locals {
  result = {
    command = ""
  }
  kubeadm_join_results = "${concat(data.external.kubeadm_join.*.result, list(local.result))}"
  kubeadm_join_command = "${lookup(local.kubeadm_join_results["0"], "command", "")}"
}

 output "kubeadm_join_command" {
  depends_on = ["null_resource.masters_provisioner"]
  value = "${local.kubeadm_join_command}"
 }

Full description here: https://groups.google.com/d/msg/terraform-tool/y9H4rAVOcLA/G5iftvErBwAJ

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[Deleted user]

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