Data sources don't return more than one TypeSet's

[kayrus]

Terraform Version

0.11.11

Affected Resource(s)

• aws_instance data source
• aws_launch_configuration data source

Terraform Configuration Files

data "aws_ami" "ubuntu" {
  most_recent = true

  filter {
    name   = "name"
    values = ["ubuntu/images/hvm-ssd/ubuntu-trusty-14.04-amd64-server-*"]
  }

  filter {
    name   = "virtualization-type"
    values = ["hvm"]
  }

  owners = ["099720109477"] # Canonical
}

resource "aws_instance" "test" {
  ami           = "${data.aws_ami.ubuntu.id}"
  instance_type = "t2.micro"

  tags = {
    Name = "kshcherban-test"
  }

  ebs_block_device {
     device_name = "/dev/sdf"
     volume_size = 10
   }
   ebs_block_device {
     device_name = "/dev/sdg"
     volume_size = 20
     volume_type = "gp2"
   }
}

data "aws_instance" "test" {
  instance_id = "${aws_instance.test.id}"
}

output "instance" {
  value = "${aws_instance.test.ebs_block_device}"
}

output "data" {
  value = "${data.aws_instance.test.ebs_block_device}"
}

Debug Output

Outputs:

data = [
    {
        delete_on_termination = 1,
        device_name = /dev/sdg,
        encrypted = 0,
        iops = 100,
        snapshot_id = ,
        volume_id = vol-014032926148b41b2,
        volume_size = 20,
        volume_type = gp2
    }
]

instance = [
    {
        delete_on_termination = 1,
        device_name = /dev/sdf,
        encrypted = 0,
        iops = 0,
        snapshot_id = ,
        volume_id = vol-061fe03c49cda6742,
        volume_size = 10,
        volume_type = standard
    },
    {
        delete_on_termination = 1,
        device_name = /dev/sdg,
        encrypted = 0,
        iops = 100,
        snapshot_id = ,
        volume_id = vol-014032926148b41b2,
        volume_size = 20,
        volume_type = gp2
    }
]

Expected Behavior

data source should return the same amount of block devices

Actual Behavior

data source returns only one device of two

Important Factoids

Test are written incorrectly:

• https://github.com/terraform-providers/terraform-provider-aws/blob/3f3977866dc3c682fbf8bb584d5263849e00135f/aws/data_source_aws_launch_configuration_test.go#L27 - ebs_block_device.# must be 2
• https://github.com/terraform-providers/terraform-provider-aws/blob/3f3977866dc3c682fbf8bb584d5263849e00135f/aws/data_source_aws_instance_test.go#L101 - data source should be checked, not the resource.

There are only two cases found. I assume there are more, and this pattern should be revised for other data sources or resources.

[kayrus]

I took a closer look into this issue and figured out that the Set function is not required, when you specify Optional: true for all subattributes in data sources and resources.

Here is the terraform code, responsible for this behavior: https://github.com/hashicorp/terraform/blob/ac4fff416318bf0915a0ab80e062a99ef3724334/helper/schema/serialize.go#L103

[ryndaniels]

Hi @kayrus - thanks for opening this bug report, and huge thanks for the work you did to discover the issue with the Set function! That link you found was the key to figuring out how to fix this! 👍 We've submitted a fix to the Terraform SDK here that will resolve this issue. As you also correctly noted, the tests for this data source do need some fixing as well, so I'm going to be working on getting that out the door here shortly. So this issue should be resolved soon and thanks again for your Set function sleuthing! 🙂

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!