dynamic block documentation bug - incorrect or unclear

[pgienger]

It would seem that the documentation around the dynamic blocks is wrong or at least confusing.

My specific case was using a vsphere_virtual_machine but I believe this is the core language doc at fault. There is a referenced bug terraform-provider-aws #8260 where it was stated to be fixed, with the proper format, but the current docs do not match.

In my environment, trying to run this block from the base module:

  extradisks  = [
    {
      name  = "disk10"
      size  = 16
      eager = false
      thin  = true
    }
  ]

which is passed into another module and used within a vm provision as so:

  dynamic "disk" {
    for_each = var.extradisks
    content {
      label            = disk.name
      size             = disk.size
      eagerly_scrub    = disk.eager
      thin_provisioned = disk.thin
      unit_number      = disk.unit_number
    }
  }

Would throw an error like in the referenced bug.

Error: Unsupported attribute

  on ..\..\modules\cent7\cent7.tf line 115, in resource "vsphere_virtual_machine" "tfdeploy":
 115:       thin_provisioned = disk.thin

This object does not have an attribute named "thin".

The way to make it work was this:

  dynamic "disk" {
    for_each = var.extradisks
    content {
      label            = disk.value.name
      size             = disk.value.size
      eagerly_scrub    = disk.value.eager
      thin_provisioned = disk.value.thin
      unit_number      = disk.value.unit_number
    }
  }

The official documentation bit here (https://www.terraform.io/docs/configuration/expressions.html) seems out of date, or at best confusing, as follows. In order to follow the fix as described above, this block in the documentation

resource "aws_security_group" "example" {
  name = "example" # can use expressions here

  dynamic "ingress" {
    for_each = var.service_ports
    content {
      from_port = ingress.value
      to_port   = ingress.value
      protocol  = "tcp"
    }
  }
}

should be something like this, making assumptions about the var.service_ports object:

resource "aws_security_group" "example" {
  name = "example" # can use expressions here

  dynamic "ingress" {
    for_each = var.service_ports
    content {
      from_port = ingress.value.from_port
      to_port   = ingress.value.to_port
      protocol  = "tcp"
    }
  }
}

[apparentlymart]

Hi @pgienger! Thanks for reporting this, and sorry for the long delay in responding.

It seems like in the meantime someone has updated the current documentation with a different example that doesn't have the bug you mentioned here, so I'm going to close this. Thanks again!

[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 have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.