Interpolating nested Removed fields silently fails

[rileykarson]

Terraform Version

Terraform 0.11.11

`google` provider `2.1.0`, `2.2.0`

Terraform Configuration Files

resource "google_compute_instance" "default" {
  name         = "test2"
  machine_type = "n1-standard-2"
  zone         = "us-central1-b"

  boot_disk {
    initialize_params {
      image = "debian-cloud/debian-9"
    }
  }

  network_interface {
    network = "default"

    access_config {
      // Ephemeral IP
    }
  }
  service_account {
    scopes = ["userinfo-email", "compute-ro", "storage-ro"]
  }
}

output "should_fail" {
  value = "${google_compute_instance.default.network_interface.0.address}"
}

Expected Behavior

google_compute_instance.default: Refreshing state... (ID: test2)

Error: Error running plan: 1 error(s) occurred:

* output.should_fail: Resource 'google_compute_instance.default' does not have attribute 'network_interface.0.address' for variable 'google_compute_instance.default.network_interface.0.address'

Actual Behavior

google_compute_instance.default: Refreshing state... (ID: test2)

Apply complete! Resources: 0 added, 0 changed, 0 destroyed.

Outputs:

should_fail =

Steps to Reproduce

terraform apply

[apparentlymart]

Thanks for reporting this, @rileykarson.

This one is a little tricky right now because the idea of "Removed" only exists in the SDK today: Terraform Core just sees these as normal attributes that happen to have a validation rule that returns an error if they are set.

To fix this properly we'll probably need to extend the schema model returned to Terraform Core to allow core itself to handle the "removed" concept. Probably we'd want to represent it at the provider protocol and core level as an entirely-separate list of names that are removed -- not part of the main schema -- and then that would allow core to produce specialized errors for uses of them without considering those names to be part of the object type derived from the schema as we do today.

I've labelled this with both "core" and "provider-sdk" because it kinda sits on the cusp between the two and will require changes on both sides.

[paultyng]

We are planning to drop support for Removed in v2, so this issue will no longer be relevant I believe.

See #320 for tracking the removal.

[ghost]

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