Diffs didn't match during apply: ignore_changes + referencing resources

[Fodoj]

Given: two instances, second references first one inside metadata.

Rough example, but you will get the idea:

resource "openstack_compute_instance_v2" "box-1" {
  name = "box-1"
  availability_zone = "${var.availability_zone}"
  image_id = "${var.image_id}"
  flavor_name = "m1.medium"
  key_pair = "${var.key_pair}"
  network {
    uuid = "${var.network_id}"
    fixed_ip_v4 = "192.168.0.21"
  }
  lifecycle {
    ignore_changes = ["user_data", "image_id"]
  }
}

resource "openstack_compute_instance_v2" "box-2" {
  name = "box-2-${count.index}"
  availability_zone = "${var.availability_zone}"
  image_id = "${var.image_id}"
  flavor_name = "m1.medium"
  key_pair = "${var.key_pair}"
  network {
    uuid = "${var.network_id}"
  }
  metadata {
    box_1_ip = "${openstack_compute_instance_v2.box-1.access_ip_v4}"
    random_var = "blah"
  }
  count = 2
  lifecycle {
    ignore_changes = ["user_data", "image_id"]
  }
}

1. Create with terraform apply
2. Change image_id
3. Terraform plan

~ openstack_compute_instance_v2.box-2.0
    metadata.box_1_ip :            "192.168.0.21" => ""
    metadata.random_var :            "blah" => ""

Wait, what, why? Nothing was supposed to be changed, metadata is the same and metadata didnt change inside Openstack.

Okay, anyways:

1. Terraform apply again

Error applying plan:

2 error(s) occurred:

* openstack_compute_instance_v2.box-2.0: diffs didn't match during apply. This is a bug with Terraform and should be reported as a GitHub Issue.

Please include the following information in your report:

    Terraform Version: 0.7.0
    Resource ID: openstack_compute_instance_v2.amadeus-ns-slave.0
    Mismatch reason: diff: Destroy; old: false, new: true

# Lots of lines, showing that "plan" promised to nullify metadata and then during apply it didnt happen and blah blah errors everywhere

Now we are doomed. because seems like ignore_changes doesnt work!

[jtopjian]

@Fodoj One reason that the metadata would change is because changing the image_id causes ForceNew to trigger. Though the values of the metadata are the same, new resources are being created on both sides.

[Fodoj]

@jtopjian which should not happen at all (I mean, no new resources should be created), because ignore_changes ignores changes to image_id

[jtopjian]

Yup, that's a good point. Sounds like it's more of a core issue, I think?

[Fodoj]

It is definitely a core issue

[mitchellh]

This is fixed in the latest release (0.7.8).

[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.

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