output_changes incorrectly calculated in the plan file

[marcinwyszynski]

Terraform Version

❯ terraform version
Terraform v0.12.24

Terraform Configuration Files

provider "random" {}

resource "random_id" "bacon" {
  keepers     = { bacon = "tasty" }
  byte_length = 16
}

output "bacon" { value = random_id.bacon.hex }

Steps to reproduce

After the change has been applied:

❯ terraform plan -out repro.plan
Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.

random_id.bacon: Refreshing state... [id=eprljZv58YrewNlMCchkQA]

------------------------------------------------------------------------

No changes. Infrastructure is up-to-date.

This means that Terraform did not detect any differences between your
configuration and real physical resources that exist. As a result, no
actions need to be performed.

❯ terraform plan -out repro.plan
Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.

random_id.bacon: Refreshing state... [id=eprljZv58YrewNlMCchkQA]

------------------------------------------------------------------------

No changes. Infrastructure is up-to-date.

This means that Terraform did not detect any differences between your
configuration and real physical resources that exist. As a result, no
actions need to be performed.

❯ terraform show -json repro.plan > repro.json
❯ cat repro.json | jq

{
  "format_version": "0.1",
  "terraform_version": "0.12.24",
  "planned_values": {
    "outputs": {
      "bacon": {
        "sensitive": false,
        "value": "7a9ae58d9bf9f18adec0d94c09c86440"
      }
    },
    "root_module": {
      "resources": [
        {
          "address": "random_id.bacon",
          "mode": "managed",
          "type": "random_id",
          "name": "bacon",
          "provider_name": "random",
          "schema_version": 0,
          "values": {
            "b64": "eprljZv58YrewNlMCchkQA",
            "b64_std": "eprljZv58YrewNlMCchkQA==",
            "b64_url": "eprljZv58YrewNlMCchkQA",
            "byte_length": 16,
            "dec": "162970085093216590396273492464954270784",
            "hex": "7a9ae58d9bf9f18adec0d94c09c86440",
            "id": "eprljZv58YrewNlMCchkQA",
            "keepers": { "bacon": "tasty" },
            "prefix": null
          }
        }
      ]
    }
  },
  "resource_changes": [
    {
      "address": "random_id.bacon",
      "mode": "managed",
      "type": "random_id",
      "name": "bacon",
      "provider_name": "random",
      "change": {
        "actions": ["no-op"],
        "before": {
          "b64": "eprljZv58YrewNlMCchkQA",
          "b64_std": "eprljZv58YrewNlMCchkQA==",
          "b64_url": "eprljZv58YrewNlMCchkQA",
          "byte_length": 16,
          "dec": "162970085093216590396273492464954270784",
          "hex": "7a9ae58d9bf9f18adec0d94c09c86440",
          "id": "eprljZv58YrewNlMCchkQA",
          "keepers": { "bacon": "tasty" },
          "prefix": null
        },
        "after": {
          "b64": "eprljZv58YrewNlMCchkQA",
          "b64_std": "eprljZv58YrewNlMCchkQA==",
          "b64_url": "eprljZv58YrewNlMCchkQA",
          "byte_length": 16,
          "dec": "162970085093216590396273492464954270784",
          "hex": "7a9ae58d9bf9f18adec0d94c09c86440",
          "id": "eprljZv58YrewNlMCchkQA",
          "keepers": { "bacon": "tasty" },
          "prefix": null
        },
        "after_unknown": {}
      }
    }
  ],
  "output_changes": {
    "bacon": {
      "actions": ["create"],
      "before": null,
      "after": "7a9ae58d9bf9f18adec0d94c09c86440",
      "after_unknown": false
    }
  },
  "prior_state": {
    "format_version": "0.1",
    "terraform_version": "0.12.24",
    "values": {
      "outputs": {
        "bacon": {
          "sensitive": false,
          "value": "7a9ae58d9bf9f18adec0d94c09c86440"
        }
      },
      "root_module": {
        "resources": [
          {
            "address": "random_id.bacon",
            "mode": "managed",
            "type": "random_id",
            "name": "bacon",
            "provider_name": "random",
            "schema_version": 0,
            "values": {
              "b64": "eprljZv58YrewNlMCchkQA",
              "b64_std": "eprljZv58YrewNlMCchkQA==",
              "b64_url": "eprljZv58YrewNlMCchkQA",
              "byte_length": 16,
              "dec": "162970085093216590396273492464954270784",
              "hex": "7a9ae58d9bf9f18adec0d94c09c86440",
              "id": "eprljZv58YrewNlMCchkQA",
              "keepers": { "bacon": "tasty" },
              "prefix": null
            }
          }
        ]
      }
    }
  },
  "configuration": {
    "provider_config": { "random": { "name": "random" } },
    "root_module": {
      "outputs": {
        "bacon": { "expression": { "references": ["random_id.bacon"] } }
      },
      "resources": [
        {
          "address": "random_id.bacon",
          "mode": "managed",
          "type": "random_id",
          "name": "bacon",
          "provider_config_key": "random",
          "expressions": {
            "byte_length": { "constant_value": 16 },
            "keepers": { "constant_value": { "bacon": "tasty" } }
          },
          "schema_version": 0
        }
      ]
    }
  }
}

Expected Behavior

The resulting JSON should set the value at $.output_changes.bacon.before to "7a9ae58d9bf9f18adec0d94c09c86440"
The resulting JSON should set the value at $.output_changes.bacon.actions to ["no-op"]

Actual Behavior

The resulting JSON sets the value at $.output_changes.bacon.before to null
The resulting JSON incorrectly sets the value at $.output_changes.bacon.actions to ["create"]

[danieldreier]

Thanks for reporting this! If I'm reading this right, it looks like you're reporting an issue specific to the random provider rather than one with terraform core. I've labeled it, and it will get moved over to that provider's source repository by HashiBot shortly.

Please feel free to re-open this if I'm misunderstanding this and it is in fact a core issue.

[ghost]

This issue has been automatically migrated to hashicorp/terraform-provider-random#110 because it looks like an issue with that provider. If you believe this is not an issue with the provider, please reply to hashicorp/terraform-provider-random#110.

[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.

[kmoe]

I believe this is a known Core issue, not an issue with the random provider. For all output_changes, no matter the provider, actions is always ["create"], no matter the value of the output in the state file.

It is documented that "In the Terraform CLI 0.12.0 release, Terraform is not yet fully able to track changes to output values, so the actions indicated may not be fully accurate, but the "after" value will always be correct."

[skorfmann]

I believe this is a known Core issue, not an issue with the random provider. For all output_changes, no matter the provider, actions is always ["create"], no matter the value of the output in the state file.

Yes, I just reproduced this in https://github.com/hashicorp/terraform-cdk

[pselle]

@skorfmann I made a reproduction of this here, and wasn't able to reproduce on master https://github.com/danieldreier/terraform-issue-reproductions/tree/master/24628 nor on the v0.14 branch. Could you help with a reproduction?

[kmoe]

I've tested https://github.com/danieldreier/terraform-issue-reproductions/tree/master/24628 with 0.12.29, 0.13.6, and 0.14.4. The former two versions show:

{
  "bacon": {
    "actions": [
      "create"
    ],
    "before": null,
    "after": "3eaf3393733ab75d0a1b567728508d62",
    "after_unknown": false
  }
}

and 0.14.4 shows:

{
  "bacon": {
    "actions": [
      "no-op"
    ],
    "before": "11f6a28096acfe941a034ed6460b1d02",
    "after": "11f6a28096acfe941a034ed6460b1d02",
    "after_unknown": false
  }
}

I therefore believe this bug was fixed somewhere between 0.13.6 and 0.14.4.

I'd still like someone from Core to comment on the documentation: "In the Terraform CLI 0.12.0 release, Terraform is not yet fully able to track changes to output values, so the actions indicated may not be fully accurate, but the "after" value will always be correct." Is this still true?

[crw]

I am going to close this issue due to age. Also, as @kmoe has subsequently joined the Core team, if the question still needed an answer presumably it can now be found. :)