Partial diff is not done for jsondecode

[orgads]

Terraform Version

Terraform v1.8.0
on windows_amd64
+ provider registry.terraform.io/hashicorp/random v3.6.1

Terraform Configuration Files

resource "random_string" "test" {
  length  = 8 # Change this to 9 and reapply
  special = false
}

resource "terraform_data" "test" {
  triggers_replace = jsondecode(jsonencode({
    constant = "constant"
    random   = random_string.test.result
  }))
}

Debug Output

https://gist.github.com/orgads/bddc77184dd63e8c176e0b5d4ea2bbd6

Expected Behavior

constant should remain unchanged, and only the changed attribute should be displayed as diff:

  # terraform_data.test must be replaced
-/+ resource "terraform_data" "test" {
      ~ id               = "cec378fc-caa3-04a1-2f95-24d7aa08c00a" -> (known after apply)
      ~ triggers_replace = {
          ~ random   = "txsdyUJC" -> (known after apply)
            # (1 unchanged attribute hidden)
        }
    }

Actual Behavior

  # terraform_data.test must be replaced
-/+ resource "terraform_data" "test" {
      ~ id               = "cca8891a-0e87-736c-ad5e-64b2723e16d6" -> (known after apply)
      ~ triggers_replace = {
          - constant = "constant"
          - random   = "txsdyUJC"
        } -> (known after apply) # forces replacement
    }

Steps to Reproduce

1. terraform init
2. terraform apply
3. Change length to 9
4. terraform apply

Additional Context

No response

References

No response

[jbardin]

Hi @orgads,

Thanks for filing the issue. The plan renderer is working as expected here, because you have create a single value which is entirely unknown. Passing the entire map through jsonencode then jsondecode leaves the final value entirely unknown, which is why the whole map is marked with -> (known after apply). The intermediate value after jsonencode is a single unknown string, the jsonedecode function has no way to determine which map values were originally unknown from that string.

We use GitHub issues for tracking bugs and enhancements, rather than for questions. While we can sometimes help with certain simple problems here, it's better to use the community forum where there are more people ready to help.

Thanks!

[orgads]

I thought that was a bug, but given your explanation I realize it is expected. Thanks!

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