Bucket custom placement config values not normalised causing replacement on every apply

[VenelinMartinov]

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Terraform Version & Provider Version(s)

Terraform v1.8.2
on darwin_arm64

• provider registry.terraform.io/hashicorp/google-beta v5.28.0

Affected Resource(s)

google_storage_bucket

Terraform Configuration

provider "google" {
  region = "us-central1"
}

terraform {
  required_providers {
    google = {
      source  = "hashicorp/google-beta"
      version = "5.28.0"
    }
  }
}

resource "google_storage_bucket" "example" {
  name          = "example-dual-region-bucket-au"
  location      = "AU"
  custom_placement_config {
    data_locations = [ "australia-southeast1", "australia-southeast2" ]
  }
}

Debug Output

https://gist.github.com/VenelinMartinov/9ac1801364ef4e5c494b377e708dd714

Expected Behavior

The bucket gets replaced each time.

Note that upper-casing the locations fixes this - seems like they need to be normalised before diffing.

Actual Behavior

Should not get replaced

Steps to reproduce

1. terraform apply
2. terraform plan

Important Factoids

No response

References

No response

b/340346616

[ggtisc]

Confirmed issue:

As user reports after bucket creation when it exists with the provided code and configuration, when a terraform plan is executed it recognizes as a change to destroy and then create replacement but if the locations of the attribute data_locations is set in uppercase [ "AUSTRALIA-SOUTHEAST1", "AUSTRALIA-SOUTHEAST2" ] instead of lowercase [ "australia-southeast1", "australia-southeast2" ] it returns a message saying: No changes. Your infrastructure matches the configuration

[kautikdk]

It appears that the StatFunc inside the TypeSet elements won't work because of this known issue:hashicorp/terraform-plugin-sdk#160. That may be the reason why there is no StatFunc for custom_placement_config because it is TypeSet and It won't work.
location field is having StatFunc https://github.com/GoogleCloudPlatform/magic-modules/blob/main/mmv1/third_party/terraform/services/storage/resource_storage_bucket.go.erb#L124 and it is working as expected because it is not nested attribute.
I don't see any clear solution to this issue and maybe the only thing that can be done here is to clearly specify and document that Input values should be in the uppercase.