coalesce does not work with data output parameter

[davidshay]

Terraform Version

Terraform v0.12.16
+ provider.aws v2.40.0
+ provider.external v1.2.0

Terraform Configuration Files

data "aws_vpc" "vpc" {
  default= true
}

data "aws_subnet_ids" "subnets" {
  vpc_id = data.aws_vpc.vpc.id
}

output "subnet" {
    value = coalesce(data.aws_subnet_ids.subnets.ids ...)
}

Debug Output

Crash Output

Expected Behavior

Outputs:

subnet = subnet-05f4cf7c847430427

Actual Behavior

Error: Invalid expanding argument value

  on test.tf line 18, in output "subnet":
  18:     value = coalesce(data.aws_subnet_ids.vpc_etl_pubsnet1.ids ...)

The expanding argument (indicated by ...) must be of a tuple, list, or set
type.

Steps to Reproduce

1. terraform init
2. terraform apply

Additional Context

It actually works fine from the Terraform console.

References

[hashibot]

Hello! 🤖

This issue seems to be covering the same problem or request as #22404, so we're going to close it just to consolidate the discussion over there. Thanks!

[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.