Terraform syntax warnings do not check data source or output blocks

[gdavison]

The terraform init and terraform validate commands output syntax warnings for deprecated interpolation syntax for resources, but do not return warnings when the deprecated interpolation is on data source or output blocks.

Terraform Version

This error occurs in both 0.12 and 0.13

$ terraform version
Terraform v0.12.29
+ provider.aws v3.1.0

$ terraform version
Terraform v0.13.0
+ provider registry.terraform.io/hashicorp/aws v3.1.0

Terraform Configuration Files

variable "api_gateway_name" {
  type = string
}

data "aws_api_gateway_rest_api" "selected" {
  name = "${var.api_gateway_name}"
}

data "aws_cognito_user_pools" "selected" {
  name = "selected"
}

resource "aws_api_gateway_authorizer" "cognito" {
  name          = "cognito"
  type          = "COGNITO_USER_POOLS"
  rest_api_id   = "${data.aws_api_gateway_rest_api.selected.id}"
  provider_arns = data.aws_cognito_user_pools.selected.arns
}

output "api_id" {
  value = "${aws_api_gateway_authorizer.cognito.rest_api_id}"
}

Expected Behavior

The warning

Warning: Interpolation-only expressions are deprecated

should be generated for

• data source aws_api_gateway_rest_api.selected name
• resource aws_api_gateway_authorizer.cognito rest_api_id
• output api_id value

Actual Behavior

The warning

Warning: Interpolation-only expressions are deprecated

is only generated for

• resource aws_api_gateway_authorizer.cognito rest_api_id

Steps to Reproduce

1. terraform init
2. (Optionally) terraform validate

[alisdair]

Thanks for reporting this! Quoting a previous response from Martin to a related issue (#25430):

Technically this is working as intended -- it was intentionally only implemented for these two blocks so far -- but it feels weird to mark a deprecation warning as an "enhancement" so I'm going to label this as a bug in the configuration package and we can decide what to do about it at a later time. We generally add new deprecation warnings only later in a major release cycle so folks don't have to change lots of unrelated stuff as part of upgrading to a major release, and 0.13.0 is due in a few weeks so we'll need to wait a little while before potentially adding more deprecation warnings of this type.

There's a pending PR to fix the other issue (#25465), which I think we could reasonably extend to also add these deprecations to data sources and objects.

[gdavison]

Thanks, @alisdair! We've been using the syntax warnings (imported by tflint) to clean up the AWS Provider documentation and prevent old syntax from getting back in from PRs.

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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