json: cannot unmarshal object into Go value of type string // Show Inputs and Outputs of External Data Command

[hashibot]

This issue was originally opened by @Miserlou as hashicorp/terraform#13991. It was migrated here as part of the provider split. The original body of the issue is below.

---

Terraform Version

Terraform v0.9.3

Affected Resource(s)

• data.external

Terraform Configuration Files

data "external" "template" {
  program =  ["zappa", "template",  "-r", "'${aws_iam_role.iam_for_my_lambda.arn}'", "-l", "'${aws_lambda_function.my_lambda.arn}'", "--json"]
  depends_on = ["aws_lambda_function.my_lambda"]
}

Debug Output

* data.external.template: data.external.template: command "zappa" produced invalid JSON: json: cannot unmarshal object into Go value of type string

Expected Behavior

The error shows the command which was executed and the output of that command.

Actual Behavior

I receive no useful information about the arguments of the executed command, or the output which failed to be parsed to JSON.

I don't now if this is a "Terraform-can't-parse-valid-JSON" bug, or a "My-program-pooped-the-bed" bug, because the output has no useful information in it, which makes it a "Terraform should be more helpful here in the UX department" bug.

Steps to Reproduce

0. Create a complex command.
1. terraform apply

Important Factoids

Running the command manually in my terminal produces valid JSON.