Terraform: command "Powershell.exe" produced invalid JSON: unexpected end of JSON input

Question

I am trying to use Terraform's external provider to run a PowerShell script.

I am not able to pass parameters to the script from Terraform.

I am using the following code to run the script:

variable "file_path" {
  type        = "string"
  description = "Enter the powershell file path"
  default     = "../../Services/azurerm_iam_role/Powershell_Scripts/test.ps1"
}

data "external" "powershell_test" {
  program = ["Powershell.exe", "${var.file_path}"]

  query = {
    foo = "asdf"
    bar = "Hardcoded"
  }
}

The following is my PowerShell script file code:

# Read stdin as string
$jsonpayload = [Console]::In.ReadLine()

# Convert to JSON
$json = ConvertFrom-Json $jsonpayload

# Access JSON values
$foo = $json.foo
$bar = $json.bar

while executing terraform apply I got the following error:

command "Powershell.exe" produced invalid JSON: unexpected end of JSON input

Is there a fix or alternate solution?

Peter Mortensen · Accepted Answer · 2018-11-05 20:15:53Z

2

A data source needs to output something which you don't currently appear to be doing. The external data source in particular needs JSON output on stdout which could then be accessed under the result attribute of the data source.

So to continue your example PowerShell script you might want something like this (untested):

# Read stdin as string
$jsonpayload = [Console]::In.ReadLine()

# Convert to JSON
$json = ConvertFrom-Json $jsonpayload

# Access JSON values
$foo = $json.foo
$bar = $json.bar

# Set foobar based on foo and bar
$foobar = "$foo$bar"

# Return foo and foobar
@{
    foobar=$foobar;
    foo=$foo;
} | ConvertTo-Json

edited Nov 5, 2018 at 20:15

Peter Mortensen

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answered Nov 5, 2018 at 7:02

ydaetskcoR

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5 Comments

Clijsters Over a year ago

I would definitely use ConvertTo-Json instead of just writing a String to the Ouptut. It could get malformed, depending on the variables content.

ydaetskcoR Over a year ago

@Clijsters I know basically nothing about Powershell, having avoided Windows for the last 5 years as much as possible. I had planned on using CovertTo-Json in the answer but had no way to test it and the online IDE at tio.run/# was giving me issues. If you can suggest an edit that makes the answer better than I'd be grateful.

Kailash P Over a year ago

@ydaetskcoR i have tried ur solution and i am getting the following error Error: Error refreshing state: 1 error(s) occurred: * data.external.powershell_test: 1 error(s) occurred: * data.external.powershell_test: data.external.powershell_test: command "Powershell.exe" produced invalid JSON: invalid character ',' looking for beginning of value

Clijsters Over a year ago

@ydaetskcoR PowerShell (core) is vailable on mostly any human-interactable operating system I can think of. U might want to give it a try ;) Neverthless your answer addresses the problem and is totally valid. I'll give it a small edit.

Clijsters Over a year ago

@KailashP: Please try the edited example. Some quote marks weren't escaped.

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