Arguments not parsed when running Python script from before_hook

[kstevensonnv]

Describe the bug

When I run a Python script from before_hook and use the argparse library arguments are not parsed.

Steps To Reproduce

.
├── deployment
│   └── terragrunt.hcl
└── modules
    └── some-module
        ├── main.tf
        └── my_script.py

deployment/terragrunt.hcl:

terraform {
  source = "../modules//some-module"

  before_hook "python_script" {
    commands     = ["plan", "apply"]
    execute      = [
      "./my_script.py",
      "--arg1 argument1",
      "--arg2 argument2",
      "--arg3 argument3"
    ]
  }
}

modules/some-module/main.tf:

output "my_output" {
    value = "value"
}

modules/some-module/my_script.py:

#!/usr/bin/env python3

import argparse


if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument("-a", "--arg1", type=str, required=True)
    parser.add_argument("-b", "--arg2", type=str, required=True)
    parser.add_argument("-c", "--arg3", type=str, required=True)
    args = parser.parse_args()

    print(args)

Expected behavior

Arguments are parsed.

Device:some-module username$ ./my_script.py --arg1 argument1 --arg2 argument2 --arg3 argument3
Namespace(arg1='argument1', arg2='argument2', arg3='argument3')

Nice to haves

Device:deployment username$ terragrunt apply
16:00:23.455 INFO   Downloading Terraform configurations from ../modules into ./.terragrunt-cache/MRg6BF8iUt6goQDYcu5OoqH_p3k/HfCJfD21cilNj44BjpZsrrU6T90
16:00:23.655 INFO   terraform: Initializing the backend...
16:00:23.657 INFO   terraform: Initializing provider plugins...
16:00:23.657 INFO   terraform: Terraform has been successfully initialized!
16:00:23.657 INFO   terraform: 
16:00:23.657 INFO   terraform: You may now begin working with Terraform. Try running "terraform plan" to see
16:00:23.657 INFO   terraform: any changes that are required for your infrastructure. All Terraform commands
16:00:23.657 INFO   terraform: should now work.
16:00:23.657 INFO   terraform: If you ever set or change modules or backend configuration for Terraform,
16:00:23.657 INFO   terraform: rerun this command to reinitialize your working directory. If you forget, other
16:00:23.657 INFO   terraform: commands will detect it and remind you to do so if necessary.
16:00:23.661 INFO   Executing hook: python_script
usage: my_script.py [-h] -a ARG1 -b ARG2 -c ARG3
my_script.py: error: the following arguments are required: -a/--arg1, -b/--arg2, -c/--arg3
16:00:24.059 ERROR  Error running hook python_script with message: Failed to execute "./my_script.py --arg1 argument1 --arg2 argument2 --arg3 argument3" in ./.terragrunt-cache/MRg6BF8iUt6goQDYcu5OoqH_p3k/HfCJfD21cilNj44BjpZsrrU6T90/some-module
usage: my_script.py [-h] -a ARG1 -b ARG2 -c ARG3
my_script.py: error: the following arguments are required: -a/--arg1, -b/--arg2, -c/--arg3

exit status 2
16:00:24.059 ERROR  Errors encountered running before_hooks. Not running 'terraform'.
16:00:24.060 ERROR  error occurred:

* Failed to execute "./my_script.py --arg1 argument1 --arg2 argument2 --arg3 argument3" in ./.terragrunt-cache/MRg6BF8iUt6goQDYcu5OoqH_p3k/HfCJfD21cilNj44BjpZsrrU6T90/some-module
  usage: my_script.py [-h] -a ARG1 -b ARG2 -c ARG3
  my_script.py: error: the following arguments are required: -a/--arg1, -b/--arg2, -c/--arg3
  
  exit status 2

Device:deployment username$ cd ./.terragrunt-cache/MRg6BF8iUt6goQDYcu5OoqH_p3k/HfCJfD21cilNj44BjpZsrrU6T90/some-module
Device:some-module username$ ./my_script.py --arg1 argument1 --arg2 argument2 --arg3 argument3
Namespace(arg1='argument1', arg2='argument2', arg3='argument3')

Versions

• Terragrunt version: v0.72.5
• Terraform version: v1.10.5 on darwin_arm64
• Environment details (Ubuntu 20.04, Windows 10, etc.): macOS 15.1.1 (24B91)

Additional context

Add any other context about the problem here.

[yhakbar]

Hey @kstevensonnv ,

Try doing this instead:

terraform {
  source = "../modules//some-module"

  before_hook "python_script" {
    commands     = ["plan", "apply"]
    execute      = [
      "./my_script.py",
      "--arg1", "argument1",
      "--arg2", "argument2",
      "--arg3", "argument3",
    ]
  }
}

You're not splitting up the arguments for your script correctly in your snippet.

[kstevensonnv]

Thanks for the quick response and correcting the hook @yhakbar.

16:32:52.374 INFO   Executing hook: python_script
Namespace(arg1='argument1', arg2='argument2', arg3='argument3')

Closing.