action hangs with terraform_wrapper: true when variables aren't defined

[jorupp]

I was following https://learn.hashicorp.com/tutorials/terraform/github-actions, but forgot to prefix my environment variables with TF_VAR_, so they weren't being populated, causing terraform plan to prompt for them at runtime. However, with terraform_wrapper: true (the default), the terraform plan just ran for a while (I killed it after 10 minutes) without exiting. Once I disabled the wrapper, it exited with an error in a second. Based on that message, I was able to find and fix my error, and with that fixed, it worked with the wrapper again.

I wonder if terraform plan when run with the wrapper is waiting for an input that will never come to it's "enter a value for the variable" prompt? If so, I wonder if the fix involves passing an empty input to @actions/exec.exec?

setup-terraform/wrapper/terraform.js

Lines 29 to 33 in 625cb76

	const options = {
	listeners,
	ignoreReturnCode: true
	};
	const exitCode = await exec(pathToCLI, args, options);

[jorupp]

Repro: https://github.com/jorupp/terraform-wrapper-test

Wrapper disabled, variable not defined

https://github.com/jorupp/terraform-wrapper-test/actions/runs/1888449826
Fails with:

The root module input variable "TEST_VALUE" is not set, and has no default
value. Use a -var or -var-file command line argument to provide a value for
this variable.
  Enter a value: 

Wrapper enabled, variable defined

https://github.com/jorupp/terraform-wrapper-test/actions/runs/1888449906

Succeeds

Wrapper enabled, variable not defined

https://github.com/jorupp/terraform-wrapper-test/actions/runs/1888450051

terraform plan ran for 20 minutes before I killed it.