preconditions for internally undefined variables

[klauern]

I have a task file that checks for a set variable as part of a precondition.

  run-local:
    desc: Run locally on a single service
    cmds:
      - task: run
    preconditions:
      - sh: test ! "{{.ACCOUNT}}" = "<no value>"
        msg: Must supply an account ID (e.g., `task run-local ACCOUNT=12345678`)
      - sh: test ! "{{.SERVICE}}" = "<no value>"
        msg: Must supply a service name (e.g., `task run-local SERVICE=thing`)

I discovered that variables were being set to <no value>, but I am not sure if that's a realible means to test for this. As the precondition is based on a shell command, I am essentially escaping the Taskfile to test for a variable that is set externally, when it could be referenced locally. Is there an equivalent precondition check that I can use to validate that a variable has been set correctly? Will <no value> be reliably set everywhere?

[dolfelt]

@klauern Another way to do something like this could be:

  run-local:
    desc: Run locally on a single service
    cmds:
      - task: run
    preconditions:
      - sh: '{{ if not .ACCOUNT }}exit 1;{{ end }}'
        msg: Must supply an account ID (e.g., `task run-local ACCOUNT=12345678`)
      - sh: '{{ if not .SERVICE }}exit 1;{{ end }}'
        msg: Must supply a service name (e.g., `task run-local SERVICE=thing`)

[andreynering]

Hey @klauern,

@dolfelt's suggestion sounds a bit better, indeed. I agree that's still verbose, though. See #495 as a proposal to improve this use case.