Is it possible to specify a `stack.yaml` file for a haskell script?

Question

Let's say I have the following script inside my haskell project directory:

#!/usr/bin/env stack
-- stack --resolver lts-12.5 script

-- some imports here

main :: IO ()
main = do
  -- some code here

I'd like to use the stack.yaml file that exists inside the project directory, in order to get the required packages, as I want to get them from a specific git commit instead of lts-12.5.

I've tried adding --stack-yaml stack.yaml after --resolver lts-12.5 but I'm getting this warning when I run the script: Ignoring override stack.yaml file for script command: stack.yaml.

Is it possible to use my stack.yaml file for the script? or is it possible to specify the git commit from which I want to get the package (like using location with commit and git inside stack.yaml)?

Answer 1

You can achieve this using custom snapshot files. For example, in snapshot.yaml:

resolver: ghc-8.4.3
name: has-acme-missiles
packages:
- acme-missiles-0.3

In Main.hs:

#!/usr/bin/env stack
-- stack --resolver snapshot.yaml script
import Acme.Missiles

main :: IO ()
main = launchMissiles

Results in:

$ ./Main.hs 
Nuclear launch detected.