Conditionally Enabling Nix within a Stack Project Depending on Whether You're Running NixOS

Question

When running stack on a NixOS laptop, I require

nix:
  enable: true

in my stack.yaml for it to work.

Problem: When I run stack within a project on a non-NixOS laptop, this generates an error.

Question: Is there a way for stack.yaml to conditionally enable nix if and only if you are running NixOS?

Answer 1

The stack.yaml file can not contain the logic you're requesting, but you can solve the problem by moving it into the user-specific or machine-specific config files, ~/.stack/config.yaml or /etc/stack/config.yaml:

nix:
  enable: true

This will then be the default on your machine/user, so you can leave out the nix/enable flag from the project-specific stack.yaml.