How to fix `evaluation warning: 'system' has been renamed to/replaced by 'stdenv.hostPlatform.system'`

waffle8946 · November 14, 2025, 7:59pm

This is an antipattern anyway. It should be replaced.

Also an antipattern. In NixOS config users should be setting nixpkgs.hostPlatform. No it’s not going to fix this warning, but the underlying reasoning is the same: system does not specify the platform explicitly enough, and passing system to lib.nixosSystem has long been deprecated for the same reason.

I expect a warning to eventually come for this antipattern too.

I think you mean --option abort-on-warn true --show-trace and tbh it did not work for me.

What did work for me is prefixing the command with NIX_ABORT_ON_WARN=1 and using --impure if building with flakes (to ensure the envvar is picked up).

EDIT: I’ve figured out why - lix does not have a builtins.warn since it was only added in nix 2.23 and lix branched off at 2.18. Hence my advice is compatible with more nix versions.

github.com/NixOS/nixpkgs

lib/trivial.nix

a007aee4e


      
          warn =
            # Since Nix 2.23, https://github.com/NixOS/nix/pull/10592
            builtins.warn or (
              let
                mustAbort = lib.elem (builtins.getEnv "NIX_ABORT_ON_WARN") [
                  "1"
                  "true"
                  "yes"
                ];
              in
              # Do not eta reduce v, so that we have the same strictness as `builtins.warn`.
              msg: v:
              # `builtins.warn` requires a string message, so we enforce that in our implementation, so that callers aren't accidentally incompatible with newer Nix versions.
              assert isString msg;
              if mustAbort then
                builtins.trace "[1;31mevaluation warning:[0m ${msg}" (
                  abort "NIX_ABORT_ON_WARN=true; warnings are treated as unrecoverable errors."
                )
              else
                builtins.trace "[1;35mevaluation warning:[0m ${msg}" v
            );

TLDR use NIX_ABORT_ON_WARN=1 not the abort-on-warn option.