Find source of a deprecation warning

anpin · May 20, 2023, 7:49pm

Hi, lately I’m getting a lot of warnings when I do nixos-rebuild switch --flake, such as

They all seems to come from outside of my repo, meaning in the flake inputs. What is the best approach to find exact source of the warning, so I can fix it or open some issues?

(edit: please note that on the screenshot update is just alias for nixos-rebuild switch --flake .#host)

emmanuelrosa · May 21, 2023, 8:28pm

You can try adding the --stacktrace flag to potentially get more information about where those deprecation warnings are coming from. The difficulty here is that stack traces produced by Nix can often be hard to comprehend; Especially when it involves Nixpkgs.

An alternative method (and what I would do personally) is to grab a clone of the Nixpkgs repo, check out the Nixpkgs commit referenced in your flake.lock, and then git grep for those deprecation warnings. That should point you to the exact *.nix files. Ex: git grep "cartesianProductOfSets instead".

anpin · May 22, 2023, 5:45am

thanks, I was hoping to avoid using grep for that

Atemu · May 22, 2023, 8:04am

Set NIX_ABORT_ON_WARN=true, that way you can get stack traces.

github.com

NixOS/nixpkgs/blob/c538b5fc56c57211ba49525bec288c1593284c7b/lib/trivial.nix#L337-L350

    
      
          /*
            Print a warning before returning the second argument. This function behaves
            like `builtins.trace`, but requires a string message and formats it as a
            warning, including the `warning: ` prefix.
          
          
  To get a call stack trace and abort evaluation, set the environment variable
            `NIX_ABORT_ON_WARN=true` and set the Nix options `--option pure-eval false --show-trace`
          
          
  Type: string -> a -> a
          */
          warn =
            if lib.elem (builtins.getEnv "NIX_ABORT_ON_WARN") ["1" "true" "yes"]
            then msg: builtins.trace "[1;31mwarning: ${msg}[0m" (abort "NIX_ABORT_ON_WARN=true; warnings are treated as unrecoverable errors.")
            else msg: builtins.trace "[1;31mwarning: ${msg}[0m";

NobbZ · May 22, 2023, 9:10am

This does of course not work with flakes/pure evaluation.

R-VdP · May 22, 2023, 9:31am

The majority seem to come from a recent change in the module system: lib/modules.nix: Make some functions private · NixOS/nixpkgs@3633bf9 · GitHub

What are the inputs to your flake?
And are you using any of these module system functions directly?

roberth · May 22, 2023, 9:46am

For flakes, pass the --impure option when you set environment variable NIX_ABORT_ON_WARN=1.

NobbZ · May 22, 2023, 10:06am

Yes, but we also need to be aware that --impure does do so much more than just reading exactly the one environment variable you actually want to be read.

All of a sudden ~/.config/nixpkgs/overlay.nix is considered, or a config.nix in the same folder…