Name conflict

[masaeedu]

At least on my Arch Linux, installing snack using nix-env -f ./default.nix -iA snack-exe breaks future use of nix-channel --update && nix-env -u, because apparently there's a broken top level Python package in nixpkgs called snack.

Here's the error:

➜  haskell git:(master) nix-env -u
error: while trying to find an upgrade for 'snack':
while evaluating the attribute 'handled' at /nix/store/4drj41xi9a8z5kaag2vq0j1qiwss25hx-nixpkgs-19.09pre181045.61f0936d1cd/nixpkgs/pkgs/stdenv/generic/check-meta.nix:253:7:
while evaluating 'handleEvalIssue' at /nix/store/4drj41xi9a8z5kaag2vq0j1qiwss25hx-nixpkgs-19.09pre181045.61f0936d1cd/nixpkgs/pkgs/stdenv/generic/check-meta.nix:146:38, called from /nix/store/4drj41xi9a8z5kaag2vq0j1qiwss25hx-nixpkgs-19.09pre181045.61f0936d1cd/nixpkgs/pkgs/stdenv/generic/check-meta.nix:254:14:
Package ‘snack-2.2.10’ in /nix/store/4drj41xi9a8z5kaag2vq0j1qiwss25hx-nixpkgs-19.09pre181045.61f0936d1cd/nixpkgs/pkgs/development/libraries/snack/default.nix:30 is marked as broken, refusing to evaluate.

a) For `nixos-rebuild` you can set
  { nixpkgs.config.allowBroken = true; }
in configuration.nix to override this.

b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
  { allowBroken = true; }
to ~/.config/nixpkgs/config.nix.

[nmattia]

indeed, that's a problem! I've never hit that because I don't use channels. I'll look into to see what exactly is used as the key. Probably the derivation name?