findutils/xargs has a subtle undeclared runtime dependency on an external echo command

[abathur]

Describe the bug
If you run xargs without specifying the command argument, it falls back on running echo (this is roughly documented in the man page, but the note there mistakenly claims the default is /bin/echo, but this was changed back in 2011...). If it can't find echo, xargs throws a .../bin/xargs: echo: No such file or directory error.

To Reproduce
This example is a little synthetic (not very similar to how I found the issue), but a simple way to demonstrate it is: nix-shell -p findutils --run 'echo heh | env -i PATH= $(type -p xargs)'

Additional context
The checkPhase of the CI build for my shell-script dependency resolver invokes a test script like env -i <script> to demonstrate that it's depending on resolved executable paths--not the environment. The test script in turn sources a resolved copy of shunit2 (which contains a bare xargs invocation). This has been running okay in macOS and Linux (but obviously, with a hidden dependency leaking in), but I noticed today that it errors on NixOS.

It's not hard to patch this with substitute:

find_some_utils = pkgs.findutils.overrideAttrs (oldAttrs: rec {
    prePatch = ''
      substituteInPlace xargs/xargs.c --replace 'char default_cmd[] = "echo";' 'char default_cmd[] = "${coreutils}/bin/echo";'
    '';
  });

I'm not, however, sure if it is "right" to try to fix this at all, nor if this is the right approach.

Notify maintainers
@veprbl @disassembler @vcunat

[veprbl]

@abathur Open a PR for this?

[abathur]

@veprbl Sure. Still counting on someone else to make sure this is appropriate, though.

[stale]

I marked this as stale due to inactivity. → More info

[abathur]

This was fixed by #89063