Piping commands into nix develop doesn't set up the environment correctly

[soenkehahn]

Describe the bug

I have the following flake.nix file:

{
  inputs.nixpkgs.url = "github:NixOS/nixpkgs";
  inputs.flake-utils.url = "github:numtide/flake-utils";

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let pkgs = nixpkgs.legacyPackages.${system}; in
      {
        devShells.default = pkgs.mkShell {
          buildInputs = [ pkgs.hello ];
        };
      }
    );
}

In I shell I can do this:

$ echo 'hello\nexit' | nix develop -c bash
Hello, world!
$ echo 'hello\nexit' | nix develop
bash: line 1: hello: command not found
$

As you can see, the two commands behave differently. nix develop -c bash allows me to pipe commands into the started shell. This behaves as I would expect it to. nix develop (without -c bash) however doesn't seem to execute the command inside a devShell that is set up correctly. This seems like a bug to me.

Note that piping commands into nix develop does execute commands inside bash, just not inside the right environment. So the following works as expected:

$ echo 'echo foo\nexit' | nix develop
foo
$

Also note that nix develop spawns a bash process with some flags, e.g. bash --rcfile /tmp/nix-shell.zW1tMH. Whereas nix develop -c bash does not. So I'm guessing that's somehow causing the difference in behavior.

Using nix-env (Nix) 2.13.3.

(For me personally, fixing this bug, if it is a bug, doesn't have a high priority. I would be more interested in figuring out why this happens and whether this is in fact a bug or intended behavior.)

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