bash autocompletion in nix shell (nix command)

[roberth]

Is your feature request related to a problem? Please describe.

It's frustrating when autocompletion doesn't work in a shell.

Describe the solution you'd like

Simple option: add entries to XDG_DATA_DIRS.

Complicated option: make nix shell use stdenv, which can take care of this logic, at the cost of a Nixpkgs dependency.

Describe alternatives you've considered

Write GUIs for everything that shouldn't have a GUI.

Additional context

Completions are available for derivation-based shells since NixOS/nixpkgs#103501

nix-shell also needs adjustment, see #4452

[roberth]

Another way to make this work is by using passthru to inform how a package should added to the environment variables, generically. See also env noun suggestion

This is similar to what the stdenv machinery does in a package build, but simplified and specifically for use outside a package build.
Perhaps this should be incorporated into the "app" concept or vice versa.

[roberth]

Basically what I'm suggesting is to treat "environment variables" as a serious deployment target, where a package can tell Nix exactly what to do, or rely on the default (PATH + possibly XDG_DATA_DIRS)

Something like

passthru.useViaEnvironment = {
  PATH = "${self.outPath}/bin:${commonlyUsedRuntimeDep}/bin";
  XDG_DATA_DIRS = "${self.outPath}/share/foo";
  shellHook = "echo To initialize the foo package config, run foo init";
}

just to illustrate the concept.

I'm assuming NixOS/nixpkgs#119942 for simplicity on the Nix side of this interface. The self-referential nature of this feature can be worked around with placeholders, but I would prefer to exploit the existing language instead.

How the exactly the environment variables should be merged isn't obvious. Nix could hardcode some of them. Nixpkgs doesn't know how to do it yet either NixOS/nixpkgs#122244.

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/confusion-about-bash-completions-flake-related/14579/16

[SuperSandro2000]

Is this similar to nix-community/lorri#61 ?

[roberth]

@SuperSandro2000 yes, it's all necessary to make completions work beyond simple nix-shell + stdenv (NixOS/nixpkgs#103501)

[roberth]

nix shell (or whatever it will be called #4715) could solve this by depending on NixOS/nixpkgs#132617, allowing a small amount of behavior to be added, without burdening Nix itself with it.

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/interactive-bash-with-nix-develop-flake/15486/4