Completion support in nix-shell

[copumpkin]

We do have nice completion support for nix-env-installed programs, but as someone who primarily uses nix-shell, I'm sad to not get completions, even though man pages and other niceties work. Does anyone know what it would take to make completions work?

[matthewbauer]

Just to clarify, you want completion for commands within nix-shell not for nix-shell itself? (because there definitely is at least ZSH support for completion of nix-* commands.

I wonder if we could have an output called something like "completion" that would use paths /share/bash-completion/completions and /share/zsh/site-functions? Obviously it wouldn't be a huge win for closure sizes, but would make things a little cleaner.

I have this in my .bashrc that should work:

# Check whether we're running a version of Bash that has support for
# programmable completion. If we do, enable all modules installed in
# the system (and user profile).
if shopt -q progcomp &>/dev/null; then
    . "@bash-completion@/etc/profile.d/bash_completion.sh"
    nullglobStatus=$(shopt -p nullglob)
    shopt -s nullglob
    for m in "@out@/etc/bash_completion.d/"* "@out@/share/bash-completion/completions/"*; do
        . $m
    done
    eval "$nullglobStatus"
    unset nullglobStatus p m
fi

You should be able to use that in nix-shell I think (replacing @out@ with the environment and @bash-completion@ with wherever pkgs.bash-completion is).

The problem is it's Bash-only. ZSH is alot easier:

# Tell zsh how to find installed completions
fpath+=(@out@/share/zsh/site-functions @out@/share/zsh/$ZSH_VERSION/functions)

If you want those to work "by default" I think they would need to be in nix-profile: https://github.com/NixOS/nix/blob/fb2dd3210072a03526e881cd2547cf4c2df4ba52/scripts/nix-profile.sh.in#L84. Of course the .profile is supposed to be for all

[roberth]

for p in ${buildInputs}; do XDG_DATA_DIRS="$XDG_DATA_DIRS:$p/share"; done

This does the trick and uses the lazy loading method of adding bash completions.
You can even run it when the nix-shell is already up, so it's quite flexible.

I suppose we could add this as a default shell hook in stdenv, or possibly in stdenv itself. I can imagine that in rare cases, build scripts use this variable, so it would fix those. I suppose it should be nativeBuildInputs in that case though...

On more thing is that we should probably check the existence of $p/share before adding it. And p should be a local variable.

Perhaps someone who's more familiar with the cross compiling stuff can chip in?

[stale]

Thank you for your contributions.

This has been automatically marked as stale because it has had no activity for 180 days.

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[gomain]

important to me :)

[stale]

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

[roberth]

Almost done. I've added support for file based shells in #103501. Remember to use nativeBuildInputs.

Will write a Nix pr for the nix-shell command line.

[stale]

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

[roberth]

Nixpkgs supports completion for nativeBuildInputs in shell.nix files. nix-shell -p completions can not be implemented properly in Nixpkgs itself, so here's issue NixOS/nix#4254 and a PR that solves it NixOS/nix#4452.

If completions don't work for you, it's more effective to open a new issue.