Different shell?

[yajo]

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

I'm used to fish, makes me more productive.

I'm using startup hooks, so direnv doesn't solve the problem.

Describe the solution you'd like

Respect user's $SHELL if it's available after running nix develop.

Describe alternatives you've considered

TBH I have not found any 😕

Additional context

[zimbatm]

How do you handle when there are two shells loading the same environment, is the second one detecting that all the processes have started?

For now, I have worked with the assumption that it's best to start the processes manually to give the user more control. And startup hooks would only be used for initialization.

[yajo]

Usually it's not a problem because the services use either a pidfile or a port, so they'll just fail to boot in that case.

[yajo]

For now I have found this workaround, but I guess it would be awesome if it could be added by default:

nix-shell --command "$SHELL"

[zimbatm]

If you use direnv, then it also acts as an interface between your shell and whatever environment variables nix-shell is providing.

[yajo]

I've found out that you can get current user's shell with:

grep ^$USER: /etc/passwd | cut -f 7 -d :

So it would be great if that can be added as a hook and then that is the shell that gets spawned when doing nix-shell or nix develop.

The main problem with #171 (comment) is that services do not get reaped after exiting the shell.

[zimbatm]

I think $SHELL is more reliable because sometimes the shell gets overridden in the Terminal emulator configuration. On Linux you can also look at /proc/$PPID/exe. But yeah, those are all heuristics

[yajo]

The problem with $SHELL is that it's already overriden by devshell. Or you mean not overriding it?

[zimbatm]

I mean as a source of information. But devshell would have to be modified to take that into account. It also opens a bunch of questions like what to do with --pure if the original shell is not available in the PATH.

[yajo]

I don't think --pure has much sense while developing. In any case, IMHO it shouldn't be very hard: just search for the variable and set it only if missing. Isn't it? El lun, 11 abr 2022 18:12, Jonas Chevalier ***@***.***> escribió:

…

I mean as a source of information. But devshell would have to be modified to take that into account. It also opens a bunch of questions like what to do with --pure if the original shell is not available in the PATH. — Reply to this email directly, view it on GitHub <#171 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAHNXDLTAJ4F3EXYGAJY7MLVERMQLANCNFSM5O6MOHFA> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[blaggacao]

Tangentially I'm also currently trying to find ways how to add proper multi-shell support. I'd be interested in exploring. My current thinking is just: don't at all:

{
      devshell.startup.completion = l.stringsWithDeps.noDepEntry ''
        # bash | zsh | oil
        source <(std _carapace)

        # elvish
        # eval (std _carapace | slurp)

        # fish
        # std _carapace | source

        # nushell
        # std _carapace nushell | save out.nu
        # source out.nu


        # powershell
        # Set-PSReadLineOption -Colors @{ "Selection" = "`e[7m" }
        # Set-PSReadlineKeyHandler -Key Tab -Function MenuComplete
        # std _carapace | Out-String | Invoke-Expression

        # tcsh
        # set autolist
        # eval `std _carapace tcsh`

        # xonsh
        # COMPLETIONS_CONFIRM=True
        # exec($(std _carapace))
      '';
}

[blaggacao]

Here are my findings, so far while trying to get shell completion to work across different shells:

• nix develop --command "$SHELL" is potentially slow since it reloads the entire shell again.
• nix develop in general is not a good interface to load a devshell since it fixes the shell to bash and foregoes pretty much all the features of the host shell.
• result/entrypoint - when sourced loads the environment efficiently, when run, switches hard-coded to bash.

direnv

• when direnv sources result/entrypoint it's not interactive so the interactive commands don't load and the sourcing environment is also bash, therefore shell-specific completion scripts aren't loaded either.

[blaggacao]

So this PR is a direct conclusion of the above analysis: #205

[blaggacao]

After furthed research, I conclude that it would be best to use nix print-dev-env --json ... which returns something link the following JSON

JSON

{
  "bashFunctions": {
    "runHook":" \n    eval \"$shellHook\";\n    unset runHook\n"
  },
  "variables": {
    "BASH": {"type": "var", "value": "/noshell"},
    "BASHOPTS": {"type": "unknown"},
    "BASHPID": {"type": "unknown"},
    "COMP_WORDBREAKS": {"type": "var", "value": " \t\n\"'@><=;|&(:"},
    "EPOCHREALTIME": {"type": "var", "value": "1653957355.162904"},
    "EPOCHSECONDS": {"type": "var", "value": "1653957355"},
    "HOME": {"type": "exported", "value": "/homeless-shelter"},
    "HOSTTYPE": {"type": "var", "value": "x86_64"},
    "IFS": {"type": "var", "value": " \t\n"},
    "IN_NIX_SHELL": {"type": "exported", "value": "impure"},
    "LINENO": {"type": "var", "value": "73"},
    "MACHTYPE": {"type": "var", "value": "x86_64-pc-linux-gnu"},
    "NIX_BUILD_CORES": {"type": "exported", "value": "4"},
    "NIX_BUILD_TOP": {"type": "exported", "value": "/build"},
    "NIX_LOG_FD": {"type": "exported", "value": "2"},
    "NIX_STORE": {"type": "exported", "value": "/nix/store"},
    "OLDPWD": {"type": "exported", "value": ""},
    "OPTERR": {"type": "var", "value": "1"},
    "OPTIND": {"type": "unknown"},
    "OSTYPE": {"type": "var", "value": "linux-gnu"},
    "PATH": {"type": "exported", "value": "/path-not-set"},
    "PS4": {"type": "var", "value": "+ "},
    "SHELL": {"type": "var", "value": "/noshell"},
    "SHELLOPTS": {"type": "unknown"},
    "SRANDOM": {"type": "unknown"},
    "TEMP": {"type": "exported", "value": "/build"},
    "TEMPDIR": {"type": "exported", "value": "/build"},
    "TERM": {"type": "exported", "value": "xterm-256color"},
    "TMP": {"type": "exported", "value": "/build"},
    "TMPDIR": {"type": "exported", "value": "/build"},
    "builder": {"type": "exported", "value": "/nix/store/d60gkg5dkw4y5kc055n4m0xyvcjz65im-bash-interactive-5.1-p16/bin/bash"},
    "dontAddDisableDepTrack": {"type": "exported", "value": "1"},
    "name": {"type": "exported", "value": "Standard"},
    "out": {"type": "exported", "value": "/nix/store/wg3jq1c0y99vx35pl2p1a9py83z1qwsj-Standard-env"},
    "outputs": {"type": "var", "value": "out"},
    "shellHook": {"type": "exported", "value": "# Remove all the unnecessary noise that is set by the build env\nunset NIX_BUILD_TOP NIX_BUILD_CORES NIX_STORE\nunset TEMP TEMPDIR TMP TMPDIR\nunset builder name out shellHook stdenv system\n# Flakes stuff\nunset dontAddDisableDepTrack outputs\n\n# For `nix develop`\nif [[ \"$SHELL\" == \"/noshell\" ]]; then\n  export SHELL=/nix/store/d60gkg5dkw4y5kc055n4m0xyvcjz65im-bash-interactive-5.1-p16/bin/bash\nfi\n\n# Load the environment\nsource \"/nix/store/2qpifmmkcrqn7nmj9bh718ah1xq9x1xv-devshell-dir/env.bash\"\n"},
    "stdenv": {"type": "exported", "value": "/nix/store/bq3ply37g51zxb6qqh04rhb2gawhii4l-naked-stdenv"},
    "system": {"type": "exported", "value": "x86_64-linux"}
  }
}

It should be relatively straight forward to write a rendered that would render this for:

• bash (already built-in)
• zsh, et al. -- maybe keep on par with: https://rsteube.github.io/carapace/carapace/gen/hiddenSubcommand.html

Then a new devshell would be launched with something a long these lines:

nix print-dev-env --json ... | devshell render --elvish > ./tempfile
# will/should properly increment SHLVL
elvish -c "source ./tempfile" # or whatever the right syntax would be

and that could be shortened to magic, still:

devshell apply  # detecting the right shell based on `SHELL`

[blaggacao]

Looks like we can have this a lot easier:

nix build "${nix_args[@]}" --profile "$profile_path/shell-profile"
bash -c "source $profile_path/shell-profile/env.bash; SHLVL=$SHLVL; exec $SHELL -i"

• your current shell (required to have the -i flag, but could be shimmed easily)
• with the devshell's env additions
• and the correct SHLVL
• correct $SHELL as opposed to after invoking nix develop ...
• CTRL+D drops you one shell deeper and reverts the env (as expected)

In context: divnix/std@37529d6