Commit 0e062cb6 authored by Robert Hensing's avatar Robert Hensing
Browse files

nixos-rebuild: Add nixos-rebuild repl 

Apologies to the non-flake users; your repl isn't quite as fancy,
but at least evaluates your config exactly as you would expect,
unlike flakes which are only evaluated impurely for now.
parent 584463c7

nixos/doc/manual/installation/changing-config.chapter.md

+8 −0
Original line number Diff line number Diff line
@@ -55,6 +55,14 @@ which causes the new configuration (and previous ones created using 
This can be useful to separate test configurations from "stable"

configurations.



A repl, or read-eval-print loop, is also available. You can inspect your configuration and use the Nix language with



```ShellSession

# nixos-rebuild repl

```



Your configuration is loaded into the `config` variable. Use tab for autocompletion, use the `:r` command to reload the configuration files. See `:?` or [`nix repl` in the Nix manual](https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-repl.html) to learn more.



Finally, you can do



```ShellSession

pkgs/os-specific/linux/nixos-rebuild/nixos-rebuild.8

+5 −1
Original line number Diff line number Diff line
@@ -10,7 +10,7 @@ 
.Sh SYNOPSIS

.Nm

.Bro

.Cm switch | boot | test | build | dry-build | dry-activate | edit | build-vm | build-vm-with-bootloader | list-generations Op Fl -json

.Cm switch | boot | test | build | dry-build | dry-activate | edit | repl | build-vm | build-vm-with-bootloader | list-generations Op Fl -json

.Brc

.br

.Op Fl -upgrade | -upgrade-all
@@ -143,6 +143,10 @@ Opens 
.Pa configuration.nix

in the default editor.

.

.It Cm repl

Opens the configuration in

.Ic nix repl Ns .

.

.It Cm build-vm

Build a script that starts a NixOS virtual machine with the desired

configuration. It leaves a symlink

pkgs/os-specific/linux/nixos-rebuild/nixos-rebuild.sh

+63 −1
Original line number Diff line number Diff line
@@ -49,7 +49,7 @@ while [ "$#" -gt 0 ]; do 
      --help)

        showSyntax

        ;;

      switch|boot|test|build|edit|dry-build|dry-run|dry-activate|build-vm|build-vm-with-bootloader|list-generations)

      switch|boot|test|build|edit|repl|dry-build|dry-run|dry-activate|build-vm|build-vm-with-bootloader|list-generations)

        if [ "$i" = dry-run ]; then i=dry-build; fi

        # exactly one action mandatory, bail out if multiple are given

        if [ -n "$action" ]; then showSyntax; fi
@@ -511,6 +511,68 @@ if [ "$action" = dry-build ]; then 
    extraBuildFlags+=(--dry-run)

fi



if [ "$action" = repl ]; then

    # This is a very end user command, implemented using sub-optimal means.

    # You should feel free to improve its behavior, as well as resolve tech

    # debt in "breaking" ways. Humans adapt quite well.

    if [[ -z $flake ]]; then

        exec nix repl '<nixpkgs/nixos>' "${extraBuildFlags[@]}"

    else

        if [[ -n "${lockFlags[0]}" ]]; then

            # nix repl itself does not support locking flags

            log "nixos-rebuild repl does not support locking flags yet"

            exit 1

        fi

        d='$'

        q='"'

        bold="$(echo -e '\033[1m')"

        blue="$(echo -e '\033[34;1m')"

        attention="$(echo -e '\033[35;1m')"

        reset="$(echo -e '\033[0m')"

        # This nix repl invocation is impure, because usually the flakeref is.

        # For a solution that preserves the motd and custom scope, we need

        # something like https://github.com/NixOS/nix/issues/8679.

        exec nix repl --impure --expr "

          let flake = builtins.getFlake ''$flake'';

              configuration = flake.$flakeAttr;

              motd = ''

                $d{$q\n$q}

                Hello and welcome to the NixOS configuration

                    $flakeAttr

                    in $flake



                The following is loaded into nix repl's scope:



                    - ${blue}config${reset}   All option values

                    - ${blue}options${reset}  Option data and metadata

                    - ${blue}pkgs${reset}     Nixpkgs package set

                    - other module arguments



                    - ${blue}flake${reset}    Flake outputs, inputs and source info of $flake



                Use tab completion to browse around ${blue}config${reset}.



                Use ${bold}:r${reset} to ${bold}reload${reset} everything after making a change in the flake.

                  (assuming $flake is a mutable flake ref)



                See ${bold}:?${reset} for more repl commands.



                ${attention}warning:${reset} nixos-rebuild repl does not currently enforce pure evaluation.

              '';

              scope =

                assert configuration._type or null == ''configuration'';

                assert configuration.class or ''nixos'' == ''nixos'';

                configuration._module.args //

                configuration._module.specialArgs //

                {

                  inherit (configuration) config options;

                  inherit flake;

                };

          in builtins.seq scope builtins.trace motd scope

        " "${extraBuildFlags[@]}"

    fi

fi



if [ "$action" = list-generations ]; then

    if [ ! -L "$profile" ]; then

        log "No profile \`$(basename "$profile")' found"