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lix/doc/manual/rl-next/repl-overlays.md
Rebecca Turner 4f20a973f1
Add repl-overlays 
Adds a `repl-overlays` option, which specifies files that can overlay
and modify the top-level bindings in `nix repl`. For example, with the
following contents in `~/.config/nix/repl.nix`:

    info: final: prev: let
      optionalAttrs = predicate: attrs:
        if predicate
        then attrs
        else {};
    in
      optionalAttrs (prev ? legacyPackages && prev.legacyPackages ? ${info.currentSystem})
      {
        pkgs = prev.legacyPackages.${info.currentSystem};
      }

We can run `nix repl` and use `pkgs` to refer to `legacyPackages.${currentSystem}`:

    $ nix repl --repl-overlays ~/.config/nix/repl.nix nixpkgs
    Lix 2.90.0
    Type :? for help.
    Loading installable 'flake:nixpkgs#'...
    Added 5 variables.
    Loading 'repl-overlays'...
    Added 6 variables.
    nix-repl> pkgs.bash
    «derivation /nix/store/g08b5vkwwh0j8ic9rkmd8mpj878rk62z-bash-5.2p26.drv»

Change-Id: Ic12e0f2f210b2f46e920c33088dfe1083f42391a
2024-04-08 17:11:47 -07:00

926 B
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synopsis prs cls
Add `repl-overlays` option 10203 504

A repl-overlays option has been added, which specifies files that can overlay and modify the top-level bindings in nix repl. For example, with the following contents in ~/.config/nix/repl.nix:

info: final: prev: let
  optionalAttrs = predicate: attrs:
    if predicate
    then attrs
    else {};
in
  optionalAttrs (prev ? legacyPackages && prev.legacyPackages ? ${info.currentSystem})
  {
    pkgs = prev.legacyPackages.${info.currentSystem};
  }

We can run nix repl and use pkgs to refer to legacyPackages.${currentSystem}:

$ nix repl --repl-overlays ~/.config/nix/repl.nix nixpkgs
Lix 2.90.0
Type :? for help.
Loading installable 'flake:nixpkgs#'...
Added 5 variables.
Loading 'repl-overlays'...
Added 6 variables.
nix-repl> pkgs.bash
«derivation /nix/store/g08b5vkwwh0j8ic9rkmd8mpj878rk62z-bash-5.2p26.drv»