Hi all, @domenkozar,
thank you for the awesome devenv!
I have question which I’ve been struggling to answer on my own: given devenv, is it possible to override stdenv?
The Context
I’ve got a flakified env for building swift projects (e.g. this one):
{
outputs = { self, nixpkgs, flake-utils, }:
flake-utils.lib.eachDefaultSystem (system:
let
pkgs = nixpkgs.legacyPackages.${system};
in
{
# https://github.com/NixOS/nixpkgs/issues/242779#issuecomment-1732558769
devShells.default = pkgs.mkShell.override { stdenv = pkgs.swift.stdenv; } {
buildInputs = with pkgs;[
swift
swiftpm
swiftPackages.Foundation
darwin.apple_sdk.frameworks.AppKit
];
# https://github.com/NixOS/nix/issues/6677
shellHook = ''
export PS1='\n\[\033[1;32m\][nix-shell:\w]\$\[\033[0m\] '
'';
};
});
}
as per swift on nixos can't compile hello world: error: undefined reference to '__dso_handle' · Issue #242779 · NixOS/nixpkgs · GitHub, stdenv overriding is required, otherwise things fall apart (e.g. Foundation not being found).
The issue
I can’t properly translate stdenv overriding to devenv concepts (replaceStdenv is a last resort and doesn’t count):
{
inputs = {
nixpkgs.url = "nixpkgs/nixpkgs-unstable";
devenv.url = "github:cachix/devenv";
};
nixConfig = {
extra-trusted-public-keys = "devenv.cachix.org-1:w1cLUi8dv3hnoSPGAuibQv+f9TZLr6cv/Hm9XgU50cw=";
extra-substituters = "https://devenv.cachix.org";
};
outputs = { self, nixpkgs, devenv, flake-utils, }@inputs:
flake-utils.lib.eachDefaultSystem (system:
let
# fully rebuilds the toolchain - not a replacement for nixpkgs.mkShell.override
pkgs = import nixpkgs {
inherit system;
config.replaceStdenv = {pkgs}: pkgs.swift.stdenv;
};
in
{
devShells.default = devenv.lib.mkShell {
inherit inputs pkgs;
modules = [
({ pkgs, config, ... }: {
languages.nix.enable = true;
pre-commit.hooks = {
nixpkgs-fmt.enable = true;
yamllint.enable = true;
};
# https://github.com/NixOS/nix/issues/6677
enterShell = ''
export PS1='\n\[\033[1;32m\][nix-shell:\w]\$\[\033[0m\] '
'';
packages = with pkgs;[
swift
swiftpm
swiftPackages.Foundation
darwin.apple_sdk.frameworks.AppKit
];
})
];
};
});
}
Hacking around
Digging thru sources has lead me to the referred devshell’s mkNakedShell. devenv’s (re)-implementation declares stdenv as input parameter, which confused me, as the let expression which follows, redeclares it?
It made me doubt if it actually would’ve worked, if I had figured out a less intrusive way to solve my problem (which I have not).
Disclaimer: that’s just noob’s attempt to get a grasp on things, so everything stated here has a potential to be the opposite of the truth 
Thanks a lot!
Peter
