Nix Grymoire

Include local repo submodules in =nix build=

2024-10-23T10:50:00Z

Include local repo submodules in `nix build`

Another beautiful little piece of a priori knowledge, how to get a local nix flake build to include the repo's submodules:

You do not add the submodule itself as an input, you need to add the submodules=1 query parameter to the input that has the submodule.

shell

nix build .?submodules=1

How to prevent double-wrapping of =nixpkgs= apps

2024-06-10T16:15:00Z

How to prevent double-wrapping of `nixpkgs` apps

Recently pantalaimon stopped working, complaining that it couldn't do GObject introspection to load the DBus library it uses for its user interface. I spent some time digging in to it because i like using Ement.el more than element-desktop, and found that GTK/GNOME apps require these "typelib" files to be in a known path to do the object introspection. (I don't know how you GNOME/GTK people live like this, but that's a different conversation)

My first attempt injected them with a custom wrapProgram invocation since wrapGAppsHook was used for GUI stuff:

nix

postFixup = let
  typelibPath = lib.makeSearchPath "/lib/girepository-1.0" [
    (placeholder "out")
    (lib.getLib glib)
  ];
in ''
  for pgm in pantalaimon panctl; do 
    wrapProgram "$out/bin/$pgm" \
      --prefix GI_TYPELIB_PATH : "$GI_TYPELIB_PATH:${typelibPath}"
  done
'';

The reviewer on my nixpkgs pull request for this recommended using wrapGAppsNoGuiHook which I hadn't seen before, but then said that it had to prevent "double-wrapping", a thing I've seen myself but never resolved:

[rrix@virtuous-cassette:~/Code/nixpkgs]$ ls -alh /nix/store/kxddbaf1w5wwwfpi02fscmqfmc6jfgqz-pantalaimon-0.10.5/bin/
total 37K
dr-xr-xr-x 2 root root    8 Dec 31  1969 .
dr-xr-xr-x 6 root root    6 Dec 31  1969 ..
-r-xr-xr-x 1 root root  16K Dec 31  1969 panctl
-r-xr-xr-x 1 root root  16K Dec 31  1969 .panctl-wrapped
-r-xr-xr-x 1 root root 6.6K Dec 31  1969 ..panctl-wrapped-wrapped
-r-xr-xr-x 1 root root  16K Dec 31  1969 pantalaimon
-r-xr-xr-x 1 root root  16K Dec 31  1969 .pantalaimon-wrapped
-r-xr-xr-x 1 root root 6.6K Dec 31  1969 ..pantalaimon-wrapped-wrapped

The person recommended the following, which I did and does work, yet another Nixpkgs A Priori Pattern...:

nix

nativeBuildInputs = [
  wrapGAppsNoGuiHook
  gobject-introspection
];

# Prevent double wrapping from wrapGApps and wrapPythonProgram
dontWrapGApps = true;
makeWrapperArgs = [
  "\${gappsWrapperArgs[@]}"
];

aye aye aye...

Building a Plasma package or entire environment using =ccache=

2024-06-02T15:45:00Z

Building a Plasma package or entire environment using `ccache`

I've tried a few times now to build software on my nixos system using ccache, but I failed mostly because programs.ccache.packageNames didn't reliably recurse in to the attrset which all the KDE packages are hidden in. Anyways, I don't compile things very often, so it was mostly shelved.

I've been for a few months now dealing with a difficult to reproduce crasher bug in Plasma KWin Wayland and I am more motivated than ever to try to track this down. Especially after david edmundson dropped a patch that is "close but no cigar", I wanted to get to the point where I could build KWin and not have it be a full recompile every time I added a debug statement.

This is what ccache is for!

In my custom package overlay I was only able to get ccache used for these builds by overriding the plasma5Packages "scope" -- another essentially undocumented Nixpkgs A Priori Pattern. This would cause ccache to be used for every binary, and cause Binary Cache misses; every Plasma package would be compiled from source! 😩

But you can do Some Computer :( Bullshit to override the scope just for KWin and inject my local source checkout in the process, I wonder if someone can suggest something more legible:

nix

final: prev:
{
  plasma5Packages = let
    p5pcc = pkgs.plasma5Packages.overrideScope (pFinal: pPrev: rec {
      stdenv = pkgs.ccacheStdenv;
    });
  in
    pkgs.plasma5Packages.overrideScope (plasmaFinal: plasmaPrev: rec {
      kwin = p5pcc.kwin.overrideAttrs (old: {
        src = /home/rrix/Code/kwin;
      });
    });
}

create a plasma5Packages scope with the ccacheStdenv injected in to it called p5pcc
override the "stock" plasma5Packages to:
- take the KWin package and override its src attribute to point to my local fs
- use the scope with ccache in it for KWin and its dependencies

Know when to use the undocumented =mkMerge= command

2024-02-14T16:42:00Z

Know when to use the undocumented `mkMerge` command

When writing NixOS modules, you often need to make sure that attrsets with dynamic or cfg.enable or other mkIf thing are merged lazily; this is done with the un-documented nixpkgs function lib.mkMerge...

Copying a nix closure to a =nixos-enter='d NixOS Install (rescue environment, installer, etc)

2024-01-11T09:56:00Z

Copying a nix closure to a =nixos-enter='d NixOS Install (rescue environment, installer, etc)

shell

nix copy --to ssh://root@192.168.69.36?remote-store=local?root=/mnt /nix/store/dalm2ggzvgd2b09m0lrff61gbqf8gy05-morph --no-check-sigs

I hosed my server pretty hard, and ended up having to deploy a new version of grub configuration, mountpoints etc, while I only had access to a rescue environment attached to the server. While I plan to write a full postmortem of that incident, this is useful for myself and for others, i found it discussed only in a github issue for nix, presumably the options passed to the ssh path are documented somewhere but this will copy in to a store mounted under /mnt/nix/store which sure is nice!

Adding a flake check to run pytest

2023-11-01T21:00:00Z

Adding a flake check to run pytest

nix

checks.pytest = pkgs.stdenvNoCC.mkDerivation {
  name = "pytest";
  src =./.;
  dontBuild = true;
  doCheck = true;
  nativeBuildInputs = [
    pkgs.python3.pkgs.pytest
    pkgs.callPackage ./default.nix {};
  ];
  checkPhase = "pytest test";
  installPhase = "mkdir $out";
};

Nix Grymoire

Include local repo submodules in =nix build=

Include local repo submodules in nix build

How to prevent double-wrapping of =nixpkgs= apps

How to prevent double-wrapping of nixpkgs apps

Building a Plasma package or entire environment using =ccache=

Building a Plasma package or entire environment using ccache

Know when to use the undocumented =mkMerge= command

Know when to use the undocumented mkMerge command

Copying a nix closure to a =nixos-enter='d NixOS Install (rescue environment, installer, etc)

Copying a nix closure to a =nixos-enter='d NixOS Install (rescue environment, installer, etc)

Adding a flake check to run pytest

Adding a flake check to run pytest

Include local repo submodules in `nix build`

How to prevent double-wrapping of `nixpkgs` apps

Building a Plasma package or entire environment using `ccache`

Know when to use the undocumented `mkMerge` command