nix-doom-emacs-unstraightened

nix-doom-emacs-unstraightened (referred to as "Unstraightened" below) builds Doom Emacs using Nix bundling a user configuration directory and the dependencies specified by it. It is very similar to nix-doom-emacs, but is implemented differently.

Status

Tested and working on Linux, with emacs-overlay and Doom inputs updated automatically. If you're reading this on Github, there should be a CI status badge above: if CI is passing, Unstraightened installs an up-to-date version of Doom Emacs and (almost) all module dependencies.

Not yet tested on macOS. Likely works as long as you do not need an "app" (you launch Emacs from the commandline or through other means). I intend to fix this.

You may encounter "Cannot find Git revision" errors on Nix versions newer than 2.18.x (see #14). Try enabling experimentalFetchTree to work around this (see below).

Please report any issues.

How to use

Test run

1. Check out this repository
2. Optional: run nix flake update nixpkgs (Nix 2.19 or up) or nix flake lock --update-input nixpkgs (earlier versions). If nixpkgs is in the system registry (which it is by default on NixOS 24.05 and up) this will make Unstraightened reuse more dependencies already on your system.

Note

Updating other inputs (with nix flake update) is not recommended. These inputs are automatically updated daily as long as tests pass. Updating manually may update to an incompatible version of Doom or Emacs packages.

3. Copy your Doom configuration into doomdir (overwriting what's there)
4. Make sure all files are added (git add doomdir)
5. Run nix run .#doom-emacs.

If this does not work, the "with flakes" setup below is unlikely to work either. Please file an issue.

With flakes

Add this flake as an input in flake.nix:

inputs = {
  nix-doom-emacs-unstraightened.url = "github:marienz/nix-doom-emacs-unstraightened";
  # Optional, to download less. Neither the module nor the overlay uses this input.
  nix-doom-emacs-unstraightened.inputs.nixpkgs.follows = "";
};

If your Doom configuration lives in a different repository, add that as input too:

inputs = {
  doom-config.url = "...";
  doom-config.flake = false;
};

Home Manager

If you use Home Manager, add Unstraightened's home-manager module in flake.nix:

outputs = inputs @ { nixpkgs, home-manager, ... }: {
  homeConfigurations."username" = home-manager.lib.homeManagerConfiguration {
    modules = [
      inputs.nix-doom-emacs-unstraightened.hmModule
      ./home.nix
    ];
    extraSpecialArgs = { inherit inputs; };
  };
};

Configure it in home.nix:

  programs.doom-emacs = {
    enable = true;
    doomDir = inputs.doom-config;  # or e.g. `./doom.d` for a local configuration
  };

There are a few other configurable options, see below.

If you set services.emacs.enable = true, that will run Unstraightened as well (Unstraightened sets itself as services.emacs.package). Set programs.doom-emacs.provideEmacs = false or override services.emacs.package if you want a vanilla Emacs daemon instead.

Warning

Using the overlay described below with programs.emacs.package will not work correctly (see [HACKING.md] for details).

Overlay

If you don't use Home Manager or prefer not to use Unstraightened's Home Manager module, add Unstraightened's overlay. Typically that means adding:

nixpkgs.overlays = [ inputs.nix-doom-emacs-unstraightened.overlays.default ];

to a home-manager or NixOS module.

The overlay adds two packages:

• To install Unstraightened in parallel with a normal Emacs, add:

  (pkgs.doomEmacs {
    doomDir = inputs.doom-config;
    # If you stored your Doom configuration in the same flake, use
    #   doomDir = ./path/to/doom/config;
    # instead.
    doomLocalDir = "~/.local/share/nix-doom";
  })

  to your installed packages (see below for what doomLocalDir is for). This installs a binary named doom-emacs.

• To install Unstraightened as your default Emacs, use pkgs.emacsWithDoom instead of pkgs.doomEmacs. This installs a binary named emacs as well as emacsclient and other helpers (similar to emacsWithPackages in nixpkgs).

Without flakes

This is currently not explicitly supported, but should be possible (use pkgs.callPackages ./nix-doom-emacs-unstraightened). PRs extending this part of the documentation are welcome, as are (within reason) changes necessary to support use without flakes.

Options

doomEmacs and emacsWithDoom support the following options:

• doomDir: your configuration directory (also known as DOOMDIR, Doom private directory / module). Required.

• doomLocalDir: value Doom should use as DOOMLOCALDIR. Required, because by default Doom would use its source directory, which is read-only.

Note

This supports ~ expansion but does not support shell variable expansion. Using $XDG_DATA_HOME will not work.

Note

Because Unstraightened uses Doom's profile system, using the same value you used with vanilla Doom will not result in Unstraightened finding your files. See below.

• emacs: Emacs package to use. Defaults to pkgs.emacs. Must be at least Emacs 29. Use this to select different Emacs variants like pkgs.emacs29-pgtk. Required in Nixpkgs < 24.05, where pkgs.emacs is Emacs 28.

• doomSource: Doom source tree. Defaults to a flake input: overriding that input is probably easier than passing this.

• extraBinPackages: packages to add to $PATH. Defaults to Git, ripgrep and fd.

• extraPackages: Specify extra Emacs packages from nixpkgs to be available to Doom Emacs. Defaults to this function epkgs: [ ] (no extra packages). For example to include Emacs package treesit-grammars.with-all-grammars: extraPackages = epkgs: [ epkgs.treesit-grammars.with-all-grammars ];.

• experimentalFetchTree: fetch packages using fetchTree, which is more efficient but considered experimental in Nix (subject to changes which might break fetches).

There are a few other settings but they are not typically useful. See the source.

The home-manager module supports the same options, as well as:

• provideEmacs: disable this to only provide a doom-emacs binary, not an emacs binary (that is: it switches from emacsWithDoom to doomEmacs). Use this if you want to install vanilla Emacs in parallel.

Comparison to "normal" Doom Emacs

• Unstraightened updates Doom and its dependencies along with the rest of your Nix packages, removing the need to run doom sync and similar Doom-specific commands.

• Doom pins its direct dependencies, but still pulls the live version of some packages from MELPA or other repositories. Its pins are also applied to build recipes whose source is not pinned. This makes Doom installs not fully reproducible and can cause intermittent breakage.

  Unstraightened pulls these dependencies from nixpkgs or emacs-overlay. Pinning emacs-overlay pins all build recipes and packages not already pinned by Doom.

• Unstraightened stores your Doom configuration (~/.doom.d/~/.config/doom/$DOOMDIR) in the Nix store. This has advantages (the configuration's enabled modules always match available dependencies), but also some disadvantages (see known problems below).

• Unstraightened uses Doom's profiles under the hood. This affects where Doom stores local state:

  Variable	Doom	Unstraightened
  doom-cache-dir	$DOOMLOCALDIR/cache	~/.cache/doom
  doom-data-dir	$DOOMLOCALDIR/etc	~/.local/share/doom
  doom-state-dir	$DOOMLOCALDIR/state	~/.local/state/doom

  (Doom also stores some things in per-profile subdirectories below the above directories: the default profile name used by Unstraightened is nix, resulting in paths like ~/.cache/doom/nix. All of these also respect the usual XDG_*_DIR environment variables.)

  When migrating from "normal" Doom, you may need to move some files around.

  If this bothers you, you can try setting noProfileHack = true. This makes Unstraightened use the usual paths (relative to doomLocalDir), but is experimental.

Comparison to nix-doom-emacs

• Unstraightened does not attempt to use straight.el at all. Instead, it uses Doom's CLI to make Doom export its dependencies, then uses Nix's emacsWithPackages to install them all, then configures Doom to use the "built-in" version for all its dependencies. This approach seems simpler to me, but time will have to tell how well it holds up.

• Unstraightened respects Doom's pins. I believe this is necessary for a system like this to work: Doom really does frequently make local changes to adjust to changes or work around bugs in its dependencies.

• Unstraightened is much younger. It is simpler in places because it assumes Emacs >=29. It probably still has some problems already solved by nix-doom-emacs, and it is too soon to tell how robust it is.

Bugs

Do not report bugs upstream. If you think it's a bug in Doom, reproduce it without Unstraightened first, or report it here first.

There are a few known current bugs and likely future bugs in Unstraightened:

Pins can break

The way Unstraightened applies Doom's pins to Nix instead of straight.el build recipes is a hack. Although it seems to work fairly well (better than I expected), it will break at times.

If it breaks, it should break at build time, but I do not know all failure modes to expect yet.

One likely failure mode is an error about Git commits not being present in the upstream repository. To fix this, try building against a revision of the emacs-overlay flake that is closer to the age of doomemacs. This is a fundamental limitation: Doom assumes its pins are applied to straight.el build recipes, while we use nixpkgs / emacs-overlay. If these diverge, our build breaks.

Another possible problem is a package failing to build or run because one of its dependencies is missing. Unstraightened currently uses dependencies from the original (emacs-overlay) package. This is largely a performance optimization, that can be revisited if it breaks too frequently.

Saving Custom changes fails

Saving changes through Custom will not work, because custom-file is read-only. I am open to suggestions for how this should work:

• Currently, DOOMDIR/custom.el is loaded, but changes need to be applied manually.
• If we set custom-file to a writable location, that fixes saving but breaks loading. If the user copies their custom-file out of their DOOMDIR to this location once, they are not alerted to changes they may want to copy back.
• If we try to use home-manager, I would expect to hit the same problems and/or collisions on activation, but I have not experimented with this.

Flag-controlled packages may be broken

Doom supports listing all packages (including ones pulled in by modules that are not currently enabled). Unstraightened uses this to build-test them. However, this does not include packages enabled through currently-disabled flags.

This is tricky because Doom seems to not support accessing supported flags programmatically, and because some flags are mutually exclusive.

I may end up approximating this by checking in a hardcoded init.el with all (or at least most) currently-available flags enabled.

doom doctor fails with / complains about...

"Checking for stale elc files... File is missing"

> Checking for stale elc files...
x There was an unexpected runtime error
  Message: File is missing
  Details: ("Opening directory" "No such file or directory" "/home/marienz/.local/share/nix-doom-unstraightened/straight/build-29.3")

For now, just create the directory.

I would like to fix this but have not thought of the least messy way yet.

"Doom is installed in a non-standard location"

Ignore it.

Unstraightened uses --init-directory, as the doctor recommends.

"Found another Emacs config:"

Safe to ignore, for the same reason as the previous warning.

tree-sitter error on initialization with file-error "Opening output file" "Read-only file system"

The ABI loaded for some grammars from nixpkgs is too new (14) compared to what vanilla Doom Emacs receives (13). This results in tree-sitter and some particular grammars to be incompatible. This issue is currently confirmed to affect golang.

See issue #7 for a more detailed explanation.

Considering that Doom Emacs will likely use the Emacs 29+ built-in tree-sitter at some point at least as an opt-in (see related Doom Emacs issue) this particular issue for Unstraightened is unlikely to get solved.

As a workaround the following is possible:

• Temporarily disable Doom Emacs from handling tree-sitter in init.el.
• Define your nix Emacs package to be compiled with native tree-sitter support.
• Use package treesit-auto (e.g. it to packages.el) to gracefully include activation of tree-sitter specific modes of a programming language, depending on if a particular grammer is installed or not.
• Include Emacs package treesit-grammars.with-all-grammars from nixpkgs, e.g. use the home-manager option extraPackages like so: extraPackages = epkgs: [ epkgs.treesit-grammars.with-all-grammars ];.

As a result tree-sitter (built-in to Emacs) will be compatible with the current ABI for grammars included in nixpkgs.

Frequently Anticipated Questions

How do I add more packages?

Add (package! foo) to packages.el.

Do not wrap emacsWithDoom in emacsWithPackages. See HACKING.md for why this will not work.

The home-manager option extraPackages is available to add extra Emacs packages from nixpkgs to Doom Emacs. If this is not sufficient, please file an issue.

How do I add packages not in Emacs overlay?

Add (package! foo :recipe ...) to packages.el.

If this is not sufficient, file an issue explaining what you're trying to do.

What's wrong with straight.el?

straight.el is great, but its features are somewhat at odds with Nix:

• straight.el can fetch package build recipes and packages. We cannot use this from within Nix's build sandbox: we would need to build a system similar to how emacs-overlay updates elpa / melpa and get straight.el to use it.
• straight.el maintains a tree of mutable Git checkouts: you can edit these directly or use straight.el to maintain them. The Nix store is immutable so none of this will work.
• straight.el can build packages, but so can nixpkgs / emacs-overlay.

Doom heavily uses straight.el during doom sync, but it does not use it at all at startup and barely uses it after that. Since we're replacing doom sync in its entirety, bypassing straight.el seems simpler than trying to use it just for package builds.

Unstraightened seems to use package.el. Isn't that bad?

Doom's FAQ offers several arguments against package.el. They boil down to two problems, neither of which applies to Unstraightened:

• package.el always builds from head: no rollback, no pinning, no reproducibility, no way to override the package source used. Unstraightened does not use package.el to fetch packages: it leaves that to Nix. We can handle pinning there, and Nix flakes add further reproducibility and rollback beyond what Doom's pins offer.
• package.el can be slow to initialize. Doom normally speeds up startup by combining autoloads from all installed packages into one file. Because package.el produces autoload files much like straight.el does, and we're loading everything from the immutable Nix store, we can apply exactly the same approach to package.el. Unstraightened startup performance should be about the same as vanilla Doom.

It's so slow to build!

Parallel builds should help (set Nix's max-jobs to something greater than 1), but it is a bit slow.

There are a few issues:

• Unstraightened uses IFD to determine packages to install and to determine package dependencies for packages not in emacs-overlay. Especially the latter is slow.

• Doom (currently) does not native-compile ahead of time, but Unstraightened (or nixpkgs, really), does.

  • It should be possible to disable nativecomp and/or move it to runtime, but see the next point...

• Unstraightened's packages should be cacheable, but I don't have that set up yet.

  • In particular, Unstraightened's generated derivations for elisp packages do not depend on the exact Doom source or configuration they're generated from. They depend on the pinned version and Emacs binary used to build them, but not much else. So it should be possible to build a Doom configuration with just a few modules enabled using commonly-used versions of Emacs from CI and push the results to a binary cache like https://cachix.org/.

Required disclaimer

This is not an officially supported Google product. It is a personal side project.