Emacs overlay for Nixpkgs

Quickstart

To get up and running quickly, add the following lines to your /etc/nixos/configuration.nix:

{config, pkgs, callPackage, ... }:
{
# ...

  services.emacs.package = pkgs.emacs-unstable;

  nixpkgs.overlays = [
    (import (builtins.fetchTarball {
      url = https://github.com/nix-community/emacs-overlay/archive/master.tar.gz;
    }))
  ];

# ...
}

This configuration will enable this overlay, and define your system-wide emacs package as the emacs-unstable attribute it provides.

NOTE: Read the “Usage of the overlay” section below for further explanation of this configuration. This has the potential to break things, and will frequently trigger full source rebuilds of emacs.

If you want to enable daemon/server mode, add the following line to the same configuration:

services.emacs.enable = true;

It is recommended you read Nixpkgs and NixOS documentation on package overlays and overrides to familiarize yourself with the concepts:

• https://nixos.wiki/wiki/Overlays
• https://nixos.org/nixpkgs/manual/#chap-overlays

Contents of the overlay

This overlay consists of two overlays: emacs and package.

You can use both of them as a whole overlay or only one of them.

package overlay

Elpa

Daily generations of Elpa.

Melpa / Melpa stable

Daily generations of Melpa & Melpa stable attribute sets.

EXWM & needed dependencies

This overlay provides fresh versions of EXWM and dependencies. This is updated daily.

emacs overlay

Emacs from Git and latest (including pre-releases)

This overlay also provides two versions (latest from git) for Emacs. These are updated daily.

These attributes are named emacsGit and emacs-unstable. emacsGit is built from the latest master branch and emacs-unstable is built from the latest tag.

Emacs from git is not guaranteed stable and may break your setup at any time, if it breaks you get to keep both pieces.

We also provide two attributes named emacsGit-nox and emacs-unstable-nox if you wish to have Emacs built without X dependencies. emacsPgtk uses the experimental pgtk feature which supports Wayland natively.

Extra library functionality

This overlay comes with extra functions to generate an Emacs closure from various types of dependency declaration. (These are abstractions on top of emacsWithPackages.)

For example, emacsWithPackagesFromUsePackage adds packages which are required in a user’s config via use-package or leaf.

{ pkgs, ... }:
{
  environment.systemPackages = [
    (pkgs.emacsWithPackagesFromUsePackage {
      # Your Emacs config file. Org mode babel files are also
      # supported.
      # NB: Config files cannot contain unicode characters, since
      #     they're being parsed in nix, which lacks unicode
      #     support.
      # config = ./emacs.org;
      config = ./emacs.el;

      # Whether to include your config as a default init file.
      # If being bool, the value of config is used.
      # Its value can also be a derivation like this if you want to do some
      # substitution:
      #   defaultInitFile = pkgs.substituteAll {
      #     name = "default.el";
      #     src = ./emacs.el;
      #     inherit (config.xdg) configHome dataHome;
      #   };
      defaultInitFile = true;

      # Package is optional, defaults to pkgs.emacs
      package = pkgs.emacsGit;

      # By default emacsWithPackagesFromUsePackage will only pull in
      # packages with `:ensure`, `:ensure t` or `:ensure <package name>`.
      # Setting `alwaysEnsure` to `true` emulates `use-package-always-ensure`
      # and pulls in all use-package references not explicitly disabled via
      # `:ensure nil` or `:disabled`.
      # Note that this is NOT recommended unless you've actually set
      # `use-package-always-ensure` to `t` in your config.
      alwaysEnsure = true;

      # For Org mode babel files, by default only code blocks with
      # `:tangle yes` are considered. Setting `alwaysTangle` to `true`
      # will include all code blocks missing the `:tangle` argument,
      # defaulting it to `yes`.
      # Note that this is NOT recommended unless you have something like
      # `#+PROPERTY: header-args:emacs-lisp :tangle yes` in your config,
      # which defaults `:tangle` to `yes`.
      alwaysTangle = true;

      # Optionally provide extra packages not in the configuration file.
      extraEmacsPackages = epkgs: [
        epkgs.cask
      ];

      # Optionally override derivations.
      override = final: prev: {
        weechat = prev.melpaPackages.weechat.overrideAttrs(old: {
          patches = [ ./weechat-el.patch ];
        });
      };
    })
  ];
}

Similarly, emacsWithPackagesFromPackageRequires adds packages which are declared in a .el package file’s Package-Requires header, which can be handy for CI purposes:

...
let
  emacsForCI = pkgs.emacsWithPackagesFromPackageRequires {
    packageElisp = builtins.readFile ./flycheck.el;
    extraEmacsPackages = epkgs: [
      epkgs.package-lint
    ];
  };
pkgs.mkShell {
  buildInputs = [ emacsForCI ];
}

Usage of the overlay

Latest master each rebuild

One way, and probably the most convenient way to pull in this overlay is by just fetching the tarball of latest master on rebuild.

This has side-effects if packages breaks or things like that you may want to be in control of which revision of the overlay you run.

Adding the overlay this way will extend your Emacs packages set to contain the latest EXWM and dependencies from their respective master and make the package emacsGit available. These of course change quite rapidly and will cause compilation time.

{
  nixpkgs.overlays = [
    (import (builtins.fetchTarball {
      url = https://github.com/nix-community/emacs-overlay/archive/master.tar.gz;
    }))
  ];
}

Binary cache

You will want to use the nix-community binary cache. Where the overlay’s build artefacts are pushed. See here for installation instructions.

Install directly from the overlay

The repository is meant to be used as an overlay as is explained above. Still, for experimental purposes, you might want to install a package directly from the overlay. For example, you can install emacsGit from a clone of this repository with the following command:

nix-build --expr 'with (import <nixpkgs> { overlays = [ (import ./.) ]; }); emacsGit'

Community

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