.github | ||
examples | ||
.gitignore | ||
default.nix | ||
flake.nix | ||
flattenTree.nix | ||
LICENSE | ||
README.md | ||
simpleFlake.nix |
flake-utils
STATUS: alpha
Pure Nix flake utility functions.
The goal of this project is to build a collection of pure Nix functions that don't depend on nixpkgs, and that are useful in the context of writing other Nix flakes.
Usage
allSystems -> [<system>]
A list of all systems defined in nixpkgs. For a smaller list see defaultSystems
defaultSystems -> [<system>]
The list of systems supported by nixpkgs and built by hydra. Useful if you want add additional platforms:
eachSystem (defaultSystems ++ ["armv7l-linux"]) (system: { hello = 42; })
eachSystem -> [<system>] -> (<system> -> attrs)
A common case is to build the same structure for each system. Instead of building the hierarchy manually or per prefix, iterate over each systems and then re-build the hierarchy.
Eg:
eachSystem ["x86_64-linux"] (system: { hello = 42; })
# => { hello.x86_64-linux.hello = 42; }
eachSystem allSystems (system: { hello = 42; })
# => {
hello.aarch64-darwin = 42,
hello.aarch64-genode = 42,
hello.aarch64-linux = 42,
...
hello.x86_64-redox = 42,
hello.x86_64-solaris = 42,
hello.x86_64-windows = 42
}
eachDefaultSystem -> (<system> -> attrs)
eachSystem
pre-populated with defaultSystems
.
Example
$ examples/each-system/flake.nix as nix
{
description = "Flake utils demo";
inputs.flake-utils.url = "github:numtide/flake-utils";
outputs = { self, nixpkgs, flake-utils }:
flake-utils.lib.eachDefaultSystem (system:
let pkgs = nixpkgs.legacyPackages.${system}; in
rec {
packages = flake-utils.lib.flattenTree {
hello = pkgs.hello;
gitAndTools = pkgs.gitAndTools;
};
defaultPackage = packages.hello;
apps.hello = flake-utils.lib.mkApp { drv = packages.hello; };
defaultApp = apps.hello;
}
);
}
mkApp { drv, name ? drv.pname or drv.name, execPath ? drv.passthru.execPath or "/bin/${name}"
A small utility that builds the structure expected by the special apps
and defaultApp
prefixes.
flattenTree -> attrs -> attrs
Nix flakes insists on having a flat attribute set of derivations in
various places like the packages
and checks
attributes.
This function traverses a tree of attributes (by respecting recurseIntoAttrs) and only returns their derivations, with a flattened key-space.
Eg:
flattenTree { hello = pkgs.hello; gitAndTools = pkgs.gitAndTools }
Returns:
{
hello = «derivation»;
"gitAndTools/git" = «derivation»;
"gitAndTools/hub" = «derivation»;
# ...
}
simpleFlake -> attrs -> attrs
This function should be useful for most common use-cases where you have a simple flake that builds a package. It takes nixpkgs and a bunch of other parameters and outputs a value that is compatible as a flake output.
Input:
{
# pass an instance of self
self
, # pass an instance of the nixpkgs flake
nixpkgs
, # we assume that the name maps to the project name, and also that the
# overlay has an attribute with the `name` prefix that contains all of the
# project's packages.
name
, # nixpkgs config
config ? { }
, # pass either a function or a file
overlay ? null
, # use this to load other flakes overlays to supplement nixpkgs
preOverlays ? [ ]
, # maps to the devShell output. Pass in a shell.nix file or function.
shell ? null
, # pass the list of supported systems
systems ? [ "x86_64-linux" ]
}: null
Example
Here is how it looks like in practice:
$ examples/simple-flake/flake.nix as nix
{
description = "Flake utils demo";
inputs.flake-utils.url = "github:numtide/flake-utils/simple-flake";
outputs = { self, nixpkgs, flake-utils }:
flake-utils.lib.simpleFlake {
inherit self nixpkgs;
name = "simple-flake";
overlay = ./overlay.nix;
shell = ./shell.nix;
};
}
Known issues
$ nix flake check
warning: unknown flake output 'lib'
nixpkgs is currently having the same issue so I assume that it will be eventually standardized.