Flakes: Difference between revisions

Pigs (talk | contribs)
Moved flake-utils usage to its own page; formatting and wording improvements
Pigs (talk | contribs)
Move flake-compat content to it's own page and link to new page
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When output <code>apps.<system>.myapp</code> is not defined, <code>nix run myapp</code> runs <code><packages or legacyPackages.<system>.myapp>/bin/<myapp.meta.mainProgram or myapp.pname or myapp.name (the non-version part)></code>
When output <code>apps.<system>.myapp</code> is not defined, <code>nix run myapp</code> runs <code><packages or legacyPackages.<system>.myapp>/bin/<myapp.meta.mainProgram or myapp.pname or myapp.name (the non-version part)></code>


== Using flakes with stable Nix == <!--T:50-->
== Flake support in projects without flakes == <!--T:50-->


<!--T:51-->
<!--T:51-->
There exists the [https://github.com/edolstra/flake-compat flake-compat] library that you can use to shim <code>default.nix</code> and <code>shell.nix</code> files. It will download the inputs of the flake, pass them to the flake’s <code>outputs</code> function and return an attribute set containing <code>defaultNix</code> and <code>shellNix</code> attributes. The attributes will contain the output attribute set with an extra <code>default</code> attribute pointing to current platform’s <code>defaultPackage</code> (resp. <code>devShell</code> for <code>shellNix</code>).
The [https://github.com/edolstra/flake-compat flake-compat] library provides a compatibility layer that allows projects using traditional <code>default.nix</code> and <code>shell.nix</code> files to operate with flakes. For more details and usage examples, see the [[Flake Compat]] page.
 
<!--T:52-->
Place the following into <code>default.nix</code> (for <code>shell.nix</code>, replace <code>defaultNix</code> with <code>shellNix</code>) to use the shim:
 
</translate>
<syntaxHighlight lang=nix>
(import (
  fetchTarball {
    url = "https://github.com/edolstra/flake-compat/archive/12c64ca55c1014cdc1b16ed5a804aa8576601ff2.tar.gz";
    sha256 = "0jm6nzb83wa6ai17ly9fzpqc40wg1viib8klq8lby54agpl213w5"; }
) {
  src =  ./.;
}).defaultNix
</syntaxHighlight>
<translate>
 
<!--T:54-->
You can also use the lockfile to make updating the hashes easier using <code>nix flake lock --update-input flake-compat</code>. Add the following to your <code>flake.nix</code>:
 
</translate>
<syntaxHighlight lang=nix>
  inputs.flake-compat = {
    url = "github:edolstra/flake-compat";
    flake = false;
  };
</syntaxHighlight>
<translate>
 
<!--T:56-->
and add <code>flake-compat</code> to the arguments of <code>outputs</code> attribute. Then you will be able to use <code>default.nix</code> like the following:
 
</translate>
<syntaxhighlight lang="nix">
(import (
  let
    lock = builtins.fromJSON (builtins.readFile ./flake.lock);
    nodeName = lock.nodes.root.inputs.flake-compat;
  in
  fetchTarball {
    url =
      lock.nodes.${nodeName}.locked.url
        or "https://github.com/edolstra/flake-compat/archive/${lock.nodes.${nodeName}.locked.rev}.tar.gz";
    sha256 = lock.nodes.${nodeName}.locked.narHash;
  }
) { src = ./.; }).defaultNix
</syntaxhighlight>
<translate>


== Accessing flakes from Nix expressions == <!--T:58-->
== Accessing flakes from Nix expressions == <!--T:58-->