apply-pr-to-flake

name	apply-pr-to-flake
description	Apply a nixpkgs PR override to the flake.nix configuration
license	MIT
metadata	{"audience":"nixos-admins","workflow":"pr-application"}

What I do

Apply a nixpkgs PR to flake.nix by creating an input and overlay to override a specific package version. This follows the documented pattern in flake.nix lines 120-137.

When to use me

Use this when you want to apply a PR from the main nixpkgs repository to override a package version in your flake without merging it upstream yet.

Questions I'll ask

1. PR number - The pull request number (e.g., 500995)
2. Repository - Which nixpkgs repository to use (default: NixOS/nixpkgs)
3. Package name - Which nixpkgs package to override
4. Input name - Descriptive name for the input (e.g., pr500995, pr471984)
5. Version check - Should I verify the package version is not newer than a specific version? (default: null, no check)
   • If yes: Provide the maximum allowed version in semantic version format (e.g., "8401")
   • If no: Set to null to skip version checking
6. Create module file - Should I create modules/pr-overlays.nix for declarative management?
   • Yes: Creates a NixOS module with option myconfig.prOverlays.enable and list of overlays [{package, prNumber, inputName, maxVersion?, prUrl}]
   • No: Only modify flake.nix
   • Default: Yes for new setups

Implementation steps

1. Get the PR commit hash by fetching PR details
2. Create the input in the inputs section after other inputs:

   {input}.url = "github:{owner}/{repo}/{commit-hash}";
   

3. Add the overlay in the PR patch section using the pattern:

   nixpkgs.overlays = map
     ({ input, pkg }:
     (_: _:
       { "${pkg}" =
         (import inputs."${input}" {
           inherit (pkgs) config system;
         })."${pkg}";
       })
     )
     [
       { input = "{input}"; pkg = "{package}"; }
     ];
   

4. Run ./nixfmtall.sh to format all Nix files
5. Run nix flake check to validate the configuration

Notes

• Follow the pattern exactly by placing the overlay module after the core system module and before other overlays
• Use descriptive input names: pr<PR-number> is preferred (e.g., pr500995)
• Comment out the URL in the template section for easy reference
• Always run nix flake check after making changes to ensure validity
• The overlay will only override the package; other packages remain from the main nixpkgs
• The entry should be placed near the other PR-related comments in the PR template section