packages: apply overlays to output packages

Apply overlays to output packages so we can easily use a modified
package.

flake.nix

@@ -26,26 +26,29 @@
       externOverlays = [ nur.overlay devshell.overlay ];
       externModules = [ home.nixosModules.home-manager ];
 
+      pkgs' = unstable:
+        let
+          override = import ./pkgs/override.nix;
+          overlays = (attrValues self.overlays)
+            ++ externOverlays
+            ++ [ self.overlay (override unstable) ];
+        in
+        pkgImport nixos overlays;
+
+      unstable' = pkgImport master [ ];
+
       osSystem = "x86_64-linux";
 
       outputs =
         let
           system = osSystem;
-          pkgset =
-            let
-              overlays =
-                (attrValues self.overlays)
-                ++ externOverlays
-                ++ [ self.overlay ];
-            in
-            genPkgset {
-              inherit master nixos overlays system;
-            };
+          unstablePkgs = unstable' system;
+          osPkgs = pkgs' unstablePkgs system;
         in
         {
           nixosConfigurations =
             import ./hosts (recursiveUpdate inputs {
-              inherit lib pkgset utils externModules system;
+              inherit lib osPkgs unstablePkgs utils externModules system;
             });
 
           overlay = import ./pkgs;
@@ -65,11 +68,8 @@
       (eachDefaultSystem
         (system:
           let
-            pkgs = pkgImport {
-              inherit system;
-              pkgs = nixos;
-              overlays = [ devshell.overlay ];
-            };
+            unstablePkgs = unstable' system;
+            pkgs = pkgs' unstablePkgs system;
 
             packages = flattenTreeSystem system
               (genPackages {

hosts/default.nix

@@ -2,9 +2,10 @@
 , lib
 , nixos
 , master
-, pkgset
+, osPkgs
 , self
 , system
+, unstablePkgs
 , utils
 , externModules
 , ...
@@ -12,7 +13,6 @@
 let
   inherit (utils) recImport;
   inherit (builtins) attrValues removeAttrs;
-  inherit (pkgset) osPkgs unstablePkgs;
 
   unstableModules = [ ];
   addToDisabledModules = [ ];
@@ -65,14 +65,6 @@ let
             system.configurationRevision = lib.mkIf (self ? rev) self.rev;
           };
 
-          overrides = {
-            nixpkgs.overlays =
-              let
-                override = import ../pkgs/override.nix unstablePkgs;
-              in
-              [ override ];
-          };
-
           local = import "${toString ./.}/${hostName}.nix";
 
           # Everything in `./modules/list.nix`.
@@ -84,7 +76,6 @@ let
           core
           global
           local
-          overrides
           modOverrides
         ] ++ externModules;
 

lib/utils.nix

@@ -1,8 +1,8 @@
 { lib, ... }:
 let
-  inherit (builtins) attrNames isAttrs readDir listToAttrs;
+  inherit (builtins) attrNames attrValues isAttrs readDir listToAttrs mapAttrs;
 
-  inherit (lib) filterAttrs hasSuffix mapAttrs' nameValuePair removeSuffix
+  inherit (lib) fold filterAttrs hasSuffix mapAttrs' nameValuePair removeSuffix
     recursiveUpdate genAttrs;
 
   # mapFilterAttrs ::
@@ -14,8 +14,8 @@ let
   # Generate an attribute set by mapping a function over a list of values.
   genAttrs' = values: f: listToAttrs (map f values);
 
-  pkgImport = { pkgs, system, overlays }:
-    import pkgs {
+  pkgImport = nixpkgs: overlays: system:
+    import nixpkgs {
       inherit system overlays;
       config = { allowUnfree = true; };
     };
@@ -33,20 +33,6 @@ in
 {
   inherit mapFilterAttrs genAttrs' pkgImport pathsToImportedAttrs;
 
-  genPkgset = { master, nixos, overlays, system }:
-    {
-      osPkgs = pkgImport {
-        inherit system overlays;
-        pkgs = nixos;
-      };
-
-      unstablePkgs = pkgImport {
-        inherit system;
-        overlays = [];
-        pkgs = master;
-      };
-    };
-
   overlayPaths =
     let
       overlayDir = ../overlays;
@@ -86,12 +72,19 @@ in
   genPackages = { self, pkgs }:
     let
       inherit (self) overlay overlays;
-      packages = overlay pkgs pkgs;
-      overlayPkgs =
-        genAttrs
-          (attrNames overlays)
-          (name: (overlays."${name}" pkgs pkgs)."${name}");
+      packagesNames = attrNames (overlay null null)
+        ++ attrNames (fold
+        (attr: sum: recursiveUpdate sum attr)
+        { }
+        (attrValues
+          (mapAttrs (_: v: v null null) overlays)
+        )
+      );
     in
-    recursiveUpdate packages overlayPkgs;
-
+    fold
+      (key: sum: recursiveUpdate sum {
+        ${key} = pkgs.${key};
+      })
+      { }
+      packagesNames;
 }