modules: system: nix: DRY inputs handling

modules/system/nix/default.nix

@@ -2,6 +2,21 @@
 { config, inputs, lib, options, pkgs, ... }:
 let
   cfg = config.my.system.nix;
+
+  channels = lib.my.merge [
+    {
+      # Allow me to use my custom package using `nix run self#pkg`
+      self = inputs.self;
+      # Add NUR to run some packages that are only present there
+      nur = inputs.nur;
+      # Use pinned nixpkgs when using `nix run pkgs#<whatever>`
+      pkgs = inputs.nixpkgs;
+    }
+    (lib.optionalAttrs cfg.overrideNixpkgs {
+      # ... And with `nix run nixpkgs#<whatever>`
+      nixpkgs = inputs.nixpkgs;
+    })
+  ];
 in
 {
   options.my.system.nix = with lib; {
@@ -40,16 +55,12 @@ in
     }
 
     (lib.mkIf cfg.addToRegistry {
-      nix.registry = {
+      nix.registry =
-        # Allow me to use my custom package using `nix run self#pkg`
+        let
-        self.flake = inputs.self;
+          makeEntry = v: { flake = v; };
-        # Use pinned nixpkgs when using `nix run pkgs#<whatever>`
+          makeEntries = lib.mapAttrs (lib.const makeEntry);
-        pkgs.flake = inputs.nixpkgs;
+        in
-        # ... And with `nix run nixpkgs#<whatever>`
+        makeEntries channels;
-        nixpkgs.flake = lib.mkIf cfg.overrideNixpkgs inputs.nixpkgs;
-        # Add NUR to run some packages that are only present there
-        nur.flake = inputs.nur;
-      };
     })
 
     (lib.mkIf cfg.linkInputs {
@@ -60,13 +71,6 @@ in
             value = { source = v.outPath; };
           };
           makeLinks = lib.mapAttrs' makeLink;
-          channels = {
-            self = inputs.self;
-            pkgs = inputs.nixpkgs;
-            nur = inputs.nur;
-          } // lib.optionalAttrs cfg.overrideNixpkgs {
-            nixpkgs = inputs.nixpkgs;
-          };
         in
         makeLinks channels;
     })