feat(shells)!: redefine in terms of createThings

modules/flake/shells/default.nix

@@ -0,0 +1,77 @@
+{ lib, config, self, inputs, ... }:
+
+let
+  inherit (config.lib)
+    createThings;
+in
+let
+  createDevShells = baseDir:
+    createThings {
+      inherit baseDir;
+      thingType = "devShell";
+      raw = false;
+      extras.systems = {
+        default = lib.const true;
+      };
+    };
+in
+{
+  options = let
+    inherit (lib) types;
+  in {
+    flake.autoDevShells = lib.mkOption {
+      description = ''
+        Automagically generate devShells from walking directories with Nix files
+      '';
+      type = types.submodule (submodule: {
+        options = {
+          enable = lib.mkEnableOption "Automatic devShells extraction";
+          dir = lib.mkOption {
+            description = ''
+              Base directory of the contained devShells
+            '';
+            type = types.path;
+            default = "${self}/shells";
+            defaultText = ''''${self}/shells'';
+          };
+          result = lib.mkOption {
+            description = ''
+              The resulting automatic devShells
+            '';
+            type = types.attrsOf (types.submodule { options = {
+              devShell = lib.mkOption { type = types.unspecified; };
+              systems = lib.mkOption { type = types.functionTo types.bool; };
+            };});
+            readOnly = true;
+            internal = true;
+            default =
+              lib.optionalAttrs
+                config.flake.autoDevShells.enable
+                (createDevShells config.flake.autoDevShells.dir);
+          };
+        };
+      });
+      default = {};
+    };
+  };
+
+  config = {
+    perSystem = { lib, pkgs, system, ... }: let
+      devShells =
+        lib.pipe
+          config.flake.autoDevShells.result
+          [
+            (lib.filterAttrs
+              (name: { devShell, systems }:
+                pkgs.callPackage systems {
+                  inherit (pkgs) lib hostPlatform targetPlatform;
+                }))
+            (lib.mapAttrs
+              (name: { devShell, systems }:
+                pkgs.callPackage devShell { inherit inputs; }))
+          ];
+    in {
+      inherit devShells;
+    };
+  };
+}