node inheritance + group parsing

nix/snow/lib/default.nix

@@ -0,0 +1,27 @@
+# Copyright 2025-2026 _cry64 (Emile Clark-Boman)
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+{
+  nt,
+  mix,
+  ...
+} @ args: let
+  inherit (nt) findImport;
+in
+  mix.newMixture args (mixture: {
+    includes.public = [
+      ./nixpkgs.nix
+    ];
+
+    inherit findImport;
+  })

nix/snow/lib/nixpkgs.nix

@@ -0,0 +1,51 @@
+{
+  inputs,
+  lib,
+  ...
+}: let
+  inherit
+    (lib)
+    mkOption
+    types
+    ;
+
+  # A best effort, lenient estimate. Please use a recent nixpkgs lib if you
+  # override it at all.
+  minVersion = "23.05pre-git";
+
+  isNixpkgsValidVersion = let
+    revInfo = lib.optional (inputs.nixpkgs?rev) " (nixpkgs-lib.rev: ${inputs.nixpkgs.rev})";
+  in
+    (builtins.compareVersions lib.version minVersion < 0)
+    || abort ''
+      The nixpkgs dependency of snow was overridden but is too old.
+      The minimum supported version of nixpkgs-lib is ${minVersion},
+      but the actual version is ${lib.version}${revInfo}.
+    '';
+in
+  assert isNixpkgsValidVersion; {
+    # Helper function for defining a per-system option that
+    # gets transposed by the usual flake system logic to a
+    # top-level outputs attribute.
+    mkPerSystemFlakeOutput = {
+      name,
+      option,
+      file,
+    }: {
+      _file = file;
+
+      options = {
+        outputs.${name} = mkOption {
+          type = types.attrsWith {
+            elemType = option.type;
+            lazy = true;
+            placeholder = "system";
+          };
+          default = {};
+          description = ''
+            See {option}`perSystem.${name}` for description and examples.
+          '';
+        };
+      };
+    };
+  }

nix/snow/lib/nodes.nix

@@ -1,96 +0,0 @@
-# Copyright 2025-2026 _cry64 (Emile Clark-Boman)
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#    http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-{nt, ...}: let
-  inherit
-    (builtins)
-    concatLists
-    elem
-    filter
-    isAttrs
-    mapAttrs
-    pathExists
-    typeOf
-    ;
-
-  rootGroupName = "all";
-
-  parseGroupsDecl = groups: let
-    validGroup = g:
-      isAttrs g
-      || throw ''
-        Cerulean Nexus groups must be provided as attribute sets, got "${typeOf g}" instead!
-        Ensure all the group definitions are attribute sets under your call to `cerulean.mkNexus`.
-        NOTE: Groups can be accessed via `self.groups.PATH.TO.YOUR.GROUP`
-      '';
-    delegate = parent: gName: g: let
-      result =
-        (g
-          // {
-            _name = gName;
-            _parent = parent;
-          })
-        |> mapAttrs (name: value:
-          if elem name ["_name" "_parent"]
-          # ignore metadata fields
-          then value
-          else assert validGroup value; (delegate result name value));
-    in
-      result;
-  in
-    assert validGroup groups;
-      delegate null rootGroupName groups;
-
-  getGroupModules = root: groups:
-  # ensure root group is always added
-    groups
-    # add all inherited groups via _parent
-    |> map (let
-      delegate = g:
-        if g._parent == null
-        then [g]
-        else [g] ++ delegate (g._parent);
-    in
-      delegate)
-    # flatten recursion result
-    |> concatLists
-    # find import location
-    |> map (group: nt.findImport /${root}/groups/${group._name})
-    # filter by uniqueness
-    |> nt.prim.unique
-    # ignore missing groups
-    |> filter pathExists;
-in {
-  mapNodes = nodes: f:
-    nodes.nodes
-    |> mapAttrs (name: node: let
-      # use per-node base or default to nodes' base
-      base =
-        if node.base != null
-        then node.base
-        else if nodes.base != null
-        then nodes.base
-        else
-          abort ''
-            Cerulean cannot construct nodes node "${name}" without a base package source.
-            Ensure `nodes.nodes.*.base` or `nodes.base` is a flake reference to the github:NixOS/nixpkgs repository.
-          '';
-    in
-      f rec {
-        inherit name node base;
-        inherit (base) lib;
-
-        groups = node.groups (parseGroupsDecl nodes.groups);
-        groupModules = root: getGroupModules root groups;
-      });
-}