minimal working state

flake.lock

@@ -9,11 +9,11 @@
         "utils": "utils"
       },
       "locked": {
-        "lastModified": 1766051518,
+        "lastModified": 1770019181,
-        "narHash": "sha256-znKOwPXQnt3o7lDb3hdf19oDo0BLP4MfBOYiWkEHoik=",
+        "narHash": "sha256-hwsYgDnby50JNVpTRYlF3UR/Rrpt01OrxVuryF40CFY=",
         "owner": "serokell",
         "repo": "deploy-rs",
-        "rev": "d5eff7f948535b9c723d60cd8239f8f11ddc90fa",
+        "rev": "77c906c0ba56aabdbc72041bf9111b565cdd6171",
         "type": "github"
       },
       "original": {
@@ -68,11 +68,11 @@
         "spectrum": "spectrum"
       },
       "locked": {
-        "lastModified": 1771365290,
+        "lastModified": 1773018425,
-        "narHash": "sha256-1XJOslVyF7yzf6yd/yl1VjGLywsbtwmQh3X1LuJcLI4=",
+        "narHash": "sha256-fpgZBmZpKoEXEowBK/6m8g9FcOLWQ4UxhXHqCw2CpSM=",
         "owner": "microvm-nix",
         "repo": "microvm.nix",
-        "rev": "789c90b164b55b4379e7a94af8b9c01489024c18",
+        "rev": "25ebda3c558e923720c965832dc9a04f559a055c",
         "type": "github"
       },
       "original": {
@@ -129,11 +129,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1768323494,
+        "lastModified": 1773375660,
-        "narHash": "sha256-yBXJLE6WCtrGo7LKiB6NOt6nisBEEkguC/lq/rP3zRQ=",
+        "narHash": "sha256-SEzUWw2Rf5Ki3bcM26nSKgbeoqi2uYy8IHVBqOKjX3w=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "2c3e5ec5df46d3aeee2a1da0bfedd74e21f4bf3a",
+        "rev": "3e20095fe3c6cbb1ddcef89b26969a69a1570776",
         "type": "github"
       },
       "original": {
@@ -166,11 +166,11 @@
         "systems": "systems_2"
       },
       "locked": {
-        "lastModified": 1770975056,
+        "lastModified": 1773738366,
-        "narHash": "sha256-ZXTz/P3zUbbM6lNXzt91u8EwfNqhXpYMu8+wvFZqQHE=",
+        "narHash": "sha256-oH22HyNHEdCoCQo734sQCHUr6C0jmGQJMZ13dsgEHkk=",
         "owner": "cry128",
         "repo": "nt",
-        "rev": "f42dcdd49a7921a7f433512e83d5f93696632412",
+        "rev": "f32c3a726a3d608d30aaaa1df2301c1eaf5ef8f4",
         "type": "github"
       },
       "original": {
@@ -212,11 +212,11 @@
     "spectrum": {
       "flake": false,
       "locked": {
-        "lastModified": 1759482047,
+        "lastModified": 1772189877,
-        "narHash": "sha256-H1wiXRQHxxPyMMlP39ce3ROKCwI5/tUn36P8x6dFiiQ=",
+        "narHash": "sha256-i1p90Rgssb//aNiTDFq46ZG/fk3LmyRLChtp/9lddyA=",
         "ref": "refs/heads/main",
-        "rev": "c5d5786d3dc938af0b279c542d1e43bce381b4b9",
+        "rev": "fe39e122d898f66e89ffa17d4f4209989ccb5358",
-        "revCount": 996,
+        "revCount": 1255,
         "type": "git",
         "url": "https://spectrum-os.org/git/spectrum"
       },

nix/default.nix

@@ -15,22 +15,28 @@
   mix,
   inputs,
   ...
-} @ args:
+} @ args: let
-mix.newMixture args (mixture: {
+  mixArgs =
-  submods.public = [
+    args
-    ./snow
+    // {
-  ];
+      inherit (inputs.nixpkgs) lib;
+    };
+in
+  mix.newMixture mixArgs (mixture: {
+    submods.public = [
+      ./snow
+    ];
 
-  version = "0.2.6-alpha";
+    version = "0.2.6-alpha";
 
-  overlays = [
+    overlays = [
-    # build deploy-rs as a package not from the flake input,
+      # build deploy-rs as a package not from the flake input,
-    # hence we can rely on a nixpkg binary cache.
+      # hence we can rely on a nixpkg binary cache.
-    inputs.deploy-rs.overlays.default
+      inputs.deploy-rs.overlays.default
-  ];
+    ];
 
-  nixosModules = rec {
+    nixosModules = rec {
-    default = cerulean;
+      default = cerulean;
-    cerulean = ./nixos;
+      cerulean = ./nixos;
-  };
+    };
-})
+  })

nix/nixos/default.nix

@@ -18,13 +18,13 @@
   node,
   pkgs,
   lib,
-  _cerulean,
+  _snow,
   ...
 } @ args: {
   imports =
     [
-      _cerulean.inputs.sops-nix.nixosModules.sops
+      _snow.inputs.sops-nix.nixosModules.sops
-      # _cerulean.inputs.microvm.nixosModules.microvm
+      # _snow.inputs.microvm.nixosModules.microvm
 
       # add support for `options.legacyImports`
       # ./legacy-imports.nix
@@ -36,7 +36,7 @@
       (import /${root}/nixpkgs.nix)
     ]
     # homemanager options declarations
-    ++ (lib.optional (_cerulean.homeManager != null) ./home.nix)
+    ++ (lib.optional (_snow.homeManager != null) ./home.nix)
     # remote deployment configuration
     ++ (lib.optional (node.deploy.ssh.host != null) ./remote-deploy);
 
@@ -46,7 +46,7 @@
     (with pkgs; [
       sops
     ])
-    ++ (with _cerulean.inputs; [
+    ++ (with _snow.inputs; [
       deploy-rs.packages.${system}.default
     ]);
 }

nix/nixos/home.nix

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 {
-  _cerulean,
+  _snow,
   config,
   root,
   lib,
@@ -30,7 +30,7 @@
     ;
 in {
   imports = [
-    _cerulean.homeManager.nixosModules.default
+    _snow.homeManager.nixosModules.default
   ];
 
   options = {
@@ -69,7 +69,7 @@ in {
           _module.args.username = name;
         });
 
-      extraSpecialArgs = _cerulean.specialArgs;
+      extraSpecialArgs = _snow.specialArgs;
       sharedModules = [
         ../home
 

nix/snow/default.nix

@@ -11,12 +11,17 @@
 # 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.
-{mix, ...} @ args:
+{
-mix.newMixture args (mixture: {
+  nt,
-  includes = {
+  mix,
-    public = [
+  ...
-      ./flake
+} @ args:
-      ./lib
+mix.newMixture (removeAttrs args ["this"]) (mixture: {
-    ];
+  submods.public = [
-  };
+    ./lib
+  ];
+
+  includes.public = [
+    ./flake
+  ];
 })

nix/snow/flake/default.nix

@@ -1,4 +1,5 @@
 {
+  self,
   this,
   inputs,
   systems,
@@ -16,14 +17,20 @@
   inherit (inputs.nixpkgs) lib;
 in {
   # snow.flake
+  # XXX: TODO: stop taking in root as parameter (maybe take self instead?)
   flake = flakeInputs: root: let
     snowflake = lib.evalModules {
       class = "snowflake";
       specialArgs = let
         reservedSpecialArgs = {
-          inherit (this) snow;
+          # inherit (this) snow;
+          snow = this;
           inherit systems root;
           inputs = flakeInputs;
+
+          _snowFlake = {
+            inherit self inputs;
+          };
         };
 
         warnIfReserved = let
@@ -50,7 +57,10 @@ in {
           flakeInputs // reservedSpecialArgs;
 
       modules = [
-        ./module.nix
+        ./nodes
+        ./modules
+        ./outputs
+        (this.lib.findImport /${root}/snow)
       ];
     };
   in

nix/snow/flake/module.nix

@@ -1,24 +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.
-{
-  root,
-  snow,
-  ...
-}: {
-  imports = [
-    ./nodes
-    ./modules
-    (snow.findImport /${root}/snow)
-  ];
-}

nix/snow/flake/modules/apps.nix

@@ -10,7 +10,7 @@
     ;
 
   inherit
-    (snow)
+    (snow.lib)
     mkPerSystemFlakeOutput
     ;
 

nix/snow/flake/modules/checks.nix

@@ -9,7 +9,7 @@
     types
     ;
   inherit
-    (snow)
+    (snow.lib)
     mkPerSystemFlakeOutput
     ;
 in

nix/snow/flake/modules/devShells.nix

@@ -10,7 +10,7 @@
     literalExpression
     ;
   inherit
-    (snow)
+    (snow.lib)
     mkPerSystemFlakeOutput
     ;
 in

nix/snow/flake/modules/formatter.nix

@@ -9,7 +9,7 @@
     types
     ;
   inherit
-    (snow)
+    (snow.lib)
     mkPerSystemFlakeOutput
     ;
 in

nix/snow/flake/modules/legacyPackages.nix

@@ -9,7 +9,7 @@
     types
     ;
   inherit
-    (snow)
+    (snow.lib)
     mkPerSystemFlakeOutput
     ;
 in

nix/snow/flake/modules/outputs.nix

@@ -8,38 +8,39 @@
     mkOption
     types
     ;
-
-  outputs = mkOption {
-    type = types.submoduleWith {
-      modules = [
-        {
-          freeformType =
-            types.lazyAttrsOf
-            (types.unique
-              {
-                message = ''
-                  No option has been declared for this flake output attribute, so its definitions can't be merged automatically.
-                  Possible solutions:
-                    - Load a module that defines this flake output attribute
-                    - Declare an option for this flake output attribute
-                    - Make sure the output attribute is spelled correctly
-                    - Define the value only once, with a single definition in a single module
-                '';
-              }
-              types.raw);
-        }
-      ];
-    };
-    description = ''
-      Raw flake output attributes. Any attribute can be set here, but some
-      attributes are represented by options, to provide appropriate
-      configuration merging.
-    '';
-  };
 in {
   options = {
-    inherit outputs;
+    outputs = mkOption {
+      type = types.submoduleWith {
+        modules = [
+          {
+            freeformType =
+              types.lazyAttrsOf
+              (types.unique
+                {
+                  message = ''
+                    No option has been declared for this flake output attribute, so its definitions can't be merged automatically.
+                    Possible solutions:
+                      - Load a module that defines this flake output attribute
+                      - Declare an option for this flake output attribute
+                      - Make sure the output attribute is spelled correctly
+                      - Define the value only once, with a single definition in a single module
+                  '';
+                }
+                types.raw);
+          }
+        ];
+      };
+      description = ''
+        Raw flake output attributes. Any attribute can be set here, but some
+        attributes are represented by options, to provide appropriate
+        configuration merging.
+      '';
+    };
   };
 
-  config = {inherit (config) flake;};
+  config = {
+    # ensure a minimal version is set
+    outputs = {};
+  };
 }

nix/snow/flake/modules/packages.nix

@@ -10,7 +10,7 @@
     ;
 
   inherit
-    (snow)
+    (snow.lib)
     mkPerSystemFlakeOutput
     ;
 in

nix/snow/flake/nodes/default.nix

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 {
-  _snow,
+  _snowFlake,
   lib,
   specialArgs,
   ...
@@ -39,7 +39,7 @@
 
   config = {
     nodes = {
-      base = _snow.inputs.nixpkgs;
+      base = _snowFlake.inputs.nixpkgs;
     };
   };
 }

nix/snow/flake/nodes/groups.nix

@@ -1,73 +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";
-in {
-  parseGroupsDecl = groups: let
-    validGroup = g:
-      isAttrs g
-      || throw ''
-        Snow node groups must be provided as attribute sets, got "${typeOf g}" instead!
-        Ensure all the group definitions are attribute sets under your call to `snow.flake`.
-        NOTE: Groups can be accessed via `self.groups.PATH.TO.YOUR.GROUP`
-      '';
-    delegate = parent: gName: g: let
-      result =
-        (g
-          // {
-            _name = gName;
-            _parent = parent;
-          })
-        |> mapAttrs (name: value:
-          if elem name ["_name" "_parent"]
-          # ignore metadata fields
-          then value
-          else assert validGroup value; (delegate result name value));
-    in
-      result;
-  in
-    assert validGroup groups;
-      delegate null rootGroupName groups;
-
-  getGroupModules = root: groups:
-  # ensure root group is always added
-    groups
-    # add all inherited groups via _parent
-    |> map (let
-      delegate = g:
-        if g._parent == null
-        then [g]
-        else [g] ++ delegate (g._parent);
-    in
-      delegate)
-    # flatten recursion result
-    |> concatLists
-    # find import location
-    |> map (group: nt.findImport /${root}/groups/${group._name})
-    # filter by uniqueness
-    |> nt.prim.unique
-    # ignore missing groups
-    |> filter pathExists;
-}

nix/snow/flake/nodes/node.nix

@@ -14,8 +14,9 @@
 {
   lib,
   systems,
-  config,
   nodesConfig,
+  groups,
+  groupLibs,
   ...
 }: {
   options = let
@@ -25,6 +26,11 @@
       types
       ;
 
+    inherit
+      (groupLibs)
+      resolveGroupsInheritance
+      ;
+
     flakeRef = types.either types.str types.path;
   in {
     enabled = lib.mkOption {
@@ -113,8 +119,8 @@
         A function from the `groups` hierarchy to a list of groups this node inherits from.
       '';
 
-      apply = groupsFn:
+      # apply = groupsFn:
-        groupsFn nodesConfig.groups;
+      #   groupsFn nodesConfig.groups |> resolveGroupsInheritance;
     };
 
     deploy = {
@@ -266,32 +272,32 @@
     };
   };
 
-  config = let
+  # config = let
-    throwGotNull = name:
+  #   throwGotNull = name:
-      throw ''
+  #     throw ''
-        [snow] `nodes.<name>.${name}` must be set for all nodes! (got: <null>)
+  #       [snow] `nodes.<name>.${name}` must be set for all nodes! (got: <null>)
-      '';
+  #     '';
-    givenSystem =
+  #   givenSystem =
-      (config.system != null)
+  #     (config.system != null)
-      || throwGotNull "system";
+  #     || throwGotNull "system";
 
-    givenBase =
+  #   givenBase =
-      (config.base != null)
+  #     (config.base != null)
-      || throwGotNull "base";
+  #     || throwGotNull "base";
 
-    givenHomeManager =
+  #   givenHomeManager =
-      (config.homeManager != null)
+  #     (config.homeManager != null)
-      || throwGotNull "homeManager";
+  #     || throwGotNull "homeManager";
 
-    givenDeployHost =
+  #   givenDeployHost =
-      (config.deploy.ssh.host != null)
+  #     (config.deploy.ssh.host != null)
-      || throwGotNull "deploy.ssh.host";
+  #     || throwGotNull "deploy.ssh.host";
-  in
+  # in
-    assert givenSystem
+  #   assert givenSystem
-    && givenBase
+  #   && givenBase
-    && givenHomeManager
+  #   && givenHomeManager
-    && givenDeployHost; {
+  #   && givenDeployHost; {
-      # extend these from the nodes configuration
+  #     # extend these from the nodes configuration
-      inherit (nodesConfig) modules args;
+  #     inherit (nodesConfig) modules args;
-    };
+  #   };
 }

nix/snow/flake/nodes/nodes.nix

@@ -12,7 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 {
-  _snow,
+  _snowFlake,
+  snow,
+  root,
   lib,
   config,
   specialArgs,
@@ -26,7 +28,10 @@
 
   flakeRef = types.either types.str types.path;
 
-  groupLibs = import ./groups.nix {inherit (_snow.inputs) nt;};
+  groupLibs = import ./groups.nix {
+    inherit snow root;
+    inherit (_snowFlake.inputs) nt;
+  };
 in {
   options = {
     base = lib.mkOption {
@@ -94,8 +99,6 @@ in {
       description = ''
         Hierarchical groups that nodes can be a member of.
       '';
-
-      apply = groupLibs.parseGroupsDecl;
     };
 
     nodes = mkOption {
@@ -103,7 +106,8 @@ in {
         specialArgs =
           specialArgs
           // {
-            nodeConfig = config;
+            nodesConfig = config;
+            inherit groupLibs;
           };
         modules = [./node.nix];
       });

nix/snow/flake/outputs/checks.nix

@@ -1,10 +1,10 @@
 {
   config,
-  _snow,
+  _snowFlake,
   ...
 }: {
   outputs.checks =
-    _snow.inputs.deploy-rs.lib
+    _snowFlake.inputs.deploy-rs.lib
     |> builtins.mapAttrs (system: deployLib:
       deployLib.deployChecks config.outputs.deploy);
 }

nix/snow/flake/outputs/default.nix

@@ -0,0 +1,7 @@
+{...}: {
+  imports = [
+    ./checks.nix
+    ./deploy.nix
+    ./nixosConfigurations.nix
+  ];
+}

nix/snow/flake/outputs/deploy.nix

@@ -1,37 +1,10 @@
 {
-  _snow,
+  _snowFlake,
+  snow,
   config,
   ...
-}: let
+}: {
-  inherit
+  outputs.deploy.nodes = snow.lib.mapNodes config.nodes ({
-    (builtins)
-    mapAttrs
-    ;
-
-  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 ''
-            snow 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;
-      });
-in {
-  outputs.deploy.nodes = mapNodes config.nodes ({
     name,
     node,
     ...
@@ -49,7 +22,7 @@ in {
       confirmTimeout
       ;
 
-    nixosFor = system: _snow.inputs.deploy-rs.lib.${system}.activate.nixos;
+    nixosFor = system: _snowFlake.inputs.deploy-rs.lib.${system}.activate.nixos;
   in {
     hostname =
       if ssh.host != null

nix/snow/flake/outputs/nixosConfigurations.nix

@@ -1,14 +1,5 @@
-# {
-#   _module = { ... };
-#   _type = "configuration";
-#   class = null;
-#   config = { ... };
-#   extendModules = «lambda extendModules @ /nix/store/9hfp0agnm43kz72l5lpfn9var5p0x2fa-source/lib/modules.nix:340:9»;
-#   graph = [ ... ];
-#   options = { ... };
-#   type = { ... };
-# }
 {
+  _snowFlake,
   snow,
   config,
   systems,
@@ -27,59 +18,67 @@
     nodes
     ;
 in {
-  outputs.nixosConfigurations = mapNodes nodes (
+  outputs.nixosConfigurations = let
-    {
+    groups = snow.lib.parseGroupDecls root config.nodes.groups;
-      base,
+  in
-      lib,
+    snow.lib.mapNodes nodes (
-      name,
+      {
-      node,
+        base,
-      groupModules,
+        lib,
-      ...
+        name,
-    }: let
+        node,
-      homeManager =
+        ...
-        if node.homeManager != null
+      }: let
-        then node.homeManager
+        nodeGroups =
-        else if nodes.homeManager != null
+          (node.groups groups)
-        then nodes.homeManager
+          |> snow.lib.resolveGroupsInheritance
-        else
+          |> snow.lib.groupModules;
-          warn ''
-            [snowflake] Neither `nodes.homeManager` nor `nodes.nodes.${name}.homeManager` were specified!
-            [snowflake] home-manager will NOT be used! User configuration will be ignored!
-          ''
-          null;
 
-      userArgs = nodes.args // node.args;
+        homeManager =
-      snowArgs = {
+          if node.homeManager != null
-        inherit systems snow root base nodes node;
+          then node.homeManager
-        inherit (node) system;
+          else if nodes.homeManager != null
-        hostname = name;
+          then nodes.homeManager
+          else
+            warn ''
+              [snowflake] Neither `nodes.homeManager` nor `nodes.nodes.${name}.homeManager` were specified!
+              [snowflake] home-manager will NOT be used! User configuration will be ignored!
+            ''
+            null;
 
-        _snow = {
+        userArgs = nodes.args // node.args;
-          inherit inputs userArgs snowArgs homeManager;
+        snowArgs = {
-          specialArgs = userArgs // snowArgs;
+          inherit systems snow root base nodes node;
+          inherit (node) system;
+          hostname = name;
+
+          _snow = {
+            inherit (_snowFlake) inputs;
+            inherit userArgs snowArgs homeManager;
+            specialArgs = userArgs // snowArgs;
+          };
         };
-      };
+        specialArgs = assert (userArgs
-      specialArgs = assert (userArgs
+          |> attrNames
-        |> attrNames
+          |> all (argName:
-        |> all (argName:
+            ! snowArgs ? argName
-          ! snowArgs ? argName
+            || abort ''
-          || abort ''
+              `specialArgs` are like super important to Snow my love... </3
-            `specialArgs` are like super important to Snow my love... </3
+              But `args.${argName}` is a reserved argument name :(
-            But `args.${argName}` is a reserved argument name :(
+            ''));
-          ''));
+          snowArgs._snow.specialArgs;
-        snowArgs._snow.specialArgs;
+      in
-    in
+        lib.nixosSystem {
-      lib.nixosSystem {
+          inherit (node) system;
-        inherit (node) system;
+          inherit specialArgs;
-        inherit specialArgs;
+          modules =
-        modules =
+            [
-          [
+              _snowFlake.self.nixosModules.default
-            snow.nixosModules.default
+              (snow.lib.findImport /${root}/hosts/${name})
-            (snow.findImport /${root}/hosts/${name})
+            ]
-          ]
+            ++ nodeGroups
-          ++ (groupModules root)
+            ++ node.modules
-          ++ node.modules
+            ++ nodes.modules;
-          ++ nodes.modules;
+        }
-      }
+    );
-  );
 }

nix/snow/lib/default.nix

@@ -15,13 +15,11 @@
   nt,
   mix,
   ...
-} @ args: let
+} @ args:
-  inherit (nt) findImport;
+mix.newMixture args (mixture: {
-in
+  includes.public = [
-  mix.newMixture args (mixture: {
+    ./util.nix
-    includes.public = [
+    ./nixpkgs.nix
-      ./nixpkgs.nix
+    ./nodes.nix
-    ];
+  ];
-
+})
-    inherit findImport;
-  })

nix/snow/lib/nixpkgs.nix

@@ -14,9 +14,12 @@
   minVersion = "23.05pre-git";
 
   isNixpkgsValidVersion = let
-    revInfo = lib.optional (inputs.nixpkgs?rev) " (nixpkgs-lib.rev: ${inputs.nixpkgs.rev})";
+    revInfo =
+      if inputs.nixpkgs?rev
+      then " (nixpkgs-lib.rev: ${inputs.nixpkgs.rev})"
+      else "";
   in
-    (builtins.compareVersions lib.version minVersion < 0)
+    (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},

nix/snow/lib/nodes.nix

@@ -0,0 +1,87 @@
+{
+  this,
+  nt,
+  ...
+}: let
+  inherit
+    (builtins)
+    concatLists
+    elem
+    filter
+    isAttrs
+    mapAttrs
+    pathExists
+    typeOf
+    ;
+
+  inherit (nt.prim) uniq;
+
+  rootGroupName = "all";
+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 ''
+            snow cannot construct nodes node "${name}" without a base package source.
+            Ensure `nodes.nodes.*.base` or `nodes.base` is a flake reference to the github:NixOS/nixpkgs repository.
+          '';
+    in
+      f rec {
+        inherit name node base;
+        inherit (base) lib;
+
+        inherit (node) groups;
+      });
+
+  groupModules = map (group: group._module);
+
+  parseGroupDecls = root: groupDecls: let
+    validGroup = g:
+      isAttrs g
+      || throw ''
+        Snow node groups must be provided as attribute sets, got "${typeOf g}" instead!
+        Ensure all the group definitions are attribute sets under your call to `snow.flake`.
+      '';
+    delegate = parent: gName: g: let
+      result =
+        (g
+          // {
+            _name = gName;
+            _parent = parent;
+            _module = this.lib.findImport /${root}/groups/${gName};
+          })
+        |> mapAttrs (name: value:
+          if elem name ["_name" "_parent" "_module"]
+          # ignore metadata fields
+          then value
+          else assert validGroup value; (delegate result name value));
+    in
+      result;
+  in
+    assert validGroup groupDecls;
+      delegate null rootGroupName groupDecls;
+
+  resolveGroupsInheritance = groups:
+    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
+    # ignore missing groups
+    |> filter (group: pathExists group._module)
+    # filter by uniqueness
+    |> uniq;
+}

nix/snow/lib/util.nix

@@ -0,0 +1,3 @@
+{nt, ...}: {
+  inherit (nt) findImport;
+}