Replace nixpkgs nullOr type with custom type

`nullOr`'s merge function requires definitions to all be null or all be
non-null. It was being used where the intent was that null be used as a
value representing unset, and as such the merge should return null if
all definitions are null and ignore nulls otherwise. This adds a type
with that merge semantics.

builtinModules/apps.nix

@@ -5,8 +5,8 @@
 { config, lib, flakelight, genSystems, ... }:
 let
   inherit (lib) isFunction mapAttrs mkIf mkMerge mkOption;
-  inherit (lib.types) lazyAttrsOf nullOr raw;
+  inherit (lib.types) lazyAttrsOf raw;
-  inherit (flakelight.types) optFunctionTo;
+  inherit (flakelight.types) nullable optFunctionTo;
 
   isApp = x: (x ? type) && (x.type == "app") && (x ? program);
 
@@ -17,12 +17,12 @@ in
 {
   options = {
     app = mkOption {
-      type = nullOr raw;
+      type = nullable raw;
       default = null;
     };
 
     apps = mkOption {
-      type = nullOr (optFunctionTo (lazyAttrsOf raw));
+      type = nullable (optFunctionTo (lazyAttrsOf raw));
       default = null;
     };
   };

builtinModules/builtinOverlay.nix

@@ -5,14 +5,15 @@
 { config, src, lib, inputs, outputs, flakelight, moduleArgs, ... }:
 let
   inherit (lib) isList mkOption mkOrder mapAttrs optionalAttrs;
-  inherit (lib.types) listOf nullOr oneOf str;
+  inherit (lib.types) listOf oneOf str;
   inherit (builtins) pathExists;
   inherit (flakelight) selectAttr;
+  inherit (flakelight.types) nullable;
 in
 {
   options = {
     description = mkOption {
-      type = nullOr str;
+      type = nullable str;
       default =
         if pathExists (src + /flake.nix)
         then (import (src + /flake.nix)).description or null
@@ -20,7 +21,7 @@ in
     };
 
     license = mkOption {
-      type = nullOr (oneOf [ str (listOf str) ]);
+      type = nullable (oneOf [ str (listOf str) ]);
       default = null;
     };
   };

builtinModules/bundlers.nix

@@ -5,8 +5,8 @@
 { config, lib, flakelight, genSystems, ... }:
 let
   inherit (lib) isFunction mapAttrs mkMerge mkOption mkIf;
-  inherit (lib.types) lazyAttrsOf nullOr;
+  inherit (lib.types) lazyAttrsOf;
-  inherit (flakelight.types) function optFunctionTo;
+  inherit (flakelight.types) function nullable optFunctionTo;
 
   wrapBundler = pkgs: bundler: drv:
     if isFunction (bundler (pkgs // drv))
@@ -16,12 +16,12 @@ in
 {
   options = {
     bundler = mkOption {
-      type = nullOr function;
+      type = nullable function;
       default = null;
     };
 
     bundlers = mkOption {
-      type = nullOr (optFunctionTo (lazyAttrsOf function));
+      type = nullable (optFunctionTo (lazyAttrsOf function));
       default = null;
     };
   };

builtinModules/checks.nix

@@ -5,8 +5,8 @@
 { config, src, lib, flakelight, genSystems, ... }:
 let
   inherit (lib) isDerivation isFunction mkOption mkIf mapAttrs;
-  inherit (lib.types) lazyAttrsOf nullOr raw;
+  inherit (lib.types) lazyAttrsOf raw;
-  inherit (flakelight.types) optFunctionTo;
+  inherit (flakelight.types) nullable optFunctionTo;
 
   mkCheck = pkgs: name: cmd:
     let cmd' = if isFunction cmd then cmd pkgs else cmd; in
@@ -20,7 +20,7 @@ let
 in
 {
   options.checks = mkOption {
-    type = nullOr (optFunctionTo (lazyAttrsOf raw));
+    type = nullable (optFunctionTo (lazyAttrsOf raw));
     default = null;
   };
 

builtinModules/devShells.nix

@@ -6,10 +6,11 @@
 let
   inherit (lib) filterAttrs functionArgs mapAttrs mkDefault mkIf mkMerge
     mkOption;
-  inherit (lib.types) attrs coercedTo functionTo lazyAttrsOf lines listOf nullOr
+  inherit (lib.types) attrs coercedTo functionTo lazyAttrsOf lines listOf
     package str submodule;
   inherit (flakelight) supportedSystem;
-  inherit (flakelight.types) function optCallWith optFunctionTo packageDef;
+  inherit (flakelight.types) function nullable optCallWith optFunctionTo
+    packageDef;
 
   devShellModule.options = {
     inputsFrom = mkOption {
@@ -38,7 +39,7 @@ let
     };
 
     overrideShell = mkOption {
-      type = nullOr packageDef;
+      type = nullable packageDef;
       internal = true;
       default = null;
     };
@@ -53,7 +54,7 @@ in
   options = {
     devShell = mkOption {
       default = null;
-      type = nullOr (coercedTo function wrapFn
+      type = nullable (coercedTo function wrapFn
         (coercedTo attrs (x: _: x)
           (functionTo (submodule devShellModule))));
     };

builtinModules/flakelightModules.nix

@@ -5,13 +5,13 @@
 { config, lib, flakelight, moduleArgs, ... }:
 let
   inherit (lib) mkOption mkIf mkMerge;
-  inherit (lib.types) lazyAttrsOf nullOr;
+  inherit (lib.types) lazyAttrsOf;
-  inherit (flakelight.types) module optCallWith;
+  inherit (flakelight.types) module nullable optCallWith;
 in
 {
   options = {
     flakelightModule = mkOption {
-      type = nullOr module;
+      type = nullable module;
       default = null;
     };
 

builtinModules/formatter.nix

@@ -5,17 +5,17 @@
 { config, src, lib, flakelight, genSystems, ... }:
 let
   inherit (lib) mkDefault mkMerge mkOption mkIf mapAttrsToList;
-  inherit (lib.types) functionTo lazyAttrsOf nullOr package str;
+  inherit (lib.types) functionTo lazyAttrsOf package str;
-  inherit (flakelight.types) optFunctionTo;
+  inherit (flakelight.types) nullable optFunctionTo;
 in
 {
   options = {
     formatter = mkOption {
-      type = nullOr (functionTo package);
+      type = nullable (functionTo package);
       default = null;
     };
     formatters = mkOption {
-      type = nullOr (optFunctionTo (lazyAttrsOf str));
+      type = nullable (optFunctionTo (lazyAttrsOf str));
       default = null;
     };
   };

builtinModules/functor.nix

@@ -2,14 +2,15 @@
 # Copyright (C) 2023 Archit Gupta <archit@accelbread.com>
 # SPDX-License-Identifier: MIT
 
-{ config, lib, ... }:
+{ config, lib, flakelight, ... }:
 let
   inherit (lib) mkOption mkIf;
-  inherit (lib.types) functionTo nullOr raw uniq;
+  inherit (lib.types) functionTo raw uniq;
+  inherit (flakelight.types) nullable;
 in
 {
   options.functor = mkOption {
-    type = nullOr (uniq (functionTo (functionTo raw)));
+    type = nullable (uniq (functionTo (functionTo raw)));
     default = null;
   };
 

builtinModules/homeModules.nix

@@ -5,13 +5,13 @@
 { config, lib, flakelight, moduleArgs, ... }:
 let
   inherit (lib) mkOption mkIf mkMerge;
-  inherit (lib.types) lazyAttrsOf nullOr;
+  inherit (lib.types) lazyAttrsOf;
-  inherit (flakelight.types) module optCallWith;
+  inherit (flakelight.types) module nullable optCallWith;
 in
 {
   options = {
     homeModule = mkOption {
-      type = nullOr module;
+      type = nullable module;
       default = null;
     };
 

builtinModules/legacyPackages.nix

@@ -2,14 +2,15 @@
 # Copyright (C) 2023 Archit Gupta <archit@accelbread.com>
 # SPDX-License-Identifier: MIT
 
-{ config, lib, genSystems, ... }:
+{ config, lib, flakelight, genSystems, ... }:
 let
   inherit (lib) mkIf mkOption;
-  inherit (lib.types) functionTo nullOr pkgs;
+  inherit (lib.types) functionTo pkgs;
+  inherit (flakelight.types) nullable;
 in
 {
   options.legacyPackages = mkOption {
-    type = nullOr (functionTo pkgs);
+    type = nullable (functionTo pkgs);
     default = null;
   };
 

builtinModules/nixosModules.nix

@@ -5,13 +5,13 @@
 { config, lib, flakelight, moduleArgs, ... }:
 let
   inherit (lib) mkOption mkIf mkMerge;
-  inherit (lib.types) lazyAttrsOf nullOr;
+  inherit (lib.types) lazyAttrsOf;
-  inherit (flakelight.types) module optCallWith;
+  inherit (flakelight.types) module nullable optCallWith;
 in
 {
   options = {
     nixosModule = mkOption {
-      type = nullOr module;
+      type = nullable module;
       default = null;
     };
 

builtinModules/overlays.nix

@@ -5,13 +5,13 @@
 { config, lib, flakelight, moduleArgs, ... }:
 let
   inherit (lib) mkMerge mkOption mkIf;
-  inherit (lib.types) lazyAttrsOf nullOr;
+  inherit (lib.types) lazyAttrsOf;
-  inherit (flakelight.types) optCallWith overlay;
+  inherit (flakelight.types) nullable optCallWith overlay;
 in
 {
   options = {
     overlay = mkOption {
-      type = nullOr overlay;
+      type = nullable overlay;
       default = null;
     };
 

builtinModules/packages.nix

@@ -7,9 +7,9 @@ let
   inherit (builtins) hasAttr parseDrvName tryEval;
   inherit (lib) filterAttrs findFirst functionArgs mapAttrs' mapAttrs mkIf
     mkMerge mkOption nameValuePair optionalAttrs;
-  inherit (lib.types) lazyAttrsOf nullOr str uniq;
+  inherit (lib.types) lazyAttrsOf str uniq;
   inherit (flakelight) supportedSystem;
-  inherit (flakelight.types) optCallWith overlay packageDef;
+  inherit (flakelight.types) nullable optCallWith overlay packageDef;
 
   genPkg = final: prev: name: pkg:
     let
@@ -32,7 +32,7 @@ in
 {
   options = {
     package = mkOption {
-      type = nullOr packageDef;
+      type = nullable packageDef;
       default = null;
     };
 
@@ -42,7 +42,7 @@ in
     };
 
     pname = mkOption {
-      type = nullOr str;
+      type = nullable str;
       default = null;
     };
 

builtinModules/templates.nix

@@ -6,9 +6,9 @@
 let
   inherit (builtins) isPath isString;
   inherit (lib) mkOption mkOptionType mkIf mkMerge;
-  inherit (lib.types) lazyAttrsOf nullOr;
+  inherit (lib.types) lazyAttrsOf;
   inherit (lib.options) mergeEqualOption;
-  inherit (flakelight.types) optCallWith;
+  inherit (flakelight.types) nullable optCallWith;
 
   template = mkOptionType {
     name = "template";
@@ -23,7 +23,7 @@ in
 {
   options = {
     template = mkOption {
-      type = nullOr (optCallWith moduleArgs template);
+      type = nullable (optCallWith moduleArgs template);
       default = null;
     };
 

default.nix

@@ -6,11 +6,12 @@ inputs:
 let
   inherit (inputs) nixpkgs;
   inherit (builtins) isAttrs isPath readDir;
-  inherit (nixpkgs.lib) attrNames composeManyExtensions evalModules filter
+  inherit (nixpkgs.lib) all attrNames composeManyExtensions evalModules filter
     findFirst fix genAttrs getValues hasSuffix isFunction isList mapAttrs
     mapAttrsToList mkDefault mkOptionType pathExists pipe removePrefix
     removeSuffix singleton warn;
-  inherit (nixpkgs.lib.types) coercedTo functionTo listOf;
+  inherit (nixpkgs.lib.types) coercedTo defaultFunctor functionTo listOf
+    optionDescriptionPhrase;
   inherit (nixpkgs.lib.options) mergeEqualOption mergeOneOption;
 
   builtinModules = mapAttrsToList (k: _: ./builtinModules + ("/" + k))
@@ -40,7 +41,7 @@ let
       supportedSystem types;
   };
 
-  types = {
+  types = rec {
     overlay = mkOptionType {
       name = "overlay";
       description = "nixpkgs overlay";
@@ -95,6 +96,25 @@ let
 
     optCallWith = args: elemType: coercedTo (functionTo elemType) (x: x args)
       elemType;
+
+    nullable = elemType: mkOptionType {
+      name = "nullable";
+      description = "nullable ${optionDescriptionPhrase
+        (class: class == "noun" || class == "composite") elemType}";
+      descriptionClass = "noun";
+      check = x: x == null || elemType.check x;
+      merge = loc: defs:
+        if all (def: def.value == null) defs then null
+        else elemType.merge loc (filter (def: def.value != null) defs);
+      emptyValue.value = null;
+      inherit (elemType) getSubOptions getSubModules;
+      substSubModules = m: nullable (elemType.substSubModules m);
+      functor = (defaultFunctor "nullable") // {
+        type = nullable;
+        wrapped = elemType;
+      };
+      nestedTypes = { inherit elemType; };
+    };
   };
 
   supportedSystem = { lib, stdenv, ... }: