From 58b1de7ebf6e133f12bac249901fe701ad17f3f1 Mon Sep 17 00:00:00 2001
From: Matt Sturgeon <matt@sturgeon.me.uk>
Date: Thu, 12 Jun 2025 23:00:37 +0100
Subject: [PATCH] stylix: refactor `base16Scheme` and `lib.stylix.colors`
 assertion (#1446)

Instead of having a nullable `base16Scheme` option, the default will
throw when `stylix.image` is null. Not only does this better represent
the "required" nature of this option, it also ensures the assertion is
evaluated early enough to actually be checked.

This causes the assertion to evaluate when the default definition is
read, instead of later when the `assertions` option is checked.

Link: https://github.com/nix-community/stylix/pull/1446

Tested-by: https://github.com/NovaViper
Approved-by: https://github.com/NovaViper
Reviewed-by: NAHO <90870942+trueNAHO@users.noreply.github.com>
---
 stylix/palette.nix | 42 +++++++++++++++---------------------------
 1 file changed, 15 insertions(+), 27 deletions(-)

diff --git a/stylix/palette.nix b/stylix/palette.nix
index 0ae7bf47..718683f7 100644
--- a/stylix/palette.nix
+++ b/stylix/palette.nix
@@ -8,7 +8,7 @@
 
 let
   cfg = config.stylix;
-
+  opts = options.stylix;
 in
 {
   options.stylix = {
@@ -117,18 +117,23 @@ in
       '';
       type =
         with lib.types;
-        nullOr (oneOf [
+        oneOf [
           path
           lines
           attrs
-        ]);
-      # defaults to null when cfg.image is also null, in order to trigger the assertion below correctly
-      default = if cfg.image == null then null else cfg.generated.palette;
+        ];
+      # We add an assertion here, because this value is used throughout Stylix.
+      # Using the assertions option is ineffective because it is checked after
+      # the errors caused by reading `base16Scheme` have occurred.
+      # See https://github.com/nix-community/stylix/pull/1408
+      # and https://github.com/nix-community/stylix/pull/1446
+      default =
+        lib.throwIf (cfg.image == null)
+          "stylix: one of `${opts.image}' or `${opts.base16Scheme}' must be set."
+          cfg.generated.palette;
       defaultText = lib.literalMD ''
-        The colors used in the theming.
-
-        Those are automatically selected from the background image by default,
-        but could be overridden manually.
+        Automatically selected from the background image. The default will
+        throw if `stylix.image` is null.
       '';
     };
 
@@ -167,24 +172,7 @@ in
   config = {
     # This attrset can be used like a function too, see
     # https://github.com/SenchoPens/base16.nix/blob/b390e87cd404e65ab4d786666351f1292e89162a/README.md#theme-step-22
-    #
-    # NOTE: base16Scheme is nullable. If null, we cannot pass it to mkSchemeAttrs.
-    # See https://github.com/nix-community/stylix/pull/1408
-    lib.stylix.colors =
-      if cfg.base16Scheme == null then
-        null
-      else
-        (cfg.base16.mkSchemeAttrs cfg.base16Scheme).override cfg.override;
-
-    assertions = lib.mkIf cfg.enable [
-      {
-        assertion = !(cfg.image == null && cfg.base16Scheme == null);
-
-        message = ''
-          stylix: one of `stylix.image` or `stylix.base16Scheme` must be set
-        '';
-      }
-    ];
+    lib.stylix.colors = (cfg.base16.mkSchemeAttrs cfg.base16Scheme).override cfg.override;
 
     stylix.generated.fileTree = {
       # The raw output of the palette generator.