From 74b7349bd3c8ee59488ff356a3229784f501f4dd Mon Sep 17 00:00:00 2001
From: Alois Wohlschlager <alois1@gmx-topmail.de>
Date: Tue, 23 Sep 2025 20:41:54 +0200
Subject: [PATCH] nlohmann_json: fix musl build

Musl does not support LC_NUMERIC [1], so the relevant test introduced in
nlohmann_json 3.12 fails. To restore compatibility, the error has been turned
into a warning upstream [2]. Pick the patch.

[1] https://wiki.musl-libc.org/open-issues.html
[2] https://github.com/nlohmann/json/pull/4770
---
 pkgs/by-name/nl/nlohmann_json/package.nix | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/pkgs/by-name/nl/nlohmann_json/package.nix b/pkgs/by-name/nl/nlohmann_json/package.nix
index c07501a80c14..e11fa98c8373 100644
--- a/pkgs/by-name/nl/nlohmann_json/package.nix
+++ b/pkgs/by-name/nl/nlohmann_json/package.nix
@@ -2,6 +2,7 @@
   stdenv,
   lib,
   fetchFromGitHub,
+  fetchpatch,
   cmake,
 }:
 let
@@ -23,6 +24,16 @@ stdenv.mkDerivation (finalAttrs: {
     hash = "sha256-cECvDOLxgX7Q9R3IE86Hj9JJUxraDQvhoyPDF03B2CY=";
   };
 
+  patches = lib.optionals stdenv.hostPlatform.isMusl [
+    # Musl does not support LC_NUMERIC, causing a test failure.
+    # Turn the error into a warning to make the test succeed.
+    # https://github.com/nlohmann/json/pull/4770
+    (fetchpatch {
+      url = "https://github.com/nlohmann/json/commit/0a8b48ac6a89131deaeb0d57047c9462a23b34a2.diff";
+      hash = "sha256-gOZfRyDRI6USdUIY+sH7cygPrSIKGIo8AWcjqc/GQNI=";
+    })
+  ];
+
   nativeBuildInputs = [ cmake ];
 
   cmakeFlags = [