From ca59048a4242bf0741813794d805a153f5f95c2a Mon Sep 17 00:00:00 2001
From: Eman Resu <78693624+quatquatt@users.noreply.github.com>
Date: Tue, 7 Oct 2025 20:50:13 -0400
Subject: [PATCH] lib.filesystem.listFilesRecursive: only flatten once

---
 lib/filesystem.nix | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/lib/filesystem.nix b/lib/filesystem.nix
index a950720602a7..afc4c2698291 100644
--- a/lib/filesystem.nix
+++ b/lib/filesystem.nix
@@ -239,16 +239,15 @@ in
     ```
   */
   listFilesRecursive =
-    dir:
-    lib.flatten (
-      lib.mapAttrsToList (
-        name: type:
-        if type == "directory" then
-          lib.filesystem.listFilesRecursive (dir + "/${name}")
-        else
-          dir + "/${name}"
-      ) (builtins.readDir dir)
-    );
+    let
+      # We only flatten at the very end, as flatten is recursive.
+      internalFunc =
+        dir:
+        (lib.mapAttrsToList (
+          name: type: if type == "directory" then internalFunc (dir + "/${name}") else dir + "/${name}"
+        ) (builtins.readDir dir));
+    in
+    dir: lib.flatten (internalFunc dir);
 
   /**
     Transform a directory tree containing package files suitable for