From a64ab557a09c60d260fe2330e97b136529ccdecb Mon Sep 17 00:00:00 2001
From: Eman Resu <78693624+quatquatt@users.noreply.github.com>
Date: Tue, 19 May 2026 21:53:22 -0400
Subject: [PATCH] lib.fetchers.normalizeHash: avoid expensive builtins.tail
 call

---
 lib/fetchers.nix | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/fetchers.nix b/lib/fetchers.nix
index a2abddf89de4..2ce5483e86e2 100644
--- a/lib/fetchers.nix
+++ b/lib/fetchers.nix
@@ -15,7 +15,7 @@ let
   inherit (lib)
     concatMapStringsSep
     head
-    tail
+    length
     throwIf
     ;
   inherit (lib.attrsets)
@@ -125,7 +125,7 @@ rec {
           in
           if hashesAsNVPairs == [ ] then
             throwIf required "fetcher called without `hash`" null
-          else if tail hashesAsNVPairs != [ ] then
+          else if length hashesAsNVPairs != 1 then
             throw "fetcher called with mutually-incompatible arguments: ${
               concatMapStringsSep ", " (a: a.name) hashesAsNVPairs
             }"