From fde4f1c5a0583e00bee4a91efb675deb9d74785d Mon Sep 17 00:00:00 2001
From: Eman Resu <78693624+quatquatt@users.noreply.github.com>
Date: Sat, 9 May 2026 18:21:20 -0400
Subject: [PATCH] stdenv.mkDerivation: check meta.mainProgram from original
 meta

We define a meta variable in the same let block as the result of
the `commonMeta` call. Avoiding evaluating the result of that call
until we need to is preferable.
---
 pkgs/stdenv/generic/make-derivation.nix | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pkgs/stdenv/generic/make-derivation.nix b/pkgs/stdenv/generic/make-derivation.nix
index eaa2ca0d6afc..54282e05df77 100644
--- a/pkgs/stdenv/generic/make-derivation.nix
+++ b/pkgs/stdenv/generic/make-derivation.nix
@@ -866,7 +866,8 @@ let
       );
 
     let
-      env' = if meta ? mainProgram then env // { NIX_MAIN_PROGRAM = meta.mainProgram; } else env;
+      env' =
+        if attrs ? meta.mainProgram then env // { NIX_MAIN_PROGRAM = attrs.meta.mainProgram; } else env;
 
       derivationArg = makeDerivationArgument (
         removeAttrs attrs [