From fc43f076bbba14e7754f7f200509b95704796674 Mon Sep 17 00:00:00 2001
From: Eman Resu <78693624+quatquatt@users.noreply.github.com>
Date: Sat, 9 May 2026 19:14:25 -0400
Subject: [PATCH] stdenv.mkDerivation: avoid listToAttrs if outputChecks will
 end up empty

---
 pkgs/stdenv/generic/make-derivation.nix | 68 ++++++++++++++-----------
 1 file changed, 39 insertions(+), 29 deletions(-)

diff --git a/pkgs/stdenv/generic/make-derivation.nix b/pkgs/stdenv/generic/make-derivation.nix
index a64b1119fead..701c1a1b0c93 100644
--- a/pkgs/stdenv/generic/make-derivation.nix
+++ b/pkgs/stdenv/generic/make-derivation.nix
@@ -775,35 +775,45 @@ let
               attrsOutputChecks = makeOutputChecks attrs;
               attrsOutputChecksFiltered = filterAttrs (_: v: v != null) attrsOutputChecks;
             in
-            builtins.listToAttrs (
-              map (name: {
-                inherit name;
-                value =
-                  let
-                    raw =
-                      if attrs ? outputChecks.${name} then
-                        zipAttrsWith (_: concatLists) [
-                          attrsOutputChecksFiltered
-                          (makeOutputChecks attrs.outputChecks.${name})
-                        ]
-                      else
-                        attrsOutputChecksFiltered;
-                  in
-                  # separateDebugInfo = true will put all sorts of files in
-                  # the debug output which could carry references, but
-                  # that's "normal". Notably it symlinks to the source.
-                  # So disable reference checking for the debug output
-                  if separateDebugInfo' && name == "debug" then
-                    removeAttrs raw [
-                      "allowedReferences"
-                      "allowedRequisites"
-                      "disallowedReferences"
-                      "disallowedRequisites"
-                    ]
-                  else
-                    raw;
-              }) outputs
-            );
+            # to avoid the listToAttrs in most common situations, we replicate
+            # what it would produce for most derivations. this can be improved
+            # in the future at the cost of a mass rebuild - empty attrsets for
+            # each output is a noop
+            if
+              !attrs ? outputs
+              && !attrs ? outputChecks
+              && (attrsOutputChecks == { } || attrsOutputChecksFiltered == { })
+            then
+              {
+                out = { };
+                ${if separateDebugInfo' then "debug" else null} = { };
+              }
+            else
+              builtins.listToAttrs (
+                map (name: {
+                  inherit name;
+                  value =
+                    let
+                      raw = zipAttrsWith (_: concatLists) [
+                        attrsOutputChecksFiltered
+                        (makeOutputChecks (attrs.outputChecks.${name} or { }))
+                      ];
+                    in
+                    # separateDebugInfo = true will put all sorts of files in
+                    # the debug output which could carry references, but
+                    # that's "normal". Notably it symlinks to the source.
+                    # So disable reference checking for the debug output
+                    if separateDebugInfo' && name == "debug" then
+                      removeAttrs raw [
+                        "allowedReferences"
+                        "allowedRequisites"
+                        "disallowedReferences"
+                        "disallowedRequisites"
+                      ]
+                    else
+                      raw;
+                }) outputs
+              );
         };
       in
       derivationArg;