From de48b6a845e7f206d8c11075a507814b6b5d13c7 Mon Sep 17 00:00:00 2001
From: Yueh-Shun Li <shamrocklee@posteo.net>
Date: Mon, 5 Jan 2026 16:06:56 +0800
Subject: [PATCH] buildPython*: extend overrideStdenvCompat to fixed-point
 arguments

with `passthru.__stdenvPythonCompat`

Co-authored-by: Matt Sturgeon <matt@sturgeon.me.uk>
---
 .../interpreters/python/mk-python-derivation.nix      |  1 +
 .../interpreters/python/python-packages-base.nix      | 11 +++++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/pkgs/development/interpreters/python/mk-python-derivation.nix b/pkgs/development/interpreters/python/mk-python-derivation.nix
index f3e5249c189e..0fb0a1326025 100644
--- a/pkgs/development/interpreters/python/mk-python-derivation.nix
+++ b/pkgs/development/interpreters/python/mk-python-derivation.nix
@@ -418,6 +418,7 @@ lib.extendMkDerivation {
           optional-dependencies
           ;
         updateScript = nix-update-script { };
+        ${if attrs ? stdenv then "__stdenvPythonCompat" else null} = attrs.stdenv;
       }
       // attrs.passthru or { };
 
diff --git a/pkgs/development/interpreters/python/python-packages-base.nix b/pkgs/development/interpreters/python/python-packages-base.nix
index 1fe5fcbaf60e..77ac26630161 100644
--- a/pkgs/development/interpreters/python/python-packages-base.nix
+++ b/pkgs/development/interpreters/python/python-packages-base.nix
@@ -54,6 +54,7 @@ let
       lib.mirrorFunctionArgs f (
         args:
         let
+          result = f args;
           getName = x: x.pname or (lib.getName (x.name or "<unnamed>"));
           applyMsgStdenvArg =
             name:
@@ -62,12 +63,18 @@ let
                 buildPythonPackage.override { stdenv = customStdenv; } { }
             '';
         in
-        if !(lib.isFunction args) && (args ? stdenv) then
+        if lib.isFunction args && result ? __stdenvPythonCompat then
+          # Less reliable, as constructing with the wrong `stdenv` might lead to evaluation errors in the package definition.
+          f'.override { stdenv = applyMsgStdenvArg (getName result) result.__stdenvPythonCompat; } (
+            finalAttrs: removeAttrs (args finalAttrs) [ "stdenv" ]
+          )
+        else if (!lib.isFunction args) && (args ? stdenv) then
+          # More reliable, but only works when args is not `(finalAttrs: { })`
           f'.override { stdenv = applyMsgStdenvArg (getName args) args.stdenv; } (
             removeAttrs args [ "stdenv" ]
           )
         else
-          f args
+          result
       )
       // {
         # Preserve the effect of overrideStdenvCompat when calling `buildPython*.override`.