From bd47c5721f8a297588620b89cd2ace7a30d3e91d Mon Sep 17 00:00:00 2001
From: Frederik Rietdijk <fridh@fridh.nl>
Date: Sat, 27 Jul 2019 09:30:34 +0200
Subject: [PATCH] Python: introduce NIX_PYTHONEXECUTABLE in order to set
 sys.executable

This is needed in case of `python.buildEnv` to make sure sys.executable
does not point to the unwrapped executable.
---
 pkgs/development/interpreters/python/sitecustomize.py | 8 ++++++++
 pkgs/development/interpreters/python/wrapper.nix      | 3 ++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/pkgs/development/interpreters/python/sitecustomize.py b/pkgs/development/interpreters/python/sitecustomize.py
index 7e43be56147..e03b244dbc0 100644
--- a/pkgs/development/interpreters/python/sitecustomize.py
+++ b/pkgs/development/interpreters/python/sitecustomize.py
@@ -8,11 +8,19 @@ The paths listed in `PYTHONPATH` are added to `sys.path` afterwards, but they
 will be added before the entries we add here and thus take precedence.
 
 Note the `NIX_PYTHONPATH` environment variable is unset in order to prevent leakage.
+
+Similarly, this module listens to the environment variable `NIX_PYTHONEXECUTABLE`
+and sets `sys.executable` to its value.
 """
 import site
+import sys
 import os
 import functools
 
 paths = os.environ.pop('NIX_PYTHONPATH', None)
 if paths:
     functools.reduce(lambda k, p: site.addsitedir(p, k), paths.split(':'), site._init_pathinfo())
+
+executable = os.environ.pop('NIX_PYTHONEXECUTABLE', None)
+if 'PYTHONEXECUTABLE' not in os.environ and executable:
+    sys.executable = executable
diff --git a/pkgs/development/interpreters/python/wrapper.nix b/pkgs/development/interpreters/python/wrapper.nix
index d97bef222a1..b437584024f 100644
--- a/pkgs/development/interpreters/python/wrapper.nix
+++ b/pkgs/development/interpreters/python/wrapper.nix
@@ -14,6 +14,7 @@ let
   env = let
     paths = requiredPythonModules (extraLibs ++ [ python ] ) ;
     pythonPath = "${placeholder "out"}/${python.sitePackages}";
+    pythonExecutable = "${placeholder "out"}/bin/${python.executable}";
   in buildEnv {
     name = "${python.name}-env";
 
@@ -36,7 +37,7 @@ let
             if [ -f "$prg" ]; then
               rm -f "$out/bin/$prg"
               if [ -x "$prg" ]; then
-                makeWrapper "$path/bin/$prg" "$out/bin/$prg" --set NIX_PYTHONPATH ${pythonPath} ${if permitUserSite then "" else ''--set PYTHONNOUSERSITE "true"''} ${stdenv.lib.concatStringsSep " " makeWrapperArgs}
+                makeWrapper "$path/bin/$prg" "$out/bin/$prg" --set NIX_PYTHONEXECUTABLE ${pythonExecutable} --set NIX_PYTHONPATH ${pythonPath} ${if permitUserSite then "" else ''--set PYTHONNOUSERSITE "true"''} ${stdenv.lib.concatStringsSep " " makeWrapperArgs}
               fi
             fi
           done