From 04386f7d69d9c370eb4367ca41d89ac5990ac02e Mon Sep 17 00:00:00 2001
From: Jeremy Fleischman <jeremyfleischman@gmail.com>
Date: Thu, 14 Jul 2022 23:11:02 -0700
Subject: [PATCH] nix develop: do not assume that saved vars are set

This fixes https://github.com/NixOS/nix/issues/6809
---
 src/nix/develop.cc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/nix/develop.cc b/src/nix/develop.cc
index 6d9ad9942..ba7ba7c25 100644
--- a/src/nix/develop.cc
+++ b/src/nix/develop.cc
@@ -288,8 +288,10 @@ struct Common : InstallableCommand, MixProfile
 
         out << "unset shellHook\n";
 
-        for (auto & var : savedVars)
+        for (auto & var : savedVars) {
+            out << fmt("%s=${%s:-}\n", var, var);
             out << fmt("nix_saved_%s=\"$%s\"\n", var, var);
+        }
 
         buildEnvironment.toBash(out, ignoreVars);