From e1131b59279f7cf9f9bea93b5355608d78097f65 Mon Sep 17 00:00:00 2001
From: Rodney Lorrimar <dev@rodney.id.au>
Date: Sun, 4 Feb 2024 12:02:06 +0800
Subject: [PATCH] print-dev-env: Avoid using unbound shellHook variable

Some tools which consume the "nix print-dev-env" rc script (such as
"nix-direnv") are sensitive to the use of unbound variables. They use
"set -u".

The "nix print-dev-env" rc script initially unsets "shellHook", then
loads variables from the derivation, and then evaluates "shellHook".
However, most derivations don't have a "shellHook" attribute.

So users get the error "shellHook: unbound variable". This can be
demonstrated with the command:

    nix print-dev-env nixpkgs#hello | bash -u

This commit changes the rc script to provide an empty fallback value
for the "shellHook" variable.

Closes: #7951 #8253
---
 src/nix/develop.cc            | 2 +-
 tests/functional/nix-shell.sh | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/nix/develop.cc b/src/nix/develop.cc
index 1f2891378..403178a5d 100644
--- a/src/nix/develop.cc
+++ b/src/nix/develop.cc
@@ -354,7 +354,7 @@ struct Common : InstallableCommand, MixProfile
         for (auto & i : {"TMP", "TMPDIR", "TEMP", "TEMPDIR"})
             out << fmt("export %s=\"$NIX_BUILD_TOP\"\n", i);
 
-        out << "eval \"$shellHook\"\n";
+        out << "eval \"${shellHook:-}\"\n";
 
         auto script = out.str();
 
diff --git a/tests/functional/nix-shell.sh b/tests/functional/nix-shell.sh
index 13403fadb..04c83138e 100644
--- a/tests/functional/nix-shell.sh
+++ b/tests/functional/nix-shell.sh
@@ -118,10 +118,10 @@ diff $TEST_ROOT/dev-env{,2}.json
 # Ensure `nix print-dev-env --json` contains variable assignments.
 [[ $(jq -r .variables.arr1.value[2] $TEST_ROOT/dev-env.json) = '3 4' ]]
 
-# Run tests involving `source <(nix print-dev-inv)` in subshells to avoid modifying the current
+# Run tests involving `source <(nix print-dev-env)` in subshells to avoid modifying the current
 # environment.
 
-set +u # FIXME: Make print-dev-env `set -u` compliant (issue #7951)
+set -u
 
 # Ensure `source <(nix print-dev-env)` modifies the environment.
 (