From d29eb085630aac6cbefeafe51937314ce0263593 Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Thu, 12 Jan 2023 20:41:29 -0500
Subject: [PATCH] Assert on construction that `OutputsSpec::Names` is non-empty

---
 src/libstore/outputs-spec.hh       | 9 ++++++---
 src/libstore/tests/outputs-spec.cc | 6 ++++++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/libstore/outputs-spec.hh b/src/libstore/outputs-spec.hh
index 82dfad479..46bc35ebc 100644
--- a/src/libstore/outputs-spec.hh
+++ b/src/libstore/outputs-spec.hh
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <cassert>
 #include <optional>
 #include <set>
 #include <variant>
@@ -11,13 +12,15 @@ namespace nix {
 struct OutputNames : std::set<std::string> {
     using std::set<std::string>::set;
 
-    // These need to be "inherited manually"
+    /* These need to be "inherited manually" */
+
     OutputNames(const std::set<std::string> & s)
         : std::set<std::string>(s)
-    { }
+    { assert(!empty()); }
+
     OutputNames(std::set<std::string> && s)
         : std::set<std::string>(s)
-    { }
+    { assert(!empty()); }
 
     /* This set should always be non-empty, so we delete this
        constructor in order make creating empty ones by mistake harder.
diff --git a/src/libstore/tests/outputs-spec.cc b/src/libstore/tests/outputs-spec.cc
index 5daac9234..c5e3f382b 100644
--- a/src/libstore/tests/outputs-spec.cc
+++ b/src/libstore/tests/outputs-spec.cc
@@ -4,6 +4,12 @@
 
 namespace nix {
 
+#ifndef NDEBUG
+TEST(OutputsSpec, no_empty_names) {
+    ASSERT_DEATH(OutputsSpec::Names { std::set<std::string> { } }, "");
+}
+#endif
+
 #define TEST_DONT_PARSE(NAME, STR)           \
     TEST(OutputsSpec, bad_ ## NAME) {        \
         std::optional OutputsSpecOpt =       \