From 1521a819b75810e9c0f0450745d66b4620fff3da Mon Sep 17 00:00:00 2001
From: Cole Helbling <cole.helbling@determinate.systems>
Date: Mon, 30 Jun 2025 10:18:10 -0700
Subject: [PATCH] external-derivation-builder: `args` must always be specified

I don't want to figure out how to make nlohmann treat std::optional<>
the same way Rust's serde_json treats Option<> (i.e. skip it if it's
not there).
---
 src/libstore/include/nix/store/globals.hh              | 2 +-
 src/libstore/unix/build/external-derivation-builder.cc | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/libstore/include/nix/store/globals.hh b/src/libstore/include/nix/store/globals.hh
index 2976ee57a..f7c714777 100644
--- a/src/libstore/include/nix/store/globals.hh
+++ b/src/libstore/include/nix/store/globals.hh
@@ -1241,7 +1241,7 @@ public:
     {
         std::vector<std::string> systems;
         Path program;
-        std::optional<std::vector<std::string>> args;
+        std::vector<std::string> args;
     };
 
     using ExternalBuilders = std::vector<ExternalBuilder>;
diff --git a/src/libstore/unix/build/external-derivation-builder.cc b/src/libstore/unix/build/external-derivation-builder.cc
index 0757ed51f..1906ddd70 100644
--- a/src/libstore/unix/build/external-derivation-builder.cc
+++ b/src/libstore/unix/build/external-derivation-builder.cc
@@ -94,8 +94,8 @@ struct ExternalDerivationBuilder : DerivationBuilderImpl
 
                 Strings args = {externalBuilder.program};
 
-                if (externalBuilder.args) {
-                    args.insert(args.end(), externalBuilder.args->begin(), externalBuilder.args->end());
+                if (!externalBuilder.args.empty()) {
+                    args.insert(args.end(), externalBuilder.args.begin(), externalBuilder.args.end());
                 }
 
                 args.insert(args.end(), jsonFile);