Create nlohmann serializers for `std::optional` and use

This is somewhat tricky.

1 files changed, 19 insertions, 0 deletions

diff --git a/src/libutil/json-utils.cc b/src/libutil/json-utils.cc
new file mode 100644
index 000000000..d7220e71d
--- /dev/null
+++ b/src/libutil/json-utils.cc
@@ -0,0 +1,19 @@
+#include "json-utils.hh"
+
+namespace nix {
+
+const nlohmann::json * get(const nlohmann::json & map, const std::string & key)
+{
+    auto i = map.find(key);
+    if (i == map.end()) return nullptr;
+    return &*i;
+}
+
+nlohmann::json * get(nlohmann::json & map, const std::string & key)
+{
+    auto i = map.find(key);
+    if (i == map.end()) return nullptr;
+    return &*i;
+}
+
+}