Shamelessly copy Josiah

source/lib/json/tests/abi/diag/diag_on.cpp

@@ -0,0 +1,30 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.11.2
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2022 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+#undef JSON_DIAGNOSTICS
+#define JSON_DIAGNOSTICS 1
+#include <nlohmann/json.hpp>
+
+#include "diag.hpp"
+
+std::size_t json_sizeof_diag_on()
+{
+    return sizeof(nlohmann::json);
+}
+
+std::size_t json_sizeof_diag_on_explicit()
+{
+    return sizeof(::NLOHMANN_JSON_NAMESPACE::json);
+}
+
+void json_at_diag_on()
+{
+    using nlohmann::json;
+    json j = json{{"foo", json::object()}};
+    j.at(json::json_pointer("/foo/bar"));
+}