From 5c3738b9b11cf46f4a6cc13dc03ff557b418a432 Mon Sep 17 00:00:00 2001
From: Jonas Wittbrodt <jonas.wittbrodt@desy.de>
Date: Wed, 25 Aug 2021 12:53:49 +0200
Subject: [PATCH] add explicit conversion of null into float NaN

---
 .../nlohmann/detail/conversions/from_json.hpp | 30 +++++++++++++++--
 test/src/unit-conversions.cpp                 | 33 +++++++++++++++----
 2 files changed, 55 insertions(+), 8 deletions(-)

diff --git a/include/nlohmann/detail/conversions/from_json.hpp b/include/nlohmann/detail/conversions/from_json.hpp
index c7bd018e3..61c95cbe0 100644
--- a/include/nlohmann/detail/conversions/from_json.hpp
+++ b/include/nlohmann/detail/conversions/from_json.hpp
@@ -57,8 +57,21 @@ void get_arithmetic_value(const BasicJsonType& j, ArithmeticType& val)
             val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::number_float_t*>());
             break;
         }
-
         case value_t::null:
+        {
+            if(std::numeric_limits<ArithmeticType>::has_quiet_NaN)
+            {
+                val = std::numeric_limits<ArithmeticType>::quiet_NaN();
+                break;
+            }
+            else if(std::numeric_limits<ArithmeticType>::has_signaling_NaN)
+            {
+                val = std::numeric_limits<ArithmeticType>::signaling_NaN();
+                break;
+            }
+            // [[fallthrough]];
+        }
+
         case value_t::object:
         case value_t::array:
         case value_t::string:
@@ -349,8 +362,21 @@ void from_json(const BasicJsonType& j, ArithmeticType& val)
             val = static_cast<ArithmeticType>(*j.template get_ptr<const typename BasicJsonType::boolean_t*>());
             break;
         }
-
         case value_t::null:
+        {
+            if(std::numeric_limits<ArithmeticType>::has_quiet_NaN)
+            {
+                val = std::numeric_limits<ArithmeticType>::quiet_NaN();
+                break;
+            }
+            else if(std::numeric_limits<ArithmeticType>::has_signaling_NaN)
+            {
+                val = std::numeric_limits<ArithmeticType>::signaling_NaN();
+                break;
+            }
+            // [[fallthrough]];
+        }
+
         case value_t::object:
         case value_t::array:
         case value_t::string:
diff --git a/test/src/unit-conversions.cpp b/test/src/unit-conversions.cpp
index bc1ad24d6..c7dba44f3 100644
--- a/test/src/unit-conversions.cpp
+++ b/test/src/unit-conversions.cpp
@@ -1207,10 +1207,31 @@ TEST_CASE("value conversion")
             CHECK(json(n).m_value.number_float == Approx(j.m_value.number_float));
         }
 
-        SECTION("exception in case of a non-string type")
+        SECTION("null as NaN")
         {
-            CHECK_THROWS_AS(json(json::value_t::null).get<json::number_float_t>(),
-                            json::type_error&);
+            json jNull(nullptr);
+            SECTION("number_float_t")
+            {
+                auto n = jNull.get<json::number_float_t>();
+                CHECK(std::isnan(n));
+            }
+
+            SECTION("float")
+            {
+                auto n = jNull.get<float>();
+                CHECK(std::isnan(n));
+            }
+
+            SECTION("double")
+            {
+                auto n = jNull.get<double>();
+                CHECK(std::isnan(n));
+            }
+        }
+        SECTION("exception in case of a non-numeric type")
+        {
+            // CHECK_THROWS_AS(json(json::value_t::null).get<json::number_float_t>(),
+            //                 json::type_error&);
             CHECK_THROWS_AS(json(json::value_t::object).get<json::number_float_t>(),
                             json::type_error&);
             CHECK_THROWS_AS(json(json::value_t::array).get<json::number_float_t>(),
@@ -1220,9 +1241,9 @@ TEST_CASE("value conversion")
             CHECK_THROWS_AS(json(json::value_t::boolean).get<json::number_float_t>(),
                             json::type_error&);
 
-            CHECK_THROWS_WITH(
-                json(json::value_t::null).get<json::number_float_t>(),
-                "[json.exception.type_error.302] type must be number, but is null");
+            // CHECK_THROWS_WITH(
+            //     json(json::value_t::null).get<json::number_float_t>(),
+            //     "[json.exception.type_error.302] type must be number, but is null");
             CHECK_THROWS_WITH(
                 json(json::value_t::object).get<json::number_float_t>(),
                 "[json.exception.type_error.302] type must be number, but is object");