fix null value exception (#15)

* fix null value exception

* bug fix

---------

Co-authored-by: Wenxi Zeng <[email protected]>

Author: wenxi-zeng

Serialization.NET/Segment/Serialization/JsonConvertersForMS.cs

@@ -76,6 +76,9 @@ private JsonObject ReadObject(ref Utf8JsonReader reader, JsonSerializerOptions o
                     case JsonTokenType.StartArray:
                         value = JsonSerializer.Deserialize<JsonArray>(ref reader, options);
                         break;
+                    case JsonTokenType.Null:
+                        value = JsonNull.Instance;
+                        break;
                     default:
                         value = JsonSerializer.Deserialize<JsonPrimitive>(ref reader, options);
                         break;
@@ -120,6 +123,9 @@ private JsonArray ReadArray(ref Utf8JsonReader reader, JsonSerializerOptions opt
                     case JsonTokenType.StartArray:
                         value = JsonSerializer.Deserialize<JsonArray>(ref reader, options);
                         break;
+                    case JsonTokenType.Null:
+                        value = JsonNull.Instance;
+                        break;
                     default:
                         value = JsonSerializer.Deserialize<JsonPrimitive>(ref reader, options);
                         break;

Serialization.NET/Segment/Serialization/JsonElement.cs

@@ -187,7 +187,7 @@ IEnumerator IEnumerable.GetEnumerator()
         public JsonElement this[string key]
         {
             get => Content[key];
-            set => Content[key] = value;
+            set => Content[key] = value ?? JsonNull.Instance;
         }
     }
 
@@ -240,7 +240,7 @@ IEnumerator IEnumerable.GetEnumerator()
         public JsonElement this[int index]
         {
             get => Content[index];
-            set => Content[index] = value;
+            set => Content[index] = value ?? JsonNull.Instance;
         }
     }
 

Tests/JsonUtilityTest.cs

@@ -17,6 +17,7 @@ public class JsonUtilityTest
             ["bool"] = true,
             ["datetime"] = "2015-12-10T04:08:31.905Z",
             ["date"] = s_date,
+            ["null"] = null,
             ["object"] = new JsonObject
             {
                 ["another object"] = "obj"
@@ -31,7 +32,7 @@ public class JsonUtilityTest
         };
 
         private readonly string _jsonStr =
-            "{\"int\": 1,\"float\": 1,\"long\": 1,\"double\": 1,\"string\": \"1\",\"bool\": true,\"datetime\": \"2015-12-10T04:08:31.905Z\",\"date\": \"" + s_date + "\",\"object\": {\"another object\": \"obj\"},\"array\": [1,1,1,1,\"1\",true,{\"object in array\": \"obj\"}]}";
+            "{\"int\": 1,\"float\": 1,\"long\": 1,\"double\": 1,\"string\": \"1\",\"bool\": true,\"datetime\": \"2015-12-10T04:08:31.905Z\",\"date\": \"" + s_date + "\",\"null\": null,\"object\": {\"another object\": \"obj\"},\"array\": [1,1,1,1,\"1\",true,{\"object in array\": \"obj\"}]}";
 
         [Fact]
         public void Test_ToJson()