Merge pull request #681 from eventflow/null-single-value-objects

Fix: Deserializing "null" into nullable SingleValueObjects
eventflow · Sep 12, 2019 · e65346b · e65346b
2 parents ff3be92 + bf03083
commit e65346b
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Showing 3 changed files with 30 additions and 7 deletions.
diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
@@ -1,6 +1,8 @@
 ### New in 0.75 (not released yet)
 
-* _Nothing yet_
+* Fix: When deserializing the JSON value `"null"` into a struct value like
+  `int`, the `SingleValueObjectConverter` threw an exception instead of
+  merely returning `null` representing an absent `SingleValueObject<int>` value
 
 ### New in 0.74.3948 (released 2019-07-01)
 

diff --git a/Source/EventFlow.Tests/UnitTests/ValueObjects/SingleValueObjectTests.cs b/Source/EventFlow.Tests/UnitTests/ValueObjects/SingleValueObjectTests.cs
@@ -168,7 +168,8 @@ public void EqualsForDifferentValues()
 
         private static readonly JsonSerializerSettings Settings = new JsonSerializerSettings
             {
-                DefaultValueHandling = DefaultValueHandling.Ignore
+                DefaultValueHandling = DefaultValueHandling.Ignore,
+                NullValueHandling = NullValueHandling.Ignore
             };
 
         [JsonConverter(typeof(SingleValueObjectConverter))]
@@ -202,6 +203,20 @@ public void DeserializeNullableIntWithoutValue()
             with.I.Should().BeNull();
         }
 
+        [Test]
+        public void DeserializeNullableIntWithNullValue()
+        {
+            // Arrange
+            var json = "{\"i\":null}";
+
+            // Act
+            var with = JsonConvert.DeserializeObject<WithNullableIntSingleValue>(json);
+
+            // Assert
+            with.Should().NotBeNull();
+            with.I.Should().BeNull();
+        }
+
         [Test]
         public void DeserializeNullableIntWithValue()
         {

diff --git a/Source/EventFlow/ValueObjects/SingleValueObjectConverter.cs b/Source/EventFlow/ValueObjects/SingleValueObjectConverter.cs
@@ -31,21 +31,26 @@ namespace EventFlow.ValueObjects
 {
     public class SingleValueObjectConverter : JsonConverter
     {
-        private static readonly ConcurrentDictionary<Type, Type> ConstructorArgumenTypes = new ConcurrentDictionary<Type, Type>();
+        private static readonly ConcurrentDictionary<Type, Type> ConstructorArgumentTypes = new ConcurrentDictionary<Type, Type>();
 
         public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
         {
-            var singleValueObject = value as ISingleValueObject;
-            if (singleValueObject == null)
+            if (!(value is ISingleValueObject singleValueObject))
             {
                 return;
             }
+
             serializer.Serialize(writer, singleValueObject.GetValue());
         }
 
         public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
         {
-            var parameterType = ConstructorArgumenTypes.GetOrAdd(
+            if (reader.Value == null)
+            {
+                return null;
+            }
+
+            var parameterType = ConstructorArgumentTypes.GetOrAdd(
                 objectType,
                 t =>
                     {
@@ -55,7 +60,8 @@ public override object ReadJson(JsonReader reader, Type objectType, object exist
                     });
 
             var value = serializer.Deserialize(reader, parameterType);
-            return Activator.CreateInstance(objectType, new[] { value });
+
+            return Activator.CreateInstance(objectType, value);
         }
 
         public override bool CanConvert(Type objectType)