Merge branch 'is-reference-bug' of https://github.com/TylerBrinkley/Newtonsoft.Json into TylerBrinkley-is-reference-bug

Src/Newtonsoft.Json.Tests/Serialization/PreserveReferencesHandlingTests.cs

@@ -656,6 +656,66 @@ namespace Newtonsoft.Json.Tests.Serialization
             Assert.AreEqual(employees[0], employees[1].Manager);
         }
 
+        [JsonObject(IsReference = true)]
+        private class Condition
+        {
+            public int Value { get; }
+
+            public Condition(int value)
+            {
+                Value = value;
+            }
+        }
+
+        private class ClassWithConditions
+        {
+            public Condition Condition1 { get; }
+
+            public Condition Condition2 { get; }
+
+            public ClassWithConditions(Condition condition1, Condition condition2)
+            {
+                Condition1 = condition1;
+                Condition2 = condition2;
+            }
+        }
+
+        [Test]
+        public void SerializeIsReferenceReadonlyProperty()
+        {
+            Condition condition = new Condition(1);
+            ClassWithConditions value = new ClassWithConditions(condition, condition);
+
+            string json = JsonConvert.SerializeObject(value, Formatting.Indented);
+            StringAssert.AreEqual(@"{
+  ""Condition1"": {
+    ""$id"": ""1"",
+    ""Value"": 1
+  },
+  ""Condition2"": {
+    ""$ref"": ""1""
+  }
+}", json);
+        }
+
+        [Test]
+        public void DeserializeIsReferenceReadonlyProperty()
+        {
+            string json = @"{
+  ""Condition1"": {
+    ""$id"": ""1"",
+    ""Value"": 1
+  },
+  ""Condition2"": {
+    ""$ref"": ""1""
+  }
+}";
+
+            ClassWithConditions value = JsonConvert.DeserializeObject<ClassWithConditions>(json);
+            Assert.AreEqual(value.Condition1.Value, 1);
+            Assert.AreEqual(value.Condition1, value.Condition2);
+        }
+
         [Test]
         public void SerializeCircularReference()
         {

Src/Newtonsoft.Json/Serialization/JsonSerializerInternalWriter.cs

@@ -577,8 +577,8 @@ namespace Newtonsoft.Json.Serialization
             writer.WriteStartObject();
 
             bool isReference = ResolveIsReference(contract, member, collectionContract, containerProperty) ?? HasFlag(Serializer._preserveReferencesHandling, PreserveReferencesHandling.Objects);
-            // don't make readonly fields the referenced value because they can't be deserialized to
-            if (isReference && (member == null || member.Writable))
+            // don't make readonly fields that aren't creator parameters the referenced value because they can't be deserialized to
+            if (isReference && (member == null || member.Writable || ((collectionContract as JsonObjectContract)?.CreatorParameters.Contains(member.PropertyName) ?? false)))
             {
                 WriteReferenceIdProperty(writer, contract.UnderlyingType, value);
             }
@@ -804,8 +804,8 @@ namespace Newtonsoft.Json.Serialization
         private bool WriteStartArray(JsonWriter writer, object values, JsonArrayContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)
         {
             bool isReference = ResolveIsReference(contract, member, containerContract, containerProperty) ?? HasFlag(Serializer._preserveReferencesHandling, PreserveReferencesHandling.Arrays);
-            // don't make readonly fields the referenced value because they can't be deserialized to
-            isReference = (isReference && (member == null || member.Writable));
+            // don't make readonly fields that aren't creator parameters the referenced value because they can't be deserialized to
+            isReference = (isReference && (member == null || member.Writable || ((containerContract as JsonObjectContract)?.CreatorParameters.Contains(member.PropertyName) ?? false)));
 
             bool includeTypeDetails = ShouldWriteType(TypeNameHandling.Arrays, contract, member, containerContract, containerProperty);
             bool writeMetadataObject = isReference || includeTypeDetails;