Fix issue where DeserializeFn is not cleared by reset (#536)

Co-authored-by: Arjan Veenstra <arjan@xldata.nl>

Author: AVee

src/ServiceStack.Text/Json/JsonReader.Generic.cs

@@ -72,6 +72,7 @@ public static void Refresh()
                 return;
 
             ReadFn = JsonReader.Instance.GetParseStringSpanFn<T>();
+            JsConfig.AddUniqueType(typeof(T));
         }
 
         public static ParseStringDelegate GetParseFn() => ReadFn != null 

src/ServiceStack.Text/Json/JsonWriter.Generic.cs

@@ -167,6 +167,7 @@ public static void Refresh()
             CacheFn = typeof(T) == typeof(object)
                 ? JsonWriter.WriteLateBoundObject
                 : JsonWriter.Instance.GetWriteFn<T>();
+            JsConfig.AddUniqueType(typeof(T));
         }
 
         public static WriteObjectDelegate WriteFn()

src/ServiceStack.Text/Jsv/JsvReader.Generic.cs

@@ -70,6 +70,7 @@ public static void Refresh()
                 return;
 
             ReadFn = JsvReader.Instance.GetParseStringSpanFn<T>();
+            JsConfig.AddUniqueType(typeof(T));
         }
 
         public static ParseStringDelegate GetParseFn() => ReadFn != null

src/ServiceStack.Text/Jsv/JsvWriter.Generic.cs

@@ -124,6 +124,7 @@ public static void Refresh()
             CacheFn = typeof(T) == typeof(object)
                 ? JsvWriter.WriteLateBoundObject
                 : JsvWriter.Instance.GetWriteFn<T>();
+            JsConfig.AddUniqueType(typeof(T));
         }
 
         public static WriteObjectDelegate WriteFn()

tests/ServiceStack.Text.Tests/Issues/JsConfigIssues.cs

@@ -22,6 +22,11 @@ public CustomFormatType(int value)
             {
                 _value = value;
             }
+
+            public override string ToString()
+            {
+                return _value.ToString();
+            }
         }
 
         class Dto
@@ -44,6 +49,18 @@ public void CallReset_AfterSerializingOnce_WithCustomSerializationForProperty_Do
 
             TestRoundTripValue(dto);
         }
+        
+        [Test]
+        public void CallReset_AfterSerializingOnce_WithCustomSerializationForProperty_MustClearCustomSerialization()
+        {
+            var dto = new Dto { CustomFormatTypeProperty = new CustomFormatType(12345) };
+            JsConfig<CustomFormatType>.DeSerializeFn = str => 
+                new CustomFormatType(int.Parse(str));
+            var json = dto.ToJson();
+            JsConfig.Reset();
+            var fromJson = json.FromJson<Dto>();
+            Assert.That(fromJson.CustomFormatTypeProperty.Value, Is.EqualTo(0));
+        }
 
         private static void ConfigureCustomFormatType()
         {