-Generic JsonConverter WIP + initial tests

Src/Newtonsoft.Json.Tests/Converters/GenericJsonConverterTests.cs

@@ -0,0 +1,156 @@
+#region License
+// Copyright (c) 2007 James Newton-King
+//
+// Permission is hereby granted, free of charge, to any person
+// obtaining a copy of this software and associated documentation
+// files (the "Software"), to deal in the Software without
+// restriction, including without limitation the rights to use,
+// copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following
+// conditions:
+//
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+// OTHER DEALINGS IN THE SOFTWARE.
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+#if !(NET20 || DNXCORE50)
+using System.Data.Linq;
+#endif
+#if !DNXCORE50
+using System.Data.SqlTypes;
+#endif
+using System.Text;
+using Newtonsoft.Json.Converters;
+#if DNXCORE50
+using Xunit;
+using Test = Xunit.FactAttribute;
+using Assert = Newtonsoft.Json.Tests.XUnitAssert;
+#else
+using NUnit.Framework;
+
+#endif
+
+namespace Newtonsoft.Json.Tests.Converters
+{
+    [TestFixture]
+    public class GenericJsonConverterTests : TestFixtureBase
+    {
+        public class TestGenericConverter : JsonConverter<string>
+        {
+            public override void WriteJson(JsonWriter writer, string value, JsonSerializer serializer)
+            {
+                writer.WriteValue(value);
+            }
+
+            public override string ReadJson(JsonReader reader, Type objectType, string existingValue, bool hasExistingValue, JsonSerializer serializer)
+            {
+                return (string)reader.Value + existingValue;
+            }
+        }
+
+        [Test]
+        public void WriteJsonObject()
+        {
+            StringWriter sw = new StringWriter();
+            JsonTextWriter jsonWriter = new JsonTextWriter(sw);
+
+            TestGenericConverter converter = new TestGenericConverter();
+            converter.WriteJson(jsonWriter, (object)"String!", null);
+
+            Assert.AreEqual(@"""String!""", sw.ToString());
+        }
+
+        [Test]
+        public void WriteJsonGeneric()
+        {
+            StringWriter sw = new StringWriter();
+            JsonTextWriter jsonWriter = new JsonTextWriter(sw);
+
+            TestGenericConverter converter = new TestGenericConverter();
+            converter.WriteJson(jsonWriter, "String!", null);
+
+            Assert.AreEqual(@"""String!""", sw.ToString());
+        }
+
+        [Test]
+        public void WriteJsonBadType()
+        {
+            StringWriter sw = new StringWriter();
+            JsonTextWriter jsonWriter = new JsonTextWriter(sw);
+
+            TestGenericConverter converter = new TestGenericConverter();
+
+            ExceptionAssert.Throws<JsonSerializationException>(() =>
+            {
+                converter.WriteJson(jsonWriter, 123, null);
+            }, "Converter cannot write specified value to JSON. System.String is required.");
+        }
+
+        [Test]
+        public void ReadJsonGenericExistingValueNull()
+        {
+            StringReader sr = new StringReader("'String!'");
+            JsonTextReader jsonReader = new JsonTextReader(sr);
+            jsonReader.Read();
+
+            TestGenericConverter converter = new TestGenericConverter();
+            string s = converter.ReadJson(jsonReader, typeof(string), null, false, null);
+
+            Assert.AreEqual(@"String!", s);
+        }
+
+        [Test]
+        public void ReadJsonGenericExistingValueString()
+        {
+            StringReader sr = new StringReader("'String!'");
+            JsonTextReader jsonReader = new JsonTextReader(sr);
+            jsonReader.Read();
+
+            TestGenericConverter converter = new TestGenericConverter();
+            string s = converter.ReadJson(jsonReader, typeof(string), "Existing!", true, null);
+
+            Assert.AreEqual(@"String!Existing!", s);
+        }
+
+        [Test]
+        public void ReadJsonObjectExistingValueNull()
+        {
+            StringReader sr = new StringReader("'String!'");
+            JsonTextReader jsonReader = new JsonTextReader(sr);
+            jsonReader.Read();
+
+            TestGenericConverter converter = new TestGenericConverter();
+            string s = (string)converter.ReadJson(jsonReader, typeof(string), null, null);
+
+            Assert.AreEqual(@"String!", s);
+        }
+
+        [Test]
+        public void ReadJsonObjectExistingValueWrongType()
+        {
+            StringReader sr = new StringReader("'String!'");
+            JsonTextReader jsonReader = new JsonTextReader(sr);
+            jsonReader.Read();
+
+            TestGenericConverter converter = new TestGenericConverter();
+
+            ExceptionAssert.Throws<JsonSerializationException>(() =>
+            {
+                converter.ReadJson(jsonReader, typeof(string), 12345, null);
+            }, "Converter cannot read JSON with the specified existing value. System.String is required.");
+        }
+    }
+}

Src/Newtonsoft.Json/Converters/BsonObjectIdConverter.cs

@@ -44,6 +44,12 @@ namespace Newtonsoft.Json.Converters
         /// <param name="serializer">The calling serializer.</param>
         public override void WriteJson(JsonWriter writer, BsonObjectId value, JsonSerializer serializer)
         {
+            if (value == null)
+            {
+                writer.WriteNull();
+                return;
+            }
+
             BsonWriter bsonWriter = writer as BsonWriter;
             if (bsonWriter != null)
             {
@@ -60,11 +66,11 @@ namespace Newtonsoft.Json.Converters
         /// </summary>
         /// <param name="reader">The <see cref="JsonReader"/> to read from.</param>
         /// <param name="objectType">Type of the object.</param>
-        /// <param name="existingHasValue">The existing value has a value.</param>
-        /// <param name="existingValue">The existing value of object being read.</param>
+        /// <param name="existingValue">The existing value of object being read. If there is no existing value then <c>null</c> will be used.</param>
+        /// <param name="hasExistingValue">The existing value has a value.</param>
         /// <param name="serializer">The calling serializer.</param>
         /// <returns>The object value.</returns>
-        public override BsonObjectId ReadJson(JsonReader reader, Type objectType, bool existingHasValue, BsonObjectId existingValue, JsonSerializer serializer)
+        public override BsonObjectId ReadJson(JsonReader reader, Type objectType, BsonObjectId existingValue, bool hasExistingValue, JsonSerializer serializer)
         {
             if (reader.TokenType != JsonToken.Bytes)
             {

Src/Newtonsoft.Json/Converters/DataSetConverter.cs

@@ -43,6 +43,12 @@ namespace Newtonsoft.Json.Converters
         /// <param name="serializer">The calling serializer.</param>
         public override void WriteJson(JsonWriter writer, DataSet value, JsonSerializer serializer)
         {
+            if (value == null)
+            {
+                writer.WriteNull();
+                return;
+            }
+
             DefaultContractResolver resolver = serializer.ContractResolver as DefaultContractResolver;
 
             DataTableConverter converter = new DataTableConverter();
@@ -64,11 +70,11 @@ namespace Newtonsoft.Json.Converters
         /// </summary>
         /// <param name="reader">The <see cref="JsonReader"/> to read from.</param>
         /// <param name="objectType">Type of the object.</param>
-        /// <param name="existingHasValue">The existing value has a value.</param>
-        /// <param name="existingValue">The existing value of object being read.</param>
+        /// <param name="existingValue">The existing value of object being read. If there is no existing value then <c>null</c> will be used.</param>
+        /// <param name="hasExistingValue">The existing value has a value.</param>
         /// <param name="serializer">The calling serializer.</param>
         /// <returns>The object value.</returns>
-        public override DataSet ReadJson(JsonReader reader, Type objectType, bool existingHasValue, DataSet existingValue, JsonSerializer serializer)
+        public override DataSet ReadJson(JsonReader reader, Type objectType, DataSet existingValue, bool hasExistingValue, JsonSerializer serializer)
         {
             if (reader.TokenType == JsonToken.Null)
             {

Src/Newtonsoft.Json/Converters/DataTableConverter.cs

@@ -47,6 +47,12 @@ namespace Newtonsoft.Json.Converters
         /// <param name="serializer">The calling serializer.</param>
         public override void WriteJson(JsonWriter writer, DataTable value, JsonSerializer serializer)
         {
+            if (value == null)
+            {
+                writer.WriteNull();
+                return;
+            }
+
             DefaultContractResolver resolver = serializer.ContractResolver as DefaultContractResolver;
 
             writer.WriteStartArray();
@@ -77,11 +83,11 @@ namespace Newtonsoft.Json.Converters
         /// </summary>
         /// <param name="reader">The <see cref="JsonReader"/> to read from.</param>
         /// <param name="objectType">Type of the object.</param>
-        /// <param name="existingHasValue">The existing value has a value.</param>
-        /// <param name="existingValue">The existing value of object being read.</param>
+        /// <param name="existingValue">The existing value of object being read. If there is no existing value then <c>null</c> will be used.</param>
+        /// <param name="hasExistingValue">The existing value has a value.</param>
         /// <param name="serializer">The calling serializer.</param>
         /// <returns>The object value.</returns>
-        public override DataTable ReadJson(JsonReader reader, Type objectType, bool existingHasValue, DataTable existingValue, JsonSerializer serializer)
+        public override DataTable ReadJson(JsonReader reader, Type objectType, DataTable existingValue, bool hasExistingValue, JsonSerializer serializer)
         {
             if (reader.TokenType == JsonToken.Null)
             {
@@ -90,7 +96,7 @@ namespace Newtonsoft.Json.Converters
 
             DataTable dt = existingValue;
 
-            if (!existingHasValue)
+            if (!hasExistingValue)
             {
                 // handle typed datasets
                 dt = (objectType == typeof(DataTable))

Src/Newtonsoft.Json/Converters/VersionConverter.cs

@@ -45,7 +45,9 @@ namespace Newtonsoft.Json.Converters
             if (value == null)
             {
                 writer.WriteNull();
+                return;
             }
+
             writer.WriteValue(value.ToString());
         }
 
@@ -54,11 +56,11 @@ namespace Newtonsoft.Json.Converters
         /// </summary>
         /// <param name="reader">The <see cref="JsonReader"/> to read from.</param>
         /// <param name="objectType">Type of the object.</param>
-        /// <param name="existingHasValue">The existing value has a value.</param>
-        /// <param name="existingValue">The existing property value of the JSON that is being converted.</param>
+        /// <param name="existingValue">The existing value of object being read. If there is no existing value then <c>null</c> will be used.</param>
+        /// <param name="hasExistingValue">The existing value has a value.</param>
         /// <param name="serializer">The calling serializer.</param>
         /// <returns>The object value.</returns>
-        public override Version ReadJson(JsonReader reader, Type objectType, bool existingHasValue, Version existingValue, JsonSerializer serializer)
+        public override Version ReadJson(JsonReader reader, Type objectType, Version existingValue, bool hasExistingValue, JsonSerializer serializer)
         {
             if (reader.TokenType == JsonToken.Null)
             {

Src/Newtonsoft.Json/JsonConverter.cs

@@ -86,7 +86,7 @@ namespace Newtonsoft.Json
     /// <summary>
     /// Converts an object to and from JSON.
     /// </summary>
-    /// <typeparam name="T"></typeparam>
+    /// <typeparam name="T">The object type to convert.</typeparam>
     public abstract class JsonConverter<T> : JsonConverter
     {
         /// <summary>
@@ -99,7 +99,7 @@ namespace Newtonsoft.Json
         {
             if (!(value != null ? value is T : ReflectionUtils.IsNullable(typeof(T))))
             {
-                throw new JsonSerializationException("This converter cannot convert {0} of type {1}".FormatWith(CultureInfo.InvariantCulture, value, value?.GetType()));
+                throw new JsonSerializationException("Converter cannot write specified value to JSON. {0} is required.".FormatWith(CultureInfo.InvariantCulture, typeof(T)));
             }
             WriteJson(writer, (T)value, serializer);
         }
@@ -122,12 +122,12 @@ namespace Newtonsoft.Json
         /// <returns>The object value.</returns>
         public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
         {
-            var existingIsNull = existingValue == null;
+            bool existingIsNull = existingValue == null;
             if (!(existingIsNull || existingValue is T))
             {
-                throw new JsonSerializationException("This converter cannot convert {0} of type {1}".FormatWith(CultureInfo.InvariantCulture, existingValue, existingValue.GetType()));
+                throw new JsonSerializationException("Converter cannot read JSON with the specified existing value. {0} is required.".FormatWith(CultureInfo.InvariantCulture, typeof(T)));
             }
-            return ReadJson(reader, objectType, !existingIsNull, existingIsNull ? default(T) : (T)existingValue, serializer);
+            return ReadJson(reader, objectType, existingIsNull ? default(T) : (T)existingValue, !existingIsNull, serializer);
         }
 
         /// <summary>
@@ -135,11 +135,11 @@ namespace Newtonsoft.Json
         /// </summary>
         /// <param name="reader">The <see cref="JsonReader"/> to read from.</param>
         /// <param name="objectType">Type of the object.</param>
-        /// <param name="existingHasValue">The existing value has a value.</param>
-        /// <param name="existingValue">The existing value of object being read.</param>
+        /// <param name="existingValue">The existing value of object being read. If there is no existing value then <c>null</c> will be used.</param>
+        /// <param name="hasExistingValue">The existing value has a value.</param>
         /// <param name="serializer">The calling serializer.</param>
         /// <returns>The object value.</returns>
-        public abstract T ReadJson(JsonReader reader, Type objectType, bool existingHasValue, T existingValue, JsonSerializer serializer);
+        public abstract T ReadJson(JsonReader reader, Type objectType, T existingValue, bool hasExistingValue, JsonSerializer serializer);
 
         /// <summary>
         /// Determines whether this instance can convert the specified object type.