add flag converters nullable serialization (#857)

src/Microsoft.SqlTools.DataProtocol.Contracts/AssemblyInfo.cs

@@ -0,0 +1,3 @@
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Microsoft.SqlTools.Hosting.UnitTests")]

src/Microsoft.SqlTools.DataProtocol.Contracts/Utilities/FlagsIntConverter.cs

@@ -26,11 +26,16 @@ namespace Microsoft.SqlTools.DataProtocol.Contracts.Utilities
 
         public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
         {
-            // TODO: Fix to handle nullables properly
+            var jToken = JToken.Load(reader);
+            if (jToken.Type == JTokenType.Null)
+            {
+                return null;
+            }
 
-            int[] values = JArray.Load(reader).Values<int>().ToArray();
+            int[] values = ((JArray)jToken).Values<int>().ToArray();
+            var pureType = NullableUtils.GetUnderlyingTypeIfNullable(objectType);
 
-            FieldInfo[] enumFields = objectType.GetFields(BindingFlags.Public | BindingFlags.Static);
+            FieldInfo[] enumFields = pureType.GetFields(BindingFlags.Public | BindingFlags.Static);
             int setFlags = 0;
             foreach (FieldInfo enumField in enumFields)
             {
@@ -45,7 +50,7 @@ namespace Microsoft.SqlTools.DataProtocol.Contracts.Utilities
                 }
             }
 
-            return Enum.ToObject(objectType, setFlags);
+            return Enum.ToObject(pureType, setFlags);
         }
 
         public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
@@ -71,7 +76,7 @@ namespace Microsoft.SqlTools.DataProtocol.Contracts.Utilities
             writer.WriteRawValue($"[{joinedFlags}]");
         }
 
-        #endregion
+        #endregion Public Methods
 
         [AttributeUsage(AttributeTargets.Field)]
         internal class SerializeValueAttribute : Attribute

src/Microsoft.SqlTools.DataProtocol.Contracts/Utilities/FlagsStringConverter.cs

@@ -27,8 +27,6 @@ namespace Microsoft.SqlTools.DataProtocol.Contracts.Utilities
 
         public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
         {
-            // TODO: Fix to handle nullables properly
-            
             JToken jToken = JToken.Load(reader);
             if (jToken.Type == JTokenType.Null)
             {
@@ -36,8 +34,9 @@ namespace Microsoft.SqlTools.DataProtocol.Contracts.Utilities
             }
 
             string[] values = ((JArray)jToken).Values<string>().ToArray();
+            var pureType = NullableUtils.GetUnderlyingTypeIfNullable(objectType);
 
-            FieldInfo[] enumFields = objectType.GetFields(BindingFlags.Public | BindingFlags.Static);
+            FieldInfo[] enumFields = pureType.GetFields(BindingFlags.Public | BindingFlags.Static);
             int setFlags = 0;
             foreach (FieldInfo enumField in enumFields)
             {
@@ -56,7 +55,7 @@ namespace Microsoft.SqlTools.DataProtocol.Contracts.Utilities
                 }
             }
 
-            return Enum.ToObject(objectType, setFlags);
+            return Enum.ToObject(pureType, setFlags);
         }
 
         public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
@@ -86,7 +85,7 @@ namespace Microsoft.SqlTools.DataProtocol.Contracts.Utilities
             writer.WriteRawValue($"[{joinedFlags}]");
         }
 
-        #endregion
+        #endregion Public Methods
 
         [AttributeUsage(AttributeTargets.Field)]
         internal class SerializeValueAttribute : Attribute

src/Microsoft.SqlTools.DataProtocol.Contracts/Utilities/NullableUtils.cs

@@ -0,0 +1,36 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+
+namespace Microsoft.SqlTools.DataProtocol.Contracts.Utilities
+{
+    internal static class NullableUtils
+    {
+        /// <summary>
+        /// Determines whether the type is <see cref="Nullable{T}"/>.
+        /// </summary>
+        /// <param name="t">The type.</param>
+        /// <returns>
+        ///   <c>true</c> if <paramref name="t"/> is <see cref="Nullable{T}"/>; otherwise, <c>false</c>.
+        /// </returns>
+        public static bool IsNullable(Type t)
+        {
+            return t.IsGenericType && t.GetGenericTypeDefinition() == typeof(Nullable<>);
+        }
+
+        /// <summary>
+        /// Unwraps the <see cref="Nullable{T}"/> if necessary and returns the underlying value type.
+        /// </summary>
+        /// <param name="t">The type.</param>
+        /// <returns>The underlying value type the <see cref="Nullable{T}"/> type was produced from,
+        /// or the <paramref name="t"/> type if the type is not <see cref="Nullable{T}"/>.
+        /// </returns>
+        public static Type GetUnderlyingTypeIfNullable(Type t)
+        {
+            return IsNullable(t) ? Nullable.GetUnderlyingType(t) : t;
+        }
+    }
+}

test/Microsoft.SqlTools.Hosting.UnitTests/Contracts/Utilities/FlagsIntConverterTests.cs

@@ -0,0 +1,65 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using Microsoft.SqlTools.DataProtocol.Contracts.Utilities;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+using System;
+using Xunit;
+
+namespace Microsoft.SqlTools.Hosting.UnitTests.Contracts.Utilities
+{
+    public class FlagsIntConverterTests
+    {
+        [Fact]
+        public void NullableValueCanBeDeserialized()
+        {
+            var jsonObject = JObject.Parse("{\"optionalValue\": [1, 2]}");
+            var contract = jsonObject.ToObject<DataContract>();
+            Assert.NotNull(contract);
+            Assert.NotNull(contract.OptionalValue);
+            Assert.Equal(TestFlags.FirstItem | TestFlags.SecondItem, contract.OptionalValue);
+        }
+
+        [Fact]
+        public void RegularValueCanBeDeserialized()
+        {
+            var jsonObject = JObject.Parse("{\"Value\": [1, 3]}");
+            var contract = jsonObject.ToObject<DataContract>();
+            Assert.NotNull(contract);
+            Assert.Equal(TestFlags.FirstItem | TestFlags.ThirdItem, contract.Value);
+        }
+
+        [Fact]
+        public void ExplicitNullCanBeDeserialized()
+        {
+            var jsonObject = JObject.Parse("{\"optionalValue\": null}");
+            var contract = jsonObject.ToObject<DataContract>();
+            Assert.NotNull(contract);
+            Assert.Null(contract.OptionalValue);
+        }
+
+        [Flags]
+        [JsonConverter(typeof(FlagsIntConverter))]
+        private enum TestFlags
+        {
+            [FlagsIntConverter.SerializeValue(1)]
+            FirstItem = 1 << 0,
+
+            [FlagsIntConverter.SerializeValue(2)]
+            SecondItem = 1 << 1,
+
+            [FlagsIntConverter.SerializeValue(3)]
+            ThirdItem = 1 << 2,
+        }
+
+        private class DataContract
+        {
+            public TestFlags? OptionalValue { get; set; }
+
+            public TestFlags Value { get; set; }
+        }
+    }
+}

test/Microsoft.SqlTools.Hosting.UnitTests/Contracts/Utilities/FlagsStringConverterTests.cs

@@ -0,0 +1,65 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using Microsoft.SqlTools.DataProtocol.Contracts.Utilities;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+using Xunit;
+
+namespace Microsoft.SqlTools.Hosting.UnitTests.Contracts.Utilities
+{
+    public class FlagsStringConverterTests
+    {
+        [Fact]
+        public void NullableValueCanBeDeserialized()
+        {
+            var jsonObject = JObject.Parse("{\"optionalValue\": [\"First\", \"Second\"]}");
+            var contract = jsonObject.ToObject<DataContract>();
+            Assert.NotNull(contract);
+            Assert.NotNull(contract.OptionalValue);
+            Assert.Equal(TestFlags.FirstItem | TestFlags.SecondItem, contract.OptionalValue);
+        }
+
+        [Fact]
+        public void RegularValueCanBeDeserialized()
+        {
+            var jsonObject = JObject.Parse("{\"Value\": [\"First\", \"Third\"]}");
+            var contract = jsonObject.ToObject<DataContract>();
+            Assert.NotNull(contract);
+            Assert.Equal(TestFlags.FirstItem | TestFlags.ThirdItem, contract.Value);
+        }
+
+        [Fact]
+        public void ExplicitNullCanBeDeserialized()
+        {
+            var jsonObject = JObject.Parse("{\"optionalValue\": null}");
+            var contract = jsonObject.ToObject<DataContract>();
+            Assert.NotNull(contract);
+            Assert.Null(contract.OptionalValue);
+        }
+
+        [Flags]
+        [JsonConverter(typeof(FlagsStringConverter))]
+        private enum TestFlags
+        {
+            [FlagsStringConverter.SerializeValue("First")]
+            FirstItem = 1 << 0,
+
+            [FlagsStringConverter.SerializeValue("Second")]
+            SecondItem = 1 << 1,
+
+            [FlagsStringConverter.SerializeValue("Third")]
+            ThirdItem = 1 << 2,
+        }
+
+        private class DataContract
+        {
+            public TestFlags? OptionalValue { get; set; }
+
+            public TestFlags Value { get; set; }
+        }
+    }
+}