Enable roundtrip for F# struct record with datamember attribute

Src/Newtonsoft.Json.Tests/Issues/Issue1295.cs

@@ -0,0 +1,34 @@
+using Newtonsoft.Json.Tests.TestObjects;
+#if DNXCORE50
+using Xunit;
+using Test = Xunit.FactAttribute;
+using Assert = Newtonsoft.Json.Tests.XUnitAssert;
+#else
+using NUnit.Framework;
+#endif
+
+namespace Newtonsoft.Json.Tests.Issues
+{
+    [TestFixture]
+    public class Issue1295 : TestFixtureBase
+    {
+        [Test]
+        public void Test()
+        {
+            var fsharpStructRecord = new FSharpStructRecordWithDataMember("Hi there");
+            var asJson = JsonConvert.SerializeObject(fsharpStructRecord);
+            var deserialized = JsonConvert.DeserializeObject<FSharpStructRecordWithDataMember>(asJson);
+
+            Assert.AreEqual(fsharpStructRecord.Foo, deserialized.Foo);
+        }
+
+        [Test]
+        public void TestJsonSanity()
+        {
+            var fsharpStructRecord = new FSharpStructRecordWithDataMember("42");
+            var asJson = JsonConvert.SerializeObject(fsharpStructRecord);         
+
+            Assert.AreEqual(@"{""foo_field"":""42""}", asJson);
+        }
+    }
+}

Src/Newtonsoft.Json.Tests/TestObjects/FsharpStructRecordWithDataMember.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+#if !NET20
+using System.Runtime.Serialization;
+#endif
+
+namespace Newtonsoft.Json.Tests.TestObjects
+{
+#if !NET20
+    [Serializable]   
+    [DataContract]
+#endif
+    // This mimics what F# compiler produces for a simple [<Struct>] record which is also using DataMember attribute
+    // Follows https://github.com/JamesNK/Newtonsoft.Json/issues/1295#issuecomment-1534807350 , simplified to have it compile
+    public struct FSharpStructRecordWithDataMember
+    {
+        [CompilerGenerated]
+        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
+        internal string Foo_;
+#if !NET20
+        [DataMember(Name = "foo_field")]
+#endif
+        public readonly string Foo
+        {
+            [CompilerGenerated]
+            [DebuggerNonUserCode]
+            get
+            {
+                return Foo_;
+            }
+        }
+
+        public FSharpStructRecordWithDataMember(string foo)
+        {
+            Foo_ = foo;
+        }
+
+        [CompilerGenerated]
+        public override string ToString()
+        {
+            return "FSharpStructRecordWithDataMember { Foo = " + Foo + " }";
+        }
+    }
+}

Src/Newtonsoft.Json/Serialization/DefaultContractResolver.cs

@@ -640,7 +640,8 @@ IEnumerator IEnumerable.GetEnumerator()
                     {
                         foreach (ParameterInfo parameterInfo in parameters)
                         {
-                            JsonProperty? memberProperty = MatchProperty(memberProperties, parameterInfo.Name!, parameterInfo.ParameterType);
+                            JsonProperty? memberProperty = 
+                                MatchConstructorProperty(memberProperties, parameterInfo.Name!, parameterInfo.ParameterType);
                             if (memberProperty == null || memberProperty.Writable)
                             {
                                 return null;
@@ -697,7 +698,7 @@ protected virtual IList<JsonProperty> CreateConstructorParameters(ConstructorInf
                     continue;
                 }
 
-                JsonProperty? matchingMemberProperty = MatchProperty(memberProperties, parameterInfo.Name, parameterInfo.ParameterType);
+                JsonProperty? matchingMemberProperty = MatchConstructorProperty(memberProperties, parameterInfo.Name, parameterInfo.ParameterType);
 
                 // ensure that property will have a name from matching property or from parameterinfo
                 // parameterinfo could have no name if generated by a proxy (I'm looking at you Castle)
@@ -715,7 +716,7 @@ protected virtual IList<JsonProperty> CreateConstructorParameters(ConstructorInf
             return parameterCollection;
         }
 
-        private JsonProperty? MatchProperty(JsonPropertyCollection properties, string name, Type type)
+        private JsonProperty? MatchConstructorProperty(JsonPropertyCollection properties, string name, Type type)
         {
             // it is possible to generate a member with a null name using Reflection.Emit
             // protect against an ArgumentNullException from GetClosestMatchProperty by testing for null here
@@ -724,7 +725,9 @@ protected virtual IList<JsonProperty> CreateConstructorParameters(ConstructorInf
                 return null;
             }
 
-            JsonProperty? property = properties.GetClosestMatchProperty(name);
+            JsonProperty? property = 
+                properties.GetClosestMatchProperty(name) ??
+                properties.GetByUnderlyingName(name);
             // must match type as well as name
             if (property == null || property.PropertyType != type)
             {

Src/Newtonsoft.Json/Serialization/JsonPropertyCollection.cs

@@ -135,7 +135,7 @@ public void AddProperty(JsonProperty property)
         /// <param name="propertyName">Name of the property.</param>
         /// <returns>A matching property if found.</returns>
         public JsonProperty? GetClosestMatchProperty(string propertyName)
-        {
+        {       
             JsonProperty? property = GetProperty(propertyName, StringComparison.Ordinal);
             if (property == null)
             {
@@ -186,5 +186,22 @@ private bool TryGetProperty(string key, [NotNullWhen(true)]out JsonProperty? ite
 
             return null;
         }
+
+        /// <summary>
+        /// Gets a property by underlying name. This makes a difference when using name-mapping attributes such as DataMember
+        /// </summary>
+        /// <param name="propertyName">The name of the property to get.</param>   
+        /// <returns>A matching property if found.</returns>
+        public JsonProperty? GetByUnderlyingName(string propertyName)
+        {
+            for (int i = 0; i < _list.Count; i++)
+            {
+                JsonProperty property = _list[i];
+                if (string.Equals(propertyName, property.UnderlyingName, StringComparison.OrdinalIgnoreCase))
+                    return property;
+            }
+
+            return null;
+        }
     }
 }