Initial commit to demonstrate method

Author: matt-whitfield-scopely

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "2.1.500"
+    "version": "2.1.818"
   },
   "msbuild-sdks": {
     "MSBuild.Sdk.Extras": "1.5.4",

src/protobuf-net.Test/protobuf-net.Test.csproj

@@ -3,11 +3,11 @@
   <PropertyGroup>
     <GenerateDocumentationFile>false</GenerateDocumentationFile>
     <!--<TargetFrameworks>netcoreapp1.1;net452</TargetFrameworks>-->
-    <TargetFrameworks>net452</TargetFrameworks>
+    <TargetFrameworks>netcoreapp2.1</TargetFrameworks>
     <LibImport>net</LibImport>
     <Configurations>Debug;Release;VS</Configurations>
   </PropertyGroup>
-  <PropertyGroup Condition="$(TargetFramework)=='netcoreapp1.1'">
+  <PropertyGroup Condition="$(TargetFramework)=='netcoreapp2.1'">
     <DefineConstants>FEAT_COMPILER;NO_NHIBERNATE;COREFX;NO_INTERNAL_CONTEXT</DefineConstants>
     <LibImport>core</LibImport>
   </PropertyGroup>

src/protobuf-net/ProtoReader.cs

@@ -33,6 +33,11 @@ public sealed class ProtoReader : IDisposable
         /// </summary>
         public int FieldNumber => fieldNumber;
 
+        /// <summary>
+        /// Returns true if the field being processed is an empty list.
+        /// </summary>
+        public bool IsEmptyList => (fieldNumber & Serializer.EmptyListFlag) == Serializer.EmptyListFlag;
+
         /// <summary>
         /// Indicates the underlying proto serialization format on the wire.
         /// </summary>

src/protobuf-net/Serializer.cs

@@ -18,6 +18,8 @@ namespace ProtoBuf
     /// </remarks>
     public static class Serializer
     {
+        public const int EmptyListFlag = 0x01000000;
+
 #if !NO_RUNTIME
         /// <summary>
         /// Suggest a .proto definition for the given type

src/protobuf-net/Serializers/ListDecorator.cs

@@ -494,10 +494,12 @@ public override void Write(object value, ProtoWriter dest)
                 token = new SubItemToken(); // default
             }
             bool checkForNull = !SupportNull;
+            bool isEmpty = true;
             foreach (object subItem in (IEnumerable)value)
             {
                 if (checkForNull && subItem == null) { throw new NullReferenceException(); }
                 Tail.Write(subItem, dest);
+                isEmpty = false;
             }
             if (writePacked)
             {
@@ -510,6 +512,11 @@ public override void Write(object value, ProtoWriter dest)
                     ProtoWriter.EndSubItem(token, dest);
                 }
             }
+            else if (isEmpty)
+            {
+                ProtoWriter.WriteFieldHeader(fieldNumber | Serializer.EmptyListFlag, WireType.String, dest);
+                ProtoWriter.WriteString("", dest);
+            }
         }
 
         private bool CanUsePackedPrefix(object obj) =>
@@ -522,6 +529,11 @@ public override object Read(object value, ProtoReader source)
                 int field = source.FieldNumber;
                 object origValue = value;
                 if (value == null) value = Activator.CreateInstance(concreteType);
+                if (source.IsEmptyList)
+                {
+                    return value;
+                }
+
                 bool isList = IsList && !SuppressIList;
                 if (packedWireType != WireType.None && source.WireType == WireType.String)
                 {

src/protobuf-net/Serializers/TypeSerializer.cs

@@ -198,6 +198,7 @@ public object Read(object value, ProtoReader source)
                 }
                 for (int i = lastFieldIndex; i < fieldNumbers.Length; i++)
                 {
+                    fieldNumber &= ~Serializer.EmptyListFlag;
                     if (fieldNumbers[i] == fieldNumber)
                     {
                         IProtoSerializer ser = serializers[i];

src/protobuf-net/protobuf-net.csproj

@@ -3,7 +3,7 @@
     <AssemblyName>protobuf-net</AssemblyName>
     <Title>protobuf-net</Title>
     <Description>Provides simple access to fast and efficient "Protocol Buffers" serialization from .NET applications</Description>
-    <TargetFrameworks>net35;net451;netstandard2.0;netcoreapp2.1</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <DefineConstants>EMIT_ASSEMBLY_INFO</DefineConstants>
     <!-- new build tools spit these out -->