Investigate support for Unity

[jtattermusch]

quoting @jskeet:
"There's suspicion the current version of C# protobufs won't work with Unity, but we can add another build target for that later when we find a need - we can create a new minor version of the NuGet package for that with no problems.

My experience with the "old" protobuf-csharp-port is that Unity on iOS has various issues, so I think we'll want to investigate them pretty thoroughly before trying to support it anyway - and we may need to conditionally compile out some features. We'll see... but I'd like to avoid having Unity support block a dotnetcore release."

also see #638

[dreis2211]

+1

[Lyve1981]

+1

[jay-allan]

+1

[jskeet]

Three +1s in the space of a few minutes suggests this is being linked to from somewhere - it would be nice if someone could provide the context. It would be even nicer if someone with Unity support could try this and inform us where there are problems :)

[jay-allan]

I can only speak for myself, but in my case we are developing a mobile game with Unity and a Java backend. In order to keep our client compatible with iOS, we are using protobuf-net. Unfortunately, protobuf-net has some known bugs and does not support the latest Protobuf versions, so an official solution from Google would be very interesting for us.

[jskeet]

@jayallanjethwa: But how did you happen to reach this issue? It seems unlikely that three people would find an issue raised nearly two months ago entirely independently but within the same 5 minute window. I'm only asking so that I can try to get more context that might help resolve the issue. (I'd love to be able to support Unity - but I foresee some tricky issues, based on previous experience of bug reports.)

[asuuma]

@jskeet I started to use protobuf v3 in Unity, and I found two problems.
First of all, Unity is using .NET 3.5 and there were some compile errors when I copied to Unity project, so I had to modify some code with .NET 4.5 specific. This made me working protobuf v3 with Unity for simple case. Secondly, when I trying JsonFormatter.Format(IMessage) in iOS, Unity will threw exception of System.Reflection.Emit is not permitted., because iOS doesn't allow JIT.
So far I found these problems, but there may be other problems because I am not using full functions of v3.

[jskeet]

@asuuma: Right. Supporting both .NET 3.5 and modern PCLs is painful. I'm hoping that it won't be too long before Unity moves on in terms of runtime - after all, .NET 4.0 was released a long time ago. Could you give the details of the stack trace around Reflection.Emit? I suspect the problem is the use of expression trees, which would be feasible to fix, though annoying.

(I'm going to need to balance the importance of supporting a wide variety of platforms with the additional code maintenance headaches and possible performance degredations of doing so. The more I know before making this judgement call, the better...)

[asuuma]

@jskeet Yeah, everyone are hoping to move on newer runtime in near future... They opened roadmap of Unity and it says they are researching about upgrading .NET profile.
Here is the stack trace.

NotSupportedException: /Users/builduser/buildslave/unity/build/Tools/il2cpp/il2cpp/libil2cpp/icalls/mscorlib/System.Reflection.Emit/DynamicMethod.cpp(21) : Unsupported internal call for IL2CPP:DynamicMethod::create_dynamic_method - System.Reflection.Emit is not supported.
  at System.Reflection.Emit.DynamicMethod.CreateDelegate (System.Type delegateType, System.Object target) [0x00000] in <filename unknown>:0 
  at System.Linq.Expressions.Expression`1[TDelegate].Compile () [0x00000] in <filename unknown>:0 
  at Google.Protobuf.Reflection.FieldAccessorBase..ctor (System.Reflection.PropertyInfo property, Google.Protobuf.Reflection.FieldDescriptor descriptor) [0x00000] in <filename unknown>:0 
  at Google.Protobuf.Reflection.SingleFieldAccessor..ctor (System.Reflection.PropertyInfo property, Google.Protobuf.Reflection.FieldDescriptor descriptor) [0x00000] in <filename unknown>:0 
  at Google.Protobuf.Reflection.FieldDescriptor.CreateAccessor (System.String propertyName) [0x00000] in <filename unknown>:0 
  at Google.Protobuf.Reflection.FieldDescriptor.CrossLink () [0x00000] in <filename unknown>:0 
  at Google.Protobuf.Reflection.MessageDescriptor.CrossLink () [0x00000] in <filename unknown>:0 
  at Google.Protobuf.Reflection.FileDescriptor.CrossLink () [0x00000] in <filename unknown>:0 
  at Google.Protobuf.Reflection.FileDescriptor.BuildFrom (Google.Protobuf.ByteString descriptorData, Google.Protobuf.Reflection.FileDescriptorProto proto, Google.Protobuf.Reflection.FileDescriptor[] dependencies, Boolean allowUnknownDependencies, Google.Protobuf.Reflection.GeneratedCodeInfo generatedCodeInfo) [0x00000] in <filename unknown>:0 
  at Google.Protobuf.Reflection.FileDescriptor.InternalBuildGeneratedFileFrom (System.Byte[] descriptorData, Google.Protobuf.Reflection.FileDescriptor[] dependencies, Google.Protobuf.Reflection.GeneratedCodeInfo generatedCodeInfo) [0x00000] in <filename unknown>:0 
  at Test..cctor () [0x00000] in <filename unknown>:0 
  at Test.get_Descriptor () [0x00000] in <filename unknown>:0 
  at Google.Protobuf.JsonFormatter.Format (IMessage message) [0x00000] in <filename unknown>:0 

[jskeet]

Right, thanks - so that is expression tree compilation. It's definitely feasible to write a workaround for that particular one.

[dreis2211]

@asuuma Could you elaborate on what you did to workaround the .NET version mismatch?

[asuuma]

@dreis2211 Oh very sorry, I missed your message.
Here is diff of what I changed, just fixing compile errors.

diff -u -r Google.Protobuf/Compatibility/PropertyInfoExtensions.cs protubuf-unity/Compatibility/PropertyInfoExtensions.cs
--- Google.Protobuf/Compatibility/PropertyInfoExtensions.cs 2015-09-10 20:05:51.000000000 +0900
+++ protubuf-unity/Compatibility/PropertyInfoExtensions.cs  2015-10-06 12:36:43.000000000 +0900
@@ -47,7 +47,7 @@
         /// </summary>
         internal static MethodInfo GetGetMethod(this PropertyInfo target)
         {
-            var method = target.GetMethod;
+            var method = target.GetGetMethod();
             return method != null && method.IsPublic ? method : null;
         }

@@ -57,7 +57,7 @@
         /// </summary>
         internal static MethodInfo GetSetMethod(this PropertyInfo target)
         {
-            var method = target.SetMethod;
+            var method = target.GetSetMethod();
             return method != null && method.IsPublic ? method : null;
         }
     }
diff -u -r Google.Protobuf/Compatibility/TypeExtensions.cs protubuf-unity/Compatibility/TypeExtensions.cs
--- Google.Protobuf/Compatibility/TypeExtensions.cs 2015-09-10 20:05:51.000000000 +0900
+++ protubuf-unity/Compatibility/TypeExtensions.cs  2015-10-06 12:36:43.000000000 +0900
@@ -51,7 +51,8 @@
         /// </summary>
         internal static bool IsValueType(this Type target)
         {
-            return target.GetTypeInfo().IsValueType;
+//            return target.GetTypeInfo().IsValueType;
+           return target.GetType().IsValueType;
         }

         /// <summary>
@@ -59,7 +60,8 @@
         /// </summary>
         internal static bool IsAssignableFrom(this Type target, Type c)
         {
-            return target.GetTypeInfo().IsAssignableFrom(c.GetTypeInfo());
+//            return target.GetTypeInfo().IsAssignableFrom(c.GetTypeInfo());
+           return target.GetType().IsAssignableFrom(c.GetType());
         }

         /// <summary>
@@ -72,9 +74,9 @@
             // GetDeclaredProperty only returns properties declared in the given type, so we need to recurse.
             while (target != null)
             {
-                var typeInfo = target.GetTypeInfo();
-                var ret = typeInfo.GetDeclaredProperty(name);
-                if (ret != null && ((ret.CanRead && ret.GetMethod.IsPublic) || (ret.CanWrite && ret.SetMethod.IsPublic)))
+                var typeInfo = target.GetType();
+                var ret = typeInfo.GetProperty(name);
+                if (ret != null && ((ret.CanRead && ret.GetGetMethod().IsPublic) || (ret.CanWrite && ret.GetSetMethod().IsPublic)))
                 {
                     return ret;
                 }
@@ -99,8 +101,8 @@
             // GetDeclaredMethod only returns methods declared in the given type, so we need to recurse.
             while (target != null)
             {
-                var typeInfo = target.GetTypeInfo();
-                var ret = typeInfo.GetDeclaredMethod(name);
+                var typeInfo = target.GetType();
+                var ret = typeInfo.GetMethod(name);
                 if (ret != null && ret.IsPublic)
                 {
                     return ret;
diff -u -r Google.Protobuf/JsonFormatter.cs protubuf-unity/JsonFormatter.cs
--- Google.Protobuf/JsonFormatter.cs    2015-09-10 20:05:51.000000000 +0900
+++ protubuf-unity/JsonFormatter.cs 2015-10-23 10:14:41.000000000 +0900
@@ -496,7 +496,7 @@
         private void WriteFieldMask(StringBuilder builder, IMessage value)
         {
             IList paths = (IList) value.Descriptor.Fields[FieldMask.PathsFieldNumber].Accessor.GetValue(value);
-            AppendEscapedString(builder, string.Join(",", paths.Cast<string>().Select(ToCamelCase)));
+            AppendEscapedString(builder, string.Join(",", paths.Cast<string>().Select(s => ToCamelCase(s)).ToArray()));
         }

         /// <summary>
diff -u -r Google.Protobuf/WellKnownTypes/TimeExtensions.cs protubuf-unity/WellKnownTypes/TimeExtensions.cs
--- Google.Protobuf/WellKnownTypes/TimeExtensions.cs    2015-09-10 20:05:51.000000000 +0900
+++ protubuf-unity/WellKnownTypes/TimeExtensions.cs 2015-10-23 10:13:48.000000000 +0900
@@ -34,7 +34,6 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
-using System.Threading.Tasks;

 namespace Google.Protobuf.WellKnownTypes
 {

[zeroZshadow]

I've applied this patch (without the commented out code) and can confirm this work in unity3d 5.2.2f
This also keeps working when used in a WebGL export. Although i am not using any fancy protobuf features (only string, int, etc and repeated)