Revamp to reflection.

Changes in brief:
1. Descriptor is now the entry point for all reflection.
2. IReflectedMessage has gone; there's now a Descriptor property in IMessage, which is explicitly implemented (due to the static property).
3. FieldAccessorTable has gone away
4. IFieldAccessor and OneofFieldAccessor still exist; we *could* put the functionality straight into FieldDescriptor and OneofDescriptor... I'm unsure about that.
5. There's a temporary property MessageDescriptor.FieldAccessorsByFieldNumber to make the test changes small - we probably want this to go away
6. Discovery for delegates is now via attributes applied to properties and the Clear method of a oneof

I'm happy with 1-3.
4 I'm unsure about - feedback welcome.
5 will go away
6 I'm unsure about, both in design and implementation. Should we have a ProtobufMessageAttribute too? Should we find all the relevant attributes in MessageDescriptor and pass them down, to avoid an O(N^2) scenario?

Generated code changes coming in the next commit.

1 files changed, 29 insertions, 7 deletions

diff --git a/csharp/src/Google.Protobuf/Reflection/FileDescriptor.cs b/csharp/src/Google.Protobuf/Reflection/FileDescriptor.cs
index db393480..a10e617b 100644
--- a/csharp/src/Google.Protobuf/Reflection/FileDescriptor.cs
+++ b/csharp/src/Google.Protobuf/Reflection/FileDescriptor.cs
@@ -62,11 +62,12 @@ namespace Google.Protobuf.Reflection
             get { return proto.Syntax == "proto3" ? ProtoSyntax.Proto3 : ProtoSyntax.Proto2; }
         }
 
-        private FileDescriptor(FileDescriptorProto proto, FileDescriptor[] dependencies, DescriptorPool pool, bool allowUnknownDependencies)
+        private FileDescriptor(FileDescriptorProto proto, FileDescriptor[] dependencies, DescriptorPool pool, bool allowUnknownDependencies, Type[] generatedTypes)
         {
             this.pool = pool;
             this.proto = proto;
             this.dependencies = new ReadOnlyCollection<FileDescriptor>((FileDescriptor[]) dependencies.Clone());
+            IEnumerator<Type> generatedTypeIterator = generatedTypes == null ? null : ((IEnumerable<Type>)generatedTypes).GetEnumerator();
 
             publicDependencies = DeterminePublicDependencies(this, proto, dependencies, allowUnknownDependencies);
 
@@ -74,15 +75,21 @@ namespace Google.Protobuf.Reflection
 
             messageTypes = DescriptorUtil.ConvertAndMakeReadOnly(proto.MessageType,
                                                                  (message, index) =>
-                                                                 new MessageDescriptor(message, this, null, index));
+                                                                 new MessageDescriptor(message, this, null, index, generatedTypeIterator));
 
             enumTypes = DescriptorUtil.ConvertAndMakeReadOnly(proto.EnumType,
                                                               (enumType, index) =>
-                                                              new EnumDescriptor(enumType, this, null, index));
+                                                              new EnumDescriptor(enumType, this, null, index, ReflectionUtil.GetNextType(generatedTypeIterator)));
 
             services = DescriptorUtil.ConvertAndMakeReadOnly(proto.Service,
                                                              (service, index) =>
                                                              new ServiceDescriptor(service, this, index));
+
+            // We should now have consumed all the generated types.
+            if (generatedTypeIterator != null && generatedTypeIterator.MoveNext())
+            {
+                throw new ArgumentException("More generated types left over after consuming all expected ones", "generatedTypes");
+            }
         }
 
         /// <summary>
@@ -265,7 +272,7 @@ namespace Google.Protobuf.Reflection
         /// <exception cref="DescriptorValidationException">If <paramref name="proto"/> is not
         /// a valid descriptor. This can occur for a number of reasons, such as a field
         /// having an undefined type or because two messages were defined with the same name.</exception>
-        private static FileDescriptor BuildFrom(FileDescriptorProto proto, FileDescriptor[] dependencies, bool allowUnknownDependencies)
+        private static FileDescriptor BuildFrom(FileDescriptorProto proto, FileDescriptor[] dependencies, bool allowUnknownDependencies, Type[] generatedTypes)
         {
             // Building descriptors involves two steps: translating and linking.
             // In the translation step (implemented by FileDescriptor's
@@ -282,7 +289,7 @@ namespace Google.Protobuf.Reflection
             }
 
             DescriptorPool pool = new DescriptorPool(dependencies);
-            FileDescriptor result = new FileDescriptor(proto, dependencies, pool, allowUnknownDependencies);
+            FileDescriptor result = new FileDescriptor(proto, dependencies, pool, allowUnknownDependencies, generatedTypes);
 
             // TODO(jonskeet): Reinstate these checks, or get rid of them entirely. They aren't in the Java code,
             // and fail for the CustomOptions test right now. (We get "descriptor.proto" vs "google/protobuf/descriptor.proto".)
@@ -319,8 +326,23 @@ namespace Google.Protobuf.Reflection
             }
         }
 
+        /// <summary>
+        /// Creates an instance for generated code.
+        /// </summary>
+        /// <remarks>
+        /// The <paramref name="generatedTypes"/> parameter should be null for descriptors which don't correspond to
+        /// generated types. Otherwise, the array should be represent all the generated types in the file: messages then
+        /// enums. Within each message, there can be nested messages and enums, which must be specified "inline" in the array:
+        /// containing message, nested messages, nested enums - and of course each nested message may contain *more* nested messages,
+        /// etc. All messages within the descriptor should be represented, even if they do not have a generated type - any
+        /// type without a corresponding generated type (such as map entries) should respond to a null element.
+        /// For example, a file with a messages OuterMessage and InnerMessage, and enums OuterEnum and InnerEnum (where
+        /// InnerMessage and InnerEnum are nested within InnerMessage) would result in an array of
+        /// OuterMessage, InnerMessage, InnerEnum, OuterEnum.
+        /// </remarks>
         public static FileDescriptor InternalBuildGeneratedFileFrom(byte[] descriptorData,
-                                                                    FileDescriptor[] dependencies)
+                                                                    FileDescriptor[] dependencies,
+                                                                    Type[] generatedTypes)
         {
             FileDescriptorProto proto;
             try
@@ -336,7 +358,7 @@ namespace Google.Protobuf.Reflection
             {
                 // When building descriptors for generated code, we allow unknown
                 // dependencies by default.
-                return BuildFrom(proto, dependencies, true);
+                return BuildFrom(proto, dependencies, true, generatedTypes);
             }
             catch (DescriptorValidationException e)
             {