Merge pull request #634 from jskeet/reflection2

Reflection part 2 - for discussion

csharp/src/Google.Protobuf.Test/Google.Protobuf.Test.csproj

-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
@@ -82,6 +82,7 @@
     <Compile Include="Collections\RepeatedFieldTest.cs" />
     <Compile Include="JsonFormatterTest.cs" />
     <Compile Include="Reflection\DescriptorsTest.cs" />
+    <Compile Include="Reflection\FieldAccessTest.cs" />
     <Compile Include="SampleEnum.cs" />
     <Compile Include="SampleMessages.cs" />
     <Compile Include="TestProtos\MapUnittestProto3.cs" />

csharp/src/Google.Protobuf.Test/Reflection/DescriptorsTest.cs

@@ -33,6 +33,7 @@
 using System.Linq;
 using Google.Protobuf.TestProtos;
 using NUnit.Framework;
+using UnitTest.Issues.TestProtos;
 
 namespace Google.Protobuf.Reflection
 {
@@ -102,15 +103,16 @@ namespace Google.Protobuf.Reflection
             Assert.AreEqual(UnittestProto3.Descriptor, nestedType.File);
             Assert.AreEqual(messageType, nestedType.ContainingType);
 
-            FieldDescriptor field = messageType.Fields[0];
+            FieldDescriptor field = messageType.Fields.InDeclarationOrder()[0];
             Assert.AreEqual("single_int32", field.Name);
             Assert.AreEqual(field, messageType.FindDescriptor<FieldDescriptor>("single_int32"));
             Assert.Null(messageType.FindDescriptor<FieldDescriptor>("no_such_field"));
             Assert.AreEqual(field, messageType.FindFieldByNumber(1));
             Assert.Null(messageType.FindFieldByNumber(571283));
-            for (int i = 0; i < messageType.Fields.Count; i++)
+            var fieldsInDeclarationOrder = messageType.Fields.InDeclarationOrder();
+            for (int i = 0; i < fieldsInDeclarationOrder.Count; i++)
             {
-                Assert.AreEqual(i, messageType.Fields[i].Index);
+                Assert.AreEqual(i, fieldsInDeclarationOrder[i].Index);
             }
 
             Assert.AreEqual(nestedType, messageType.NestedTypes[0]);
@@ -220,5 +222,19 @@ namespace Google.Protobuf.Reflection
 
             CollectionAssert.AreEquivalent(expectedFields, descriptor.Fields);
         }
+
+        [Test]
+        public void ConstructionWithoutGeneratedCodeInfo()
+        {
+            var data = UnittestIssues.Descriptor.Proto.ToByteArray();
+            var newDescriptor = Google.Protobuf.Reflection.FileDescriptor.InternalBuildGeneratedFileFrom(data, new Reflection.FileDescriptor[] { }, null);
+
+            // We should still be able to get at a field...
+            var messageDescriptor = newDescriptor.FindTypeByName<MessageDescriptor>("ItemField");
+            var fieldDescriptor = messageDescriptor.FindFieldByName("item");
+            // But there shouldn't be an accessor (or a generated type for the message)
+            Assert.IsNull(fieldDescriptor.Accessor);
+            Assert.IsNull(messageDescriptor.GeneratedType);
+        }
     }
-}
+}
\ No newline at end of file

csharp/src/Google.Protobuf.Test/WellKnownTypes/WrappersTest.cs

@@ -192,23 +192,23 @@ namespace Google.Protobuf.WellKnownTypes
                 Uint32Field = 3,
                 Uint64Field = 4
             };
-            var fields = TestWellKnownTypes.Descriptor.FieldAccessorsByFieldNumber;
+            var fields = TestWellKnownTypes.Descriptor.Fields;
 
-            Assert.AreEqual("x", fields[TestWellKnownTypes.StringFieldFieldNumber].GetValue(message));
-            Assert.AreEqual(ByteString.CopyFrom(1, 2, 3), fields[TestWellKnownTypes.BytesFieldFieldNumber].GetValue(message));
-            Assert.AreEqual(true, fields[TestWellKnownTypes.BoolFieldFieldNumber].GetValue(message));
-            Assert.AreEqual(12.5f, fields[TestWellKnownTypes.FloatFieldFieldNumber].GetValue(message));
-            Assert.AreEqual(12.25d, fields[TestWellKnownTypes.DoubleFieldFieldNumber].GetValue(message));
-            Assert.AreEqual(1, fields[TestWellKnownTypes.Int32FieldFieldNumber].GetValue(message));
-            Assert.AreEqual(2L, fields[TestWellKnownTypes.Int64FieldFieldNumber].GetValue(message));
-            Assert.AreEqual(3U, fields[TestWellKnownTypes.Uint32FieldFieldNumber].GetValue(message));
-            Assert.AreEqual(4UL, fields[TestWellKnownTypes.Uint64FieldFieldNumber].GetValue(message));
+            Assert.AreEqual("x", fields[TestWellKnownTypes.StringFieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(ByteString.CopyFrom(1, 2, 3), fields[TestWellKnownTypes.BytesFieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(true, fields[TestWellKnownTypes.BoolFieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(12.5f, fields[TestWellKnownTypes.FloatFieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(12.25d, fields[TestWellKnownTypes.DoubleFieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(1, fields[TestWellKnownTypes.Int32FieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(2L, fields[TestWellKnownTypes.Int64FieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(3U, fields[TestWellKnownTypes.Uint32FieldFieldNumber].Accessor.GetValue(message));
+            Assert.AreEqual(4UL, fields[TestWellKnownTypes.Uint64FieldFieldNumber].Accessor.GetValue(message));
 
             // And a couple of null fields...
             message.StringField = null;
             message.FloatField = null;
-            Assert.IsNull(fields[TestWellKnownTypes.StringFieldFieldNumber].GetValue(message));
-            Assert.IsNull(fields[TestWellKnownTypes.FloatFieldFieldNumber].GetValue(message));
+            Assert.IsNull(fields[TestWellKnownTypes.StringFieldFieldNumber].Accessor.GetValue(message));
+            Assert.IsNull(fields[TestWellKnownTypes.FloatFieldFieldNumber].Accessor.GetValue(message));
         }
 
         [Test]
@@ -216,8 +216,8 @@ namespace Google.Protobuf.WellKnownTypes
         {
             // Just a single example... note that we can't have a null value here
             var message = new RepeatedWellKnownTypes { Int32Field = { 1, 2 } };
-            var fields = RepeatedWellKnownTypes.Descriptor.FieldAccessorsByFieldNumber;
-            var list = (IList) fields[RepeatedWellKnownTypes.Int32FieldFieldNumber].GetValue(message);
+            var fields = RepeatedWellKnownTypes.Descriptor.Fields;
+            var list = (IList) fields[RepeatedWellKnownTypes.Int32FieldFieldNumber].Accessor.GetValue(message);
             CollectionAssert.AreEqual(new[] { 1, 2 }, list);
         }
 
@@ -226,8 +226,8 @@ namespace Google.Protobuf.WellKnownTypes
         {
             // Just a single example... note that we can't have a null value here
             var message = new MapWellKnownTypes { Int32Field = { { 1, 2 }, { 3, null } } };
-            var fields = MapWellKnownTypes.Descriptor.FieldAccessorsByFieldNumber;
-            var dictionary = (IDictionary) fields[MapWellKnownTypes.Int32FieldFieldNumber].GetValue(message);
+            var fields = MapWellKnownTypes.Descriptor.Fields;
+            var dictionary = (IDictionary) fields[MapWellKnownTypes.Int32FieldFieldNumber].Accessor.GetValue(message);
             Assert.AreEqual(2, dictionary[1]);
             Assert.IsNull(dictionary[3]);
             Assert.IsTrue(dictionary.Contains(3));

csharp/src/Google.Protobuf/JsonFormatter.cs

@@ -140,7 +140,7 @@ namespace Google.Protobuf
             var fields = message.Descriptor.Fields;
             bool first = true;
             // First non-oneof fields
-            foreach (var field in fields)
+            foreach (var field in fields.InFieldNumberOrder())
             {
                 var accessor = field.Accessor;
                 // Oneofs are written later

csharp/src/Google.Protobuf/Reflection/FileDescriptor.cs

@@ -231,7 +231,7 @@ namespace Google.Protobuf.Reflection
         /// Finds a type (message, enum, service or extension) in the file by name. Does not find nested types.
         /// </summary>
         /// <param name="name">The unqualified type name to look for.</param>
-        /// <typeparam name="T">The type of descriptor to look for (or ITypeDescriptor for any)</typeparam>
+        /// <typeparam name="T">The type of descriptor to look for</typeparam>
         /// <returns>The type's descriptor, or null if not found.</returns>
         public T FindTypeByName<T>(String name)
             where T : class, IDescriptor

csharp/src/Google.Protobuf/Reflection/MessageDescriptor.cs

@@ -33,6 +33,7 @@
 using Google.Protobuf.Collections;
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 
 namespace Google.Protobuf.Reflection
@@ -60,11 +61,12 @@ namespace Google.Protobuf.Reflection
         private readonly MessageDescriptor containingType;
         private readonly IList<MessageDescriptor> nestedTypes;
         private readonly IList<EnumDescriptor> enumTypes;
-        private readonly IList<FieldDescriptor> fields;
+        private readonly IList<FieldDescriptor> fieldsInDeclarationOrder;
+        private readonly IList<FieldDescriptor> fieldsInNumberOrder;
+        private readonly FieldCollection fields;
         private readonly IList<OneofDescriptor> oneofs;
         // CLR representation of the type described by this descriptor, if any.
         private readonly Type generatedType;
-        private IDictionary<int, IFieldAccessor> fieldAccessorsByFieldNumber;
         
         internal MessageDescriptor(DescriptorProto proto, FileDescriptor file, MessageDescriptor parent, int typeIndex, GeneratedCodeInfo generatedCodeInfo)
             : base(file, file.ComputeFullName(parent, proto.Name), typeIndex)
@@ -89,11 +91,13 @@ namespace Google.Protobuf.Reflection
                 (type, index) =>
                 new EnumDescriptor(type, file, this, index, generatedCodeInfo == null ? null : generatedCodeInfo.NestedEnums[index]));
 
-            fields = DescriptorUtil.ConvertAndMakeReadOnly(
+            fieldsInDeclarationOrder = DescriptorUtil.ConvertAndMakeReadOnly(
                 proto.Field,
                 (field, index) =>
                 new FieldDescriptor(field, file, this, index, generatedCodeInfo == null ? null : generatedCodeInfo.PropertyNames[index]));
+            fieldsInNumberOrder = new ReadOnlyCollection<FieldDescriptor>(fieldsInDeclarationOrder.OrderBy(field => field.FieldNumber).ToArray());
             file.DescriptorPool.AddSymbol(this);
+            fields = new FieldCollection(this);
         }
                 
         /// <summary>
@@ -136,9 +140,9 @@ namespace Google.Protobuf.Reflection
         }
 
         /// <value>
-        /// An unmodifiable list of this message type's fields.
+        /// A collection of fields, which can be retrieved by name or field number.
         /// </value>
-        public IList<FieldDescriptor> Fields
+        public FieldCollection Fields
         {
             get { return fields; }
         }
@@ -164,13 +168,6 @@ namespace Google.Protobuf.Reflection
             get { return oneofs; }
         }
 
-        /// <summary>
-        /// Returns a map from field number to accessor.
-        /// TODO: Revisit this. It's mostly in place to make the transition from FieldAccessorTable
-        /// to descriptor-based reflection simple in terms of tests. Work out what we really want.
-        /// </summary>
-        public IDictionary<int, IFieldAccessor> FieldAccessorsByFieldNumber { get { return fieldAccessorsByFieldNumber; } }
-
         /// <summary>
         /// Finds a field by field name.
         /// </summary>
@@ -213,7 +210,7 @@ namespace Google.Protobuf.Reflection
                 message.CrossLink();
             }
 
-            foreach (FieldDescriptor field in fields)
+            foreach (FieldDescriptor field in fieldsInDeclarationOrder)
             {
                 field.CrossLink();
             }
@@ -222,8 +219,79 @@ namespace Google.Protobuf.Reflection
             {
                 oneof.CrossLink();
             }
+        }
+
+        /// <summary>
+        /// A collection to simplify retrieving the field accessor for a particular field.
+        /// </summary>
+        public sealed class FieldCollection
+        {
+            private readonly MessageDescriptor messageDescriptor;
+
+            internal FieldCollection(MessageDescriptor messageDescriptor)
+            {
+                this.messageDescriptor = messageDescriptor;
+            }
 
-            fieldAccessorsByFieldNumber = new ReadOnlyDictionary<int, IFieldAccessor>(fields.ToDictionary(field => field.FieldNumber, field => field.Accessor));
+            /// <value>
+            /// Returns the fields in the message as an immutable list, in the order in which they
+            /// are declared in the source .proto file.
+            /// </value>
+            public IList<FieldDescriptor> InDeclarationOrder()
+            {
+                return messageDescriptor.fieldsInDeclarationOrder;
+            }
+
+            /// <value>
+            /// Returns the fields in the message as an immutable list, in ascending field number
+            /// order. Field numbers need not be contiguous, so there is no direct mapping from the
+            /// index in the list to the field number; to retrieve a field by field number, it is better
+            /// to use the <see cref="FieldCollection"/> indexer.
+            /// </value>
+            public IList<FieldDescriptor> InFieldNumberOrder()
+            {
+                return messageDescriptor.fieldsInDeclarationOrder;
+            }
+
+            /// <summary>
+            /// Retrieves the descriptor for the field with the given number.
+            /// </summary>
+            /// <param name="number">Number of the field to retrieve the descriptor for</param>
+            /// <returns>The accessor for the given field</returns>
+            /// <exception cref="KeyNotFoundException">The message descriptor does not contain a field
+            /// with the given number</exception>
+            public FieldDescriptor this[int number]
+            {
+                get
+                {
+                    var fieldDescriptor = messageDescriptor.FindFieldByNumber(number);
+                    if (fieldDescriptor == null)
+                    {
+                        throw new KeyNotFoundException("No such field number");
+                    }
+                    return fieldDescriptor;
+                }
+            }
+
+            /// <summary>
+            /// Retrieves the descriptor for the field with the given name.
+            /// </summary>
+            /// <param name="number">Number of the field to retrieve the descriptor for</param>
+            /// <returns>The descriptor for the given field</returns>
+            /// <exception cref="KeyNotFoundException">The message descriptor does not contain a field
+            /// with the given name</exception>
+            public FieldDescriptor this[string name]
+            {
+                get
+                {
+                    var fieldDescriptor = messageDescriptor.FindFieldByName(name);
+                    if (fieldDescriptor == null)
+                    {
+                        throw new KeyNotFoundException("No such field name");
+                    }
+                    return fieldDescriptor;
+                }
+            }
         }
     }
-}
+}
\ No newline at end of file

csharp/src/Google.Protobuf/Reflection/OneofDescriptor.cs

@@ -70,7 +70,7 @@ namespace Google.Protobuf.Reflection
         internal void CrossLink()
         {
             List<FieldDescriptor> fieldCollection = new List<FieldDescriptor>();
-            foreach (var field in ContainingType.Fields)
+            foreach (var field in ContainingType.Fields.InDeclarationOrder())
             {
                 if (field.ContainingOneof == this)
                 {