Allow custom type URL prefixes in Any.Pack

(And likewise ignore the prefix in unpack.)

Fixes issue #1459.

csharp/src/Google.Protobuf.Test/JsonFormatterTest.cs

@@ -480,6 +480,15 @@ namespace Google.Protobuf
             AssertJson("{ '@type': 'type.googleapis.com/protobuf_unittest.TestAllTypes', 'singleInt32': 10, 'singleNestedMessage': { 'bb': 20 } }", formatter.Format(any));
         }
 
+        [Test]
+        public void AnyMessageType_CustomPrefix()
+        {
+            var formatter = new JsonFormatter(new JsonFormatter.Settings(false, TypeRegistry.FromMessages(TestAllTypes.Descriptor)));
+            var message = new TestAllTypes { SingleInt32 = 10 };
+            var any = Any.Pack(message, "foo.bar/baz");
+            AssertJson("{ '@type': 'foo.bar/baz/protobuf_unittest.TestAllTypes', 'singleInt32': 10 }", formatter.Format(any));
+        }
+
         [Test]
         public void AnyNested()
         {

csharp/src/Google.Protobuf.Test/JsonParserTest.cs

@@ -810,6 +810,17 @@ namespace Google.Protobuf
             Assert.AreEqual(original, parser.Parse<Any>(valueFirstJson));
         }
 
+        [Test]
+        public void Any_CustomPrefix()
+        {
+            var registry = TypeRegistry.FromMessages(TestAllTypes.Descriptor);
+            var message = new TestAllTypes { SingleInt32 = 10 };
+            var original = Any.Pack(message, "custom.prefix/middle-part");
+            var parser = new JsonParser(new JsonParser.Settings(10, registry));
+            string json = "{ \"@type\": \"custom.prefix/middle-part/protobuf_unittest.TestAllTypes\", \"singleInt32\": 10 }";
+            Assert.AreEqual(original, parser.Parse<Any>(json));
+        }
+
         [Test]
         public void Any_UnknownType()
         {

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

@@ -46,6 +46,24 @@ namespace Google.Protobuf.WellKnownTypes
             Assert.AreEqual(message.CalculateSize(), any.Value.Length);
         }
 
+        [Test]
+        public void Pack_WithCustomPrefix()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var any = Any.Pack(message, "foo.bar/baz");
+            Assert.AreEqual("foo.bar/baz/protobuf_unittest.TestAllTypes", any.TypeUrl);
+            Assert.AreEqual(message.CalculateSize(), any.Value.Length);
+        }
+
+        [Test]
+        public void Pack_WithCustomPrefixTrailingSlash()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var any = Any.Pack(message, "foo.bar/baz/");
+            Assert.AreEqual("foo.bar/baz/protobuf_unittest.TestAllTypes", any.TypeUrl);
+            Assert.AreEqual(message.CalculateSize(), any.Value.Length);
+        }
+
         [Test]
         public void Unpack_WrongType()
         {
@@ -63,6 +81,15 @@ namespace Google.Protobuf.WellKnownTypes
             Assert.AreEqual(message, unpacked);
         }
 
+        [Test]
+        public void Unpack_CustomPrefix_Success()
+        {
+            var message = SampleMessages.CreateFullTestAllTypes();
+            var any = Any.Pack(message, "foo.bar/baz");
+            var unpacked = any.Unpack<TestAllTypes>();
+            Assert.AreEqual(message, unpacked);
+        }
+
         [Test]
         public void ToString_WithValues()
         {

csharp/src/Google.Protobuf/JsonFormatter.cs

@@ -567,7 +567,7 @@ namespace Google.Protobuf
 
             string typeUrl = (string) value.Descriptor.Fields[Any.TypeUrlFieldNumber].Accessor.GetValue(value);
             ByteString data = (ByteString) value.Descriptor.Fields[Any.ValueFieldNumber].Accessor.GetValue(value);
-            string typeName = GetTypeName(typeUrl);
+            string typeName = Any.GetTypeName(typeUrl);
             MessageDescriptor descriptor = settings.TypeRegistry.Find(typeName);
             if (descriptor == null)
             {
@@ -608,17 +608,7 @@ namespace Google.Protobuf
             writer.Write(data.ToBase64());
             writer.Write('"');
             writer.Write(" }");
-        }
-
-        internal static string GetTypeName(String typeUrl)
-        {
-            string[] parts = typeUrl.Split('/');
-            if (parts.Length != 2 || parts[0] != TypeUrlPrefix)
-            {
-                throw new InvalidProtocolBufferException($"Invalid type url: {typeUrl}");
-            }
-            return parts[1];
-        }
+        }        
 
         private void WriteStruct(TextWriter writer, IMessage message)
         {

csharp/src/Google.Protobuf/JsonParser.cs

@@ -513,7 +513,7 @@ namespace Google.Protobuf
                 throw new InvalidProtocolBufferException("Expected string value for Any.@type");
             }
             string typeUrl = token.StringValue;
-            string typeName = JsonFormatter.GetTypeName(typeUrl);
+            string typeName = Any.GetTypeName(typeUrl);
 
             MessageDescriptor descriptor = settings.TypeRegistry.Find(typeName);
             if (descriptor == null)

csharp/src/Google.Protobuf/WellKnownTypes/AnyPartial.cs

@@ -36,11 +36,27 @@ namespace Google.Protobuf.WellKnownTypes
 {
     public partial class Any
     {
+        private const string DefaultPrefix = "type.googleapis.com";
+
         // This could be moved to MessageDescriptor if we wanted to, but keeping it here means
         // all the Any-specific code is in the same place.
-        private static string GetTypeUrl(MessageDescriptor descriptor)
+        private static string GetTypeUrl(MessageDescriptor descriptor, string prefix) =>
+            prefix.EndsWith("/") ? prefix + descriptor.FullName : prefix + "/" + descriptor.FullName;
+
+        /// <summary>
+        /// Retrieves the type name for a type URL. This is always just the last part of the URL,
+        /// after the trailing slash. No validation of anything before the trailing slash is performed.
+        /// If the type URL does not include a slash, an empty string is returned rather than an exception
+        /// being thrown; this won't match any types, and the calling code is probably in a better position
+        /// to give a meaningful error.
+        /// There is no handling of fragments or queries  at the moment.
+        /// </summary>
+        /// <param name="typeUrl">The URL to extract the type name from</param>
+        /// <returns>The type name</returns>
+        internal static string GetTypeName(string typeUrl)
         {
-            return "type.googleapis.com/" + descriptor.FullName;
+            int lastSlash = typeUrl.LastIndexOf('/');
+            return lastSlash == -1 ? "" : typeUrl.Substring(lastSlash + 1);
         }
 
         /// <summary>
@@ -55,25 +71,37 @@ namespace Google.Protobuf.WellKnownTypes
             // Note: this doesn't perform as well is it might. We could take a MessageParser<T> in an alternative overload,
             // which would be expected to perform slightly better... although the difference is likely to be negligible.
             T target = new T();
-            string targetTypeUrl = GetTypeUrl(target.Descriptor);
-            if (TypeUrl != targetTypeUrl)
+            if (GetTypeName(TypeUrl) != target.Descriptor.FullName)
             {
-                throw new InvalidProtocolBufferException(string.Format("Type url for {0} is {1}; Any message's type url is {2}",
-                    target.Descriptor.Name, targetTypeUrl, TypeUrl));
+                throw new InvalidProtocolBufferException(
+                    $"Full type name for {target.Descriptor.Name} is {target.Descriptor.FullName}; Any message's type url is {TypeUrl}");
             }
             target.MergeFrom(Value);
             return target;
         }
 
         /// <summary>
-        /// Packs the specified message into an Any message.
+        /// Packs the specified message into an Any message using a type URL prefix of "type.googleapis.com".
+        /// </summary>
+        /// <param name="message">The message to pack.</param>
+        /// <returns>An Any message with the content and type URL of <paramref name="message"/>.</returns>
+        public static Any Pack(IMessage message) => Pack(message, DefaultPrefix);
+
+        /// <summary>
+        /// Packs the specified message into an Any message using the specified type URL prefix.
         /// </summary>
         /// <param name="message">The message to pack.</param>
+        /// <param name="typeUrlPrefix">The prefix for the type URL.</param>
         /// <returns>An Any message with the content and type URL of <paramref name="message"/>.</returns>
-        public static Any Pack(IMessage message)
+        public static Any Pack(IMessage message, string typeUrlPrefix)
         {
-            ProtoPreconditions.CheckNotNull(message, "message");
-            return new Any { TypeUrl = GetTypeUrl(message.Descriptor), Value = message.ToByteString() };
+            ProtoPreconditions.CheckNotNull(message, nameof(message));
+            ProtoPreconditions.CheckNotNull(typeUrlPrefix, nameof(typeUrlPrefix));
+            return new Any
+            {
+                TypeUrl = GetTypeUrl(message.Descriptor, typeUrlPrefix),
+                Value = message.ToByteString()
+            };
         }
     }
 }