Helper method on Any to allow an any to be unpacked more easily

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

@@ -30,8 +30,11 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #endregion
 
+using Google.Protobuf.Reflection;
 using Google.Protobuf.TestProtos;
 using NUnit.Framework;
+using System.Linq;
+using UnitTest.Issues.TestProtos;
 
 namespace Google.Protobuf.WellKnownTypes
 {
@@ -148,10 +151,34 @@ public void IsWrongType()
             Assert.False(any.Is(TestOneof.Descriptor));
         }
 
+        [Test]
         public void IsRightType()
         {
             var any = Any.Pack(SampleMessages.CreateFullTestAllTypes());
             Assert.True(any.Is(TestAllTypes.Descriptor));
         }
+
+        [Test]
+        public void Unpack_TypeRegistry()
+        {
+            var messages = new IMessage[]
+            {
+                SampleMessages.CreateFullTestAllTypes(),
+                new TestWellKnownTypes { BoolField = true },
+                new MoreString { Data = { "x" } },
+                new MoreBytes { Data = ByteString.CopyFromUtf8("xyz") },
+                new ReservedNames { Descriptor_ = 10 }
+            };
+            var anyMessages = messages.Select(Any.Pack);
+
+            // The type registry handles the first four of the packed messages, but not the final one.
+            var registry = TypeRegistry.FromFiles(
+                UnittestWellKnownTypesReflection.Descriptor,
+                UnittestProto3Reflection.Descriptor);
+            var unpacked = anyMessages.Select(any => any.Unpack(registry)).ToList();
+            var expected = (IMessage[]) messages.Clone();
+            expected[4] = null;
+            Assert.AreEqual(expected, unpacked);
+        }
     }
 }

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

@@ -120,6 +120,26 @@ public bool Is(MessageDescriptor descriptor)
             return true;
         }
 
+        /// <summary>
+        /// Attempts to unpack the content of this Any message into one of the message types
+        /// in the given type registry, based on the type URL.
+        /// </summary>
+        /// <param name="registry">The type registry to consult for messages.</param>
+        /// <returns>The unpacked message, or <c>null</c> if no matching message was found.</returns>
+        public IMessage Unpack(TypeRegistry registry)
+        {
+            string typeName = GetTypeName(TypeUrl);
+            MessageDescriptor descriptor = registry.Find(typeName);
+            if (descriptor == null)
+            {
+                return null;
+            }
+
+            var message = descriptor.Parser.CreateTemplate();
+            message.MergeFrom(Value);
+            return message;
+        }
+
         /// <summary>
         /// Packs the specified message into an Any message using a type URL prefix of "type.googleapis.com".
         /// </summary>