CSHARP-1265: Empty update documents should throw an exception.

Author: craiggwilson

src/MongoDB.Driver.Core.Tests/Core/Operations/BulkMixedWriteOperationTests.cs

@@ -393,6 +393,16 @@ public async Task ExecuteAsync_with_more_inserts_than_maxBatchCount()
             list.Should().HaveCount(4);
         }
 
+        [Test]
+        public void ExecuteAsync_with_an_empty_update_document_should_throw()
+        {
+            var requests = new[] { new UpdateRequest(UpdateType.Update, BsonDocument.Parse("{x: 1}"), new BsonDocument()) };
+            var subject = new BulkMixedWriteOperation(_collectionNamespace, requests, _messageEncoderSettings);
+
+            Func<Task> act = () => ExecuteOperationAsync(subject);
+            act.ShouldThrow<BsonSerializationException>();
+        }
+
         [Test]
         [RequiresServer("EnsureTestData")]
         public async Task ExecuteAsync_with_one_update_against_a_matching_document()

src/MongoDB.Driver.Core.Tests/Core/WireProtocol/Messages/Encoders/BinaryEncoders/UpdateMessageBinaryEncoderTests.cs

@@ -18,6 +18,7 @@
 using FluentAssertions;
 using MongoDB.Bson;
 using MongoDB.Bson.IO;
+using MongoDB.Driver.Core.Operations.ElementNameValidators;
 using MongoDB.Driver.Core.WireProtocol.Messages;
 using MongoDB.Driver.Core.WireProtocol.Messages.Encoders.BinaryEncoders;
 using NUnit.Framework;
@@ -152,5 +153,17 @@ public void WriteMessage_should_write_a_message()
                 bytes.Should().Equal(__testMessageBytes);
             }
         }
+
+        [Test]
+        public void WriteMessage_should_throw_if_the_update_message_is_empty_when_using_the_UpdateElementNameValidator()
+        {
+            var message = new UpdateMessage(__requestId, __collectionNamespace, __query, new BsonDocument(), UpdateElementNameValidator.Instance, false, false);
+            using (var stream = new MemoryStream())
+            {
+                var subject = new UpdateMessageBinaryEncoder(stream, __messageEncoderSettings);
+                Action act = () => subject.WriteMessage(message);
+                act.ShouldThrow<BsonSerializationException>();
+            }
+        }
     }
 }

src/MongoDB.Driver.Core/Core/Operations/BulkUpdateOperation.cs

@@ -122,8 +122,13 @@ private void SerializeUpdate(BsonBinaryWriter bsonWriter, BsonDocument update, U
                 bsonWriter.PushElementNameValidator(ElementNameValidatorFactory.ForUpdateType(updateType));
                 try
                 {
+                    var position = bsonWriter.BaseStream.Position;
                     var context = BsonSerializationContext.CreateRoot(bsonWriter);
                     BsonDocumentSerializer.Instance.Serialize(context, update);
+                    if (updateType == UpdateType.Update && bsonWriter.BaseStream.Position == position + 8)
+                    {
+                        throw new BsonSerializationException("Update documents cannot be empty.");
+                    }
                 }
                 finally
                 {

src/MongoDB.Driver.Core/Core/WireProtocol/Messages/Encoders/BinaryEncoders/UpdateMessageBinaryEncoder.cs

@@ -24,6 +24,7 @@
 using MongoDB.Bson.Serialization;
 using MongoDB.Bson.Serialization.Serializers;
 using MongoDB.Driver.Core.Misc;
+using MongoDB.Driver.Core.Operations.ElementNameValidators;
 
 namespace MongoDB.Driver.Core.WireProtocol.Messages.Encoders.BinaryEncoders
 {
@@ -126,8 +127,13 @@ private void WriteUpdate(BsonBinaryWriter binaryWriter, BsonDocument update, IEl
             binaryWriter.PushElementNameValidator(updateValidator);
             try
             {
+                var position = binaryWriter.BaseStream.Position;
                 var context = BsonSerializationContext.CreateRoot(binaryWriter);
                 BsonDocumentSerializer.Instance.Serialize(context, update);
+                if (updateValidator is UpdateElementNameValidator && binaryWriter.BaseStream.Position == position + 5)
+                {
+                    throw new BsonSerializationException("Update documents cannot be empty.");
+                }
             }
             finally
             {