CSHARP-4746: PipelineUpdateDefinition cannot be combined with any oth…

…er update definition.

src/MongoDB.Driver/UpdateDefinitionBuilder.cs

@@ -1403,6 +1403,7 @@ internal sealed class CombinedUpdateDefinition<TDocument> : UpdateDefinition<TDo
         public CombinedUpdateDefinition(IEnumerable<UpdateDefinition<TDocument>> updates)
         {
             _updates = Ensure.IsNotNull(updates, nameof(updates)).ToList();
+            ThrowIfPipelineUpdateDefinitionIsCombinedWithOtherUpdates(_updates);
         }
 
         public override BsonValue Render(IBsonSerializer<TDocument> documentSerializer, IBsonSerializerRegistry serializerRegistry, LinqProvider linqProvider)
@@ -1430,6 +1431,14 @@ public override BsonValue Render(IBsonSerializer<TDocument> documentSerializer,
             }
             return document;
         }
+
+        private void ThrowIfPipelineUpdateDefinitionIsCombinedWithOtherUpdates(List<UpdateDefinition<TDocument>> updates)
+        {
+            if (updates.Count > 1 && updates.Any(x => x is PipelineUpdateDefinition<TDocument>))
+            {
+                throw new InvalidOperationException("Pipeline update definitions cannot be combined with any other update definitions.");
+            }
+        }
     }
 
     internal sealed class BitwiseOperatorUpdateDefinition<TDocument, TField> : UpdateDefinition<TDocument>

tests/MongoDB.Driver.Tests/Linq/Linq3Implementation/Jira/CSharp4746Tests.cs

@@ -0,0 +1,54 @@
+/* Copyright 2010-present MongoDB Inc.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+using System;
+using FluentAssertions;
+using Xunit;
+
+namespace MongoDB.Driver.Tests.Linq.Linq3Implementation.Jira
+{
+    public class CSharp4746Tests : Linq3IntegrationTest
+    {
+        [Fact]
+        public void UpdateDefinitionBuilder_Combine_should_throw_when_PipelineUpdateDefinition_is_combined_with_another_update()
+        {
+            var pipeline = new EmptyPipelineDefinition<C>();
+            var pipelineUpdate = Builders<C>.Update.Pipeline(pipeline);
+            var setUpdate = Builders<C>.Update.Set(x => x.X, 2);
+
+            var exception = Record.Exception(() => new UpdateDefinitionBuilder<C>().Combine(pipelineUpdate, setUpdate));
+
+            exception.Should().BeOfType<InvalidOperationException>();
+        }
+
+        [Fact]
+        public void UpdateDefinitionBuilder_Combine_should_throw_when_an_update_is_combined_with_a_PipelineUpdateDefinition()
+        {
+            var setUpdate = Builders<C>.Update.Set(x => x.X, 2);
+            var pipeline = new EmptyPipelineDefinition<C>();
+            var pipelineUpdate = Builders<C>.Update.Pipeline(pipeline);
+
+            var exception = Record.Exception(() => new UpdateDefinitionBuilder<C>().Combine(setUpdate, pipelineUpdate));
+
+            exception.Should().BeOfType<InvalidOperationException>();
+        }
+
+        private class C
+        {
+            public int Id { get; set; }
+            public int X { get; set; }
+        }
+    }
+}