CSHARP-2239: Refactor ChangeStreamDocument to be a BsonDocumentBackedClass.

Author: rstam

src/MongoDB.Bson/Serialization/Serializers/BsonDocumentBackedClassSerializer.cs

@@ -39,18 +39,6 @@ protected BsonDocumentBackedClassSerializer()
         }
 
         // public methods
-        /// <summary>
-        /// Deserializes a value.
-        /// </summary>
-        /// <param name="context">The deserialization context.</param>
-        /// <param name="args">The deserialization args.</param>
-        /// <returns>A deserialized value.</returns>
-        public override TClass Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
-        {
-            var backingDocument = BsonDocumentSerializer.Instance.Deserialize(context);
-            return CreateInstance(backingDocument);
-        }
-
         /// <summary>
         /// Tries to get the serialization info for a member.
         /// </summary>
@@ -64,19 +52,14 @@ public virtual bool TryGetMemberSerializationInfo(string memberName, out BsonSer
             return _memberSerializationInfo.TryGetValue(memberName, out serializationInfo);
         }
 
-        /// <summary>
-        /// Serializes a value.
-        /// </summary>
-        /// <param name="context">The serialization context.</param>
-        /// <param name="args">The serialization args.</param>
-        /// <param name="value">The object.</param>
-        protected override void SerializeValue(BsonSerializationContext context, BsonSerializationArgs args, TClass value)
+        // protected methods
+        /// <inheritdoc />
+        protected override TClass DeserializeValue(BsonDeserializationContext context, BsonDeserializationArgs args)
         {
-            var backingDocument = ((BsonDocumentBackedClass)value).BackingDocument;
-            BsonDocumentSerializer.Instance.Serialize(context, backingDocument);
+            var backingDocument = BsonDocumentSerializer.Instance.Deserialize(context);
+            return CreateInstance(backingDocument);
         }
 
-        // protected methods
         /// <summary>
         /// Registers a member.
         /// </summary>
@@ -102,6 +85,13 @@ protected void RegisterMember(string memberName, string elementName, IBsonSerial
             _memberSerializationInfo.Add(memberName, info);
         }
 
+        /// <inheritdoc />
+        protected override void SerializeValue(BsonSerializationContext context, BsonSerializationArgs args, TClass value)
+        {
+            var backingDocument = ((BsonDocumentBackedClass)value).BackingDocument;
+            BsonDocumentSerializer.Instance.Serialize(context, backingDocument);
+        }
+
         /// <summary>
         /// Creates the instance.
         /// </summary>

src/MongoDB.Driver.Core/ChangeStreamDocument.cs

@@ -14,97 +14,91 @@
 */
 
 using MongoDB.Bson;
-using MongoDB.Driver.Core.Misc;
+using MongoDB.Bson.Serialization;
+using MongoDB.Bson.Serialization.Attributes;
 
 namespace MongoDB.Driver
 {
     /// <summary>
     /// An output document from a $changeStream pipeline stage.
     /// </summary>
     /// <typeparam name="TDocument">The type of the document.</typeparam>
-    public sealed class ChangeStreamDocument<TDocument>
+    [BsonSerializer(typeof(ChangeStreamDocumentSerializer<>))]
+    public sealed class ChangeStreamDocument<TDocument> : BsonDocumentBackedClass
     {
-        // private fields
-        private readonly CollectionNamespace _collectionNamespace;
-        private readonly BsonDocument _documentKey;
-        private readonly TDocument _fullDocument;
-        private readonly ChangeStreamOperationType _operationType;
-        private readonly BsonDocument _resumeToken;
-        private readonly ChangeStreamUpdateDescription _updateDescription;
-
         // constructors
         /// <summary>
-        /// Initializes a new instance of the <see cref="ChangeStreamDocument{TDocument}" /> class.
+        /// Initializes a new instance of the <see cref="ChangeStreamDocument{TDocument}"/> class.
         /// </summary>
-        /// <param name="resumeToken">The resume token.</param>
-        /// <param name="operationType">Type of the operation.</param>
-        /// <param name="collectionNamespace">Namespace of the collection.</param>
-        /// <param name="documentKey">The document key.</param>
-        /// <param name="updateDescription">The update description.</param>
-        /// <param name="fullDocument">The full document.</param>
+        /// <param name="backingDocument">The backing document.</param>
+        /// <param name="documentSerializer">The document serializer.</param>
         public ChangeStreamDocument(
-            BsonDocument resumeToken,
-            ChangeStreamOperationType operationType,
-            CollectionNamespace collectionNamespace,
-            BsonDocument documentKey,
-            ChangeStreamUpdateDescription updateDescription,
-            TDocument fullDocument)
+            BsonDocument backingDocument,
+            IBsonSerializer<TDocument> documentSerializer)
+            : base(backingDocument, new ChangeStreamDocumentSerializer<TDocument>(documentSerializer))
         {
-            _resumeToken = Ensure.IsNotNull(resumeToken, nameof(resumeToken));
-            _operationType = operationType;
-            _collectionNamespace = collectionNamespace; // can be null when operationType is Invalidate
-            _documentKey = documentKey; // can be null
-            _updateDescription = updateDescription; // can be null
-            _fullDocument = fullDocument; // can be null
         }
 
         // public properties
+        /// <summary>
+        /// Gets the backing document.
+        /// </summary>
+        new public BsonDocument BackingDocument => base.BackingDocument;
+
+        /// <summary>
+        /// Gets the cluster time.
+        /// </summary>
+        /// <value>
+        /// The cluster time.
+        /// </value>
+        public BsonDocument ClusterTime => GetValue<BsonDocument>(nameof(ClusterTime), null);
+
         /// <summary>
         /// Gets the namespace of the collection.
         /// </summary>
         /// <value>
         /// The namespace of the collection.
         /// </value>
-        public CollectionNamespace CollectionNamespace => _collectionNamespace;
+        public CollectionNamespace CollectionNamespace => GetValue<CollectionNamespace>(nameof(CollectionNamespace), null);
 
         /// <summary>
         /// Gets the document key.
         /// </summary>
         /// <value>
         /// The document key.
         /// </value>
-        public BsonDocument DocumentKey => _documentKey;
+        public BsonDocument DocumentKey => GetValue<BsonDocument>(nameof(DocumentKey), null);
 
         /// <summary>
         /// Gets the full document.
         /// </summary>
         /// <value>
         /// The full document.
         /// </value>
-        public TDocument FullDocument => _fullDocument;
+        public TDocument FullDocument => GetValue<TDocument>(nameof(FullDocument), default(TDocument));
 
         /// <summary>
         /// Gets the type of the operation.
         /// </summary>
         /// <value>
         /// The type of the operation.
         /// </value>
-        public ChangeStreamOperationType OperationType => _operationType;
+        public ChangeStreamOperationType OperationType => GetValue<ChangeStreamOperationType>(nameof(OperationType), (ChangeStreamOperationType)(-1));
 
         /// <summary>
         /// Gets the resume token.
         /// </summary>
         /// <value>
         /// The resume token.
         /// </value>
-        public BsonDocument ResumeToken => _resumeToken;
+        public BsonDocument ResumeToken => GetValue<BsonDocument>(nameof(ResumeToken), null);
 
         /// <summary>
         /// Gets the update description.
         /// </summary>
         /// <value>
         /// The update description.
         /// </value>
-        public ChangeStreamUpdateDescription UpdateDescription => _updateDescription;
+        public ChangeStreamUpdateDescription UpdateDescription => GetValue<ChangeStreamUpdateDescription>(nameof(UpdateDescription), null);
     }
 }

src/MongoDB.Driver.Core/ChangeStreamDocumentCollectionNamespaceSerializer.cs

@@ -0,0 +1,76 @@
+/* Copyright 2018-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 MongoDB.Bson.IO;
+using MongoDB.Bson.Serialization;
+using MongoDB.Bson.Serialization.Serializers;
+
+namespace MongoDB.Driver
+{
+    internal class ChangeStreamDocumentCollectionNamespaceSerializer : SealedClassSerializerBase<CollectionNamespace>
+    {
+        #region static
+        // private static fields
+        private static readonly ChangeStreamDocumentCollectionNamespaceSerializer __instance = new ChangeStreamDocumentCollectionNamespaceSerializer();
+
+        // public static properties
+        public static ChangeStreamDocumentCollectionNamespaceSerializer Instance => __instance;
+        #endregion
+
+        // public methods
+        public override CollectionNamespace Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
+        {
+            var reader = context.Reader;
+            string collectionName = null;
+            string databaseName = null;
+
+            reader.ReadStartDocument();
+            while (reader.ReadBsonType() != 0)
+            {
+                var fieldName = reader.ReadName();
+                switch (fieldName)
+                {
+                    case "db":
+                        databaseName = reader.ReadString();
+                        break;
+
+                    case "coll":
+                        collectionName = reader.ReadString();
+                        break;
+
+                    default:
+                        throw new FormatException($"Invalid field name: \"{fieldName}\".");
+                }
+            }
+            reader.ReadEndDocument();
+
+            var databaseNamespace = new DatabaseNamespace(databaseName);
+            return new CollectionNamespace(databaseNamespace, collectionName);
+        }
+
+        protected override void SerializeValue(BsonSerializationContext context, BsonSerializationArgs args, CollectionNamespace value)
+        {
+            var writer = context.Writer;
+
+            writer.WriteStartDocument();
+            writer.WriteName("db");
+            writer.WriteString(value.DatabaseNamespace.DatabaseName);
+            writer.WriteName("coll");
+            writer.WriteString(value.CollectionName);
+            writer.WriteEndDocument();
+        }
+    }
+}