CSHARP-4757: Modify BsonSerializationInfo to handle properties that are grouped in a nested document.

Author: rstam

src/MongoDB.Bson/Serialization/BsonSerializationInfo.cs

@@ -15,6 +15,8 @@
 
 using System;
 using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
 using MongoDB.Bson.IO;
 
 namespace MongoDB.Bson.Serialization
@@ -24,10 +26,26 @@ namespace MongoDB.Bson.Serialization
     /// </summary>
     public class BsonSerializationInfo
     {
+        #region static
+        /// <summary>
+        /// Creates a new instance of the BsonSerializationinfo class with an element path instead of an element name.
+        /// </summary>
+        /// <param name="elementPath">The element path.</param>
+        /// <param name="serializer">The serializer.</param>
+        /// <param name="nominalType">The nominal type.</param>
+        /// <returns>A BsonSerializationInfo.</returns>
+        public static BsonSerializationInfo CreateWithPath(IEnumerable<string> elementPath, IBsonSerializer serializer, Type nominalType)
+        {
+            return new BsonSerializationInfo(elementPath.ToList(), serializer, nominalType);
+        }
+        #endregion
+
         // private fields
-        private string _elementName;
-        private IBsonSerializer _serializer;
-        private Type _nominalType;
+        // note: while _elementName could have been modeled with an _elementPath of length 1, treating this is a special case avoids some allocations
+        private readonly string _elementName;
+        private readonly IReadOnlyList<string> _elementPath;
+        private readonly IBsonSerializer _serializer;
+        private readonly Type _nominalType;
 
         // constructors
         /// <summary>
@@ -43,13 +61,35 @@ public BsonSerializationInfo(string elementName, IBsonSerializer serializer, Typ
             _nominalType = nominalType;
         }
 
+        private BsonSerializationInfo(IReadOnlyList<string> elementPath, IBsonSerializer serializer, Type nominalType)
+        {
+            _elementPath = elementPath;
+            _serializer = serializer;
+            _nominalType = nominalType;
+        }
+
         // public properties
         /// <summary>
-        /// Gets or sets the dotted element name.
+        /// Gets the element name.
         /// </summary>
         public string ElementName
         {
-            get { return _elementName; }
+            get
+            {
+                if (_elementPath != null)
+                {
+                    throw new InvalidOperationException("When ElementPath is not null you must use it instead.");
+                }
+                return _elementName;
+            }
+        }
+
+        /// <summary>
+        /// Gets element path.
+        /// </summary>
+        public IReadOnlyList<string> ElementPath
+        {
+            get { return _elementPath; }
         }
 
         /// <summary>
@@ -92,20 +132,21 @@ public object DeserializeValue(BsonValue value)
         /// </summary>
         /// <param name="newSerializationInfo">The new info.</param>
         /// <returns>A new BsonSerializationInfo.</returns>
+        [Obsolete("This method is no longer relevant because field names are now allowed to contain dots.")]
         public BsonSerializationInfo Merge(BsonSerializationInfo newSerializationInfo)
         {
             string elementName = null;
-            if (_elementName != null && newSerializationInfo._elementName != null)
+            if (ElementName != null && newSerializationInfo.ElementName != null)
             {
-                elementName = _elementName + "." + newSerializationInfo._elementName;
+                elementName = ElementName + "." + newSerializationInfo.ElementName;
             }
-            else if (_elementName != null)
+            else if (ElementName != null)
             {
-                elementName = _elementName;
+                elementName = ElementName;
             }
-            else if (newSerializationInfo._elementName != null)
+            else if (newSerializationInfo.ElementName != null)
             {
-                elementName = newSerializationInfo._elementName;
+                elementName = newSerializationInfo.ElementName;
             }
 
             return new BsonSerializationInfo(

src/MongoDB.Driver/Linq/Linq3Implementation/Misc/DocumentSerializerHelper.cs

@@ -32,7 +32,14 @@ public static MemberSerializationInfo GetMemberSerializationInfo(IBsonSerializer
                 throw new InvalidOperationException($"Serializer for {serializer.ValueType} does not have a member named {memberName}.");
             }
 
-            return new MemberSerializationInfo(serializationInfo.ElementName, serializationInfo.Serializer);
+            if (serializationInfo.ElementPath == null)
+            {
+                return new MemberSerializationInfo(serializationInfo.ElementName, serializationInfo.Serializer);
+            }
+            else
+            {
+                return new MemberSerializationInfo(serializationInfo.ElementPath, serializationInfo.Serializer);
+            }
         }
 
         public static bool HasMemberSerializationInfo(IBsonSerializer serializer, string memberName)

src/MongoDB.Driver/Linq/Linq3Implementation/Misc/MemberSerializationInfo.cs

@@ -13,6 +13,8 @@
 * limitations under the License.
 */
 
+using System;
+using System.Collections.Generic;
 using MongoDB.Bson.Serialization;
 using MongoDB.Driver.Core.Misc;
 
@@ -22,6 +24,7 @@ internal class MemberSerializationInfo
     {
         // private fields
         private readonly string _elementName;
+        private readonly IReadOnlyList<string> _elementPath;
         private readonly IBsonSerializer _serializer;
 
         // constructors
@@ -31,8 +34,27 @@ public MemberSerializationInfo(string elementName, IBsonSerializer serializer)
             _serializer = Ensure.IsNotNull(serializer, nameof(serializer));
         }
 
+        public MemberSerializationInfo(IReadOnlyList<string> elementPath, IBsonSerializer serializer)
+        {
+            _elementPath = Ensure.IsNotNull(elementPath, nameof(elementPath));
+            _serializer = Ensure.IsNotNull(serializer, nameof(serializer));
+        }
+
         // public properties
-        public string ElementName => _elementName;
+        public string ElementName
+        {
+            get
+            {
+                if (_elementPath != null)
+                {
+                    throw new InvalidOperationException("When ElementPath is not null you must use it instead.");
+                }
+                return _elementName;
+            }
+        }
+
+        public IReadOnlyList<string> ElementPath => _elementPath;
+
         public IBsonSerializer Serializer => _serializer;
     }
 }

src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToAggregationExpressionTranslators/MemberExpressionToAggregationExpressionTranslator.cs

@@ -77,7 +77,19 @@ public static AggregationExpression Translate(TranslationContext context, Member
             }
 
             var serializationInfo = DocumentSerializerHelper.GetMemberSerializationInfo(containerTranslation.Serializer, member.Name);
-            var ast = AstExpression.GetField(containerTranslation.Ast, serializationInfo.ElementName);
+            AstExpression ast;
+            if (serializationInfo.ElementPath == null)
+            {
+                ast = AstExpression.GetField(containerTranslation.Ast, serializationInfo.ElementName);
+            }
+            else
+            {
+                ast = containerTranslation.Ast;
+                foreach (var subFieldName in serializationInfo.ElementPath)
+                {
+                    ast = AstExpression.GetField(ast, subFieldName);
+                }
+            }
             return new AggregationExpression(expression, ast, serializationInfo.Serializer);
         }
 

src/MongoDB.Driver/Linq/Linq3Implementation/Translators/ExpressionToFilterTranslators/ToFilterFieldTranslators/MemberExpressionToFilterFieldTranslator.cs

@@ -89,9 +89,21 @@ public static AstFilterField Translate(TranslationContext context, MemberExpress
             if (fieldSerializer is IBsonDocumentSerializer documentSerializer &&
                 documentSerializer.TryGetMemberSerializationInfo(memberExpression.Member.Name, out BsonSerializationInfo memberSerializationInfo))
             {
-                var subFieldName = memberSerializationInfo.ElementName;
                 var subFieldSerializer = memberSerializationInfo.Serializer;
-                return field.SubField(subFieldName, subFieldSerializer);
+                if (memberSerializationInfo.ElementPath == null)
+                {
+                    var subFieldName = memberSerializationInfo.ElementName;
+                    return field.SubField(subFieldName, subFieldSerializer);
+                }
+                else
+                {
+                    var subField = field;
+                    foreach (var subFieldName in memberSerializationInfo.ElementPath)
+                    {
+                        subField = subField.SubField(subFieldName, subFieldSerializer);
+                    }
+                    return subField;
+                }
             }
 
             if (memberExpression.Expression.Type.IsConstructedGenericType &&