CSHARP-5572: Implement new KnownSerializerFinder

Author: rstam

src/MongoDB.Bson/Serialization/IBsonSerializerExtensions.cs

@@ -50,6 +50,48 @@ public static TValue Deserialize<TValue>(this IBsonSerializer<TValue> serializer
             return serializer.Deserialize(context, args);
         }
 
+        /// <summary>
+        /// Gets the serializer for a base type starting from a serializer for a derived type.
+        /// </summary>
+        /// <param name="derivedTypeSerializer">The serializer for the derived type.</param>
+        /// <param name="baseType">The base type.</param>
+        /// <returns>The serializer for the base type.</returns>
+        public static IBsonSerializer GetBaseTypeSerializer(this IBsonSerializer derivedTypeSerializer, Type baseType)
+        {
+            if (derivedTypeSerializer.ValueType == baseType)
+            {
+                return derivedTypeSerializer;
+            }
+
+            if (!baseType.IsAssignableFrom(derivedTypeSerializer.ValueType))
+            {
+                throw new ArgumentException($"{baseType} is not assignable from {derivedTypeSerializer.ValueType}.");
+            }
+
+            return BsonSerializer.LookupSerializer(baseType); // TODO: should be able to navigate from serializer
+        }
+
+        /// <summary>
+        /// Gets the serializer for a derived type starting from a serializer for a base type.
+        /// </summary>
+        /// <param name="baseTypeSerializer">The serializer for the base type.</param>
+        /// <param name="derivedType">The derived type.</param>
+        /// <returns>The serializer for the derived type.</returns>
+        public static IBsonSerializer GetDerivedTypeSerializer(this IBsonSerializer baseTypeSerializer, Type derivedType)
+        {
+            if (baseTypeSerializer.ValueType == derivedType)
+            {
+                return baseTypeSerializer;
+            }
+
+            if (!baseTypeSerializer.ValueType.IsAssignableFrom(derivedType))
+            {
+                throw new ArgumentException($"{baseTypeSerializer.ValueType} is not assignable from {derivedType}.");
+            }
+
+            return BsonSerializer.LookupSerializer(derivedType); // TODO: should be able to navigate from serializer
+        }
+
         /// <summary>
         /// Gets the discriminator convention for a serializer.
         /// </summary>

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

@@ -13,10 +13,29 @@
 * limitations under the License.
 */
 
+using System;
 using System.Collections.Generic;
 
 namespace MongoDB.Bson.Serialization.Serializers
 {
+    /// <summary>
+    /// A static factory class for ArraySerializers.
+    /// </summary>
+    public static class ArraySerializer
+    {
+        /// <summary>
+        /// Creates an ArraySerializer.
+        /// </summary>
+        /// <param name="itemSerializer">The item serializer.</param>
+        /// <returns>An ArraySerializer.</returns>
+        public static IBsonSerializer Create(IBsonSerializer itemSerializer)
+        {
+            var itemType = itemSerializer.ValueType;
+            var arraySerializerType = typeof(ArraySerializer<>).MakeGenericType(itemType);
+            return (IBsonSerializer)Activator.CreateInstance(arraySerializerType, itemSerializer);
+        }
+    }
+
     /// <summary>
     /// Represents a serializer for one-dimensional arrays.
     /// </summary>

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

@@ -22,6 +22,15 @@ namespace MongoDB.Bson.Serialization.Serializers
     /// </summary>
     public sealed class CharSerializer : StructSerializerBase<char>, IRepresentationConfigurable<CharSerializer>
     {
+        #region static
+        private static readonly CharSerializer __instance = new();
+
+        /// <summary>
+        /// Returns the default instance of CharSerializer.
+        /// </summary>
+        public static CharSerializer Instance => __instance;
+        #endregion
+
         // private fields
         private readonly BsonType _representation;
 

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

@@ -27,7 +27,6 @@ namespace MongoDB.Bson.Serialization.Serializers
     /// <typeparam name="TDictionary">The type of the dictionary.</typeparam>
     public abstract class DictionarySerializerBase<TDictionary> :
         ClassSerializerBase<TDictionary>,
-        IBsonDocumentSerializer,
         IBsonDictionarySerializer
         where TDictionary : class, IDictionary
     {
@@ -132,22 +131,6 @@ obj is DictionarySerializerBase<TDictionary> other &&
         /// <inheritdoc/>
         public override int GetHashCode() => 0;
 
-        /// <inheritdoc/>
-        public bool TryGetMemberSerializationInfo(string memberName, out BsonSerializationInfo serializationInfo)
-        {
-            if (_dictionaryRepresentation != DictionaryRepresentation.Document)
-            {
-                serializationInfo = null;
-                return false;
-            }
-
-            serializationInfo = new BsonSerializationInfo(
-                memberName,
-                _valueSerializer,
-                _valueSerializer.ValueType);
-            return true;
-        }
-
         // protected methods
         /// <summary>
         /// Deserializes a value.
@@ -355,7 +338,6 @@ private string SerializeKeyString(object key)
     public abstract class DictionarySerializerBase<TDictionary, TKey, TValue> :
         ClassSerializerBase<TDictionary>,
         IBsonArraySerializer,
-        IBsonDocumentSerializer,
         IBsonDictionarySerializer
         where TDictionary : class, IEnumerable<KeyValuePair<TKey, TValue>>
     {
@@ -499,35 +481,14 @@ obj is DictionarySerializerBase<TDictionary, TKey, TValue> other &&
         /// <inheritdoc/>
         public bool TryGetItemSerializationInfo(out BsonSerializationInfo serializationInfo)
         {
-            if (_dictionaryRepresentation is DictionaryRepresentation.ArrayOfArrays or DictionaryRepresentation.ArrayOfDocuments)
-            {
-                var representation = _dictionaryRepresentation == DictionaryRepresentation.ArrayOfArrays
-                    ? BsonType.Array
-                    : BsonType.Document;
-                var keySerializer = _lazyKeySerializer.Value;
-                var valueSerializer = _lazyValueSerializer.Value;
-                var keyValuePairSerializer = new KeyValuePairSerializer<TKey, TValue>(representation, keySerializer, valueSerializer);
-                serializationInfo = new BsonSerializationInfo(null, keyValuePairSerializer, keyValuePairSerializer.ValueType);
-                return true;
-            }
-
-            serializationInfo = null;
-            return false;
-        }
-
-        /// <inheritdoc/>
-        public bool TryGetMemberSerializationInfo(string memberName, out BsonSerializationInfo serializationInfo)
-        {
-            if (_dictionaryRepresentation != DictionaryRepresentation.Document)
-            {
-                serializationInfo = null;
-                return false;
-            }
+            var representation = _dictionaryRepresentation == DictionaryRepresentation.ArrayOfArrays
+                ? BsonType.Array
+                : BsonType.Document;
+            var keySerializer = _lazyKeySerializer.Value;
+            var valueSerializer = _lazyValueSerializer.Value;
+            var keyValuePairSerializer = new KeyValuePairSerializer<TKey, TValue>(representation, keySerializer, valueSerializer);
 
-            serializationInfo = new BsonSerializationInfo(
-                memberName,
-                _lazyValueSerializer.Value,
-                _lazyValueSerializer.Value.ValueType);
+            serializationInfo = new BsonSerializationInfo(null, keyValuePairSerializer, keyValuePairSerializer.ValueType);
             return true;
         }
 

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

@@ -33,6 +33,73 @@ public interface INullableSerializer
     /// </summary>
     public static class NullableSerializer
     {
+        private readonly static IBsonSerializer __nullableBooleanInstance = new NullableSerializer<bool>(BooleanSerializer.Instance);
+        private readonly static IBsonSerializer __nullableDecimalInstance = new NullableSerializer<decimal>(DecimalSerializer.Instance);
+        private readonly static IBsonSerializer __nullableDecimal128Instance = new NullableSerializer<Decimal128>(Decimal128Serializer.Instance);
+        private readonly static IBsonSerializer __nullableDoubleInstance = new NullableSerializer<double>(DoubleSerializer.Instance);
+        private readonly static IBsonSerializer __nullableInt32Instance = new NullableSerializer<int>(Int32Serializer.Instance);
+        private readonly static IBsonSerializer __nullableInt64Instance = new NullableSerializer<long>(Int64Serializer.Instance);
+        private readonly static IBsonSerializer __nullableLocalDateTimeInstance = new NullableSerializer<DateTime>(DateTimeSerializer.LocalInstance);
+        private readonly static IBsonSerializer __nullableObjectIdInstance = new NullableSerializer<ObjectId>(ObjectIdSerializer.Instance);
+        private readonly static IBsonSerializer __nullableSingleInstance = new NullableSerializer<float>(SingleSerializer.Instance);
+        private readonly static IBsonSerializer __nullableStandardGuidInstance = new NullableSerializer<Guid>(GuidSerializer.StandardInstance);
+        private readonly static IBsonSerializer __nullableUtcDateTimeInstance = new NullableSerializer<DateTime>(DateTimeSerializer.UtcInstance);
+
+        /// <summary>
+        /// Gets a serializer for nullable bools.
+        /// </summary>
+        public static IBsonSerializer NullableBooleanInstance => __nullableBooleanInstance;
+
+        /// <summary>
+        /// Gets a serializer for nullable decimals.
+        /// </summary>
+        public static IBsonSerializer NullableDecimalInstance => __nullableDecimalInstance;
+
+        /// <summary>
+        /// Gets a serializer for nullable Decimal128s.
+        /// </summary>
+        public static IBsonSerializer NullableDecimal128Instance => __nullableDecimal128Instance;
+
+        /// <summary>
+        /// Gets a serializer for nullable doubles.
+        /// </summary>
+        public static IBsonSerializer NullableDoubleInstance => __nullableDoubleInstance;
+
+        /// <summary>
+        /// Gets a serializer for nullable ints.
+        /// </summary>
+        public static IBsonSerializer NullableInt32Instance => __nullableInt32Instance;
+
+        /// <summary>
+        /// Gets a serializer for nullable longs.
+        /// </summary>
+        public static IBsonSerializer NullableInt64Instance => __nullableInt64Instance;
+
+        /// <summary>
+        /// Gets a serializer for local DateTime.
+        /// </summary>
+        public static IBsonSerializer NullableLocalDateTimeInstance => __nullableLocalDateTimeInstance;
+
+        /// <summary>
+        /// Gets a serializer for nullable floats.
+        /// </summary>
+        public static IBsonSerializer NullableSingleInstance => __nullableSingleInstance;
+
+        /// <summary>
+        /// Gets a serializer for nullable ObjectIds.
+        /// </summary>
+        public static IBsonSerializer NullableObjectIdInstance => __nullableObjectIdInstance;
+
+        /// <summary>
+        /// Gets a serializer for nullable Guids with standard representation.
+        /// </summary>
+        public static IBsonSerializer NullableStandardGuidInstance => __nullableStandardGuidInstance;
+
+        /// <summary>
+        /// Gets a serializer for UTC DateTime.
+        /// </summary>
+        public static IBsonSerializer NullableUtcDateTimeInstance => __nullableUtcDateTimeInstance;
+
         /// <summary>
         /// Creates a NullableSerializer.
         /// </summary>

src/MongoDB.Driver/Linq/Linq3Implementation/ExtensionMethods/ExpressionExtensions.cs

@@ -60,5 +60,17 @@ public static TValue GetConstantValue<TValue>(this Expression expression, Expres
             var message = $"Expression must be a constant: {expression} in {containingExpression}.";
             throw new ExpressionNotSupportedException(message);
         }
+
+        public static bool IsConvert(this Expression expression, out Expression operand)
+        {
+            if (expression is UnaryExpression { NodeType: ExpressionType.Convert } unaryExpression)
+            {
+                operand = unaryExpression.Operand;
+                return true;
+            }
+
+            operand = null;
+            return false;
+        }
     }
 }

src/MongoDB.Driver/Linq/Linq3Implementation/GroupingWithOutputExpressionStageDefinitions.cs

@@ -64,7 +64,8 @@ private AstStage RenderProjectStage(
             out IBsonSerializer<TOutput> outputSerializer)
         {
             var partiallyEvaluatedOutput = (Expression<Func<TGrouping, TOutput>>)LinqExpressionPreprocessor.Preprocess(_output);
-            var context = TranslationContext.Create(translationOptions);
+            var parameter = partiallyEvaluatedOutput.Parameters.Single();
+            var context = TranslationContext.Create(partiallyEvaluatedOutput, initialNode: parameter, initialSerializer: inputSerializer, translationOptions: translationOptions);
             var outputTranslation = ExpressionToAggregationExpressionTranslator.TranslateLambdaBody(context, partiallyEvaluatedOutput, inputSerializer, asRoot: true);
             var (projectStage, projectSerializer) = ProjectionHelper.CreateProjectStage(outputTranslation);
             outputSerializer = (IBsonSerializer<TOutput>)projectSerializer;
@@ -106,7 +107,8 @@ protected override AstStage RenderGroupingStage(
             out IBsonSerializer<IGrouping<TValue, TInput>> groupingOutputSerializer)
         {
             var partiallyEvaluatedGroupBy = (Expression<Func<TInput, TValue>>)LinqExpressionPreprocessor.Preprocess(_groupBy);
-            var context = TranslationContext.Create(translationOptions);
+            var parameter = partiallyEvaluatedGroupBy.Parameters.Single();
+            var context = TranslationContext.Create(partiallyEvaluatedGroupBy, initialNode: parameter, initialSerializer: inputSerializer, translationOptions: translationOptions);
             var groupByTranslation = ExpressionToAggregationExpressionTranslator.TranslateLambdaBody(context, partiallyEvaluatedGroupBy, inputSerializer, asRoot: true);
 
             var valueSerializer = (IBsonSerializer<TValue>)groupByTranslation.Serializer;
@@ -150,7 +152,8 @@ protected override AstStage RenderGroupingStage(
             out IBsonSerializer<IGrouping<AggregateBucketAutoResultId<TValue>, TInput>> groupingOutputSerializer)
         {
             var partiallyEvaluatedGroupBy = (Expression<Func<TInput, TValue>>)LinqExpressionPreprocessor.Preprocess(_groupBy);
-            var context = TranslationContext.Create(translationOptions);
+            var parameter = partiallyEvaluatedGroupBy.Parameters.Single();
+            var context = TranslationContext.Create(partiallyEvaluatedGroupBy, initialNode: parameter, initialSerializer: inputSerializer, translationOptions: translationOptions);
             var groupByTranslation = ExpressionToAggregationExpressionTranslator.TranslateLambdaBody(context, partiallyEvaluatedGroupBy, inputSerializer, asRoot: true);
 
             var valueSerializer = (IBsonSerializer<TValue>)groupByTranslation.Serializer;
@@ -188,7 +191,8 @@ protected override AstStage RenderGroupingStage(
             out IBsonSerializer<IGrouping<TValue, TInput>> groupingOutputSerializer)
         {
             var partiallyEvaluatedGroupBy = (Expression<Func<TInput, TValue>>)LinqExpressionPreprocessor.Preprocess(_groupBy);
-            var context = TranslationContext.Create(translationOptions);
+            var parameter = partiallyEvaluatedGroupBy.Parameters.Single();
+            var context = TranslationContext.Create(partiallyEvaluatedGroupBy, initialNode: parameter, initialSerializer: inputSerializer, translationOptions: translationOptions);
             var groupByTranslation = ExpressionToAggregationExpressionTranslator.TranslateLambdaBody(context, partiallyEvaluatedGroupBy, inputSerializer, asRoot: true);
             var pushElements = AstExpression.AccumulatorField("_elements", AstUnaryAccumulatorOperator.Push, AstExpression.RootVar);
             var groupBySerializer = (IBsonSerializer<TValue>)groupByTranslation.Serializer;

src/MongoDB.Driver/Linq/Linq3Implementation/KnownSerializerFinders/KnownSerializerFinder.cs

@@ -0,0 +1,45 @@
+/* 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.Linq.Expressions;
+
+namespace MongoDB.Driver.Linq.Linq3Implementation.KnownSerializerFinders;
+
+internal static class KnownSerializerFinder
+{
+    public static void FindKnownSerializers(
+        Expression expression,
+        ExpressionTranslationOptions translationOptions,
+        KnownSerializerMap knownSerializers)
+    {
+        var visitor = new KnownSerializerFinderVisitor(translationOptions, knownSerializers);
+
+        do
+        {
+            visitor.StartPass();
+            visitor.Visit(expression);
+            visitor.EndPass();
+        }
+        while (visitor.IsMakingProgress);
+
+        //#if DEBUG
+        var expressionWithUnknownSerializer = UnknownSerializerFinder.FindExpressionWithUnknownSerializer(expression, knownSerializers);
+        if (expressionWithUnknownSerializer != null)
+        {
+            throw new ExpressionNotSupportedException(expressionWithUnknownSerializer, because: "we were unable to determine which serializer to use for the result");
+        }
+        //#endif
+    }
+}