[Internal] Query: Added custom serializer coverage tests to ExpressionToSQL.cs

Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/Linq/CosmosLinqJsonConverterTests.cs

@@ -6,7 +6,11 @@ namespace Microsoft.Azure.Cosmos.Linq
 {
     using System;
     using System.Globalization;
+    using System.IO;
+    using System.Linq;
     using System.Linq.Expressions;
+    using System.Reflection;
+    using global::Azure.Core.Serialization;
     using Microsoft.VisualStudio.TestTools.UnitTesting;
     using Newtonsoft.Json;
     using Newtonsoft.Json.Converters;
@@ -30,6 +34,102 @@ public void DateTimeKindIsPreservedTest()
             Assert.AreEqual("(a[\"StartDate\"] <= \"2022-05-26\")", sql);
         }
 
+        // Ignored for now because the test is failing in current production implementation of Cosmos SDK
+        [TestMethod, Ignore]
+        public void EnumIsPreservedAsINTest()
+        {
+            // Arrange
+            CosmosLinqSerializerOptions options = new()
+            {
+                // CustomCosmosSerializer = new TestCustomJsonSerializer()
+            };
+
+            // Act
+            TestEnum[] values = new[] { TestEnum.One, TestEnum.Two };
+            Expression<Func<TestEnumDocument, bool>> expr = a => values.Contains(a.Value);
+
+            string sql = SqlTranslator.TranslateExpression(expr.Body, options);
+
+            // Assert
+            Assert.AreEqual("(a[\"Value\"] IN (\"One\", \"Two\"))", sql);
+        }
+
+        [TestMethod]
+        public void EnumIsPreservedAsEQUALSTest()
+        {
+            // Arrange
+            CosmosLinqSerializerOptions options = new()
+            {
+                // CustomCosmosSerializer = new TestCustomJsonSerializer()
+            };
+
+            // Act
+            TestEnum statusValue = TestEnum.One;
+            Expression<Func<TestEnumDocument, bool>> expr = a => a.Value == statusValue;
+
+            string sql = SqlTranslator.TranslateExpression(expr.Body, options);
+
+            // Assert
+            Assert.AreEqual("(a[\"Value\"] = \"One\")", sql);
+        }
+
+        [TestMethod]
+        public void EnumIsPreservedAsEXPRESSIONTest()
+        {
+            // Arrange
+            CosmosLinqSerializerOptions options = new()
+            {
+                // CustomCosmosSerializer = new TestCustomJsonSerializer()
+            };
+
+            // Act
+
+            // Get status constant
+            ConstantExpression status = Expression.Constant(TestEnum.One);
+
+            // Get member access expression
+            ParameterExpression arg = Expression.Parameter(typeof(TestEnumNewtonsoftDocument), "a");
+
+            // Access the value property
+            MemberExpression docValueExpression = Expression.MakeMemberAccess(
+                arg,
+                typeof(TestEnumNewtonsoftDocument).GetProperty(nameof(TestEnumNewtonsoftDocument.Value))!
+            );
+
+            // Create comparison expression
+            BinaryExpression expression = Expression.Equal(
+                docValueExpression,
+                status
+            );
+
+            // Create lambda expression
+            Expression<Func<TestEnumNewtonsoftDocument, bool>> lambda = 
+                Expression.Lambda<Func<TestEnumNewtonsoftDocument, bool>>(expression, arg);
+
+            string sql = SqlTranslator.TranslateExpression(lambda.Body, options);
+
+            // Assert
+            Assert.AreEqual("(a[\"Value\"] = \"One\")", sql);
+        }
+
+        enum TestEnum
+        {
+            One,
+            Two,
+            Three,
+        }
+
+        class TestEnumDocument
+        {
+            public TestEnum Value { get; set; }
+        }
+
+        class TestEnumNewtonsoftDocument
+        {
+            [JsonConverter(typeof(StringEnumConverter))]
+            public TestEnum Value { get; set; }
+        }
+
         class TestDocument
         {
             [JsonConverter(typeof(DateJsonConverter))]
@@ -50,5 +150,53 @@ public override void WriteJson(JsonWriter writer, object value, JsonSerializer s
                 }
             }
         }
+
+        /// <remarks>
+        // See: https://github.com/Azure/azure-cosmos-dotnet-v3/blob/master/Microsoft.Azure.Cosmos.Samples/Usage/SystemTextJson/CosmosSystemTextJsonSerializer.cs
+        /// </remarks>
+        class TestCustomJsonSerializer : CosmosSerializer
+        {
+            private readonly JsonObjectSerializer systemTextJsonSerializer;
+
+            public static readonly System.Text.Json.JsonSerializerOptions JsonOptions = new()
+            {
+                DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull,
+                PropertyNameCaseInsensitive = true,
+                Converters = {
+                    new System.Text.Json.Serialization.JsonStringEnumConverter(),
+                }
+            };
+
+            public TestCustomJsonSerializer()
+            {
+                this.systemTextJsonSerializer = new JsonObjectSerializer(JsonOptions);
+            }
+
+            public override T FromStream<T>(Stream stream)
+            {
+                if (stream.CanSeek && stream.Length == 0)
+                {
+                    stream.Dispose();
+                    return default!;
+                }
+
+                if (typeof(Stream).IsAssignableFrom(typeof(T)))
+                    return (T)(object)stream;
+
+                using (stream)
+                {
+                    return (T)this.systemTextJsonSerializer.Deserialize(stream, typeof(T), default)!;
+                }
+            }
+
+            public override Stream ToStream<T>(T input)
+            {
+                MemoryStream stream = new ();
+
+                this.systemTextJsonSerializer.Serialize(stream, input, typeof(T), default);
+                stream.Position = 0;
+                return stream;
+            }
+        }
     }
 }