Adding translation for string.Length on Cosmos

src/EFCore.Cosmos/Query/Internal/CosmosMemberTranslatorProvider.cs

@@ -32,12 +32,12 @@ public CosmosMemberTranslatorProvider(
             IEnumerable<IMemberTranslatorPlugin> plugins)
         {
             _plugins.AddRange(plugins.SelectMany(p => p.Translators));
-            //_translators
-            //    .AddRange(
-            //    new[]
-            //    {
-            //        new NullableMemberTranslator(sqlExpressionFactory),
-            //    });
+            _translators
+                .AddRange(
+                new[]
+                {
+                    new CosmosStringMemberTranslator(sqlExpressionFactory),
+                });
         }
 
         /// <summary>

src/EFCore.Cosmos/Query/Internal/CosmosStringMemberTranslator.cs

@@ -0,0 +1,59 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Reflection;
+using Microsoft.EntityFrameworkCore.Diagnostics;
+using Microsoft.EntityFrameworkCore.Utilities;
+
+namespace Microsoft.EntityFrameworkCore.Cosmos.Query.Internal
+{
+    /// <summary>
+    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+    ///     any release. You should only use it directly in your code with extreme caution and knowing that
+    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
+    /// </summary>
+    public class CosmosStringMemberTranslator : IMemberTranslator
+    {
+        private readonly ISqlExpressionFactory _sqlExpressionFactory;
+
+        /// <summary>
+        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+        ///     any release. You should only use it directly in your code with extreme caution and knowing that
+        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
+        /// </summary>
+        public CosmosStringMemberTranslator(ISqlExpressionFactory sqlExpressionFactory)
+        {
+            _sqlExpressionFactory = sqlExpressionFactory;
+        }
+
+        /// <summary>
+        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+        ///     any release. You should only use it directly in your code with extreme caution and knowing that
+        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
+        /// </summary>
+        public virtual SqlExpression? Translate(
+            SqlExpression? instance,
+            MemberInfo member,
+            Type returnType,
+            IDiagnosticsLogger<DbLoggerCategory.Query> logger)
+        {
+            Check.NotNull(member, nameof(member));
+            Check.NotNull(returnType, nameof(returnType));
+            Check.NotNull(logger, nameof(logger));
+
+            if (member.Name == nameof(string.Length)
+                && instance?.Type == typeof(string))
+            {
+                return _sqlExpressionFactory.Function(
+                    "LENGTH",
+                    new[] { instance },
+                    returnType);
+            }
+
+            return null;
+        }
+    }
+}

test/EFCore.Cosmos.FunctionalTests/Query/NorthwindSelectQueryCosmosTest.cs

@@ -232,7 +232,7 @@ public override async Task Select_anonymous_constant_in_expression(bool async)
             await base.Select_anonymous_constant_in_expression(async);
 
             AssertSql(
-                @"SELECT c[""CustomerID""]
+                @"SELECT VALUE {""CustomerID"" : c[""CustomerID""], ""Expression"" : (LENGTH(c[""CustomerID""]) + 5)}
 FROM root c
 WHERE (c[""Discriminator""] = ""Customer"")");
         }
@@ -535,7 +535,7 @@ public override async Task Select_non_matching_value_types_from_length_introduce
             await base.Select_non_matching_value_types_from_length_introduces_explicit_cast(async);
 
             AssertSql(
-                @"SELECT c[""CustomerID""]
+                @"SELECT LENGTH(c[""CustomerID""]) AS c
 FROM root c
 WHERE ((c[""Discriminator""] = ""Order"") AND (c[""CustomerID""] = ""ALFKI""))
 ORDER BY c[""OrderID""]");

test/EFCore.Cosmos.FunctionalTests/Query/NorthwindWhereQueryCosmosTest.cs

@@ -983,15 +983,15 @@ FROM root c
 WHERE ((c[""Discriminator""] = ""Employee"") AND (c[""ReportsTo""] = null))");
         }
 
-        [ConditionalTheory(Skip = "Issue #17246")]
+        [ConditionalTheory]
         public override async Task Where_string_length(bool async)
         {
             await base.Where_string_length(async);
 
             AssertSql(
                 @"SELECT c
 FROM root c
-WHERE (c[""Discriminator""] = ""Customer"")");
+WHERE ((c[""Discriminator""] = ""Customer"") AND (LENGTH(c[""City""]) = 6))");
         }
 
         [ConditionalTheory(Skip = "Issue #17246")]