CSHARP-5463: Investigate whether calls to EnsureQueryableMethodHasNestedAsQueryableSource are actually needed.

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

@@ -27,7 +27,7 @@ public static void EnsureQueryableMethodHasNestedAsQueryableSource(MethodCallExp
             if (expression.Method.DeclaringType == typeof(Queryable) &&
                 sourceTranslation.Serializer is not INestedAsQueryableSerializer)
             {
-                throw new ExpressionNotSupportedException(expression, because: "source serializer is not a NestedAsQueryableSerializer");
+                throw new ExpressionNotSupportedException(expression, because: "source argument is an unsupported IQueryable type");
             }
         }
 

tests/MongoDB.Driver.Tests/Linq/Linq3Implementation/Jira/CSharp5463Tests.cs

@@ -0,0 +1,93 @@
+/* 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;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using MongoDB.Driver.TestHelpers;
+using FluentAssertions;
+using MongoDB.Driver.Linq;
+using Xunit;
+
+namespace MongoDB.Driver.Tests.Linq.Linq3Implementation.Jira;
+
+public class CSharp5463Tests : LinqIntegrationTest<CSharp5463Tests.ClassFixture>
+{
+    public CSharp5463Tests(ClassFixture fixture)
+        : base(fixture)
+    {
+    }
+
+    [Fact]
+    public void Nested_AsQueryable_Contains_constant_should_be_partially_evaluated()
+    {
+        var collection = Fixture.Collection;
+        var enumerable = new int[] { 1, 2, 3 };
+
+        var queryable = collection.AsQueryable()
+            .Select(x => enumerable.AsQueryable().Contains(1));
+
+        var stages = Translate(collection, queryable);
+        AssertStages(stages, "{ $project : { _v : { $in : [1, [1, 2, 3]] }, _id : 0 } }");
+
+        var result = queryable.Single();
+        result.Should().Be(true);
+    }
+
+    [Fact]
+    public void NestedQueryable_Contains_constant_should_be_partially_evaluated()
+    {
+        var collection = Fixture.Collection;
+        var nestedQueryable = new int[] { 1, 2, 3 }.AsQueryable();
+
+        var queryable = collection.AsQueryable()
+            .Select(x => nestedQueryable.Contains(1)); // PartialEvaluator turns this into Select(x => true)
+
+        var stages = Translate(collection, queryable);
+        AssertStages(stages, "{ $project : { _v : { $literal : true }, _id : 0 } }");
+
+        var result = queryable.Single();
+        result.Should().Be(true);
+    }
+
+    [Fact]
+    public void NestedQueryable_Contains_field_should_throw()
+    {
+        var collection = Fixture.Collection;
+        var nestedQueryable = new int[] { 1, 2, 3 }.AsQueryable();
+
+        var queryable = collection.AsQueryable()
+            .Select(x => nestedQueryable.Contains(x.Id));
+
+        var exception = Record.Exception(() => Translate(collection, queryable));
+        exception.Should().BeOfType<ExpressionNotSupportedException>();
+        exception.Message.Should().Contain("source argument is an unsupported IQueryable type");
+    }
+
+    public class C
+    {
+        public int Id { get; set; }
+    }
+
+    public sealed class ClassFixture : MongoCollectionFixture<C>
+    {
+        protected override IEnumerable<C> InitialData =>
+        [
+            new C { Id = 1 }
+        ];
+    }
+}