Query: Add regression test for #21490

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

@@ -1308,6 +1308,12 @@ public override Task Client_projection_via_ctor_arguments(bool async)
             return base.Client_projection_via_ctor_arguments(async);
         }
 
+        [ConditionalTheory(Skip = "Cross collection join Issue#17246")]
+        public override Task Client_projection_with_string_initialization_with_scalar_subquery(bool async)
+        {
+            return base.Client_projection_with_string_initialization_with_scalar_subquery(async);
+        }
+
         private void AssertSql(params string[] expected)
             => Fixture.TestSqlLoggerFactory.AssertBaseline(expected);
 

test/EFCore.Specification.Tests/Query/NorthwindSelectQueryTestBase.cs

@@ -2373,5 +2373,53 @@ public OrderInfo(int orderID, DateTime? orderDate)
             public DateTime? OrderDate { get; }
         }
 
+        [ConditionalTheory]
+        [MemberData(nameof(IsAsyncData))]
+        public virtual Task Client_projection_with_string_initialization_with_scalar_subquery(bool async)
+        {
+            return AssertQuery(
+              async,
+              ss => ss.Set<Customer>()
+                    .Where(c => c.CustomerID.StartsWith("F"))
+                    .Select(c => new
+                    {
+                        c.CustomerID,
+                        Order = c.Orders.FirstOrDefault(o => o.OrderID < 11000).OrderDate,
+                        InterpolatedString = $"test{c.City}",
+                        NonInterpolatedString = "test" + c.City,
+                        Collection = new List<string>
+                        {
+                            $"{c.CustomerID}@test1.com",
+                            $"{c.CustomerID}@test2.com",
+                            $"{c.CustomerID}@test3.com",
+                            $"{c.CustomerID}@test4.com"
+                        }
+                    }),
+              ss => ss.Set<Customer>()
+                    .Where(c => c.CustomerID.StartsWith("F"))
+                    .Select(c => new
+                    {
+                        c.CustomerID,
+                        Order = c.Orders.FirstOrDefault(o => o.OrderID < 11000).MaybeScalar(e => e.OrderDate),
+                        InterpolatedString = $"test{c.City}",
+                        NonInterpolatedString = "test" + c.City,
+                        Collection = new List<string>
+                        {
+                            $"{c.CustomerID}@test1.com",
+                            $"{c.CustomerID}@test2.com",
+                            $"{c.CustomerID}@test3.com",
+                            $"{c.CustomerID}@test4.com"
+                        }
+                    }),
+              elementSorter: e => e.CustomerID,
+              elementAsserter: (e, a) =>
+              {
+                  AssertEqual(e.CustomerID, a.CustomerID);
+                  AssertEqual(e.Order, a.Order);
+                  AssertEqual(e.InterpolatedString, a.InterpolatedString);
+                  AssertEqual(e.NonInterpolatedString, a.NonInterpolatedString);
+                  AssertCollection(e.Collection, a.Collection, ordered: true);
+              });
+        }
     }
 }

test/EFCore.SqlServer.FunctionalTests/Query/NorthwindSelectQuerySqlServerTest.cs

@@ -1842,6 +1842,19 @@ FROM [Customers] AS [c]
 ORDER BY [t].[CustomerID]");
         }
 
+        public override async Task Client_projection_with_string_initialization_with_scalar_subquery(bool async)
+        {
+            await base.Client_projection_with_string_initialization_with_scalar_subquery(async);
+
+            AssertSql(
+                @"SELECT [c].[CustomerID], (
+    SELECT TOP(1) [o].[OrderDate]
+    FROM [Orders] AS [o]
+    WHERE ([c].[CustomerID] = [o].[CustomerID]) AND ([o].[OrderID] < 11000)), [c].[City], N'test' + COALESCE([c].[City], N'')
+FROM [Customers] AS [c]
+WHERE [c].[CustomerID] LIKE N'F%'");
+        }
+
         private void AssertSql(params string[] expected)
             => Fixture.TestSqlLoggerFactory.AssertBaseline(expected);