Add regression tests to several bugs that were fixed previously

Resolves #21836
Resolves #22978
Resolves #23205

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

@@ -5824,5 +5824,62 @@ public virtual Task Projecting_columns_with_same_name_from_different_entities_ma
                        select new { Id1 = l1.Id, Id2 = l2.Id, Id3 = l3.Id, Name1 = l1.Name, Name2 = l2.Name }).Distinct().Select(x => new { Foo = x.Id1, Bar = x.Id2, Baz = x.Id3 }).Take(10),
                 elementSorter: e => (e.Foo, e.Bar, e.Baz));
         }
+
+        [ConditionalTheory(Skip = "issue #23302")]
+        [MemberData(nameof(IsAsyncData))]
+        public virtual Task Queryable_in_subquery_works_when_final_projection_is_List(bool async)
+        {
+            return AssertQuery(
+                async,
+                ss => from l1 in ss.Set<Level1>()
+                      orderby l1.Id
+                      let inner = (from l2 in l1.OneToMany_Optional1
+                                   where l2.Name != "Foo"
+                                   let innerL1s = from innerL1 in ss.Set<Level1>()
+                                                  where innerL1.OneToMany_Optional1.Any(innerL2 => innerL2.Id == l2.Id)
+                                                  select innerL1.Name
+                                   select innerL1s).FirstOrDefault()
+                      select inner.ToList(),
+                assertOrder: true,
+                elementAsserter: (e, a) => AssertCollection(e, a));
+        }
+
+        [ConditionalTheory(Skip = "issue #23303")]
+        [MemberData(nameof(IsAsyncData))]
+        public virtual Task Complex_query_with_let_collection_projection_FirstOrDefault_with_ToList_on_inner_and_outer(bool async)
+        {
+            return AssertQuery(
+                async,
+                ss => from l1 in ss.Set<Level1>()
+                      orderby l1.Id
+                      let inner = (from l2 in l1.OneToMany_Optional1
+                                   where l2.Name != "Foo"
+                                   let innerL1s = from innerL1 in ss.Set<Level1>()
+                                                  where innerL1.OneToMany_Optional1.Any(innerL2 => innerL2.Id == l2.Id)
+                                                  select innerL1.Name
+                                   select innerL1s.ToList()).FirstOrDefault()
+                      select inner.ToList(),
+                assertOrder: true,
+                elementAsserter: (e, a) => AssertCollection(e, a));
+        }
+
+        [ConditionalTheory]
+        [MemberData(nameof(IsAsyncData))]
+        public virtual Task Complex_query_with_let_collection_projection_FirstOrDefault(bool async)
+        {
+            return AssertQuery(
+                async,
+                ss => from l1 in ss.Set<Level1>()
+                      orderby l1.Id
+                      let inner = (from l2 in l1.OneToMany_Optional1
+                                   where l2.Name != "Foo"
+                                   let innerL1s = from innerL1 in ss.Set<Level1>()
+                                                  where innerL1.OneToMany_Optional1.Any(innerL2 => innerL2.Id == l2.Id)
+                                                  select innerL1.Name
+                                   select innerL1s.ToList()).FirstOrDefault()
+                      select inner,
+                assertOrder: true,
+                elementAsserter: (e, a) => AssertCollection(e, a));
+        }
     }
 }

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

@@ -7933,6 +7933,21 @@ public virtual Task Sum_with_no_data_nullable_double(bool async)
                 ss => ss.Set<Mission>().Where(m => m.CodeName == "Operation Foobar").Select(m => m.Rating));
         }
 
+        [ConditionalTheory]
+        [MemberData(nameof(IsAsyncData))]
+        public virtual Task FirstOrDefault_on_empty_collection_of_DateTime_in_subquery(bool async)
+        {
+            return AssertQuery(
+                async,
+                ss => from g in ss.Set<Gear>()
+                      let invalidTagIssueDate = (from t in ss.Set<CogTag>()
+                                                 where t.GearNickName == g.FullName
+                                                 orderby t.Id
+                                                 select t.IssueDate).FirstOrDefault()
+                      where g.Tag.IssueDate > invalidTagIssueDate
+                      select new { g.Nickname, invalidTagIssueDate });
+        }
+
         protected GearsOfWarContext CreateContext()
             => Fixture.CreateContext();
 

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

@@ -2456,5 +2456,15 @@ public virtual Task Two_sets_of_comparison_combine_correctly2(bool async)
                     c => (c.Region != "WA" && c.Region != "OR" && c.Region != null) || (c.Region != "WA" && c.Region != null)),
                 entryCount: 28);
         }
+
+        [ConditionalTheory]
+        [MemberData(nameof(IsAsyncData))]
+        public virtual Task Filter_with_property_compared_to_null_wrapped_in_explicit_convert_to_object(bool async)
+        {
+            return AssertQuery(
+                async,
+                ss => ss.Set<Customer>().Where(c => (object)c.Region == null),
+                entryCount: 60);
+        }
     }
 }

test/EFCore.Specification.Tests/TestModels/GearsOfWarModel/CogTag.cs

@@ -15,5 +15,6 @@ public class CogTag
         public string GearNickName { get; set; }
         public int? GearSquadId { get; set; }
         public virtual Gear Gear { get; set; }
+        public DateTime IssueDate { get; set; }
     }
 }

test/EFCore.Specification.Tests/TestModels/GearsOfWarModel/GearsOfWarData.cs

@@ -267,12 +267,12 @@ public static IReadOnlyList<Weapon> CreateWeapons()
         public static IReadOnlyList<CogTag> CreateTags()
             => new List<CogTag>
             {
-                new CogTag { Id = Guid.Parse("DF36F493-463F-4123-83F9-6B135DEEB7BA"), Note = "Dom's Tag" },
-                new CogTag { Id = Guid.Parse("A8AD98F9-E023-4E2A-9A70-C2728455BD34"), Note = "Cole's Tag" },
-                new CogTag { Id = Guid.Parse("A7BE028A-0CF2-448F-AB55-CE8BC5D8CF69"), Note = "Paduk's Tag" },
-                new CogTag { Id = Guid.Parse("70534E05-782C-4052-8720-C2C54481CE5F"), Note = "Baird's Tag" },
-                new CogTag { Id = Guid.Parse("34C8D86E-A4AC-4BE5-827F-584DDA348A07"), Note = "Marcus' Tag" },
-                new CogTag { Id = Guid.Parse("B39A6FBA-9026-4D69-828E-FD7068673E57"), Note = "K.I.A." }
+                new CogTag { Id = Guid.Parse("DF36F493-463F-4123-83F9-6B135DEEB7BA"), Note = "Dom's Tag", IssueDate = new DateTime(3, 2, 2) },
+                new CogTag { Id = Guid.Parse("A8AD98F9-E023-4E2A-9A70-C2728455BD34"), Note = "Cole's Tag", IssueDate = new DateTime(2, 10, 11) },
+                new CogTag { Id = Guid.Parse("A7BE028A-0CF2-448F-AB55-CE8BC5D8CF69"), Note = "Paduk's Tag", IssueDate = new DateTime(15, 3, 7) },
+                new CogTag { Id = Guid.Parse("70534E05-782C-4052-8720-C2C54481CE5F"), Note = "Baird's Tag", IssueDate = new DateTime(7, 5, 3) },
+                new CogTag { Id = Guid.Parse("34C8D86E-A4AC-4BE5-827F-584DDA348A07"), Note = "Marcus' Tag", IssueDate = new DateTime(1, 9, 25) },
+                new CogTag { Id = Guid.Parse("B39A6FBA-9026-4D69-828E-FD7068673E57"), Note = "K.I.A.", IssueDate = new DateTime(21, 7, 7) }
             };
 
         public static IReadOnlyList<Gear> CreateGears()

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

@@ -6046,6 +6046,33 @@ public override async Task Projecting_columns_with_same_name_from_different_enti
 ) AS [t]");
         }
 
+        public override async Task Complex_query_with_let_collection_projection_FirstOrDefault(bool async)
+        {
+            await base.Complex_query_with_let_collection_projection_FirstOrDefault(async);
+
+            AssertSql(
+                @"SELECT [t0].[c], [l].[Id], [t0].[Id], [t1].[Name], [t1].[Id]
+FROM [LevelOne] AS [l]
+LEFT JOIN (
+    SELECT [t].[c], [t].[Id], [t].[OneToMany_Optional_Inverse2Id]
+    FROM (
+        SELECT 1 AS [c], [l0].[Id], [l0].[OneToMany_Optional_Inverse2Id], ROW_NUMBER() OVER(PARTITION BY [l0].[OneToMany_Optional_Inverse2Id] ORDER BY [l0].[Id]) AS [row]
+        FROM [LevelTwo] AS [l0]
+        WHERE ([l0].[Name] <> N'Foo') OR [l0].[Name] IS NULL
+    ) AS [t]
+    WHERE [t].[row] <= 1
+) AS [t0] ON [l].[Id] = [t0].[OneToMany_Optional_Inverse2Id]
+OUTER APPLY (
+    SELECT [l1].[Name], [l1].[Id]
+    FROM [LevelOne] AS [l1]
+    WHERE EXISTS (
+        SELECT 1
+        FROM [LevelTwo] AS [l2]
+        WHERE ([l1].[Id] = [l2].[OneToMany_Optional_Inverse2Id]) AND ([l2].[Id] = [t0].[Id]))
+) AS [t1]
+ORDER BY [l].[Id], [t0].[Id], [t1].[Id]");
+        }
+
         private void AssertSql(params string[] expected)
             => Fixture.TestSqlLoggerFactory.AssertBaseline(expected);
     }