add regression tests for #23674

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

@@ -5878,5 +5878,16 @@ select innerL1s.ToList()).FirstOrDefault()
                 assertOrder: true,
                 elementAsserter: (e, a) => AssertCollection(e, a));
         }
+
+        [ConditionalTheory]
+        [MemberData(nameof(IsAsyncData))]
+        public virtual Task Include_ThenInclude_which_cycles_back_but_also_includes_additional_navigations(bool async)
+        {
+            return AssertQuery(
+                async,
+                ss => ss.Set<Level2>().AsTracking()
+                    .Include(l2 => l2.OneToMany_Optional2)
+                    .ThenInclude(l3 => l3.OneToMany_Optional_Inverse3.OneToMany_Required2));
+        }
     }
 }

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

@@ -7954,6 +7954,27 @@ public virtual Task Array_access_on_byte_array(bool async)
                 ss => ss.Set<Squad>().Where(e => e.Banner5[2] == 0x06));
         }
 
+        [ConditionalTheory(Skip = "issue #23674")]
+        [MemberData(nameof(IsAsyncData))]
+        public virtual Task Include_ThenInclude_which_cycles_back_but_also_includes_additional_navigations(bool async)
+        {
+            var expectedIncludes = new IExpectedInclude[]
+            {
+                new ExpectedInclude<Gear>(e => e.Weapons),
+                new ExpectedInclude<Weapon>(e => e.Owner, "Weapons"),
+                new ExpectedInclude<Gear>(e => e.AssignedCity, "Weapons.Owner")
+            };
+
+            return AssertQuery(
+                async,
+                ss => ss.Set<Gear>()
+                    .AsTracking()
+                    .Include(g => g.Weapons)
+                    .ThenInclude(w => w.Owner.AssignedCity),
+                elementAsserter: (e, a) => AssertInclude(e, a, expectedIncludes),
+                entryCount: 17);
+        }
+
         protected GearsOfWarContext CreateContext()
             => Fixture.CreateContext();
 

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

@@ -6073,6 +6073,22 @@ SELECT 1
 ORDER BY [l].[Id], [t0].[Id], [t1].[Id]");
         }
 
+        public override async Task Include_ThenInclude_which_cycles_back_but_also_includes_additional_navigations(bool async)
+        {
+            await base.Include_ThenInclude_which_cycles_back_but_also_includes_additional_navigations(async);
+
+            AssertSql(
+                @"SELECT [l].[Id], [l].[Date], [l].[Level1_Optional_Id], [l].[Level1_Required_Id], [l].[Name], [l].[OneToMany_Optional_Inverse2Id], [l].[OneToMany_Optional_Self_Inverse2Id], [l].[OneToMany_Required_Inverse2Id], [l].[OneToMany_Required_Self_Inverse2Id], [l].[OneToOne_Optional_PK_Inverse2Id], [l].[OneToOne_Optional_Self2Id], [t].[Id], [t].[Level2_Optional_Id], [t].[Level2_Required_Id], [t].[Name], [t].[OneToMany_Optional_Inverse3Id], [t].[OneToMany_Optional_Self_Inverse3Id], [t].[OneToMany_Required_Inverse3Id], [t].[OneToMany_Required_Self_Inverse3Id], [t].[OneToOne_Optional_PK_Inverse3Id], [t].[OneToOne_Optional_Self3Id], [t].[Id0], [t].[Date], [t].[Level1_Optional_Id], [t].[Level1_Required_Id], [t].[Name0], [t].[OneToMany_Optional_Inverse2Id], [t].[OneToMany_Optional_Self_Inverse2Id], [t].[OneToMany_Required_Inverse2Id], [t].[OneToMany_Required_Self_Inverse2Id], [t].[OneToOne_Optional_PK_Inverse2Id], [t].[OneToOne_Optional_Self2Id], [t].[Id1], [t].[Level2_Optional_Id0], [t].[Level2_Required_Id0], [t].[Name1], [t].[OneToMany_Optional_Inverse3Id0], [t].[OneToMany_Optional_Self_Inverse3Id0], [t].[OneToMany_Required_Inverse3Id0], [t].[OneToMany_Required_Self_Inverse3Id0], [t].[OneToOne_Optional_PK_Inverse3Id0], [t].[OneToOne_Optional_Self3Id0]
+FROM [LevelTwo] AS [l]
+LEFT JOIN (
+    SELECT [l0].[Id], [l0].[Level2_Optional_Id], [l0].[Level2_Required_Id], [l0].[Name], [l0].[OneToMany_Optional_Inverse3Id], [l0].[OneToMany_Optional_Self_Inverse3Id], [l0].[OneToMany_Required_Inverse3Id], [l0].[OneToMany_Required_Self_Inverse3Id], [l0].[OneToOne_Optional_PK_Inverse3Id], [l0].[OneToOne_Optional_Self3Id], [l1].[Id] AS [Id0], [l1].[Date], [l1].[Level1_Optional_Id], [l1].[Level1_Required_Id], [l1].[Name] AS [Name0], [l1].[OneToMany_Optional_Inverse2Id], [l1].[OneToMany_Optional_Self_Inverse2Id], [l1].[OneToMany_Required_Inverse2Id], [l1].[OneToMany_Required_Self_Inverse2Id], [l1].[OneToOne_Optional_PK_Inverse2Id], [l1].[OneToOne_Optional_Self2Id], [l2].[Id] AS [Id1], [l2].[Level2_Optional_Id] AS [Level2_Optional_Id0], [l2].[Level2_Required_Id] AS [Level2_Required_Id0], [l2].[Name] AS [Name1], [l2].[OneToMany_Optional_Inverse3Id] AS [OneToMany_Optional_Inverse3Id0], [l2].[OneToMany_Optional_Self_Inverse3Id] AS [OneToMany_Optional_Self_Inverse3Id0], [l2].[OneToMany_Required_Inverse3Id] AS [OneToMany_Required_Inverse3Id0], [l2].[OneToMany_Required_Self_Inverse3Id] AS [OneToMany_Required_Self_Inverse3Id0], [l2].[OneToOne_Optional_PK_Inverse3Id] AS [OneToOne_Optional_PK_Inverse3Id0], [l2].[OneToOne_Optional_Self3Id] AS [OneToOne_Optional_Self3Id0]
+    FROM [LevelThree] AS [l0]
+    LEFT JOIN [LevelTwo] AS [l1] ON [l0].[OneToMany_Optional_Inverse3Id] = [l1].[Id]
+    LEFT JOIN [LevelThree] AS [l2] ON [l1].[Id] = [l2].[OneToMany_Required_Inverse3Id]
+) AS [t] ON [l].[Id] = [t].[OneToMany_Optional_Inverse3Id]
+ORDER BY [l].[Id], [t].[Id], [t].[Id0], [t].[Id1]");
+        }
+
         private void AssertSql(params string[] expected)
             => Fixture.TestSqlLoggerFactory.AssertBaseline(expected);
     }

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

@@ -7364,6 +7364,22 @@ public override async Task Array_access_on_byte_array(bool async)
 WHERE CAST(SUBSTRING([s].[Banner5], 2 + 1, 1) AS tinyint) = CAST(6 AS tinyint)");
         }
 
+        public override async Task Include_ThenInclude_which_cycles_back_but_also_includes_additional_navigations(bool async)
+        {
+            await base.Include_ThenInclude_which_cycles_back_but_also_includes_additional_navigations(async);
+
+            AssertSql(
+                @"SELECT [g].[Nickname], [g].[SquadId], [g].[AssignedCityName], [g].[CityOfBirthName], [g].[Discriminator], [g].[FullName], [g].[HasSoulPatch], [g].[LeaderNickname], [g].[LeaderSquadId], [g].[Rank], [t].[Id], [t].[AmmunitionType], [t].[IsAutomatic], [t].[Name], [t].[OwnerFullName], [t].[SynergyWithId], [t].[Nickname], [t].[SquadId], [t].[AssignedCityName], [t].[CityOfBirthName], [t].[Discriminator], [t].[FullName], [t].[HasSoulPatch], [t].[LeaderNickname], [t].[LeaderSquadId], [t].[Rank], [t].[Name0], [t].[Location], [t].[Nation]
+FROM [Gears] AS [g]
+LEFT JOIN (
+    SELECT [w].[Id], [w].[AmmunitionType], [w].[IsAutomatic], [w].[Name], [w].[OwnerFullName], [w].[SynergyWithId], [g0].[Nickname], [g0].[SquadId], [g0].[AssignedCityName], [g0].[CityOfBirthName], [g0].[Discriminator], [g0].[FullName], [g0].[HasSoulPatch], [g0].[LeaderNickname], [g0].[LeaderSquadId], [g0].[Rank], [c].[Name] AS [Name0], [c].[Location], [c].[Nation]
+    FROM [Weapons] AS [w]
+    LEFT JOIN [Gears] AS [g0] ON [w].[OwnerFullName] = [g0].[FullName]
+    LEFT JOIN [Cities] AS [c] ON [g0].[AssignedCityName] = [c].[Name]
+) AS [t] ON [g].[FullName] = [t].[OwnerFullName]
+ORDER BY [g].[Nickname], [g].[SquadId], [t].[Id], [t].[Nickname], [t].[SquadId], [t].[Name0]");
+        }
+
         private void AssertSql(params string[] expected)
             => Fixture.TestSqlLoggerFactory.AssertBaseline(expected);
     }

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

@@ -8514,6 +8514,31 @@ public override async Task Array_access_on_byte_array(bool async)
 WHERE CAST(SUBSTRING([s].[Banner5], 2 + 1, 1) AS tinyint) = CAST(6 AS tinyint)");
         }
 
+        public override async Task Include_ThenInclude_which_cycles_back_but_also_includes_additional_navigations(bool async)
+        {
+            await base.Include_ThenInclude_which_cycles_back_but_also_includes_additional_navigations(async);
+
+            AssertSql(
+                @"SELECT [g].[Nickname], [g].[SquadId], [g].[AssignedCityName], [g].[CityOfBirthName], [g].[FullName], [g].[HasSoulPatch], [g].[LeaderNickname], [g].[LeaderSquadId], [g].[Rank], CASE
+    WHEN [o].[Nickname] IS NOT NULL THEN N'Officer'
+END AS [Discriminator], [t0].[Id], [t0].[AmmunitionType], [t0].[IsAutomatic], [t0].[Name], [t0].[OwnerFullName], [t0].[SynergyWithId], [t0].[Nickname], [t0].[SquadId], [t0].[AssignedCityName], [t0].[CityOfBirthName], [t0].[FullName], [t0].[HasSoulPatch], [t0].[LeaderNickname], [t0].[LeaderSquadId], [t0].[Rank], [t0].[Discriminator], [t0].[Name0], [t0].[Location], [t0].[Nation]
+FROM [Gears] AS [g]
+LEFT JOIN [Officers] AS [o] ON ([g].[Nickname] = [o].[Nickname]) AND ([g].[SquadId] = [o].[SquadId])
+LEFT JOIN (
+    SELECT [w].[Id], [w].[AmmunitionType], [w].[IsAutomatic], [w].[Name], [w].[OwnerFullName], [w].[SynergyWithId], [t].[Nickname], [t].[SquadId], [t].[AssignedCityName], [t].[CityOfBirthName], [t].[FullName], [t].[HasSoulPatch], [t].[LeaderNickname], [t].[LeaderSquadId], [t].[Rank], [t].[Discriminator], [c].[Name] AS [Name0], [c].[Location], [c].[Nation]
+    FROM [Weapons] AS [w]
+    LEFT JOIN (
+        SELECT [g0].[Nickname], [g0].[SquadId], [g0].[AssignedCityName], [g0].[CityOfBirthName], [g0].[FullName], [g0].[HasSoulPatch], [g0].[LeaderNickname], [g0].[LeaderSquadId], [g0].[Rank], CASE
+            WHEN [o0].[Nickname] IS NOT NULL THEN N'Officer'
+        END AS [Discriminator]
+        FROM [Gears] AS [g0]
+        LEFT JOIN [Officers] AS [o0] ON ([g0].[Nickname] = [o0].[Nickname]) AND ([g0].[SquadId] = [o0].[SquadId])
+    ) AS [t] ON [w].[OwnerFullName] = [t].[FullName]
+    LEFT JOIN [Cities] AS [c] ON [t].[AssignedCityName] = [c].[Name]
+) AS [t0] ON [g].[FullName] = [t0].[OwnerFullName]
+ORDER BY [g].[Nickname], [g].[SquadId], [t0].[Id], [t0].[Nickname], [t0].[SquadId], [t0].[Name0]");
+        }
+
         private void AssertSql(params string[] expected)
             => Fixture.TestSqlLoggerFactory.AssertBaseline(expected);
     }