From eff4df2bc5c53b077fc491eafbb01ba67a508f56 Mon Sep 17 00:00:00 2001
From: Andriy Svyryd <Andriy.Svyryd@microsoft.com>
Date: Fri, 15 Oct 2021 14:43:23 -0700
Subject: [PATCH] Configure the correct end as principal for self-ref
 collection with [ForeignKey]

Fixes #26364
---
 .../ForeignKeyAttributeConvention.cs          |  5 ++-
 .../Internal/InternalEntityTypeBuilder.cs     |  7 ++--
 .../DataAnnotationTestBase.cs                 | 42 +++++++++++++++++++
 3 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/src/EFCore/Metadata/Conventions/ForeignKeyAttributeConvention.cs b/src/EFCore/Metadata/Conventions/ForeignKeyAttributeConvention.cs
index f978752eb81..6694cc571e6 100644
--- a/src/EFCore/Metadata/Conventions/ForeignKeyAttributeConvention.cs
+++ b/src/EFCore/Metadata/Conventions/ForeignKeyAttributeConvention.cs
@@ -116,7 +116,10 @@ public virtual void ProcessEntityTypeAdded(
             foreach (var navigation in foreignKeyNavigations)
             {
                 entityTypeBuilder.HasRelationship(
-                    entityType, foreignKeyNavigations[0], setTargetAsPrincipal: true, fromDataAnnotation: true);
+                    entityType,
+                    navigation,
+                    setTargetAsPrincipal: navigation.GetMemberType().IsAssignableFrom(entityType.ClrType),
+                    fromDataAnnotation: true);
             }
         }
 
diff --git a/src/EFCore/Metadata/Internal/InternalEntityTypeBuilder.cs b/src/EFCore/Metadata/Internal/InternalEntityTypeBuilder.cs
index eaef2f1cb4f..3c7b60b1fa3 100644
--- a/src/EFCore/Metadata/Internal/InternalEntityTypeBuilder.cs
+++ b/src/EFCore/Metadata/Internal/InternalEntityTypeBuilder.cs
@@ -2825,14 +2825,15 @@ private static InternalIndexBuilder DetachIndex(Index indexToDetach)
             var navigationProperty = navigationToTarget?.MemberInfo;
             var inverseProperty = inverseNavigation?.MemberInfo;
             if (setTargetAsPrincipal == false
-                || (inverseNavigation == null
+                || (setTargetAsPrincipal == null
+                    && inverseNavigation == null
                     && navigationProperty?.GetMemberType().IsAssignableFrom(
                         targetEntityType.ClrType)
                     == false))
             {
-                // Target is expected to be dependent or only one nav specified and it can't be the nav to principal
+                // Target is dependent or only one nav specified and it can't be the nav to principal
                 return targetEntityType.Builder.HasRelationship(
-                    Metadata, null, navigationToTarget, !setTargetAsPrincipal, configurationSource, required);
+                    Metadata, inverseNavigation, navigationToTarget, setTargetAsPrincipal: true, configurationSource, required);
             }
 
             if (setTargetAsPrincipal == null
diff --git a/test/EFCore.Specification.Tests/DataAnnotationTestBase.cs b/test/EFCore.Specification.Tests/DataAnnotationTestBase.cs
index 47a595d67fc..c7ebab2e2e6 100644
--- a/test/EFCore.Specification.Tests/DataAnnotationTestBase.cs
+++ b/test/EFCore.Specification.Tests/DataAnnotationTestBase.cs
@@ -1429,6 +1429,48 @@ public class ProfileDetails12
             public int Id { get; set; }
         }
 
+        [ConditionalFact]
+        public virtual void Inverse_and_self_ref_ForeignKey()
+        {
+            var modelBuilder = CreateModelBuilder();
+
+            modelBuilder.Entity<MenuGroup>();
+
+            var model = Validate(modelBuilder);
+
+            var menuGroup = model.FindEntityType(typeof(MenuGroup));
+            var groupsNavigation = menuGroup.FindNavigation(nameof(MenuGroup.Groups));
+            Assert.Equal(nameof(MenuGroup.FkGroup), groupsNavigation.ForeignKey.Properties.Single().Name);
+
+            var pagesNavigation = menuGroup.FindNavigation(nameof(MenuGroup.Pages));
+            Assert.Equal(nameof(MenuPage.FkGroupNavigation), pagesNavigation.Inverse.Name);
+            Assert.Equal(nameof(MenuPage.FkGroup), pagesNavigation.ForeignKey.Properties.Single().Name);
+        }
+
+        protected class MenuGroup
+        {
+            public Guid Id { get; set; }
+            public Guid? FkGroup { get; set; }
+
+            [InverseProperty(nameof(MenuPage.FkGroupNavigation))]
+            public virtual ICollection<MenuPage> Pages { get; set; }
+
+            [ForeignKey(nameof(FkGroup))]
+            public virtual ICollection<MenuGroup> Groups { get; set; }
+        }
+
+        protected class MenuPage
+        {
+            public Guid Id { get; set; }
+
+            public Guid? FkGroup { get; set; }
+
+            [ForeignKey(nameof(FkGroup))]
+            [InverseProperty(nameof(MenuGroup.Pages))]
+            public virtual MenuGroup FkGroupNavigation { get; set; }
+        }
+
+
         [ConditionalFact]
         public virtual void Multiple_self_ref_ForeignKeys_on_navigations()
         {