From c73f4a301330f1c0ef7cfd5d7a8050dab775dcec Mon Sep 17 00:00:00 2001
From: Christopher Jolly <chris-jolly_au@hotmail.com>
Date: Wed, 1 Nov 2023 01:11:11 +0800
Subject: [PATCH] Add the onDelete convention so that we match the behaviour of
 sql server when configuring self-referencing skip navigations. Ends up
 configured as ClientCascade instead of Cascade

---
 .../Conventions/JetConventionSetBuilder.cs    |   2 +
 .../Conventions/JetOnDeleteConvention.cs      | 135 ++++++++++++++++++
 2 files changed, 137 insertions(+)
 create mode 100644 src/EFCore.Jet/Metadata/Conventions/JetOnDeleteConvention.cs

diff --git a/src/EFCore.Jet/Metadata/Conventions/JetConventionSetBuilder.cs b/src/EFCore.Jet/Metadata/Conventions/JetConventionSetBuilder.cs
index 8b768e4..29e155d 100644
--- a/src/EFCore.Jet/Metadata/Conventions/JetConventionSetBuilder.cs
+++ b/src/EFCore.Jet/Metadata/Conventions/JetConventionSetBuilder.cs
@@ -30,6 +30,8 @@ namespace Microsoft.EntityFrameworkCore.Metadata.Conventions
             conventionSet.Add(new RelationalMaxIdentifierLengthConvention(64, Dependencies, RelationalDependencies));
             conventionSet.Add(new JetIndexConvention(Dependencies, RelationalDependencies, _sqlGenerationHelper));
 
+            conventionSet.Replace<CascadeDeleteConvention>(
+                new JetOnDeleteConvention(Dependencies, RelationalDependencies));
             conventionSet.Replace<StoreGenerationConvention>(
                 new JetStoreGenerationConvention(Dependencies, RelationalDependencies));
             conventionSet.Replace<ValueGenerationConvention>(
diff --git a/src/EFCore.Jet/Metadata/Conventions/JetOnDeleteConvention.cs b/src/EFCore.Jet/Metadata/Conventions/JetOnDeleteConvention.cs
new file mode 100644
index 0000000..57b21cd
--- /dev/null
+++ b/src/EFCore.Jet/Metadata/Conventions/JetOnDeleteConvention.cs
@@ -0,0 +1,135 @@
+// ReSharper disable once CheckNamespace
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+using Microsoft.EntityFrameworkCore.Metadata.Conventions.Infrastructure;
+
+namespace Microsoft.EntityFrameworkCore.Metadata.Conventions;
+
+/// <summary>
+///     A convention that configures the OnDelete behavior for foreign keys on the join entity type for
+///     self-referencing skip navigations
+/// </summary>
+public class JetOnDeleteConvention : CascadeDeleteConvention,
+    ISkipNavigationForeignKeyChangedConvention,
+    IEntityTypeAnnotationChangedConvention
+{
+    public JetOnDeleteConvention(
+        ProviderConventionSetBuilderDependencies dependencies,
+        RelationalConventionSetBuilderDependencies relationalDependencies)
+        : base(dependencies)
+    {
+        RelationalDependencies = relationalDependencies;
+    }
+
+    /// <summary>
+    ///     Relational provider-specific dependencies for this service.
+    /// </summary>
+    protected virtual RelationalConventionSetBuilderDependencies RelationalDependencies { get; }
+
+    /// <inheritdoc />
+    public virtual void ProcessSkipNavigationForeignKeyChanged(
+        IConventionSkipNavigationBuilder skipNavigationBuilder,
+        IConventionForeignKey? foreignKey,
+        IConventionForeignKey? oldForeignKey,
+        IConventionContext<IConventionForeignKey> context)
+    {
+        if (foreignKey is not null && foreignKey.IsInModel)
+        {
+            foreignKey.Builder.OnDelete(GetTargetDeleteBehavior(foreignKey));
+        }
+    }
+
+    /// <inheritdoc />
+    protected override DeleteBehavior GetTargetDeleteBehavior(IConventionForeignKey foreignKey)
+    {
+        var deleteBehavior = base.GetTargetDeleteBehavior(foreignKey);
+        if (deleteBehavior != DeleteBehavior.Cascade)
+        {
+            return deleteBehavior;
+        }
+
+        return ProcessSkipNavigations(foreignKey.GetReferencingSkipNavigations()) ?? deleteBehavior;
+    }
+
+    private DeleteBehavior? ProcessSkipNavigations(IEnumerable<IConventionSkipNavigation> skipNavigations)
+    {
+        var skipNavigation = skipNavigations
+            .FirstOrDefault(
+                s => s.Inverse != null
+                    && IsMappedToSameTable(s.DeclaringEntityType, s.TargetEntityType));
+
+        if (skipNavigation != null)
+        {
+            var isFirstSkipNavigation = IsFirstSkipNavigation(skipNavigation);
+            if (!isFirstSkipNavigation)
+            {
+                skipNavigation = skipNavigation.Inverse!;
+            }
+
+            var inverseSkipNavigation = skipNavigation.Inverse!;
+
+            var deleteBehavior = DefaultDeleteBehavior(skipNavigation);
+            var inverseDeleteBehavior = DefaultDeleteBehavior(inverseSkipNavigation);
+
+            if (deleteBehavior == DeleteBehavior.Cascade
+                && inverseDeleteBehavior == DeleteBehavior.Cascade
+                && !(inverseSkipNavigation.ForeignKey!.GetDeleteBehaviorConfigurationSource() == ConfigurationSource.Explicit
+                    && inverseSkipNavigation.ForeignKey!.DeleteBehavior != DeleteBehavior.Cascade))
+            {
+                deleteBehavior = DeleteBehavior.ClientCascade;
+            }
+
+            skipNavigation.ForeignKey!.Builder.OnDelete(deleteBehavior);
+            inverseSkipNavigation.ForeignKey!.Builder.OnDelete(inverseDeleteBehavior);
+
+            return isFirstSkipNavigation ? deleteBehavior : inverseDeleteBehavior;
+        }
+
+        return null;
+
+        DeleteBehavior DefaultDeleteBehavior(IConventionSkipNavigation conventionSkipNavigation)
+            => conventionSkipNavigation.ForeignKey!.IsRequired ? DeleteBehavior.Cascade : DeleteBehavior.ClientSetNull;
+
+        bool IsMappedToSameTable(IConventionEntityType entityType1, IConventionEntityType entityType2)
+        {
+            var tableName1 = entityType1.GetTableName();
+            var tableName2 = entityType2.GetTableName();
+
+            return tableName1 != null
+                && tableName2 != null
+                && tableName1 == tableName2
+                && entityType1.GetSchema() == entityType2.GetSchema();
+        }
+
+        bool IsFirstSkipNavigation(IConventionSkipNavigation navigation)
+            => navigation.DeclaringEntityType != navigation.TargetEntityType
+                ? string.Compare(navigation.DeclaringEntityType.Name, navigation.TargetEntityType.Name, StringComparison.Ordinal) < 0
+                : string.Compare(navigation.Name, navigation.Inverse!.Name, StringComparison.Ordinal) < 0;
+    }
+
+    /// <inheritdoc />
+    public virtual void ProcessEntityTypeAnnotationChanged(
+        IConventionEntityTypeBuilder entityTypeBuilder,
+        string name,
+        IConventionAnnotation? annotation,
+        IConventionAnnotation? oldAnnotation,
+        IConventionContext<IConventionAnnotation> context)
+    {
+        if (name is RelationalAnnotationNames.TableName or RelationalAnnotationNames.Schema)
+        {
+            ProcessSkipNavigations(entityTypeBuilder.Metadata.GetDeclaredSkipNavigations());
+
+            foreach (var foreignKey in entityTypeBuilder.Metadata.GetDeclaredForeignKeys())
+            {
+                var deleteBehavior = GetTargetDeleteBehavior(foreignKey);
+                if (foreignKey.DeleteBehavior != deleteBehavior)
+                {
+                    foreignKey.Builder.OnDelete(deleteBehavior);
+                }
+            }
+        }
+    }
+}