From a5ff3f6970377f9abc1d03a575018952788c228d Mon Sep 17 00:00:00 2001
From: Alexey Kulakov <alexey.kulakov@dataobjects.net>
Date: Tue, 21 Nov 2023 16:49:47 +0500
Subject: [PATCH 1/3] Returns results as expected

---
 Orm/Xtensive.Orm/Sorting/TopologicalSorter.cs | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/Orm/Xtensive.Orm/Sorting/TopologicalSorter.cs b/Orm/Xtensive.Orm/Sorting/TopologicalSorter.cs
index 0a30a6b5e0..7f5b097afb 100644
--- a/Orm/Xtensive.Orm/Sorting/TopologicalSorter.cs
+++ b/Orm/Xtensive.Orm/Sorting/TopologicalSorter.cs
@@ -183,7 +183,13 @@ public static IReadOnlyList<TNodeItem> SortToList<TNodeItem>(
     /// In this case <paramref name="nodes"/> will contain only the loop edges.</returns>
     public static IEnumerable<TNodeItem> Sort<TNodeItem, TConnectionItem>(
       List<Node<TNodeItem, TConnectionItem>> nodes,
-      out List<Node<TNodeItem, TConnectionItem>> loops) => SortInternal(nodes, out loops).sorted ?? Array.Empty<TNodeItem>();
+      out List<Node<TNodeItem, TConnectionItem>> loops)
+    {
+      var (sorted, count) = SortInternal(nodes, out loops) /* ?? Array.Empty<TNodeItem>()*/;
+      return (sorted is not null && count == 0)
+        ? Array.Empty<TNodeItem>()
+        : sorted;
+    }
 
     /// <summary>
     /// Sorts the specified oriented graph of the nodes in their topological order
@@ -199,9 +205,11 @@ public static IReadOnlyList<TNodeItem> SortToList<TNodeItem, TConnectionItem>(
       out List<Node<TNodeItem, TConnectionItem>> loops)
     {
       var (sorted, count) = SortInternal(nodes, out loops);
-      return (sorted is null || count == 0)
-        ? Array.Empty<TNodeItem>()
-        : sorted.ToArray(count);
+      return (sorted is null)
+        ? null
+        : count == 0
+          ? Array.Empty<TNodeItem>()
+          : sorted.ToArray(count);
     }
 
     /// <summary>

From 01b28dcf1d27ad2077a58a545538cdc00bc4aad4 Mon Sep 17 00:00:00 2001
From: Alexey Kulakov <alexey.kulakov@dataobjects.net>
Date: Tue, 21 Nov 2023 16:59:51 +0500
Subject: [PATCH 2/3] TopologicalSorter:Added annotations to return types

---
 Orm/Xtensive.Orm/Sorting/TopologicalSorter.cs | 26 ++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/Orm/Xtensive.Orm/Sorting/TopologicalSorter.cs b/Orm/Xtensive.Orm/Sorting/TopologicalSorter.cs
index 7f5b097afb..282ee03543 100644
--- a/Orm/Xtensive.Orm/Sorting/TopologicalSorter.cs
+++ b/Orm/Xtensive.Orm/Sorting/TopologicalSorter.cs
@@ -9,7 +9,9 @@
 using Xtensive.Collections;
 using System.Linq;
 using Xtensive.Core;
-
+using DotNetNotNullAttribute = System.Diagnostics.CodeAnalysis.NotNullAttribute;
+using JBNotNullAttribute = JetBrains.Annotations.NotNullAttribute;
+using JBCanBeNullAttribute = JetBrains.Annotations.CanBeNullAttribute;
 
 namespace Xtensive.Sorting
 {
@@ -29,6 +31,7 @@ public static class TopologicalSorter
     /// Sorting result, if there were no loops;
     /// otherwise, <see langword="null"/>.
     /// </returns>
+    [JBCanBeNull]
     public static IEnumerable<TNodeItem> Sort<TNodeItem>(IEnumerable<TNodeItem> items, Predicate<TNodeItem, TNodeItem> connector) =>
       Sort(items, connector, out List<Node<TNodeItem, object>> loops);
 
@@ -43,6 +46,7 @@ public static IEnumerable<TNodeItem> Sort<TNodeItem>(IEnumerable<TNodeItem> item
     /// Sorting result, if there were no loops;
     /// otherwise, <see langword="null"/>.
     /// </returns>
+    [JBCanBeNull]
     public static IReadOnlyList<TNodeItem> SortToList<TNodeItem>(IEnumerable<TNodeItem> items, Predicate<TNodeItem, TNodeItem> connector) =>
       SortToList(items, connector, out List<Node<TNodeItem, object>> loops);
 
@@ -59,6 +63,7 @@ public static IReadOnlyList<TNodeItem> SortToList<TNodeItem>(IEnumerable<TNodeIt
     /// otherwise, <see langword="null"/>.
     /// In this case <paramref name="loops"/> will contain only the loop edges.
     /// </returns>
+    [JBCanBeNull]
     public static IEnumerable<TNodeItem> Sort<TNodeItem>(
       IEnumerable<TNodeItem> items,
       Predicate<TNodeItem, TNodeItem> connector,
@@ -83,6 +88,7 @@ public static IEnumerable<TNodeItem> Sort<TNodeItem>(
     /// otherwise, <see langword="null"/>.
     /// In this case <paramref name="loops"/> will contain only the loop edges.
     /// </returns>
+    [JBCanBeNull]
     public static IReadOnlyList<TNodeItem> SortToList<TNodeItem>(
       IEnumerable<TNodeItem> items,
       Predicate<TNodeItem, TNodeItem> connector,
@@ -105,6 +111,8 @@ public static IReadOnlyList<TNodeItem> SortToList<TNodeItem>(
     /// <returns>
     /// Sorting result
     /// </returns>
+    [return: DotNetNotNull]
+    [JBNotNull]
     public static IEnumerable<TNodeItem> Sort<TNodeItem>(
       IEnumerable<TNodeItem> items,
       Predicate<TNodeItem, TNodeItem> connector,
@@ -121,6 +129,8 @@ public static IEnumerable<TNodeItem> Sort<TNodeItem>(
     /// <returns>
     /// Sorting result
     /// </returns>
+    [return: DotNetNotNull]
+    [JBNotNull]
     public static IReadOnlyList<TNodeItem> SortToList<TNodeItem>(
       IEnumerable<TNodeItem> items,
       Predicate<TNodeItem, TNodeItem> connector,
@@ -138,6 +148,8 @@ public static IReadOnlyList<TNodeItem> SortToList<TNodeItem>(
     /// <returns>
     /// Sorting result
     /// </returns>
+    [return: DotNetNotNull]
+    [JBNotNull]
     public static IEnumerable<TNodeItem> Sort<TNodeItem>(
       IEnumerable<TNodeItem> items,
       Predicate<TNodeItem, TNodeItem> connector,
@@ -161,6 +173,8 @@ public static IEnumerable<TNodeItem> Sort<TNodeItem>(
     /// <returns>
     /// Sorting result
     /// </returns>
+    [return: DotNetNotNull]
+    [JBNotNull]
     public static IReadOnlyList<TNodeItem> SortToList<TNodeItem>(
       IEnumerable<TNodeItem> items,
       Predicate<TNodeItem, TNodeItem> connector,
@@ -181,6 +195,7 @@ public static IReadOnlyList<TNodeItem> SortToList<TNodeItem>(
     /// <returns>Sorting result, if there were no loops;
     /// otherwise, <see langword="null" />. 
     /// In this case <paramref name="nodes"/> will contain only the loop edges.</returns>
+    [JBCanBeNull]
     public static IEnumerable<TNodeItem> Sort<TNodeItem, TConnectionItem>(
       List<Node<TNodeItem, TConnectionItem>> nodes,
       out List<Node<TNodeItem, TConnectionItem>> loops)
@@ -200,6 +215,7 @@ public static IEnumerable<TNodeItem> Sort<TNodeItem, TConnectionItem>(
     /// <returns>Sorting result, if there were no loops;
     /// otherwise, <see langword="null" />. 
     /// In this case <paramref name="nodes"/> will contain only the loop edges.</returns>
+    [JBCanBeNull]
     public static IReadOnlyList<TNodeItem> SortToList<TNodeItem, TConnectionItem>(
       List<Node<TNodeItem, TConnectionItem>> nodes,
       out List<Node<TNodeItem, TConnectionItem>> loops)
@@ -219,6 +235,8 @@ public static IReadOnlyList<TNodeItem> SortToList<TNodeItem, TConnectionItem>(
     /// <param name="nodes">The nodes.</param>
     /// <param name="removedEdges">Edges removed to make graph non-cyclic.</param>
     /// <returns>Sorting result.</returns>
+    [return: DotNetNotNull]
+    [JBNotNull]
     public static IEnumerable<TNodeItem> Sort<TNodeItem, TConnectionItem>(
       IEnumerable<Node<TNodeItem, TConnectionItem>> nodes,
       out List<NodeConnection<TNodeItem, TConnectionItem>> removedEdges) =>
@@ -231,6 +249,8 @@ public static IEnumerable<TNodeItem> Sort<TNodeItem, TConnectionItem>(
     /// <param name="nodes">The nodes.</param>
     /// <param name="removedEdges">Edges removed to make graph non-cyclic.</param>
     /// <returns>Sorting result.</returns>
+    [return: DotNetNotNull]
+    [JBNotNull]
     public static IReadOnlyList<TNodeItem> SortToList<TNodeItem, TConnectionItem>(
       IEnumerable<Node<TNodeItem, TConnectionItem>> nodes,
       out List<NodeConnection<TNodeItem, TConnectionItem>> removedEdges) =>
@@ -244,6 +264,8 @@ public static IReadOnlyList<TNodeItem> SortToList<TNodeItem, TConnectionItem>(
     /// <param name="removedEdges">Edges removed to make graph non-cyclic.</param>
     /// <param name="removeWholeNode">If <see langword="true"/> removes whole node in the case of loop, otherwise removes only one edge.</param>
     /// <returns>Sorting result.</returns>
+    [return: DotNetNotNull]
+    [JBNotNull]
     public static IEnumerable<TNodeItem> Sort<TNodeItem, TConnectionItem>(
         IEnumerable<Node<TNodeItem, TConnectionItem>> nodes,
         out List<NodeConnection<TNodeItem, TConnectionItem>> removedEdges,
@@ -258,6 +280,8 @@ public static IEnumerable<TNodeItem> Sort<TNodeItem, TConnectionItem>(
     /// <param name="removedEdges">Edges removed to make graph non-cyclic.</param>
     /// <param name="removeWholeNode">If <see langword="true"/> removes whole node in the case of loop, otherwise removes only one edge.</param>
     /// <returns>Sorting result.</returns>
+    [return: DotNetNotNull]
+    [JBNotNull]
     public static IReadOnlyList<TNodeItem> SortToList<TNodeItem, TConnectionItem>(
       IEnumerable<Node<TNodeItem, TConnectionItem>> nodes,
       out List<NodeConnection<TNodeItem, TConnectionItem>> removedEdges,

From 44069b369d7e34d5b3997b57d1e493fedd9e9a91 Mon Sep 17 00:00:00 2001
From: Alexey Kulakov <alexey.kulakov@dataobjects.net>
Date: Wed, 22 Nov 2023 19:16:25 +0500
Subject: [PATCH 3/3] Improve changelog

---
 ChangeLog/7.1.2_dev.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/ChangeLog/7.1.2_dev.txt b/ChangeLog/7.1.2_dev.txt
index e69de29bb2..78b15d4fc6 100644
--- a/ChangeLog/7.1.2_dev.txt
+++ b/ChangeLog/7.1.2_dev.txt
@@ -0,0 +1 @@
+[main] Addressed issue when cycles in Entity dependency graph were not detected
\ No newline at end of file