[release/6.0] SQLite: Don't modify collection while enumerating inside ReclaimLeakedConnections

src/Microsoft.Data.Sqlite.Core/SqliteConnectionPool.cs

@@ -5,6 +5,7 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Linq;
 using System.Threading;
 
 namespace Microsoft.Data.Sqlite
@@ -157,17 +158,17 @@ private bool ReclaimLeakedConnections()
         {
             var leakedConnectionsFound = false;
 
+            List<SqliteConnectionInternal> leakedConnections;
             lock (_connections)
             {
-                foreach (var connection in _connections)
-                {
-                    if (connection.Leaked)
-                    {
-                        Return(connection);
+                leakedConnections = _connections.Where(c => c.Leaked).ToList();
+            }
 
-                        leakedConnectionsFound = true;
-                    }
-                }
+            foreach (var connection in leakedConnections)
+            {
+                leakedConnectionsFound = true;
+
+                Return(connection);
             }
 
             return leakedConnectionsFound;

test/Microsoft.Data.Sqlite.Tests/SqliteConnectionFactoryTest.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Data;
 using System.IO;
+using System.Runtime.CompilerServices;
 using SQLitePCL;
 using Xunit;
 
@@ -218,6 +219,26 @@ public void EnableExtensions_doesnt_bleed_across_connections()
             Assert.Equal(disabledMessage, ex.Message);
         }
 
+        [Fact]
+        public void Clear_works_when_connection_leaked()
+        {
+            using var connection = new SqliteConnection(ConnectionString);
+            connection.Open();
+
+            LeakConnection();
+            GC.Collect();
+
+            SqliteConnection.ClearPool(connection);
+
+            [MethodImpl(MethodImplOptions.NoInlining)]
+            static void LeakConnection()
+            {
+                // Don't add using!
+                var connection = new SqliteConnection(ConnectionString);
+                connection.Open();
+            }
+        }
+
         public void Dispose()
         {
             SqliteConnection.ClearAllPools();