fix: Check for nulls

CHANGELOG.md

@@ -6,6 +6,9 @@ All notable changes to **NCronJob** will be documented in this file. The project
 
 ## [Unreleased]
 
+### Fixed
+- Dispose could still lead to issues when an exception has thrown an exception.
+
 ## [2.8.5] - 2024-08-18
 
 ### Fixed

src/NCronJob/NotNullLinqExtensions.cs

@@ -0,0 +1,7 @@
+namespace NCronJob;
+
+internal static class NotNullLinqExtensions
+{
+    public static IEnumerable<T> WhereNotNull<T>(this IEnumerable<T?> source)
+        where T : class => source.Where(x => x is not null)!;
+}

src/NCronJob/Scheduler/QueueWorker.cs

@@ -13,7 +13,7 @@ internal sealed partial class QueueWorker : BackgroundService
     private readonly StartupJobManager startupJobManager;
     private readonly ILogger<QueueWorker> logger;
     private CancellationTokenSource? shutdown;
-    private readonly ConcurrentDictionary<string, Task> workerTasks = new();
+    private readonly ConcurrentDictionary<string, Task?> workerTasks = new();
     private readonly ConcurrentDictionary<string, bool> addingWorkerTasks = new();
     private volatile bool isDisposed;
 
@@ -49,6 +49,11 @@ public override async Task StopAsync(CancellationToken cancellationToken)
 
             foreach (var (jobType, task) in currentTasks)
             {
+                if (task is null)
+                {
+                    continue;
+                }
+
                 var taskEnded = task.IsCanceled || task.IsFaulted || task.IsCompleted;
                 if (taskEnded && workerTasks.TryRemove(jobType, out _))
                 {
@@ -101,7 +106,8 @@ protected override async Task ExecuteAsync(CancellationToken stoppingToken)
             CreateWorkerQueues(stopToken);
             jobQueueManager.QueueAdded += OnQueueAdded;  // this needs to come after we create the initial Worker Queues
 
-            await Task.WhenAll(workerTasks.Values).ConfigureAwait(false);
+            var tasks = workerTasks.Values.WhereNotNull();
+            await Task.WhenAll(tasks).ConfigureAwait(false);
         }
         catch (OperationCanceledException)
         {