Handle overlapped restore when build is triggered

src/NuGet.Clients/NuGet.SolutionRestoreManager/GlobalSuppressions.cs

@@ -16,6 +16,7 @@
 [assembly: SuppressMessage("Build", "CA1303:Method 'Task SolutionRestoreWorker.PromoteTaskToActiveAsync(BackgroundRestoreOperation restoreOperation, CancellationToken token)' passes a literal string as parameter 'message' of a call to 'InvalidOperationException.InvalidOperationException(string message)'. Retrieve the following string(s) from a resource table instead: \"Failed promoting pending task.\".", Justification = "<Pending>", Scope = "member", Target = "~M:NuGet.SolutionRestoreManager.SolutionRestoreWorker.PromoteTaskToActiveAsync(NuGet.SolutionRestoreManager.SolutionRestoreWorker.BackgroundRestoreOperation,System.Threading.CancellationToken)~System.Threading.Tasks.Task")]
 [assembly: SuppressMessage("Build", "CA1031:Modify 'ScheduleRestoreAsync' to catch a more specific allowed exception type, or rethrow the exception.", Justification = "<Pending>", Scope = "member", Target = "~M:NuGet.SolutionRestoreManager.SolutionRestoreWorker.ScheduleRestoreAsync(NuGet.VisualStudio.SolutionRestoreRequest,System.Threading.CancellationToken)~System.Threading.Tasks.Task{System.Boolean}")]
 [assembly: SuppressMessage("Build", "CA1031:Modify 'StartBackgroundJobRunnerAsync' to catch a more specific allowed exception type, or rethrow the exception.", Justification = "<Pending>", Scope = "member", Target = "~M:NuGet.SolutionRestoreManager.SolutionRestoreWorker.StartBackgroundJobRunnerAsync(System.Threading.CancellationToken)~System.Threading.Tasks.Task{System.Boolean}")]
+[assembly: SuppressMessage("Build", "CA1031:Modify 'NotifyWaitingForBackgroundRestoreAsync' to catch a more specific allowed exception type, or rethrow the exception.", Justification = "Informational notification; must never fail the calling restore/build path.", Scope = "member", Target = "~M:NuGet.SolutionRestoreManager.SolutionRestoreWorker.NotifyWaitingForBackgroundRestoreAsync~System.Threading.Tasks.Task")]
 [assembly: SuppressMessage("Design", "CA1031:Do not catch general exception types", Justification = "<Pending>", Scope = "member", Target = "~M:NuGet.SolutionRestoreManager.SolutionRestoreJob.ExecuteAsync(NuGet.VisualStudio.SolutionRestoreRequest,NuGet.PackageManagement.VisualStudio.SolutionRestoreJobContext,NuGet.SolutionRestoreManager.RestoreOperationLogger,System.Collections.Generic.Dictionary{System.String,System.Object},System.Lazy{NuGet.SolutionRestoreManager.IVulnerabilitiesNotificationService},System.Threading.CancellationToken)~System.Threading.Tasks.Task{System.Boolean}")]
 [assembly: SuppressMessage("Design", "CA1031:Do not catch general exception types", Justification = "<Pending>", Scope = "member", Target = "~M:NuGet.SolutionRestoreManager.VsRestoreProgressEvents.EndProjectUpdate(System.String,System.Collections.Generic.IReadOnlyList{System.String})")]
 [assembly: SuppressMessage("Design", "CA1031:Do not catch general exception types", Justification = "<Pending>", Scope = "member", Target = "~M:NuGet.SolutionRestoreManager.VsRestoreProgressEvents.EndSolutionRestore(System.Collections.Generic.IReadOnlyList{System.String})")]

src/NuGet.Clients/NuGet.SolutionRestoreManager/Resources.resx

@@ -201,4 +201,8 @@ To prevent NuGet from restoring packages during build, open the Visual Studio Op
     <value>Fix with GitHub Copilot</value>
     <comment>Do not translate GitHub or Copilot</comment>
   </data>
+  <data name="WaitingForBackgroundRestore" xml:space="preserve">
+    <value>Waiting for NuGet package restore to finish before building...</value>
+    <comment>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</comment>
+  </data>
 </root>

src/NuGet.Clients/NuGet.SolutionRestoreManager/SolutionRestoreWorker.cs

@@ -422,6 +422,38 @@ public async Task<bool> RestoreAsync(SolutionRestoreRequest request, Cancellatio
 
                     using (var restoreOperation = new BackgroundRestoreOperation())
                     {
+                        // If a background restore is already running, the caller (typically a build)
+                        // would otherwise sit silently until that restore completes. Surface a hint
+                        // in the Build output window so the user knows why the build is paused.
+                        if (IsBusy && request.RestoreSource == RestoreOperationSource.OnBuild)
+                        {
+                            await NotifyWaitingForBackgroundRestoreAsync();
+
+                            // Ride on the in-flight restore instead of queuing another one behind it,
+                            // unless the build explicitly asked for a forced restore.
+                            if (!request.ForceRestore)
+                            {
+                                Task<bool> inflight = _activeRestoreTask;
+                                bool inflightSucceeded = await inflight.WithCancellation(token);
+                                if (inflightSucceeded)
+                                {
+                                    bool queueEmpty;
+                                    lock (_lockPendingRequestsObj)
+                                    {
+                                        // If there are no pending requests and _activeRestoreTask is the same one we awaited, then we have a valid restore for the purpose of build.
+                                        // If the tasks *don't* match, it means another restore has been kicked off since we awaited, so we should queue a new restore to be safe.
+                                        // This case should be rare.
+                                        queueEmpty = _pendingRequests.Value.Count == 0 && ReferenceEquals(_activeRestoreTask, inflight);
+                                    }
+
+                                    if (queueEmpty)
+                                    {
+                                        return true;
+                                    }
+                                }
+                            }
+                        }
+
                         await PromoteTaskToActiveAsync(restoreOperation, token);
                         var restoreTrackingData = GetRestoreTrackingData(
                             restoreReason: ImplicitRestoreReason.None,
@@ -714,6 +746,21 @@ private async Task<bool> ProcessRestoreRequestAsync(
             return restoreTask;
         }
 
+        private async Task NotifyWaitingForBackgroundRestoreAsync()
+        {
+            try
+            {
+                IOutputConsole buildConsole = await _outputConsoleProvider.Value.CreateBuildOutputConsoleAsync();
+                await buildConsole.ActivateAsync();
+                await buildConsole.WriteLineAsync(Resources.WaitingForBackgroundRestore);
+            }
+            catch (Exception ex)
+            {
+                // Notification is informational; never let it fail the restore/build path.
+                Logger.LogError(ex.ToString());
+            }
+        }
+
         private async Task PromoteTaskToActiveAsync(BackgroundRestoreOperation restoreOperation, CancellationToken token)
         {
             var pendingTask = restoreOperation.Task;
@@ -726,13 +773,19 @@ private async Task PromoteTaskToActiveAsync(BackgroundRestoreOperation restoreOp
                 // Grab local copy of active task
                 var activeTask = _activeRestoreTask;
 
-                // Await for the completion of the active *unbound* task
-                var cancelTcs = new TaskCompletionSource<bool>();
+                // Await for the completion of the active *unbound* task.
+                // Use RunContinuationsAsynchronously so cancellation callbacks don't run
+                // the continuation inline on the thread that triggered the cancellation.
+                var cancelTcs = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
                 using (var ctr = token.Register(() => cancelTcs.TrySetCanceled()))
                 {
                     await Task.WhenAny(activeTask, cancelTcs.Task);
                 }
 
+                // If the wait ended because of cancellation, surface it to the caller
+                // instead of silently leaving _activeRestoreTask unchanged.
+                token.ThrowIfCancellationRequested();
+
                 // Try replacing active task with the new one.
                 // Retry from the beginning if the active task has changed.
                 retry = Interlocked.CompareExchange(

src/NuGet.Clients/NuGet.SolutionRestoreManager/xlf/Resources.cs.xlf

@@ -134,6 +134,11 @@ Když nechcete, aby aplikace NuGet obnovovala balíčky během vytváření sest
         <target state="translated">Řešení není uložené. Než začnete spravovat balíčky NuGet, řešení uložte.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WaitingForBackgroundRestore">
+        <source>Waiting for NuGet package restore to finish before building...</source>
+        <target state="new">Waiting for NuGet package restore to finish before building...</target>
+        <note>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</note>
+      </trans-unit>
     </body>
   </file>
 </xliff>

src/NuGet.Clients/NuGet.SolutionRestoreManager/xlf/Resources.de.xlf

@@ -134,6 +134,11 @@ Wenn Sie verhindern möchten, dass NuGet Pakete während des Builds wiederherste
         <target state="translated">Die Projektmappe wurde nicht gespeichert. Bitte speichern Sie Ihre Projektmappe, bevor Sie NuGet-Pakete verwalten.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WaitingForBackgroundRestore">
+        <source>Waiting for NuGet package restore to finish before building...</source>
+        <target state="new">Waiting for NuGet package restore to finish before building...</target>
+        <note>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</note>
+      </trans-unit>
     </body>
   </file>
 </xliff>

src/NuGet.Clients/NuGet.SolutionRestoreManager/xlf/Resources.es.xlf

@@ -134,6 +134,11 @@ Para evitar que NuGet restaure paquetes durante la compilación, abra el cuadro
         <target state="translated">No se guardó la solución. Guarde la solución antes de administrar los paquetes NuGet.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WaitingForBackgroundRestore">
+        <source>Waiting for NuGet package restore to finish before building...</source>
+        <target state="new">Waiting for NuGet package restore to finish before building...</target>
+        <note>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</note>
+      </trans-unit>
     </body>
   </file>
 </xliff>

src/NuGet.Clients/NuGet.SolutionRestoreManager/xlf/Resources.fr.xlf

@@ -134,6 +134,11 @@ Pour empêcher NuGet de restaurer les packages lors de la génération, ouvrez l
         <target state="translated">La solution n'est pas enregistrée. Enregistrez votre solution avant de gérer des packages NuGet.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WaitingForBackgroundRestore">
+        <source>Waiting for NuGet package restore to finish before building...</source>
+        <target state="new">Waiting for NuGet package restore to finish before building...</target>
+        <note>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</note>
+      </trans-unit>
     </body>
   </file>
 </xliff>

src/NuGet.Clients/NuGet.SolutionRestoreManager/xlf/Resources.it.xlf

@@ -134,6 +134,11 @@ Per impedire che NuGet ripristini i pacchetti durante la compilazione, aprire la
         <target state="translated">Soluzione non salvata. Salvarla prima di gestire i pacchetti NuGet.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WaitingForBackgroundRestore">
+        <source>Waiting for NuGet package restore to finish before building...</source>
+        <target state="new">Waiting for NuGet package restore to finish before building...</target>
+        <note>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</note>
+      </trans-unit>
     </body>
   </file>
 </xliff>

src/NuGet.Clients/NuGet.SolutionRestoreManager/xlf/Resources.ja.xlf

@@ -134,6 +134,11 @@ NuGet がビルド中にパッケージを復元しないようにするには
         <target state="translated">ソリューションが保存されていません。ソリューションを保存してから NuGet パッケージを管理してください。</target>
         <note />
       </trans-unit>
+      <trans-unit id="WaitingForBackgroundRestore">
+        <source>Waiting for NuGet package restore to finish before building...</source>
+        <target state="new">Waiting for NuGet package restore to finish before building...</target>
+        <note>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</note>
+      </trans-unit>
     </body>
   </file>
 </xliff>

src/NuGet.Clients/NuGet.SolutionRestoreManager/xlf/Resources.ko.xlf

@@ -134,6 +134,11 @@ To prevent NuGet from restoring packages during build, open the Visual Studio Op
         <target state="translated">솔루션이 저장되지 않았습니다. NuGet 패키지를 관리하려면 솔루션을 저장하십시오.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WaitingForBackgroundRestore">
+        <source>Waiting for NuGet package restore to finish before building...</source>
+        <target state="new">Waiting for NuGet package restore to finish before building...</target>
+        <note>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</note>
+      </trans-unit>
     </body>
   </file>
 </xliff>

src/NuGet.Clients/NuGet.SolutionRestoreManager/xlf/Resources.pl.xlf

@@ -134,6 +134,11 @@ Aby uniemożliwić narzędziu NuGet przywracanie pakietów podczas kompilacji, o
         <target state="translated">Nie zapisano rozwiązania. Zapisz rozwiązanie zanim zaczniesz zarządzać pakietami NuGet.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WaitingForBackgroundRestore">
+        <source>Waiting for NuGet package restore to finish before building...</source>
+        <target state="new">Waiting for NuGet package restore to finish before building...</target>
+        <note>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</note>
+      </trans-unit>
     </body>
   </file>
 </xliff>

src/NuGet.Clients/NuGet.SolutionRestoreManager/xlf/Resources.pt-BR.xlf

@@ -134,6 +134,11 @@ Para impedir que o NuGet restaure pacotes durante o build, abra a caixa de diál
         <target state="translated">A solução não está salva. Salve sua solução antes de gerenciar os pacotes NuGet.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WaitingForBackgroundRestore">
+        <source>Waiting for NuGet package restore to finish before building...</source>
+        <target state="new">Waiting for NuGet package restore to finish before building...</target>
+        <note>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</note>
+      </trans-unit>
     </body>
   </file>
 </xliff>

src/NuGet.Clients/NuGet.SolutionRestoreManager/xlf/Resources.ru.xlf

@@ -134,6 +134,11 @@ To prevent NuGet from restoring packages during build, open the Visual Studio Op
         <target state="translated">Решение не сохранено. Сохраните свое решение, прежде чем управлять пакетами NuGet.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WaitingForBackgroundRestore">
+        <source>Waiting for NuGet package restore to finish before building...</source>
+        <target state="new">Waiting for NuGet package restore to finish before building...</target>
+        <note>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</note>
+      </trans-unit>
     </body>
   </file>
 </xliff>

src/NuGet.Clients/NuGet.SolutionRestoreManager/xlf/Resources.tr.xlf

@@ -134,6 +134,11 @@ NuGet'in derleme sırasında paketleri geri yüklemesini önlemek için Visual S
         <target state="translated">Çözüm kaydedilmedi. Lütfen NuGet paketlerini yönetmeden önce çözümünüzü kaydedin.</target>
         <note />
       </trans-unit>
+      <trans-unit id="WaitingForBackgroundRestore">
+        <source>Waiting for NuGet package restore to finish before building...</source>
+        <target state="new">Waiting for NuGet package restore to finish before building...</target>
+        <note>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</note>
+      </trans-unit>
     </body>
   </file>
 </xliff>

src/NuGet.Clients/NuGet.SolutionRestoreManager/xlf/Resources.zh-Hans.xlf

@@ -134,6 +134,11 @@ To prevent NuGet from restoring packages during build, open the Visual Studio Op
         <target state="translated">解决方案未保存。请先保存你的解决方案，然后再管理 NuGet 包。</target>
         <note />
       </trans-unit>
+      <trans-unit id="WaitingForBackgroundRestore">
+        <source>Waiting for NuGet package restore to finish before building...</source>
+        <target state="new">Waiting for NuGet package restore to finish before building...</target>
+        <note>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</note>
+      </trans-unit>
     </body>
   </file>
 </xliff>

src/NuGet.Clients/NuGet.SolutionRestoreManager/xlf/Resources.zh-Hant.xlf

@@ -134,6 +134,11 @@ To prevent NuGet from restoring packages during build, open the Visual Studio Op
         <target state="translated">未儲存解決方案。請先儲存解決方案，再管理 NuGet 套件。</target>
         <note />
       </trans-unit>
+      <trans-unit id="WaitingForBackgroundRestore">
+        <source>Waiting for NuGet package restore to finish before building...</source>
+        <target state="new">Waiting for NuGet package restore to finish before building...</target>
+        <note>Shown in the Build output window when a build is blocked on an already-running background NuGet restore.</note>
+      </trans-unit>
     </body>
   </file>
 </xliff>