Fix idle watcher start race after PR #38

CompactGUI.Watcher/BackgroundCompactor.vb

@@ -64,24 +64,33 @@ Public Class BackgroundCompactor
  End Function
 
 
- Public Async Function StartCompactingAsync(folders As IEnumerable(Of WatchedFolder)) As Task(Of Boolean)
+ Public Async Function StartCompactingAsync(folders As IEnumerable(Of WatchedFolder), Optional startCancellationToken As CancellationToken = Nothing) As Task(Of Boolean)
  If IsCompactorActive Then Return False
+ If startCancellationToken.IsCancellationRequested Then Return False
 
  cancellationTokenSource?.Dispose()
  Dim runCancellation = New CancellationTokenSource()
  cancellationTokenSource = runCancellation
 
- WatcherLog.BackgroundCompactingStarted(_logger)
- IsCompactorActive = True
- isCompacting = True
- isCompactingPaused = False
-
  Dim currentProcess As Process = Process.GetCurrentProcess()
  Dim originalPriority As ProcessPriorityClass = ProcessPriorityClass.Normal
+ Dim priorityChanged As Boolean = False
 
  Try
+ WatcherLog.BackgroundCompactingStarted(_logger)
+ IsCompactorActive = True
+
+ 'Publish the initial pause state before marking the run active. If system activity
+ 'resumes before this point, the start token catches it below; if it resumes after
+ 'this point, PauseCompacting can safely record the pause for the new compactor.
+ isCompactingPaused = False
+ isCompacting = True
+
+ If startCancellationToken.IsCancellationRequested Then Return False
+
  originalPriority = currentProcess.PriorityClass
  currentProcess.PriorityClass = ProcessPriorityClass.Idle
+ priorityChanged = True
 
  For Each folder In folders.ToList
  If runCancellation.IsCancellationRequested Then Return False
@@ -187,13 +196,14 @@ Public Class BackgroundCompactor
  End If
  runCancellation.Dispose()
 
- Try
- currentProcess.PriorityClass = originalPriority
- Catch ex As Exception
- _logger.LogDebug(ex, "Unable to restore CompactGUI process priority.")
- Finally
- currentProcess.Dispose()
- End Try
+ If priorityChanged Then
+ Try
+ currentProcess.PriorityClass = originalPriority
+ Catch ex As Exception
+ _logger.LogDebug(ex, "Unable to restore CompactGUI process priority.")
+ End Try
+ End If
+ currentProcess.Dispose()
  End Try
  End Function
 
@@ -359,4 +369,4 @@ Public Class BackgroundCompactor
  isCompactingPaused = False ' Reset pause state on cancellation
  End Sub
 
-End Class
+End Class

CompactGUI.Watcher/Watcher.vb

@@ -26,6 +26,7 @@ Partial Public Class Watcher : Inherits ObservableRecipient : Implements IRecipi
  Private ReadOnly _parseWatchersSemaphore As New SemaphoreSlim(1, 1)
  Private ReadOnly _runWatcherSemaphore As New SemaphoreSlim(1, 1)
  Private _runCancellationTokenSource As CancellationTokenSource
+ Private _runIsIdleTriggered As Boolean
  Private ReadOnly _runCancellationLock As New Object
 
  Private ReadOnly _logger As ILogger(Of Watcher)
@@ -107,6 +108,7 @@ Partial Public Class Watcher : Inherits ObservableRecipient : Implements IRecipi
 
  SyncLock _runCancellationLock
  _runCancellationTokenSource = ownedCancellation
+ _runIsIdleTriggered = Not runAll
  End SyncLock
  IsRunning = True
 
@@ -128,7 +130,7 @@ Partial Public Class Watcher : Inherits ObservableRecipient : Implements IRecipi
  Return False
  End If
  If _parseWatchersSemaphore.CurrentCount <> 0 AndAlso (IsBackgroundCompactingEnabled OrElse runAll) Then
- Await BackgroundCompact(runAll) 'The background compactor manages its own cancellation token.
+ Await BackgroundCompact(runAll, If(runAll, CancellationToken.None, runToken)) 'The background compactor manages its own cancellation token once started.
  End If
  If runToken.IsCancellationRequested Then
  _logger.LogInformation("Watcher run cancelled by user.")
@@ -146,6 +148,7 @@ Partial Public Class Watcher : Inherits ObservableRecipient : Implements IRecipi
  SyncLock _runCancellationLock
  If Object.ReferenceEquals(_runCancellationTokenSource, ownedCancellation) Then
  _runCancellationTokenSource = Nothing
+ _runIsIdleTriggered = False
  End If
  End SyncLock
 
@@ -173,6 +176,20 @@ Partial Public Class Watcher : Inherits ObservableRecipient : Implements IRecipi
  BGCompactor.CancelCompacting()
  End Sub
 
+ Private Sub CancelIdleTriggeredRun()
+ Dim cancellation As CancellationTokenSource = Nothing
+
+ SyncLock _runCancellationLock
+ If _runIsIdleTriggered Then cancellation = _runCancellationTokenSource
+ End SyncLock
+
+ Try
+ cancellation?.Cancel()
+ Catch ex As ObjectDisposedException
+ 'The idle-triggered run completed between retrieving and cancelling its token source.
+ End Try
+ End Sub
+
 
 
  Private Sub OnSystemNotIdle(sender As Object, e As EventArgs)
@@ -183,6 +200,10 @@ Partial Public Class Watcher : Inherits ObservableRecipient : Implements IRecipi
  Dim bgMode = _settingsService.AppSettings.BackgroundModeSelection
  If bgMode <> BackgroundMode.IdleOnly Then Return
 
+ 'If activity resumes while an idle-triggered analysis is still preparing a background
+ 'run, cancel that pending transition. An already-running compactor is still paused below
+ 'so the existing idle resume behaviour remains intact.
+ CancelIdleTriggeredRun()
  BGCompactor.PauseCompacting()
  End Sub
 
@@ -449,13 +470,14 @@ Partial Public Class Watcher : Inherits ObservableRecipient : Implements IRecipi
 
  End Function
 
- Public Async Function BackgroundCompact(Optional runAll As Boolean = False) As Task
+ Public Async Function BackgroundCompact(Optional runAll As Boolean = False, Optional startCancellationToken As CancellationToken = Nothing) As Task
 
  Dim acquired = Await _parseWatchersSemaphore.WaitAsync(0)
  If Not acquired Then Return
 
  Try
 
+ If startCancellationToken.IsCancellationRequested Then Return
  If BGCompactor.IsCompactorActive Then Return
 
  RefreshWatchedFolderAvailability()
@@ -473,7 +495,8 @@ Partial Public Class Watcher : Inherits ObservableRecipient : Implements IRecipi
 
  If foldersToCompress.Any = 0 Then Return
 
- Await BGCompactor.StartCompactingAsync(foldersToCompress)
+ If startCancellationToken.IsCancellationRequested Then Return
+ Await BGCompactor.StartCompactingAsync(foldersToCompress, startCancellationToken)
 
  OnPropertyChanged(NameOf(TotalSaved))
  Finally
@@ -547,4 +570,4 @@ Partial Public Class Watcher : Inherits ObservableRecipient : Implements IRecipi
 
 
 
-End Class
+End Class