Fix directories never being unwatched after deletion on Windows.

This causes all sorts of problems, but is also blocking the introduction of new,
more detailed signals, because the backend never correctly identified the removal.

The object handle appears to be woken up before the directory is actually
deleted, thus causing QFileInfo::exists() to return true, and not doing the
removal dance. This behaviour isn't exactly documented (as far as I was able to
find out), but also seems to happen consistently, and Chromium also contains
a comment noting a similar issue.

Task-number: QTBUG-2331
Change-Id: Icfb6219b78e688852d7863a666a0ffc31bb4d573
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/src/corelib/io/qfilesystemwatcher_win.cpp b/src/corelib/io/qfilesystemwatcher_win.cpp
index 715e16bc7e..5dc72251ca 100644
--- a/src/corelib/io/qfilesystemwatcher_win.cpp
+++ b/src/corelib/io/qfilesystemwatcher_win.cpp
@@ -361,8 +361,18 @@ void QWindowsFileSystemWatcherEngineThread::run()
                 if (handles.contains(handle)) {
                     // qDebug()<<"thread"<<this<<"Acknowledged handle:"<<at<<handle;
                     QHash<QString, QWindowsFileSystemWatcherEngine::PathInfo> &h = pathInfoForHandle[handle];
+                    bool fakeRemove = false;
+
                     if (!FindNextChangeNotification(handle)) {
                         const DWORD error = GetLastError();
+
+                        if (error == ERROR_ACCESS_DENIED) {
+                            // for directories, our object's handle appears to be woken up when the target of a
+                            // watch is deleted, before the watched thing is actually deleted...
+                            // anyway.. we're given an error code of ERROR_ACCESS_DENIED in that case.
+                            fakeRemove = true;
+                        }
+
                         qErrnoWarning(error, "%s", qPrintable(msgFindNextFailed(h)));
                     }
                     QMutableHashIterator<QString, QWindowsFileSystemWatcherEngine::PathInfo> it(h);
@@ -371,7 +381,10 @@ void QWindowsFileSystemWatcherEngineThread::run()
                         QString absolutePath = x.value().absolutePath;
                         QFileInfo fileInfo(x.value().path);
                         // qDebug() << "checking" << x.key();
-                        if (!fileInfo.exists()) {
+
+                        // i'm not completely sure the fileInfo.exist() check will ever work... see QTBUG-2331
+                        // ..however, I'm not completely sure enough to remove it.
+                        if (fakeRemove || !fileInfo.exists()) {
                             // qDebug() << x.key() << "removed!";
                             if (x.value().isDir)
                                 emit directoryChanged(x.value().path, true);