QFile::moveToTrash: work with relative file paths on Windows

The system APIs expect an absolute "display name" of the file path,
so make it absolute.

The test was overly tolerant in accepting failure, as a QStorageInfo
initialized with a file path that doesn't exist is invalid, and thus
always different from the QStorageInfo of the home directory. Fix the
test to compare only valid QStorageInfo objects, and postpone the check
until the file we want to move has been created.

[ChangeLog][QtCore][QFile] moveToTrash supports relative file paths
on Windows

Change-Id: I94c8cd40c60fde469e38f76a98f867f20c6a0b15
Fixes: QTBUG-84015
Pick-to: 5.15
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/corelib/io/qfilesystemengine_win.cpp

@@ -1548,8 +1548,8 @@ bool QFileSystemEngine::moveFileToTrash(const QFileSystemEntry &source,
                                         QFileSystemEntry &newLocation, QSystemError &error)
 {
 #ifndef Q_OS_WINRT
-    // we need the "display name" of the file, so can't use nativeFilePath
-    const QString sourcePath = QDir::toNativeSeparators(source.filePath());
+    // we need the "display name" of the file, so can't use nativeAbsoluteFilePath
+    const QString sourcePath = QDir::toNativeSeparators(absoluteName(source).filePath());
 
     /*
         Windows 7 insists on showing confirmation dialogs and ignores the respective

tests/auto/corelib/io/qfile/tst_qfile.cpp

@@ -3714,13 +3714,6 @@ void tst_QFile::moveToTrash()
     QFETCH(bool, create);
     QFETCH(bool, result);
 
-    /* This test makes assumptions about the file system layout
-       which might be wrong - moveToTrash may fail if the file lives
-       on a file system that is different from the home file system, and
-       has no .Trash directory.
-    */
-    const bool mayFail = QStorageInfo(source) != QStorageInfo(QDir::home());
-
 #if defined(Q_OS_WINRT)
     QSKIP("WinRT does not have a trash", SkipAll);
 #endif
@@ -3749,9 +3742,20 @@ void tst_QFile::moveToTrash()
             sourceFile.remove();
         }
     };
+
+    ensureFile(source, create);
+
+    /* This test makes assumptions about the file system layout
+       which might be wrong - moveToTrash may fail if the file lives
+       on a file system that is different from the home file system, and
+       has no .Trash directory.
+    */
+    const QStorageInfo sourceStorage(source);
+    const bool mayFail = sourceStorage.isValid()
+                      && QStorageInfo(source) != QStorageInfo(QDir::home());
+
     // non-static version
     {
-        ensureFile(source, create);
         QFile sourceFile(source);
         const bool success = sourceFile.moveToTrash();