Make Qt aware of NTFS Junctions on Windows

On NTFS, a junction point can be created and deleted by the mklink and
rmdir commands, respectively. If a directory is not identified
correctly as a junction, then applications will likely try to remove
it using recursive methods, leading to fatal data loss.

With this change, Qt can identify file system entries as junctions,
allowing applications to use the correct file system operation to
remove it.

The test needs to delay the cleaning up of junctions and files it
creates until the checks are complete; since they might fail and make
the test function return prematurely, use a scope guard.

[ChangeLog][QtCore][QFileInfo] Add QFileInfo::isJunction so that
applications can recognize NTFS file system entries as junctions

Task-number: QTBUG-75869
Change-Id: I3c208245afbd9fb7555515fb776ff63b133ca858
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

1 files changed, 14 insertions, 11 deletions

diff --git a/tests/auto/corelib/io/qfileinfo/tst_qfileinfo.cpp b/tests/auto/corelib/io/qfileinfo/tst_qfileinfo.cpp
index 0597a7d521..09ef0ea44f 100644
--- a/tests/auto/corelib/io/qfileinfo/tst_qfileinfo.cpp
+++ b/tests/auto/corelib/io/qfileinfo/tst_qfileinfo.cpp
@@ -1813,19 +1813,22 @@ void tst_QFileInfo::ntfsJunctionPointsAndSymlinks()
     QVERIFY2(creationResult == ERROR_SUCCESS, qPrintable(errorMessage));
 
     QFileInfo fi(path);
-    const bool actualIsSymLink = fi.isSymbolicLink();
+    auto guard = qScopeGuard([&fi, this]() {
+        // Ensure that junctions, mountpoints are removed. If this fails, do not remove
+        // temporary directory to prevent it from trashing the system.
+        if (fi.isDir()) {
+            if (!QDir().rmdir(fi.filePath())) {
+                qWarning("Unable to remove NTFS junction '%ls', keeping '%ls'.",
+                         qUtf16Printable(fi.fileName()),
+                         qUtf16Printable(QDir::toNativeSeparators(m_dir.path())));
+                m_dir.setAutoRemove(false);
+            }
+        }
+    });
     const QString actualSymLinkTarget = isSymLink ? fi.symLinkTarget() : QString();
     const QString actualCanonicalFilePath = isSymLink ? fi.canonicalFilePath() : QString();
-    // Ensure that junctions, mountpoints are removed. If this fails, do not remove
-    // temporary directory to prevent it from trashing the system.
-    if (fi.isDir()) {
-        if (!QDir().rmdir(fi.filePath())) {
-            qWarning("Unable to remove NTFS junction '%s'', keeping '%s'.",
-                     qPrintable(fi.fileName()), qPrintable(QDir::toNativeSeparators(m_dir.path())));
-            m_dir.setAutoRemove(false);
-        }
-    }
-    QCOMPARE(actualIsSymLink, isSymLink);
+    QCOMPARE(fi.isJunction(), resource.type == NtfsTestResource::Junction);
+    QCOMPARE(fi.isSymbolicLink(), isSymLink);
     if (isSymLink) {
         QCOMPARE(actualSymLinkTarget, linkTarget);
         QCOMPARE(actualCanonicalFilePath, canonicalFilePath);