QFile: add supportsMoveToTrash()

[ChangeLog][QtCore][QFile] Added supportsMoveToTrash() to check if Qt
supports moving files to trash in the current OS.

Fixes: QTBUG-127580
Change-Id: Ifb754f0e28774c20aa7cfffd17e6c951ffd9d9ff
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>

src/corelib/io/qfile.cpp

@@ -452,6 +452,22 @@ QFile::remove(const QString &fileName)
     return QFile(fileName).remove();
 }
 
+/*!
+    \since 6.9
+
+    Returns \c true if Qt supports moving files to a trash (recycle bin) in the
+    current operating system using the moveToTrash() function, \c false
+    otherwise. Note that this function returning \c true does not imply
+    moveToTrash() will succeed. In particular, this function does not check if
+    the user has disabled the functionality in their settings.
+
+    \sa moveToTrash()
+*/
+bool QFile::supportsMoveToTrash()
+{
+    return QFileSystemEngine::supportsMoveFileToTrash();
+}
+
 /*!
     \since 5.15
 
@@ -479,9 +495,12 @@ QFile::remove(const QString &fileName)
     themselves mount points).
 //! [move-to-trash-common]
 
-    \note On systems where the system API doesn't report the location of the file in the
+    \note On systems where the system API doesn't report the location of the
-    trash, fileName() will be set to the null string once the file has been moved. On
+    file in the trash, fileName() will be set to the null string once the file
-    systems that don't have a trash can, this function always returns false.
+    has been moved. On systems that don't have a trash can, this function
+    always returns \c false (see supportsMoveToTrash()).
+
+    \sa supportsMoveToTrash(), remove(), QDir::remove()
 */
 bool
 QFile::moveToTrash()

src/corelib/io/qfile.h

@@ -210,6 +210,7 @@ public:
     }
 #endif // QT_CONFIG(cxx17_filesystem)
 
+    static bool supportsMoveToTrash() Q_DECL_PURE_FUNCTION;
     bool moveToTrash();
     static bool moveToTrash(const QString &fileName, QString *pathInTrash = nullptr);
 #ifdef Q_QDOC

src/corelib/io/qfilesystemengine_mac.mm

@@ -20,6 +20,16 @@ QT_BEGIN_NAMESPACE
     Using Finder would also play the trash sound, which we don't want either in
     such a core API; applications that want that can play the sound themselves.
 */
+//static
+bool QFileSystemEngine::supportsMoveFileToTrash()
+{
+#ifdef Q_OS_MACOS // desktop macOS has a trash can
+    return true;
+#else // watch, tv, iOS don't have a trash can
+    return false;
+#endif
+}
+
 //static
 bool QFileSystemEngine::moveFileToTrash(const QFileSystemEntry &source,
                                         QFileSystemEntry &newLocation, QSystemError &error)

src/corelib/io/qfilesystemengine_p.h

@@ -127,6 +127,7 @@ public:
     static bool createLink(const QFileSystemEntry &source, const QFileSystemEntry &target, QSystemError &error);
 
     static bool copyFile(const QFileSystemEntry &source, const QFileSystemEntry &target, QSystemError &error);
+    static bool supportsMoveFileToTrash();
     static bool moveFileToTrash(const QFileSystemEntry &source, QFileSystemEntry &newLocation, QSystemError &error);
     static bool renameFile(const QFileSystemEntry &source, const QFileSystemEntry &target, QSystemError &error);
     static bool renameOverwriteFile(const QFileSystemEntry &source, const QFileSystemEntry &target, QSystemError &error);

src/corelib/io/qfilesystemengine_unix.cpp

@@ -1184,6 +1184,12 @@ bool QFileSystemEngine::createLink(const QFileSystemEntry &source, const QFileSy
 // see qfilesystemengine_mac.mm
 #elif defined(QT_BOOTSTRAPPED) || !defined(AT_FDCWD)
 // bootstrapped tools don't need this, and we don't want QStorageInfo
+//static
+bool QFileSystemEngine::supportsMoveFileToTrash()
+{
+    return false;
+}
+
 //static
 bool QFileSystemEngine::moveFileToTrash(const QFileSystemEntry &, QFileSystemEntry &,
                                         QSystemError &error)
@@ -1195,6 +1201,11 @@ bool QFileSystemEngine::moveFileToTrash(const QFileSystemEntry &, QFileSystemEnt
 /*
     Implementing as per https://specifications.freedesktop.org/trash-spec/trashspec-1.0.html
 */
+//static
+bool QFileSystemEngine::supportsMoveFileToTrash()
+{
+    return true;
+}
 
 namespace {
 struct FreeDesktopTrashOperation

src/corelib/io/qfilesystemengine_win.cpp

@@ -1772,6 +1772,12 @@ bool QFileSystemEngine::removeFile(const QFileSystemEntry &entry, QSystemError &
     return ret;
 }
 
+//static
+bool QFileSystemEngine::supportsMoveFileToTrash()
+{
+    return true;
+}
+
 /*
     If possible, we use the IFileOperation implementation, which allows us to determine
     the location of the object in the trash.

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

@@ -287,6 +287,7 @@ private slots:
 
     void reuseQFile();
 
+    void supportsMoveToTrash();
     void moveToTrash_data();
     void moveToTrash();
     void moveToTrashDuplicateName();
@@ -3969,6 +3970,27 @@ void tst_QFile::reuseQFile()
     }
 }
 
+void tst_QFile::supportsMoveToTrash()
+{
+    // enforce the result according to our current implementation details
+#if defined(Q_OS_WIN) || defined(Q_OS_MACOS)
+    // Windows and macOS: definitely supported
+    QVERIFY(QFile::supportsMoveToTrash());
+#elif defined(Q_OS_DARWIN)
+    // Other Darwin platforms: not supported
+    // (though Apple docs say trashItemAtURL is supported)
+    QVERIFY(!QFile::supportsMoveToTrash());
+#elif defined(Q_OS_ANDROID)
+    // Android: not supported (we get EACCES even for $HOME files)
+    QVERIFY(!QFile::supportsMoveToTrash());
+#elif !defined(AT_FDCWD)
+    // Unix platforms without the POSIX atfile support: not supported
+    QVERIFY(!QFile::supportsMoveToTrash());
+#else
+    QVERIFY(QFile::supportsMoveToTrash());
+#endif
+}
+
 void tst_QFile::moveToTrash_data()
 {
     QTest::addColumn<QString>("source");
@@ -4025,9 +4047,9 @@ void tst_QFile::moveToTrash_data()
 
 void tst_QFile::moveToTrash()
 {
-#if defined(Q_OS_ANDROID) or defined(Q_OS_WEBOS) or defined(Q_OS_VXWORKS)
+    if (!QFile::supportsMoveToTrash())
         QSKIP("This platform doesn't implement a trash bin");
-#endif
+
     QFETCH(QString, source);
     QFETCH(bool, create);
     QFETCH(bool, result);
@@ -4127,9 +4149,9 @@ void tst_QFile::moveToTrash()
 
 void tst_QFile::moveToTrashDuplicateName()
 {
-#if defined(Q_OS_ANDROID) || defined(Q_OS_WEBOS) || defined(Q_OS_VXWORKS)
+    if (!QFile::supportsMoveToTrash())
         QSKIP("This platform doesn't implement a trash bin");
-#endif
+
     QString origFileName = []() {
         QTemporaryFile temp(QDir::homePath() + "/tst_qfile.moveToTrashOpenFile.XXXXXX");
         temp.setAutoRemove(false);
@@ -4182,9 +4204,9 @@ void tst_QFile::moveToTrashOpenFile_data()
 
 void tst_QFile::moveToTrashOpenFile()
 {
-#if defined(Q_OS_ANDROID) || defined(Q_OS_WEBOS) || defined(Q_OS_VXWORKS)
+    if (!QFile::supportsMoveToTrash())
         QSKIP("This platform doesn't implement a trash bin");
-#endif
+
     QFETCH(bool, useStatic);
     QFETCH(bool, success);
     const QByteArrayView contents = "Hello, World\n";
@@ -4242,9 +4264,9 @@ void tst_QFile::moveToTrashOpenFile()
 
 void tst_QFile::moveToTrashSymlinkToFile()
 {
-#if defined(Q_OS_ANDROID) || defined(Q_OS_WEBOS) || defined(Q_OS_VXWORKS)
+    if (!QFile::supportsMoveToTrash())
         QSKIP("This platform doesn't implement a trash bin");
-#endif
+
     QTemporaryFile temp(QDir::homePath() + "/tst_qfile.moveToTrashSymlinkFile.XXXXXX");
     QVERIFY2(temp.open(), "Failed to create temporary file: " + temp.errorString().toLocal8Bit());
 
@@ -4281,9 +4303,9 @@ void tst_QFile::moveToTrashSymlinkToDirectory_data()
 
 void tst_QFile::moveToTrashSymlinkToDirectory()
 {
-#if defined(Q_OS_ANDROID) || defined(Q_OS_WEBOS) || defined(Q_OS_VXWORKS)
+    if (!QFile::supportsMoveToTrash())
         QSKIP("This platform doesn't implement a trash bin");
-#endif
+
     QFETCH(bool, appendSlash);
     QTemporaryDir temp(QDir::homePath() + "/tst_qfile.moveToTrashSymlinkDir.XXXXXX");
     QVERIFY2(temp.isValid(), "Failed to create temporary dir: " + temp.errorString().toLocal8Bit());
@@ -4315,9 +4337,9 @@ void tst_QFile::moveToTrashSymlinkToDirectory()
 
 void tst_QFile::moveToTrashXdgSafety()
 {
-#if defined(Q_OS_VXWORKS)
+    if (!QFile::supportsMoveToTrash())
         QSKIP("This platform doesn't implement a trash bin");
-#endif
+
 #if defined(Q_OS_WIN) || defined(Q_OS_DARWIN) || defined(Q_OS_ANDROID) || defined(Q_OS_WEBOS)
     QSKIP("This test is specific to XDG Unix systems");
 #else