Don't unnecessarily delete OS files in folders

src/base/utils/fs.cpp

@@ -99,9 +99,13 @@ QString Utils::Fs::folderName(const QString &filePath)
 }
 
 /**
- * This function will first remove system cache files, e.g. `Thumbs.db`,
- * `.DS_Store`. Then will try to remove the whole tree if the tree consist
- * only of folders
+ * This function will first check if there are only system cache files, e.g. `Thumbs.db`,
+ * `.DS_Store` and/or only temp files that end with '~', e.g. `filename~`.
+ * If they are the only files it will try to remove them and delete the folder.
+ * This action will be performed for each subfolder starting from the deepest folder.
+ * There is an inherent race condition here. A file might appear after it is checked
+ * that only the above mentioned "useless" files exist but before the whole folder is removed.
+ * In this case, the folder will not be removed but the "useless" files will be deleted.
  */
 bool Utils::Fs::smartRemoveEmptyFolderTree(const QString &path)
 {
@@ -110,12 +114,12 @@ bool Utils::Fs::smartRemoveEmptyFolderTree(const QString &path)
 
     const QStringList deleteFilesList = {
         // Windows
-        "Thumbs.db",
-        "desktop.ini",
+        QLatin1String("Thumbs.db"),
+        QLatin1String("desktop.ini"),
         // Linux
-        ".directory",
+        QLatin1String(".directory"),
         // Mac OS
-        ".DS_Store"
+        QLatin1String(".DS_Store")
     };
 
     // travel from the deepest folder and remove anything unwanted on the way out.
@@ -128,18 +132,25 @@ bool Utils::Fs::smartRemoveEmptyFolderTree(const QString &path)
               , [](const QString &l, const QString &r) { return l.count('/') > r.count('/'); });
 
     for (const QString &p : asConst(dirList)) {
-        // remove unwanted files
-        for (const QString &f : deleteFilesList) {
-            forceRemove(p + f);
-        }
-
-        // remove temp files on linux (file ends with '~'), e.g. `filename~`
         const QDir dir(p);
+        // A deeper folder may have not been removed in the previous iteration
+        // so don't remove anything from this folder either.
+        if (!dir.isEmpty(QDir::Dirs | QDir::NoDotAndDotDot))
+            continue;
+
         const QStringList tmpFileList = dir.entryList(QDir::Files);
-        for (const QString &f : tmpFileList) {
-            if (f.endsWith('~'))
+
+        // deleteFilesList contains unwanted files, usually created by the OS
+        // temp files on linux usually end with '~', e.g. `filename~`
+        const bool hasOtherFiles = std::any_of(tmpFileList.cbegin(), tmpFileList.cend(), [&deleteFilesList](const QString &f)
+        {
+            return (!f.endsWith('~') && !deleteFilesList.contains(f, Qt::CaseInsensitive));
+        });
+        if (hasOtherFiles)
+            continue;
+
+        for (const QString &f : tmpFileList)
             forceRemove(p + f);
-        }
 
         // remove directory if empty
         dir.rmdir(p);