use QFileDialog helper for playlist export

src/library/baseplaylistfeature.cpp

@@ -469,23 +469,22 @@ void BasePlaylistFeature::slotExportPlaylist() {
     // Open a dialog to let the user choose the file location for playlist export.
     // The location is set to the last used directory for import/export and the file
     // name to the playlist name.
-    QString fileFilter = tr("M3U Playlist (*.m3u)");
-    QString fileLocationInput = QFileDialog::getSaveFileName(
-            nullptr,
+    const QString fileLocation = checkedFilePathWithSelectedExtension(
             tr("Export Playlist"),
-            lastPlaylistDirectory.append("/").append(playlistName),
+            lastPlaylistDirectory.append("/").append(playlistName).append(".m3u"),
             tr("M3U Playlist (*.m3u);;M3U8 Playlist (*.m3u8);;"
                "PLS Playlist (*.pls);;Text CSV (*.csv);;Readable Text (*.txt)"),
-            &fileFilter);
-    QString fileLocation = filePathWithSelectedExtension(fileLocationInput, fileFilter);
-    // Exit method if user cancelled the open dialog.
+            tr("M3U Playlist (*.m3u)"));
+    // Exit method if the file name is empty because the user cancelled the save dialog.
     if (fileLocation.isEmpty()) {
         return;
     }
-    QFileInfo fileInfo(fileLocation);
+
     // Update the import/export playlist directory
+    QString fileDirectory(fileLocation);
+    fileDirectory.truncate(fileLocation.lastIndexOf(QDir::separator()));
     m_pConfig->set(kConfigKeyLastImportExportPlaylistDirectory,
-            ConfigValue(fileInfo.dir().absolutePath()));
+            ConfigValue(fileDirectory));
 
     // The user has picked a new directory via a file dialog. This means the
     // system sandboxer (if we are sandboxed) has granted us permission to this