Fix QFileDialog::defaultSuffix on macOS

Don't prepend the default suffix to the NSSavePanel allowedFileTypes.
"If no extension is given by the user, the first item in the
allowedFileTypes array will be used as the extension for the save
panel." The user expects to get the suffix displayed to them in the
drop down filter, not the default suffix set by the developer.

Apply the default suffix if neither the user or the NSSavePanel
provide a suffix.

Task-number: QTBUG-66066
Change-Id: I64093b9f3178bd2377a7b65d6f23aed6214a4119
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

1 files changed, 8 insertions, 4 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoafiledialoghelper.mm b/src/plugins/platforms/cocoa/qcocoafiledialoghelper.mm
index 74148b7cbf..c1c7903766 100644
--- a/src/plugins/platforms/cocoa/qcocoafiledialoghelper.mm
+++ b/src/plugins/platforms/cocoa/qcocoafiledialoghelper.mm
@@ -418,6 +418,13 @@ static QString strippedText(QString s)
     } else {
         QList<QUrl> result;
         QString filename = QString::fromNSString([[mSavePanel URL] path]).normalized(QString::NormalizationForm_C);
+        const QString defaultSuffix = mOptions->defaultSuffix();
+        const QFileInfo fileInfo(filename);
+        // If neither the user or the NSSavePanel have provided a suffix, use
+        // the default suffix (if it exists).
+        if (fileInfo.suffix().isEmpty() && !defaultSuffix.isEmpty()) {
+                filename.append('.').append(defaultSuffix);
+        }
         result << QUrl::fromLocalFile(filename.remove(QLatin1String("___qt_very_unlikely_prefix_")));
         return result;
     }
@@ -445,10 +452,7 @@ static QString strippedText(QString s)
     [mPopUpButton setHidden:chooseDirsOnly];    // TODO hide the whole sunken pane instead?
 
     if (mOptions->acceptMode() == QFileDialogOptions::AcceptSave) {
-        QStringList ext = [self acceptableExtensionsForSave];
-        const QString defaultSuffix = mOptions->defaultSuffix();
-        if (!ext.isEmpty() && !defaultSuffix.isEmpty())
-            ext.prepend(defaultSuffix);
+        const QStringList ext = [self acceptableExtensionsForSave];
         [mSavePanel setAllowedFileTypes:ext.isEmpty() ? nil : qt_mac_QStringListToNSMutableArray(ext)];
     } else {
         [mOpenPanel setAllowedFileTypes:nil]; // delegate panel:shouldEnableURL: does the file filtering for NSOpenPanel