StackView: fix crash when recursively removing items

This can happen when e.g. calling clear() in Component.onDestruction
in response to a pop() call.

The patch fixes the crash by warning and returning early.

If users really need to do this, the clear() call can be delayed:

    Component.onDestruction: {
        Qt.callLater(function() { stackView.clear(StackView.Immediate) })
    }

Change-Id: If3cf07495bb34b96089522f44c36976bd6c62492
Fixes: QTBUG-80353
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

2 files changed, 21 insertions, 0 deletions

diff --git a/src/quicktemplates2/qquickstackview.cpp b/src/quicktemplates2/qquickstackview.cpp
index f7a77374..4c314904 100644
--- a/src/quicktemplates2/qquickstackview.cpp
+++ b/src/quicktemplates2/qquickstackview.cpp
@@ -651,6 +651,13 @@ void QQuickStackView::push(QQmlV4Function *args)
 void QQuickStackView::pop(QQmlV4Function *args)
 {
     Q_D(QQuickStackView);
+    if (d->removingElements) {
+        d->warn(QStringLiteral("cannot pop while already in the process of removing elements"));
+        args->setReturnValue(QV4::Encode::null());
+        return;
+    }
+
+    QScopedValueRollback<bool> removingElements(d->removingElements, true);
     QScopedValueRollback<QString> rollback(d->operation, QStringLiteral("pop"));
     int argc = args->length();
     if (d->elements.count() <= 1 || argc > 2) {
@@ -806,6 +813,13 @@ void QQuickStackView::pop(QQmlV4Function *args)
 void QQuickStackView::replace(QQmlV4Function *args)
 {
     Q_D(QQuickStackView);
+    if (d->removingElements) {
+        d->warn(QStringLiteral("cannot replace while already in the process of removing elements"));
+        args->setReturnValue(QV4::Encode::null());
+        return;
+    }
+
+    QScopedValueRollback<bool> removingElements(d->removingElements, true);
     QScopedValueRollback<QString> rollback(d->operation, QStringLiteral("replace"));
     if (args->length() <= 0) {
         d->warn(QStringLiteral("missing arguments"));
@@ -902,6 +916,12 @@ void QQuickStackView::clear(Operation operation)
     if (d->elements.isEmpty())
         return;
 
+    if (d->removingElements) {
+        d->warn(QStringLiteral("cannot clear while already in the process of removing elements"));
+        return;
+    }
+
+    QScopedValueRollback<bool> removingElements(d->removingElements, true);
     if (operation != Immediate) {
         QQuickStackElement *exit = d->elements.pop();
         exit->removal = true;
diff --git a/src/quicktemplates2/qquickstackview_p_p.h b/src/quicktemplates2/qquickstackview_p_p.h
index c20ce776..b8c4b817 100644
--- a/src/quicktemplates2/qquickstackview_p_p.h
+++ b/src/quicktemplates2/qquickstackview_p_p.h
@@ -94,6 +94,7 @@ public:
     void depthChange(int newDepth, int oldDepth);
 
     bool busy = false;
+    bool removingElements = false;
     QString operation;
     QJSValue initialItem;
     QQuickItem *currentItem = nullptr;