QTreeView with QAbstractItemModel collapses root node when selecting anything for the first time

[martintan]

In PyQt5, I have a QTreeView with a custom class extending QAbstractItemModel. I have a problem I can't seem to solve, or find the root cause, where only on the first time I select any node, the entire QTreeView collapses. When I expand the root node after, it no longer has that problem for the succeeding selections.

At the beginning, my nodes have no children. I'm fetching the data / children from the server only if the node is expanded (using QAbstractItemView.expanded signal). I overrided QAbstractItemModel.insertRow and I call the recommended functions beginInsertRows and endInsertRows before and after I update the model data. I also emit the layoutToBeChanged and layoutChanged signals.

I can't seem to figure out what causes that selection issue.

This is my code for fetching data for nodes that are expanded:

class FileTree(QTreeView):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        # Class for fetching data from server
        self.folders = Folders()
        self.setup_ui()
        self.populate()
        self.notify = NotificationDialog()

    def populate(self):
        ret, root_folders = self.folders.root()
        if ret:
            self.tree_model = TreeModel(root_folders)
            self.setModel(self.tree_model)

    def populate_folder_node(self, node, index):
        ret, children = self.folders.children(node.data['folder_id'])
        if ret:
            self.tree_model.removeRows(0, len(node.children), index)
            # Update view via model signal (Source: https://stackoverflow.com/a/51587327/5575610)
            self.tree_model.layoutAboutToBeChanged.emit()
            for i, data in enumerate(children):
                self.tree_model.insertRow(Node(data), i, index)
            self.tree_model.layoutChanged.emit()

    def on_node_expanded(self, index: QModelIndex):
        if not index.isValid():
            return
        node = index.internalPointer()
        node.opened = True
        self.populate_folder_node(node, index)

[martintan]

Resolved: It was a bug in my code