Returning a custom Python model from a slot?

I'm trying to setup up a details window for a List.

I've already set something up where clicking on an item creates a new Window with Qt.createComponent, and information from the clicked item is passed to this new Window. I then try to assign the model of a nested List to the return value of a Python function (decorated with @Slot). This function instantiates a new custom model (subclassed from QAbstractListModel) based on the information passed in, and returns it.

My problem is, when I click on an item to launch the window, it throws this error:

file:///home/cassidy/Projects/portmod/portmod/_gui/Manage/PackageDetailsWindow.qml:50: TypeError: Property 'get_local_flags_model' of object Config(0x55907ace9e70) is not a function

Here's my Python function. This is stored in a Config class that's passed to the QML context as config:

@QtCore.Slot(str, result=QtCore.QObject)  # type: ignore
def get_local_flags_model(self, atom: str) -> FlagListModel:
    return FlagListModel(get_local_flags(Atom(atom)))

Here's my custom model:

from typing import Any, Dict, Tuple, Union

from PySide6.QtCore import QAbstractListModel, QModelIndex, QPersistentModelIndex, Qt


class FlagListModel(QAbstractListModel):
    def __init__(self, use_flags: Dict[str, Tuple[bool, str]]):
        super().__init__()

        self._data = use_flags

    def rowCount(self) -> int:
        return len(self._data)

    def data(
        self,
        index: Union[QModelIndex, QPersistentModelIndex],
        role: int,
    ) -> Any:
        if role == Qt.ItemDataRole.DisplayRole:
            return list(self._data.keys())[index.row()]
        elif role == Qt.ItemDataRole.CheckStateRole:
            state = list(self._data.values())[index.row()][0]
            if state:
                return Qt.CheckState.Checked
            else:
                return Qt.CheckState.Unchecked

My details window:

import QtQuick 6.0
import QtQuick.Controls.Basic 6.0
import QtQuick.Layouts 6.0

Window {
    id: detailsWindow

    property string atom

    title: detailsWindow.atom
    height: root.height / 1.5
    width: root.width / 1.5

    ColumnLayout {
        anchors.fill: parent
        anchors.margins: 10

        // TODO: Don't show if there are no USE flags
        GroupBox {
            title: "USE Flags"
            Layout.fillWidth: true
            Layout.fillHeight: true
            ListView {
                id: useListView
                clip: true
                model: config.get_local_flags_model(detailsWindow.atom);
                width: parent.width
                height: parent.height
                delegate: CheckDelegate {
                    text: modelData
                    checkState: model.check
                    width: ListView.view.width - 20
                }
                
                ScrollBar.vertical: ScrollBar {}            
            }
        }
    }
}

1. Seems like you registered config instance as a context property.
   This is not best-practice instead use qmlRegisterSingletonInstance

2. You tried to "property bind" a Slot, AFAIK this is not feasible,you can set the model property when to component is completed. i.e

ListView{
    id: useListView
    Component.onCompleted: {useListView.model = config.get_local_flags_model(detailsWindow.atom);}

}

Note that generaly you would have pre-initialized it in the model, but I don't know what is your use-case so it is hard to tell.

sidenote: I see that you use annotations, if you are interested I have a library that creates slots based on annotations (and many other hacks), that is mypy compatible.