File drop widget not working as expected

I’m using panel 1.8.5 with python 3.12 and having problems with the filedropper widget
Is there something obviously wrong here?

Symtoms: When I drop an xml file on the widget, there is a little progress bar like it’s trying to update, but the value of the widget never actually updates.


import panel as pn
import param

pn.extension(
    'filedropper',
    notifications=True,
    disconnect_notification='Connection lost, try reloading the page'
)

class MainWindow(pn.viewable.Viewer):

    def __init__(self):
        
        self.template = pn.template.MaterialTemplate(
            title = "XML Viewer"
        )
        
        self.main = pn.Column(scroll=True, sizing_mode="stretch_both")
        self.template.main.append(self.main)
        
        self.filedrop = pn.widgets.FileDropper(
            accepted_filetypes = ['.xml'],
            multiple = False,
        )
        self.button = pn.widgets.Button(name="Peek at filedrop state",
                                       button_type='primary')
        
        self.main.objects = [
            "# Drop a .xml file here",
            self.filedrop,
            self.button
        ]
        super().__init__()
        
    @param.depends("filedrop.value", watch=True)
    def on_file_upload(self, *args):
        assert False, "This callback is never reached"

    @param.depends("button.clicks", watch=True)
    def on_button_click(self, *args):
        if self.filedrop.value:
            pn.state.notifications.success("Dictionary keys {}" % self.filedrop.value.keys())
        else:
            pn.state.notifications.info("Dictionary is empty {}" % self.filedrop.value)

    def __panel__(self):
        return self.template

if pn.state.served:
    MainWindow().servable()

Can you file an issue on GitHub?

Were you able to reproduce the problem? I just wanted to make sure it wasn’t my code