[BUG] allow_duplicate not working with clientside_callback

[T4rk1n]

Thanks for allow_duplicate, it's a very nice addition.
Everything works well, except for clientside_callback. Support for clientside_callback was supposed to be? When adding allow_duplicate, an error occurs:

If you specify several ouputs(with and without allow_duplicate), then even though there will be an error, the value will be updated for ouput without allow_duplicate, but not for output with allow_duplicate, example:

Tell me, am I doing something wrong? Thank you very much.

Full code sample (with one callback, but I think this is enough to show the error):

import dash

from dash import Dash, html, Input, Output

app = Dash(__name__)
app.layout = html.Div(
    children=[
        html.Div(
            children=['Last pressed button: ', html.Span(id='span', children='empty')]
        ),
        html.Button(
            id='button-right',
            children='right'
        )
    ]
)

# NOT WORKING FOR "SPAN", BUT WARKING FOR BUTTON-RIGHT
dash.clientside_callback(
    """
    function(n_clicks){
        return ["right", `right ${n_clicks}`];
    }
    """,
    [
        Output('span', 'children', allow_duplicate=True),
        Output('button-right', 'children')
    ],
    Input('button-right', 'n_clicks'),
    prevent_initial_call=True
)

# WORKING EXAMPLE TO UNDERSTAND HOW IT SHOULD BE (THE ONLY DIFFERENCE IS THAT NO ALLOW_DUPLICATE)
# dash.clientside_callback(
#     """
#     function(n_clicks){
#         return ["right", `right ${n_clicks}`];
#     }
#     """,
#     [
#         Output('span', 'children'),
#         Output('button-right', 'children')
#     ],
#     Input('button-right', 'n_clicks'),
#     prevent_initial_call=True
# )

if __name__ == '__main__':
    app.run_server(debug=True, port=2414)

Originally posted by @FatHare in #2414 (comment)

[leo-smi]

Thank you guys for this fix. It's a great jump for dash.