Pattern Matching Callbacks Together with Partial Updates

Dash Python
1

Hello everyone!

Long time fan, first time writer.

I have a question regarding pattern matching callbacks together with Partial Updates.

To illustrate the problem, I adapted the example from Partial Property Updates | Dash for Python Documentation | Plotly to also add a new output item for each dropdown and connect the callbacks using MATCH instead of ALL:

from dash import Dash, dcc, html, Input, Output, MATCH, Patch, callback, ctx

app = Dash(__name__, suppress_callback_exceptions=True)

app.layout = html.Div(
    [
        html.Button("Add Filter", id="add-filter-2", n_clicks=0),
        html.Div(id="dropdown-container-2", children=[]),
        html.Div(id="dropdown-container-output-2"),
    ]
)


@callback(
    Output("dropdown-container-2", "children"),
    Output("dropdown-container-output-2", "children"),
    Input("add-filter-2", "n_clicks"),
)
def display_dropdowns(n_clicks):
    patched_children = Patch()
    new_dropdown = dcc.Dropdown(
        ["NYC", "MTL", "LA", "TOKYO"],
        id={"type": "filter-dropdown-2", "index": n_clicks},
    )
    patched_children.append(new_dropdown)
    patched_outputs = Patch()
    new_output = html.Div(
        id={"type": "generated-output", "index": n_clicks},
    )
    patched_outputs.append(new_output)
    return patched_children, patched_outputs


@callback(
    Output({"type": "generated-output", "index": MATCH}, "children"),
    Input({"type": "filter-dropdown-2", "index": MATCH}, "value"),
)
def display_output(value):
    print(ctx.triggered_id)
    return html.Div("Dropdown {} = {}".format(value, value))


if __name__ == "__main__":
    app.run(debug=True)

Running this and adding new dropdowns results in triggering all callbacks every time a new item is appended.
E.g. the output of the ctx.triggered_id print statements grows for every added item:

{'index': 0, 'type': 'filter-dropdown-2'}
{'index': 1, 'type': 'filter-dropdown-2'}
{'index': 2, 'type': 'filter-dropdown-2'}
{'index': 3, 'type': 'filter-dropdown-2'}

So it seems that whenever a partial update appends a new item, all patern-matching callbacks are triggered, whereas all existing ones did not change.
Is there any way to prevent this?

Thanks in advance
Andre