[BUG] Using pattern matching ALL for running argument fails when the list is empty

[logankopas]

When using pattern matching for the running argument (ex: running=[(Output({'type': 'loading', 'id': ALL}, 'display'), 'show', 'hide')]), if there are no components on the page dash throws the error: state.paths.objs[idKey] is undefined

Describe your context
Please provide us your environment, so we can easily reproduce the issue.

• replace the result of pip list | grep dash below

dash               3.0.4

Describe the bug

When using pattern matching for the running argument (ex: running=[(Output({'type': 'loading', 'id': ALL}, 'display'), 'show', 'hide')]), if there are no components on the page dash throws the error: state.paths.objs[idKey] is undefined

Expected behavior

No error, no side updates (since there are no components)

Minimum Working Example

import dash
from dash import Dash, html, dcc, callback, Output, Input, Patch, ALL, callback_context
import time
import random


app = Dash(use_pages=True, pages_folder="")

home_page_layout = html.Div([
    dcc.Loading(
        html.Div(id={'type':'scorecard', 'id': 'home1'}),
        id={'type': 'loading', 'id': 'home1'}
    ),
    dcc.Loading(
        html.Div(id={'type':'scorecard', 'id': 'home2'}),
        id={'type': 'loading', 'id': 'home2'}
    )
])
other_page_layout = html.Div('Other')

dash.register_page('home', path='/', layout=home_page_layout)
dash.register_page('blank', path='/blank', layout=other_page_layout)

app.layout = html.Div([
    dcc.Store(id='data'),
    html.H1(children='Title of Dash App', style={'textAlign':'center'}),
    html.Div([
        html.Span([
            dcc.Link(f"{page['name']} - {page['path']}", href=page["relative_path"]), ' | '
        ]) for page in dash.page_registry.values()
    ]),
    html.Button('Reload Data', id='reload-data'),
    dash.page_container
])


@callback(
    Output('data', 'data'),
    Input('reload-data', 'n_clicks'),
    prevent_initial_call=True,
    running=[(Output({'type': 'loading', 'id': ALL}, 'display'), 'show', 'hide')]
)
def get_data(n_clicks):
    time.sleep(3)
    return random.randint(0, 10)

@callback(
    Output({'type': 'scorecard', 'id': 'home1'}, 'children'),
    Input('data', 'data'),
    prevent_initial_call=True
)
def scorecard1(data):
    return f'Data: {data}'

@callback(
    Output({'type': 'scorecard', 'id': 'home2'}, 'children'),
    Input('data', 'data'),
    prevent_initial_call=True
)
def scorecard2(data):
    return f'Data squared: {data * data}'

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

In this example, pressing the "Reload Data" button on the second page (/blank) throws the error as the loading elements are all on the first page

[fgoudreault]

Thanks for the report, I was playing around for the first time with pattern-matching callbacks in a running argument and didn't know where this cryptic error from dash clientside was coming from 😅.