plotly / plotly/dash

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

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bug P3
Dominant language
Python
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Description

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

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the minimum working example and reproduce the failure by opening /blank and pressing “Reload Data” while the matching loading components are on the home page. Done means the callback produces no error and makes no side updates when the pattern match finds no components.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
frontend
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
38/100

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