Javascript error when call back raises dash.exceptions.PreventUpdate()

Dash Python
1

In dash-renderer version 0.23.0 error Unexpected end of JSON input at line 696 in index.js when callback returns status 204 as a result of raise dash.exceptions.PreventUpdate()

2

I created a test case because you shouldn’t be raising an instance PreventUpdate, e.g. raise dash.exceptions.PreventUpdate(). You should be raising the Exception Class directly, e.g. raise dash.exceptions.PreventUpdate.

But the test case does indeed through the same error:

import dash
import dash_core_components as dcc
import dash_html_components as html

app = dash.Dash(__name__)
app.layout = html.Div([
    dcc.Interval(interval=1000, id='interval'),
    html.Div(id='dummy')
])


@app.callback(output=dash.dependencies.Output('dummy', 'children'),
              inputs=[dash.dependencies.Input('interval', 'n_intervals')])
def foo(n_intervals):
    raise dash.exceptions.PreventUpdate


if __name__ == '__main__':
    app.run_server()