[BUG] customdata is missing in clickData for Scatter objects

[limbothai]

My environment

dash                          2.9.2
dash-bootstrap-components     1.4.1
dash-core-components          2.0.0
dash-html-components          2.0.0
dash-table                    5.0.0

The bug

This bug is very similar to another one that was fixed last year, described here https://github.com/plotly/dash/issues/1663 .

I want to retrieve a custom identifier (a string) linked to a scatter object, by clicking on it. As per documentation of go.Scatter, customdata is meant for this task, but it is not behaving as expected.

Here is a sample code:

import dash
from dash import html,dcc
from dash.dependencies import Input, Output
import plotly.express as px
import plotly.graph_objects as go
import json

app = dash.Dash(__name__)

fig=go.Figure(data=[go.Scatter(x=[0, 1, 1, 0, 0],y=[1, 1, 2, 2, 1],mode='lines',fill='toself',customdata=["obj-1"]),
                    go.Scatter(x=[3, 4, 4, 3, 3],y=[4, 4, 5, 5, 4],mode='lines',fill='toself',customdata=["obj-2"])])


app.layout = html.Div([
    dcc.Graph(id="scatter-object", figure=fig),
    dcc.Textarea(id='textArea')
])

@app.callback(
    Output("textArea", "value"), 
     Input('scatter-object', 'clickData'))
def handleClick(clickData):
    return json.dumps(clickData,indent=2)

app.run_server(debug=True)

Expected behavior

clickData should contain the customdata defined in the constructor of go.Scatter. Unfortunately it doesn't.

Screenshots

As one can see on the screenshot below, when clicking on an object, clickData contains its point values, but not the custom data information:

[nickmelnikov82]

Upgrading to the latest versions of plotly and dash will fix the issue when clickData does not contain customdata. The new versions have fixed this issue, and you will get the expected information from customdata when you click on a graph.