Add n_clicks to annotationClickData so that callback is fired when clicking on an annotation multiple times

[chriddyp]

Currently dash' verifies that the old props != the new props before firing a callback.

Line: https://github.com/plotly/dash/blame/dev/dash-renderer/src/TreeContainer.js#L126
Commit: plotly/dash@05908b2

This behavior prevents multiple clicks on the same annotation from firing the callback.

Dash's comparison may not be the right behavior, but this PR will at least get around the issue.

[alexcjohnson]

@chriddyp while we investigate a deeper fix, were you able to test out the proposed workaround using circular callbacks plotly/dash#1525 to reset annotationClickData when it's consumed?

[chriddyp]

This workaround does indeed work 👍🏼

import dash
from dash.dependencies import Input, Output
import dash_core_components as dcc
import dash_html_components as html
import json
app = dash.Dash(__name__)
app.layout = html.Div([
    dcc.Graph(id='graph', figure={
        'data': [{'y': [2, 1, 5]}],
        'layout': {
            'annotations': [{
                'text': 'click me',
                'x': 0.5, 'y': 0.5, 'xref': 'paper', 'yref': 'paper',
                'captureevents': True
            }]
        }
    }),
    html.Pre(id='output')
])
@app.callback(
    Output('output', 'children'), 
    Output('graph', 'clickAnnotationData'), 
    Input('graph', 'clickAnnotationData'))
def update_output(c):
    print(c)
    return [json.dumps(c, indent=4), None]
app.run_server(debug=True)