Enable custom response support for callback functions

[oryba]

Based on issue #182 (Set a cookie from callback function).

With the following functionality callback function can return not only Dash components tree, but a customizable DashResponse with cookies, headers etc.

from dash import DashResponse
...

@app.callback(
    dash.dependencies.Output('content-block', 'children'),
    [dash.dependencies.Input('comparison-filter', 'value')])
def on_filter_change(comparison_value):
    response = DashResponse(html.Div('foo', className="test"))
    response.set_cookie('bar', 'baz')
    return response

[chriddyp]

Yeah, I like this solution. An alternative way to solve #182 would be to implement a Cookie Dash component. However, this solution is even more flexible by allowing things like headers.

[chriddyp]

missing "component" here? How about:

Flask Response extended with option to convert a regular response to
valid Dash json-encoded component.
Return a DashResponse object from a Dash callback in order to set
other properties of the response like headers or cookies

[chriddyp]

could we make this code a little bit more DRY by combining it in some way with these lines?

dash/dash/dash.py

Lines 494 to 506 in b61f0d3

	response = {
	'response': {
	'props': {
	output.component_property: output_value
	}
	}
	}
	return flask.Response(
	json.dumps(response,
	cls=plotly.utils.PlotlyJSONEncoder),
	mimetype='application/json'
	)

[chriddyp]

Looks good! In order for this to be merged, I'd like to see:

• The DRY component addressed
• A test

I think that a full integration test would be best suited here. Most of the integration tests are in the dash-renderer library (https://github.com/plotly/dash-renderer/blob/cef2313478ee2c37b91b9ef773bf6991bc96240e/tests/test_render.py). We should add an integration test to this library as well. I can make a separate PR to add a simple integration test and then we can rebase this PR off of that branch and add another integration test

[chriddyp]

I have merged #184 , so let's rebase this PR off of that and then add an integration test.

@oryba - Do you have the time to wrap up this PR from my comments above or would you like one of the core contributors to do so?

[oryba]

@chriddyp - unfortunately, now I have no time to do this, but I'm going to go back to this PR as soon as my current project will be finished

[jkseppan]

Hey @oryba - I'm interested in this feature and I'm willing to work on it, so if you don't mind I could try to add the requested test and do the refactoring?

[oryba]

Hey @jkseppan, sorry for the late answer. I don't mind, thanks for your help, glad to see someone has a chance to finalize this feature.

[alexcjohnson]

Superseded by #401 - thanks @oryba and @jkseppan! We still need to get the new one merged but I believe this older PR can be closed.