Custom response support via callback_context

[alexcjohnson]

Closes #182 using an alternative approach to #401 as mentioned in #401 (comment) - instead of making your own response object to return in place of the callback result, this PR makes a global object available that you can modify inside the callback (setting cookies or headers, for example)

I put this inside the dash.callback_context object, rather than making a new dash.callback_response, mainly to take advantage of the nice protection @T4rk1n built in there against using these outside of the callback, or accidentally clobbering them.

Per the example in the test, usage is like:

@app.callback(Output('output', 'children'), [Input('input', 'value')])
def update_output(value):
    dash.callback_context.response.set_cookie(
        'dash cookie', value + ' - cookie')
    return value + ' - output'

cc @jkseppan @plotly/dash-core

[T4rk1n]

Why change? I find that less readable. The parens are unnecessary.

[alexcjohnson]

The previous one no longer fit in 80 characters when I fixed dash.callback -> dash.callback_context.

Also, not sure if this is a pylint version issue or what, but the previous way it was written I was getting mutually exclusive errors about indentation: CI required it to be one way, my local pylint required something else. This way they both agree is acceptable.

[alexcjohnson]

oh no sorry, the pylint issue was somewhere else. This was just >80 chars.

[T4rk1n]

💃

[chriddyp]

💃

[RodrigoMejias]

How can you check the value of a cookie without changing the value?

[ghost]

i landed here from SO question https://stackoverflow.com/a/48766639/4933053. how do i redirect within a callback, eg after some validation user should go from '/' to '/start' url. Can you please provide insighte, here or at SO.

[jouvin]

I have problem very similar to @hivemall, found the SO post that redirected to this issue indirectly. I don't see how this PR helps with the problem of redirection. Is it possible to get more details or a pointer to a page giving some explanations on how to implement a "login redirect" in a callback. Is it necessary to do this by talking to Falsk directly with an approach like suggested by https://community.plotly.com/t/how-protect-dash-routes-with-login-after-dash-1-0-release/25114/3?

[Tasselmi]

I have problem very similar to @hivemall, found the SO post that redirected to this issue indirectly. I don't see how this PR helps with the problem of redirection. Is it possible to get more details or a pointer to a page giving some explanations on how to implement a "login redirect" in a callback. Is it necessary to do this by talking to Falsk directly with an approach like suggested by https://community.plotly.com/t/how-protect-dash-routes-with-login-after-dash-1-0-release/25114/3?

hi brother, I have the same issue to integrate my app with google auth. Do you solve the problem?

[jouvin]

@Tasselmi yes, I managed to implement the authentication using the approach suggested by https://community.plotly.com/t/how-protect-dash-routes-with-login-after-dash-1-0-release/25114/3 to trigger the authentication when accessing the page, using a login_required decorator applied to the Flask view /<path:path> corresponding to the Dash-managed pages. the login_required function checks the actual path to decide if this page requires a login or not. If yes, it checks if a coockie exists and is valid, else it redirect to the login page. As a result the Dash callback associated with the page uses the coockie to retrieve the user information and do the required session management.

In my case, for managing the authentication, I use the flask-mulitpass module that allows to manage several backends. But I'm pretty sure you can do this with simpler backends like flask-ldap.

[lindorffs]

Anyone landing here after this post, for the love of god, this isn't a help form. Don't post here.

This is like, necroposting x10