Obtain all callback relationship data on the server-side without going through the `app` instance

[CNFeffery]

I'm testing the development of additional features related to the query and analysis of global callback function relationships based on the new hooks.devtool(introduced starting from Dash 3.2.0). How can I obtain all known callback function relationship data on the server-side without relying on a specific app instance, since it's impossible to directly obtain the app instance in the hooks project.

At present, I only know a skillful method to obtain relevant information through javascript in the browser-side environment:

dash_stores[0].getState().dependenciesRequest.content

[T4rk1n]

You can get a reference to the app like:

    current_app: Dash = None

    @hooks.setup()
    def cloud_app_setup(app):
        nonlocal current_app
        current_app = app

There might be instances where there is multiple apps for a process, but they are rare. In which case the app could be put a dict like: apps[app.name] = app.

But this is inconvenient when adding hooks.callback or hooks.layout, we should add a new context to get the app. I think something like:

from dash import app_context, hooks

@hooks.callback(...)
def hook_cb(...):
    app: Dash = app_context.get()
    ...

so it's not linked to the callback_ctx and can be set in a flask before_request for all the routes to be set.

[T4rk1n]

There is already:

dash/dash/_get_app.py

Line 6 in fca6388

def get_app():

But I don't think it handle multi dash app, maybe refactor the function to use a context instead so it's more robust.

[T4rk1n]

And the callback info is in app._callback_list

[CNFeffery]

@T4rk1n Considering various possible scenarios, is it true that the complete callback information obtained using  dash_stores[0].getState().dependenciesRequest.content  on the browser side is the most comprehensive.

[T4rk1n]

@T4rk1n Considering various possible scenarios, is it true that the complete callback information obtained using dash_stores[0].getState().dependenciesRequest.content on the browser side is the most comprehensive.

No, there is an extra mapping of the outputs in store.getState().graphs.callbacks from the dependencies request.