Ability to access the wrapped function for testing or to import into other programs

[chriddyp]

i.e.

@app.callback(...)
def update_graph(value):
    ...

it would be helpful to be able to access or call update_graph unwrapped. Currently, if you call update_graph, you'll call the wrapped version.

Three use cases:

1. Ability to unit test update_graph
2. Ability to call update_graph in e.g. Jupyter
3. Ability to call update_graph in other programs

I believe this violates how decorators work, so we might have to expose some method on the function like .inner so the caller would call e.g. update_graph.inner(value)

[alexcjohnson]

Actually we don't do anything with the return value of the decorator right now - internal to the decorator we add the wrapped function to the callback map:

dash/dash/dash.py

Line 941 in 3ec55b5

self.callback_map[callback_id]["callback"] = add_context

But then we return the wrapped function:

dash/dash/dash.py

Line 943 in 3ec55b5

return add_context

I suspect if instead we just return func everyone will be happy 🤞 (aside from any of our own tests that use the wrapped function - those will have to reference app.callback_map instead)

[alexcjohnson]

Closed in #1839

[shea-parkes]

Just dropping a note a couple years later for others that might land here:

We were actually expecting that we'd have to do myfunc.__wrapped__ in our unit tests type work. But since the current dash.callback code returns the original func (instead of the wrapped version it created), you can just work directly with the function as-if it wasn't decorated with dash.callback().

We basically overthought things.