Flask-Login breaks when my decorator accepts param

Question

Thanks to what I learned from this question, I've been able to make a Flask-Login process with a endpoint like this:

@app.route('/top_secret')
@authorize
@login_required
def top_secret():
    return render_template("top_secret.html")

and (for now) a completely pass-through "authorize" decorator:

from functools import wraps

def authorize(func):
    @wraps(func)
    def newfunc(*args, **kwargs):
        return func(*args, **kwargs)
    return newfunc

The @wraps(func) call allows Flask to find the endpoint that it's looking for. So far, so good.

But I want to pass an group name to the "authorize" process, and things go bad when I try to make a decorator that accepts incoming parameters. This seems to be the correct syntax, unless I'm mistaken:

from functools import wraps

def authorize(group=None):
    def real_authorize(func):
        @wraps(func)
        def newfunc(*args, **kwargs):
            return func(*args, **kwargs)
        return newfunc
    return real_authorize

But once again the error appears as Flask is unable to figure out the 'top-secret' endpoint:

werkzeug.routing.BuildError: Could not build url for endpoint 'top_secret'.

I thought perhaps it needed @wraps(authorize) decoration right above def real_authorize(func), but that did nothing to help.

Can someone help me figure out where my @wraps are going wrong?

Answer 1

Decorating a function is equivalent to re-binding the name to the result of calling the decorator with the function.

@authorize
def top_secret():
    ...

# is equivalent to

def top_secret():
    ...
top_secret = authorize(top_secret)

The function you've written is a decorator factory: you call it, with an optional argument, to get a decorator.

@authorize()
def top_secret():
    ...

# is equivalent to

def top_secret():
    ...
top_secret = authorize()(top_secret)

Currently, you're passing top_secret as the group argument to the factory, so you're never actually creating a route. Since there's no route, there's no url to build either.