Flask login_required decorator

decorators.py

from flask import request, g
from functools import wraps

def login_required(f=None, url="public.login", next=None):
    """
    Check if user is logged or redirect to a certain page.
    By default go to public login.
    """

    def outer_decorator(decorated_fn):
        """
        Takes the decorated function <fn>.
        """

        @wraps(decorated_fn)
        def inner_fn(*ted_args, **ted_kw):
            """
            Takes the decorated function params <ted_args> and <ted_kw>.

            <next> workaround thanks to <mitsuhiko>:
                > that does not work:
                >     if next is None:
                >         next = request.url
                > instead you need to do
                > the_next = next
                . if the_next is None:
                .     the_next = request.url
                > and then use the_next
                > or some other variable
                > next is from an outer scope
                > overriding that does not work in python 2 and would not be threadsafe in python 3
                > yay!
                > but why does "url" don't need that?
                > you are not overriding url
                > if you would do ``url += "foo"`` it would fail too
            """

            _next = next
            if _next is None:
                _next = request.url

            ## Redirect conditions
            if not isinstance(g.user, dict):
                return redirect_to(url, next=_next)

            return decorated_fn(*ted_args, **ted_kw)

        return inner_fn

    # <f> is None when this deco is called with params
    # if f is not None:
    if callable(f):
        return outer_decorator(f)
    return outer_decorator