flask redirect from closure - redirect

Question

def check_login(func):
"""Check if user is logged in."""
def decorator(*args, **kwargs):
if not login_session_test():
print ("Not logged in - redirect to /login")
flash ("Well that was wrong. Chicken winner. No more dinner.")
return redirect(url_for('login'))
print ("Logged in, do what needs to be done.")
return func(*args, **kwargs)
return decorator
#check_login
#app.route("/sacred/secret/stuff", methods=['GET'])
def funfunfun():
return "Super fun"
It never redirects to /login but gives some garbage like page.
Swapping the #/closure order yields:
AssertionError: View function mapping is overwriting an existing endpoint function: decorator
I am not yet fully pythonized.

Answer 1

Your decorator order is incorrect, and you are not copying across the function name to the wrapper function.
Use this order:
#app.route("/sacred/secret/stuff", methods=['GET'])
#check_login
def funfunfun():
return "Super fun"
Otherwise the undecorated function is registered for the view.
Use #functools.wraps() to have various pieces of metadata copied over from the original wrapped function to the wrapper that replaces it:
from functools import wraps
def check_login(func):
"""Check if user is logged in."""
#wraps(func)
def decorator(*args, **kwargs):
if not login_session_test():
print ("Not logged in - redirect to /login")
flash ("Well that was wrong. Chicken winner. No more dinner.")
return redirect(url_for('login'))
print ("Logged in, do what needs to be done.")
return func(*args, **kwargs)
return decorator
Routes need an endpoint name, and if you don't specify one explicitly, Flask uses the name of the function (from functionobj.__name__). But your decorator wrapper object has the name decorator, so if you use the decorator more than once Flask complains that it already has used that endpoint name.
#functools.wraps() copies across the __name__ attribute, so now your decorator wrapper is also called funfunfun, whereas another decorated route function gets to keep its name too.