Django message framework and login_required

Question

I'm using the Django Message Framework to show messages to users as well as the @login_required decorator on one of my views. So if a user tries to access a certain view without being logged in, they get kicked to the login page. How would I go about adding an error message to the login page saying "In order to do ... you must be logged in". I can't add it in the view like you normally would because the non-logged in user would never get to there.

Answer 1

It took me a while to figure out a nice way of doing this, but I think I have an implementation, based on the answer of Daniel Roseman

First thing I did was creating a decorator that sets messages when a user is not logged in, exactly like login_required.

So I wrote login_required_message:

try:     from functools import wraps except ImportError:     from django.utils.functional import wraps  # Python 2.4 fallback.  from django.utils.decorators import available_attrs  from django.contrib import messages  default_message = "Please log in, in order to see the requested page."  def user_passes_test(test_func, message=default_message):     """     Decorator for views that checks that the user passes the given test,     setting a message in case of no success. The test should be a callable     that takes the user object and returns True if the user passes.     """     def decorator(view_func):         @wraps(view_func, assigned=available_attrs(view_func))         def _wrapped_view(request, *args, **kwargs):             if not test_func(request.user):                 messages.error(request, message)             return view_func(request, *args, **kwargs)         return _wrapped_view     return decorator  def login_required_message(function=None, message=default_message):     """     Decorator for views that checks that the user is logged in, redirecting     to the log-in page if necessary.     """     actual_decorator = user_passes_test(         lambda u: u.is_authenticated, #fixed by removing ()         message=message,     )     if function:         return actual_decorator(function)     return actual_decorator         

With this implementation you can now annotate your view methods like this:

from decorators import login_required_message from django.contrib.auth.decorators import login_required  @login_required_message(message="You should be logged in, in order to see the index!") @login_required def index(request):     pass 

Now first the message will be set, then the redirect will be performed.

However I actually don't want to add the login_required_message decorator everywhere. It would be much nicer to have only one decorator. So lets chain them (simply add this to your decorator.py file after login_required_message):

from django.contrib.auth import REDIRECT_FIELD_NAME from django.contrib.auth.decorators import login_required  def login_required_message_and_redirect(function=None, redirect_field_name=REDIRECT_FIELD_NAME, login_url=None, message=default_message):      if function:         return login_required_message(             login_required(function, redirect_field_name, login_url),             message         )      return lambda deferred_function: login_required_message_and_redirect(deferred_function, redirect_field_name, login_url, message) 

It took me a while to figure out this last line; but lambda's to the rescue!

Now you can replace the two decorators with only login_required_message_and_redirect: Almost there! Since actually I want to use this new login_required_message-method everywhere, I add a monkey-patch for login_required and it is used everywhere (again add to the bottom of the decorators.py file)!

from django.contrib.auth import decorators setattr(decorators, 'login_required', login_required_message_and_redirect) 

which allows me to call:

# a message will appear, since login_required is monkey patched @login_required def logout(request):     pass   # or customize the message per view @login_required(message="You should be logged in message! Available after monkey patch") def index(request):     pass 

Answer 2

There's not any obvious way. The only thing that springs to mind is to write your own version of the decorator that puts a message into the session before redirecting, then get the login template to display the message from the session.

You'd need to use the code in django.contrib.auth.decorators, in particular the user_passes_test function - the bit to add the message would have to go before return HttpResponseRedirect.