Sunday, April 29, 2018

Re: Decorator function argument woes

Yes. I don't see it in the documentation for login_required, but I believe it's so that you can do something like this in your urls.py:

urlpatterns = [
    url(r'^example$', login_required(views.example)),
]

That might be an older way of using the decorator? IDK for sure. But you can see from the code for login_required that the "test" is always a lambda that checks if the user is authenticated; there's no option to override it. If the "function" parameter is present then it is used as the function be wrapped, not the test being done.

On Mon, Apr 30, 2018 at 1:24 AM, Mike Dewhirst <miked@dewhirst.com.au> wrote:
On 30/04/2018 3:35 PM, Stephen J. Butler wrote:
@login_required doesn't take a test function. You need to use @user_passes_test directly.

Thank you Stephen.

I thought I'd start another thread to ask about my use case of being able to require login or not depending on whether the content needed a login or not ... but ... just as I was thinking about it I had another look at login_required and thought I'd ask one more question.

Its signature is ...

def login_required(function=None, redirect_field_name=REDIRECT_FIELD_NAME, login_url=None):

Are you saying that function is the the view function?

M


On Mon, Apr 30, 2018 at 12:26 AM, Mike Dewhirst <miked@dewhirst.com.au <mailto:miked@dewhirst.com.au>> wrote:

    I'm pretty sure this is a not-understanding-python problem rather
    than a Django problem but here goes ...

    In a (FBV) view I'm trying to pass a function in to the
    login_required decorator. My function is called 'is_login_needed'
    and I want the login_required decorator to effectively switch
    itself off if login is not needed.

    The scenario is on-line training and if the training instruction
    has questions with scores then obviously the user needs to login.
    On the other hand if it is simply a demonstration video or plain
    blah with no questions/answers/scores it should be viewable by
    anyone whether they are logged in or not.

    My function goes like this and the docstring reveals my
    understanding ...

    def is_login_needed(user):

        """ the login_required decorator has a user_passes_test()
    function as

        its first arg. If it returns True, no login is required.
    user.login_here

        is always set equal to the selected course.login_needed. For
    courses

        needing a login, self.is_authenticated must be True. For
    courses not

        needing a login, self.is_authenticated may return anything but
    this

        function passed to the login_required decorator must return True

        """

        if not user.login_here:

            return True


    So   the problem is that manage.py runserver reports an attribute
    error saying the function (presumably mine) does not have an
    attribute 'user' ... like this ...

      <earlier runserver traceback lines snipped> File
    "C:\Users\mike\envs\xxct3\train\course\urls.py", line 8, in <module>

        from .views import (finished_course_view, course_view, index_view,

      File "C:\Users\mike\envs\xxct3\train\course\views.py", line 172,
    in <module>

        def course_view(request, pk=None, slug=None):

      File
    "C:\Users\mike\envs\xxct3\lib\site-packages\django\contrib\auth\decorators.py",
    line 22, in _wrapped_view

        if test_func(request.user):

    AttributeError: 'function' object has no attribute 'user'

    If that 'function' is my 'is_login_needed' function I'm inclined
    to think it obviously has a 'user' attribute.

    Here is the contrib.auth.decorators.login_required source
    (preceded by user_passes_test which it calls) from Django 1.11

    My reading of the following  is that my own 'is_login_needed'
    function passed in via @login_required(is_login_needed,
    login_url='login') as the first positional argument is then passed
    to the 'user_passes_test' decorator as 'test_func'  ...


    def user_passes_test(test_func, login_url=None,
    redirect_field_name=REDIRECT_FIELD_NAME):

        """

        Decorator for views that checks that the user passes the given
    test,

        redirecting to the log-in page if necessary. 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 test_func(request.user):

                    return view_func(request, *args, **kwargs)

                path = request.build_absolute_uri()

                resolved_login_url = resolve_url(login_url or
    settings.LOGIN_URL)

                # If the login url is the same scheme and net location
    then just

                # use the path as the "next" url.

                login_scheme, login_netloc =
    urlparse(resolved_login_url)[:2]

                current_scheme, current_netloc = urlparse(path)[:2]

                if ((not login_scheme or login_scheme ==
    current_scheme) and

                        (not login_netloc or login_netloc ==
    current_netloc)):

                    path = request.get_full_path()

                from django.contrib.auth.views import redirect_to_login

                return redirect_to_login(

                    path, resolved_login_url, redirect_field_name)

            return _wrapped_view

        return decorator

    def login_required(function=None,
    redirect_field_name=REDIRECT_FIELD_NAME, login_url=None):

        """

        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,

            login_url=login_url,

            redirect_field_name=redirect_field_name

        )

        if function:

            return actual_decorator(function)

        return actual_decorator

    Could someone please explain where I'm stuffing up. I reckon I'm
    confused about which function the AttributeError is complaining.

    Many thanks for any help

    Mike




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