Introduction

django-lazysignup is a package designed to allow users to interact with a site as if they were authenticated users, but without signing up. At any time, they can convert their temporary user account to a real user account.

django-lazysignup is beta software. Bug reports, patches and extensions are welcomed. While this package is in beta, backwards-compatibility will be maintained for a single point release and a DeprecationWarning issued.

Requirements

Tested on Django 1.2.x, though should work on Django 1.0 and later (although you will need to customise one of the templates.) It requires django.contrib.auth to be in the INSTALLED_APPS list.

Installation

django-lazysignup can be installed with your favourite package management tool from PyPI:

pip install django-lazysignup

Once that's done, you need to add lazysignup to your INSTALLED_APPS. You will also need to add lazysignup's authentication backend to your site's AUTHENTICATION_BACKENDS setting:

AUTHENTICATION_BACKENDS = (
  'django.contrib.auth.backends.ModelBackend',
  'lazysignup.backends.LazySignupBackend',
)

If you are using Django prior to 1.2, you should override the lazysignup/convert.html template to remove the {% csrf_token %} template tag. This may be handled more elegantly in a future release.

Next, you need to ensure that the tables that lazysignup uses are created. You should either run python manage.py syncdb, or use the South support and run python manage.py migrate lazysignup.

Finally, you need to add lazysignup to your URLConf, using something like this:

urlpatterns += (''
    (r'^convert/', include('lazysignup.urls')),
)

Usage

The package works by creating temporary user accounts based on a user's session key whenever a flagged view is requested. You can specify which views trigger this behaviour using the lazysignup.decorators.allow_lazy_user decorator.

When an anonymous user requests such a view, a temporary user account will be created for them, and they will be logged in. The user account will have an unusable password set, so that it can't be used to log in as a regular user. The way to tell a regular use from a temporary user is to call the is_lazy_user() function from lazysignup.templatetags.lazysignup_tags. If this returns True, then the user is temporary. Note that user.is_anonymous() will return False and user.is_authenticated() will return True. See below for more information on is_lazy_user.

A view is provided to allow such users to convert their temporary account into a real user account by providing a username and a password.

A Django management command is provided to clear out stale, uncoverted user accounts - although this depends on your use of database-backed sessions, and assumes that all user accounts with an expired session are safe to delete. This may not be the case for all apps, so you may wish to provide your own cleaning script.

The allow_lazy_user decorator

Use this decorator to indicate that accessing the view should cause anonymous users to have temporary accounts created for them.

For example:

from django.http import HttpResponse
from lazysignup.decorators import allow_lazy_user

@allow_lazy_user
def my_view(request):
  return HttpResponse(request.user.username)

When accessing the above view, a very simple response containing the generated username will be displayed.

The is_lazy_user template filter

This template filter (which can also be imported from lazysignup.utils and used in your own code) will return True if the user is a generated user. You need to pass it the user to test. For example, a site navigation template might look like this:

{% load i18n lazysignup_tags %}

<nav id="account-bar">
  <ul>
    <li><a href="{% url home %}">{% trans "Home" %}</a></li>
    {% if not user|is_lazy_user %}
      <li><a href="#">{% trans "Account" %}</a></li>
      <li><a href="{% url auth_logout %}">{% trans "Log out" %}</a></li>
    {% else %}
      <li><a href="{% url lazysignup_convert %}">{% trans "Save your data" %}</a> {% trans "by setting a username and password" %}</li>
    {% endif %}
  </ul>
</nav>

This filter is very simple, and can be used directly in view code, or tests. For example:

from lazysignup.utils import is_lazy_user

def testIsLazyUserAnonymous(self):
    user = AnonymousUser()
    self.assertEqual(False, is_lazy_user(user))

Note that as of version 0.6.0, the user tested no longer needs to have been authenticated by the LazySignupBackend for lazy user detection to work.

User agent blacklisting

The middleware will not created users for certain requests from blacklisted user agents. This is simply a fairly crude method for preventing many spurious users being created by passing search engines.

The blacklist is specified with the USER_AGENT_BLACKLIST setting. This should be an iterable of regular expression strings. If the user agent string of a request matches a regex (search() is used, so the match can be anywhere in the string) then a user will not be created.

If the list is not specified, then the default is as follows

• slurp
• googlebot
• yandex
• msnbot
• baiduspider

Specifying your own USER_AGENT_BLACKLIST will replace this list.

Using the convert view

Users will be able to visit the /convert/ view. This provides a form with a username, password and password confirmation. As long as they fill in valid details, their temporary user account will be converted into a real user account that they can log in with as usual.

You may pass your own form class into the convert view in order to customise user creation. The code requires expects the following:

• It expects to be able to create the form passing in the generated User object with an instance kwarg (in general, this is fine when using a ModelForm based on the User model)
• It expects to be able to call save() on the form to convert the user to a real user
• It expects to be able to call a get_credentials() method on the form to obtain a set of credentials to authenticate the new user with. The result of this call should be a dictionary suitable for passing to django.contrib.auth.authenticate(). Typically, this would be a dict with username and password keys - but this may vary if you're using a different authentication backend.

The default configuration, using the provided UserCreationForm, should be enough for most users, but the customisation point is there if you need it.

Custom User classes

Many projects use a custom User class, augmenting that from django.contrib.auth. If you want to use such a custom class with lazysignup, then you should set the LAZYSIGNUP_USER_MODEL setting. This should be a standard dotted Django name for a model, eg:

LAZYSIGNUP_USER_MODEL = 'myapp.CustomUser'

The setting defaults to auth.User, so using Django's own User model.

If you do use a custom user class, note that lazysignup expects that class' default manager to have a create_user method, with the same signature and semantics as django.contrib.auth.models.UserManager. If your model actually subclasses Django's own user model, you may well be able to use this manager directly. For example:

from django.contrib.auth.models import User, UserManager

class MyCustomUser(User):
    objects = UserManager()

    notes = models.TextField(blank=True, null=True)

lazysignup also expects that it can fetch instances of your custom user class using a get method on the object's manager, and that looking them up by primary key and by username will work. See lazysignup.backends for more detail.

Maintenance

Over time, a number of user accounts that haven't been converted will build up. To avoid performance problems from an excessive number of user accounts, it's recommended that the remove_expired_users management command is run on a regular basis. It runs from the command line:

python manage.py remove_expired_users

In a production environment, this should be run from cron or similar.

This works be removing user accounts from the system whose associated sessions are no longer in the session table. user.delete() is called for each user, so related data will be removed as well.

Note of course that these deletes will cascade, so if you need to keep data associated with such users, you'll need to write your own cleanup job. It also expects that you're using database backed sessions. If that's not the case, then you'll again need to write your own cleanup. Finally, if you're using a custom user class where the user isn't a subclass of Django's own user model, you'll again need your own cleanup script.

Helping Out

If you want to add a feature or fix a bug, please go ahead! Fork the project on GitHub, and when you're done with your changes, let me know. Fixes and features with tests have a greater chance of being merged. To run the tests, do:

python manage.py test --settings=lazysignup.test_settings lazysignup

Note that the tests require the mock package.