Flask-Security can't initialize properly

Question

After writing my own login/registration system, I found out about Flask-Security and decided to integrate it into my app. All of my authentication and recovery code is gone, but I can't figure out why I'm getting simple errors upon starting up my application.

Here's the most stripped-down example that I can come up with:

from flask import Flask, render_template_string

from flask.ext.sqlalchemy import SQLAlchemy
from flask.ext.security import Security, SQLAlchemyUserDatastore, UserMixin, RoleMixin, current_user

app = Flask('test')
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/database.db'

db = SQLAlchemy(app)

roles_users = db.Table('roles_users',
    db.Column('user_id', db.Integer, db.ForeignKey('user.id')),
    db.Column('role_id', db.Integer, db.ForeignKey('role.id'))
)

class Role(db.Model, RoleMixin):
    id = db.Column(db.Integer(), primary_key=True)
    name = db.Column(db.String(80), unique=True)
    description = db.Column(db.String(255))

class User(db.Model, UserMixin):
    id = db.Column(db.Integer, primary_key=True)

    username = db.Column(db.String(50), unique=True)
    email = db.Column(db.String(255), unique=True)
    password = db.Column(db.String(255))

    active = db.Column(db.Boolean)
    confirmed_at = db.Column(db.DateTime)
    roles = db.relationship('Role', secondary=roles_users, backref=db.backref('users', lazy='dynamic'))

    def is_authenticated(self):
        return True

    def is_active(self):
        return True

    def is_anonymous(self):
        return False

    def get_id(self):
        return unicode(self.id)

    def __repr__(self):
        return '<User {self.username}>'.format(self=self)

user_datastore = SQLAlchemyUserDatastore(db, User, Role)
security = Security(app)

@app.before_first_request
def create_db():
    db.create_all()

@app.route('/')
def index():
    return render_template_string('''
        {% if current_user.is_authenticated() %}
            You're logged in.
        {% else %}
            You're not logged in.
        {% endif %}
    ''')

if __name__ == '__main__':
    app.run(debug=True)

Upon visiting http://localhost:5000/, I get this error:

Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/flask/app.py", line 1701, in __call__
    return self.wsgi_app(environ, start_response)
  File "/usr/lib/python2.7/site-packages/flask/app.py", line 1689, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "/usr/lib/python2.7/site-packages/flask/app.py", line 1687, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/lib/python2.7/site-packages/flask/app.py", line 1360, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/usr/lib/python2.7/site-packages/flask/app.py", line 1358, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/lib/python2.7/site-packages/flask/app.py", line 1344, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/tmp/app.py", line 62, in index
    ''')
  File "/usr/lib/python2.7/site-packages/flask/templating.py", line 140, in render_template_string
    context, ctx.app)
  File "/usr/lib/python2.7/site-packages/flask/templating.py", line 107, in _render
    rv = template.render(context)
  File "/usr/lib/python2.7/site-packages/jinja2/environment.py", line 894, in render
    return self.environment.handle_exception(exc_info, True)
  File "<template>", line 2, in top-level template code

  File "/usr/lib/python2.7/site-packages/jinja2/environment.py", line 372, in getattr
    return getattr(obj, attribute)
UndefinedError: 'current_user' is undefined

I looked at the source of both Flask-Security-Example and Flask-Social-Example, but I can't figure out where I'm going wrong here.

All help is greatly appreciated.

---

As a small side question, why is this table created like this and (more importantly) what is it for?

roles_users = db.Table('roles_users',
    db.Column('user_id', db.Integer, db.ForeignKey('user.id')),
    db.Column('role_id', db.Integer, db.ForeignKey('role.id'))
)

Answer 1

Looks like I found my problem (facepalm):

security = Security(app)

I should be passing in the datastore as a second argument:

security = Security(app, user_datastore)