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Flask Framework

Flask reusable applications are tricky (or I’m not capable enough). Here are details on how to enable this application on Flask.

Dependencies

The Flask app does not depend on any storage backend by default. There’s support for SQLAlchemy, MongoEngine and Peewee.

Installing

Install the flask core from pypi:

$ pip install social-auth-app-flask

Install any of the storage solutions:

$ pip install social-auth-app-flask-sqlalchemy
$ pip install social-auth-app-flask-mongoengine
$ pip install social-auth-app-flask-peewee

Enabling the application

The applications define a Flask Blueprint, which needs to be registered once the Flask app is configured by:

from social_flask.routes import social_auth

app.register_blueprint(social_auth)

For MongoEngine you need this setting:

SOCIAL_AUTH_STORAGE = 'social_flask_mongoengine.models.FlaskStorage'

For Peewee you need this setting:

SOCIAL_AUTH_STORAGE = 'social_flask_peewee.models.FlaskStorage'

Models Setup

At the moment the models for python-social-auth are defined inside a function because they need the reference to the current db session and the User model used on your project (check User model reference below). Once the Flask app and the database are defined, call init_social to register the models:

from social_flask_sqlalchemy.models import init_social

init_social(app, session)

For MongoEngine:

from social_flask_mongoengine.models import init_social

init_social(app, session)

For Peewee:

from social_flask_peewee.models import init_social

init_social(app, session)

So far I wasn’t able to find another way to define the models on another way rather than making it as a side-effect of calling this function since the database is not available and current_app cannot be used on init time, just run time.

User model reference

The application keeps a reference to the User model used by your project, define it by using this setting:

SOCIAL_AUTH_USER_MODEL = 'foobar.models.User'

The value must be the import path to the User model.

Global user

The application expects the current logged in user accesible at g.user, define a handler like this to ensure that:

@app.before_request
def global_user():
    g.user = get_current_logged_in_user

Flask-Login

The application works quite well with Flask-Login, ensure to have some similar handlers to these:

@login_manager.user_loader
def load_user(userid):
    try:
        return User.query.get(int(userid))
    except (TypeError, ValueError):
        pass


@app.before_request
def global_user():
    g.user = login.current_user


# Make current user available on templates
@app.context_processor
def inject_user():
    try:
        return {'user': g.user}
    except AttributeError:
        return {'user': None}

Remembering sessions

The users session can be remembered when specified on login. The common implementation for this feature is to pass a parameter from the login form (remember_me, keep, etc), to flag the action. Flask-Login will mark the session as persistent if told so.

python-social-auth will check for a given name (keep) by default, but since providers won’t pass parameters back to the application, the value must be persisted in the session before the authentication process happens.

So, the following setting is required for this to work:

SOCIAL_AUTH_FIELDS_STORED_IN_SESSION = ['keep']

It’s possible to override the default name with this setting:

SOCIAL_AUTH_REMEMBER_SESSION_NAME = 'remember_me'

Don’t use the value remember since that will clash with Flask-Login which pops the value from the session.

Then just pass the parameter keep=1 as a GET or POST parameter.

Exceptions handling

The Django application has a middleware (that fits in the framework architecture) to facilitate the different exceptions handling raised by python-social-auth. The same can be accomplished (even on a simpler way) in Flask by defining an errorhandler. For example the next code will redirect any social-auth exception to a /socialerror URL:

from social_core.exceptions import SocialAuthBaseException


@app.errorhandler(500)
def error_handler(error):
    if isinstance(error, SocialAuthBaseException):
        return redirect('/socialerror')

Be sure to set your debug and test flags to False when testing this on your development environment, otherwise the exception will be raised and error handlers won’t be called.

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