# 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 built-in app depends on sqlalchemy, there’s initial support for MongoEngine ORM too (check below for more details).

## Enabling the application

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

    from social.apps.flask_app.routes import social_auth

    app.register_blueprint(social_auth)

For MongoEngine you need this setting:

    SOCIAL_AUTH_STORAGE = 'social.apps.flask_app.me.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 instance 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.apps.flask_app.default.models import init_social

    init_social(app, db)

For MongoEngine:

    from social.apps.flask_app.me.models import init_social

    init_social(app, db)

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.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.