Added missing sessions module

flask/sessions.py

@@ -0,0 +1,168 @@
+# -*- coding: utf-8 -*-
+"""
+    flask.sessions
+    ~~~~~~~~~~~~~~
+
+    Implements cookie based sessions based on Werkzeug's secure cookie
+    system.
+
+    :copyright: (c) 2010 by Armin Ronacher.
+    :license: BSD, see LICENSE for more details.
+"""
+
+from datetime import datetime
+from werkzeug.contrib.securecookie import SecureCookie
+
+
+class SessionMixin(object):
+    """Expands a basic dictionary with an accessors that are expected
+    by Flask extensions and users for the session.
+    """
+
+    def _get_permanent(self):
+        return self.get('_permanent', False)
+
+    def _set_permanent(self, value):
+        self['_permanent'] = bool(value)
+
+    permanent = property(_get_permanent, _set_permanent)
+    del _get_permanent, _set_permanent
+
+    new = False
+    modified = True
+
+
+class SecureCookieSession(SecureCookie, SessionMixin):
+    """Expands the session with support for switching between permanent
+    and non-permanent sessions.
+    """
+
+
+class NullSession(SecureCookieSession):
+    """Class used to generate nicer error messages if sessions are not
+    available.  Will still allow read-only access to the empty session
+    but fail on setting.
+    """
+
+    def _fail(self, *args, **kwargs):
+        raise RuntimeError('the session is unavailable because no secret '
+                           'key was set.  Set the secret_key on the '
+                           'application to something unique and secret.')
+    __setitem__ = __delitem__ = clear = pop = popitem = \
+        update = setdefault = _fail
+    del _fail
+
+
+class SessionInterface(object):
+    """The basic interface you have to implement in order to replace the
+    default session interface which uses werkzeug's securecookie
+    implementation.  The only methods you have to implement are
+    :meth:`open_session` and :meth:`save_session`, the others have
+    useful defaults which you don't need to change.
+
+    The session object returned by the :meth:`open_session` method has to
+    provide a dictionary like interface plus the properties and methods
+    from the :class:`SessionMixin`.  We recommend just subclassing a dict
+    and adding that mixin::
+
+        class Session(dict, SessionMixin):
+            pass
+
+    If :meth:`open_session` returns `None` Flask will call into
+    :meth:`make_null_session` to create a session that acts as replacement
+    if the session support cannot work because some requirement is not
+    fulfilled.  The default :class:`NullSession` class that is created
+    will complain that the secret key was not set.
+
+    To replace the session interface on an application all you have to do
+    is to assign :attr:`flask.Flask.session_interface`::
+
+        app = Flask(__name__)
+        app.session_interface = MySessionInterface()
+
+    .. versionadded:: 0.7
+    """
+
+    #: :meth:`make_null_session` will look here for the class that should
+    #: be created when a null session is requested.  Likewise the
+    #: :meth:`is_null_session` method will perform a typecheck against
+    #: this type.
+    null_session_class = NullSession
+
+    def make_null_session(self, app):
+        """Creates a null session which acts as a replacement object if the
+        real session support could not be loaded due to a configuration
+        error.  This mainly aids the user experience because the job of the
+        null session is to still support lookup without complaining but
+        modifications are answered with a helpful error message of what
+        failed.
+
+        This creates an instance of :attr:`null_session_class` by default.
+        """
+        return self.null_session_class()
+
+    def is_null_session(self, obj):
+        """Checks if a given object is a null session.  Null sessions are
+        not asked to be saved.
+
+        This checks if the object is an instance of :attr:`null_session_class`
+        by default.
+        """
+        return isinstance(obj, self.null_session_class)
+
+    def get_cookie_domain(self, app):
+        """Helpful helper method that returns the cookie domain that should
+        be used for the session cookie if session cookies are used.
+        """
+        if app.config['SERVER_NAME'] is not None:
+            # chop of the port which is usually not supported by browsers
+            return '.' + app.config['SERVER_NAME'].rsplit(':', 1)[0]
+
+    def get_expiration_time(self, app, session):
+        """A helper method that returns an expiration date for the session
+        or `None` if the session is linked to the browser session.  The
+        default implementation returns now + the permanent session
+        lifetime configured on the application.
+        """
+        if session.permanent:
+            return datetime.utcnow() + app.permanent_session_lifetime
+
+    def open_session(self, app, request):
+        """This method has to be implemented and must either return `None`
+        in case the loading failed because of a configuration error or an
+        instance of a session object which implements a dictionary like
+        interface + the methods and attributes on :class:`SessionMixin`.
+        """
+        raise NotImplementedError()
+
+    def save_session(self, app, session, response):
+        """This is called for actual sessions returned by :meth:`open_session`
+        at the end of the request.  This is still called during a request
+        context so if you absolutely need access to the request you can do
+        that.
+        """
+        raise NotImplementedError()
+
+
+class SecureCookieSessionInterface(SessionInterface):
+    """The cookie session interface that uses the Werkzeug securecookie
+    as client side session backend.
+    """
+    session_class = SecureCookieSession
+
+    def open_session(self, app, request):
+        key = app.secret_key
+        if key is not None:
+            return self.session_class.load_cookie(request,
+                                                  app.session_cookie_name,
+                                                  secret_key=key)
+
+    def save_session(self, app, session, response):
+        expires = self.get_expiration_time(app, session)
+        domain = self.get_cookie_domain(app)
+        if session.modified and not session:
+            response.delete_cookie(app.session_cookie_name,
+                                   domain=domain)
+        else:
+            session.save_cookie(response, app.session_cookie_name,
+                                expires=expires, httponly=True, domain=domain)