Guarantee a session factory to be set.

Issue #891

atramhasis/__init__.py

@@ -1,10 +1,16 @@
+import logging
 import os
 
 from pyramid.config import Configurator
+from pyramid.config import PHASE3_CONFIG
+from pyramid.interfaces import ISessionFactory
+from pyramid.session import SignedCookieSessionFactory
 from pyramid.settings import aslist
 
 from atramhasis.renderers import json_renderer_verbose
 
+LOG = logging.getLogger(__name__)
+
 
 DEFAULT_SETTINGS = {
     "cache.tree.backend": "dogpile.cache.memory",
@@ -47,6 +53,38 @@ def includeme(config):
     config.scan()
 
 
+def configure_session(config):
+    """
+    Configure pyramid's session factory.
+
+    People can configure their own session factory, but if no factory is registered
+    atramhasis will try configuring its own.
+    """
+
+    def check_session_factory_set():
+        session_factory = config.registry.queryUtility(ISessionFactory)
+        if session_factory:
+            return
+
+        settings = config.registry.settings
+        if 'atramhasis.session_factory.secret' not in settings:
+            msg = (
+                'No session factory is configured, and '
+                'atramhasis.session_factory.secret setting is missing.'
+            )
+            raise ValueError(msg)
+
+        LOG.info('Using default SignedCookieSessionFactory.')
+        default_session_factory = SignedCookieSessionFactory(
+            settings['atramhasis.session_factory.secret']
+        )
+        config.registry.registerUtility(default_session_factory, ISessionFactory)
+
+    config.action(
+        'check_session_factory_set', check_session_factory_set, order=PHASE3_CONFIG + 1
+    )
+
+
 def main(global_config, **settings):
     """ This function returns a Pyramid WSGI application.
     """

tests/test_views.py

@@ -658,7 +658,7 @@ def __init__(self):
     def setUp(self):
         pyramid_settings = Settings(settings)
         config = testing.setUp(settings=pyramid_settings)
-        atramhasis.load_app(config, pyramid_settings)
+        atramhasis.load_app(config)
         self.request = DummyRequest()
         self.request.application_url = "http://localhost:6543"
         apply_request_extensions(self.request)