Add Flask.request_globals_class to customize g.

Requested by toothr on #pocoo.

CHANGES

@@ -66,6 +66,8 @@ Relase date to be decided, codename to be chosen.
   flashing on sessions implementations which use external storage.
 - Changed the behavior of tuple return values from functions.  They are no
   longer arguments to the response object, they now have a defined meaning.
+- Added :attr:`flask.Flask.request_globals_class` to allow a specific class to
+  be used on creation of the :data:`~flask.g` instance of each request.
 
 Version 0.8.1
 -------------

flask/app.py

@@ -28,7 +28,7 @@ from .helpers import _PackageBoundObject, url_for, get_flashed_messages, \
     find_package
 from .wrappers import Request, Response
 from .config import ConfigAttribute, Config
-from .ctx import RequestContext, AppContext
+from .ctx import RequestContext, AppContext, _RequestGlobals
 from .globals import _request_ctx_stack, request
 from .sessions import SecureCookieSessionInterface
 from .module import blueprint_is_module
@@ -148,6 +148,11 @@ class Flask(_PackageBoundObject):
     #: :class:`~flask.Response` for more information.
     response_class = Response
 
+    #: The class that is used for the :data:`~flask.g` instance.
+    #:
+    #: .. versionadded:: 0.9
+    request_globals_class = _RequestGlobals
+
     #: The debug flag.  Set this to `True` to enable debugging of the
     #: application.  In debug mode the debugger will kick in when an unhandled
     #: exception ocurrs and the integrated server will automatically reload

flask/ctx.py

@@ -18,6 +18,7 @@ from .module import blueprint_is_module
 
 
 class _RequestGlobals(object):
+    """A plain object."""
     pass
 
 
@@ -139,7 +140,7 @@ class RequestContext(object):
         self.app = app
         self.request = app.request_class(environ)
         self.url_adapter = app.create_url_adapter(self.request)
-        self.g = _RequestGlobals()
+        self.g = app.request_globals_class()
         self.flashes = None
         self.session = None
 

flask/testsuite/appctx.py

@@ -65,6 +65,16 @@ class AppContextTestCase(FlaskTestCase):
 
         self.assert_equal(cleanup_stuff, [None])
 
+    def test_custom_request_globals_class(self):
+        class CustomRequestGlobals(object):
+            def __init__(self):
+                self.spam = 'eggs'
+        app = flask.Flask(__name__)
+        app.request_globals_class = CustomRequestGlobals
+        with app.test_request_context():
+            self.assert_equal(
+                flask.render_template_string('{{ g.spam }}'), 'eggs')
+
 
 def suite():
     suite = unittest.TestSuite()