Better support for namespace packages.

CHANGES

@@ -24,6 +24,8 @@ Version 1.0
   templates will be reloaded only if the application is running in 
   debug mode. For higher performance it’s possible to disable that.
 - Added a workaround for a limitation in Python 3.3's namespace loader.
+- Added support for explicit root paths when using Python 3.3's namespace
+  packages.
 
 Version 0.10.2
 --------------

flask/app.py

@@ -118,6 +118,9 @@ class Flask(_PackageBoundObject):
        The `instance_path` and `instance_relative_config` parameters were
        added.
 
+    .. versionadded:: 1.0
+       The `root_path` parameter was added.
+
     :param import_name: the name of the application package
     :param static_url_path: can be used to specify a different path for the
                             static files on the web.  Defaults to the name
@@ -137,6 +140,11 @@ class Flask(_PackageBoundObject):
                                      for loading the config are assumed to
                                      be relative to the instance path instead
                                      of the application root.
+    :param root_path: Flask by default will automatically calculate the path
+                      to the root of the application.  In certain situations
+                      this cannot be achieved (for instance if the package
+                      is a Python 3 namespace package) and needs to be
+                      manually defined.
     """
 
     #: The class that is used for request objects.  See :class:`~flask.Request`
@@ -327,9 +335,11 @@ class Flask(_PackageBoundObject):
 
     def __init__(self, import_name, static_path=None, static_url_path=None,
                  static_folder='static', template_folder='templates',
-                 instance_path=None, instance_relative_config=False):
+                 instance_path=None, instance_relative_config=False,
+                 root_path=None):
         _PackageBoundObject.__init__(self, import_name,
-                                     template_folder=template_folder)
+                                     template_folder=template_folder,
+                                     root_path=root_path)
         if static_path is not None:
             from warnings import warn
             warn(DeprecationWarning('static_path is now called '

flask/blueprints.py

@@ -91,8 +91,10 @@ class Blueprint(_PackageBoundObject):
 
     def __init__(self, name, import_name, static_folder=None,
                  static_url_path=None, template_folder=None,
-                 url_prefix=None, subdomain=None, url_defaults=None):
+                 url_prefix=None, subdomain=None, url_defaults=None,
-        _PackageBoundObject.__init__(self, import_name, template_folder)
+                 root_path=None):
+        _PackageBoundObject.__init__(self, import_name, template_folder,
+                                     root_path=root_path)
         self.name = name
         self.url_prefix = url_prefix
         self.subdomain = subdomain

flask/helpers.py

@@ -650,7 +650,20 @@ def get_root_path(import_name):
     else:
         # Fall back to imports.
         __import__(import_name)
-        filepath = sys.modules[import_name].__file__
+        mod = sys.modules[import_name]
+        filepath = getattr(mod, '__file__', None)
+
+        # If we don't have a filepath it might be because we are a
+        # namespace package.  In this case we pick the root path from the
+        # first module that is contained in our package.
+        if filepath is None:
+            raise RuntimeError('No root path can be found for the provided '
+                               'module "%s".  This can happen because the '
+                               'module came from an import hook that does '
+                               'not provide file name information or because '
+                               'it\'s a namespace package.  In this case '
+                               'the root path needs to be explictly '
+                               'provided.' % import_name)
 
     # filepath is import_name.py for a module, or __init__.py for a package.
     return os.path.dirname(os.path.abspath(filepath))
@@ -762,7 +775,7 @@ class locked_cached_property(object):
 
 class _PackageBoundObject(object):
 
-    def __init__(self, import_name, template_folder=None):
+    def __init__(self, import_name, template_folder=None, root_path=None):
         #: The name of the package or module.  Do not change this once
         #: it was set by the constructor.
         self.import_name = import_name
@@ -771,8 +784,11 @@ class _PackageBoundObject(object):
         #: exposed.
         self.template_folder = template_folder
 
+        if root_path is None:
+            root_path = get_root_path(self.import_name)
+
         #: Where is the app root located?
-        self.root_path = get_root_path(self.import_name)
+        self.root_path = root_path
 
         self._static_folder = None
         self._static_url_path = None