[MRG] Pass extension configuration to extension handlers

jupyter_server/extension/application.py

@@ -7,6 +7,7 @@
     default, 
     validate
 )
+from traitlets.config import Config
 
 from jupyter_core.application import JupyterApp
 
@@ -141,6 +142,14 @@ def initialize_templates(self):
         """Override this method to add handling of template files."""
         pass
 
+    def _prepare_config(self):
+        """Builds a Config object from the extension's traits and passes
+        the object to the webapp's settings as `<extension_name>_config`.  
+        """
+        traits = self.class_own_traits().keys()
+        config = Config({t: getattr(self, t) for t in traits})
+        self.settings['{}_config'.format(self.extension_name)] = config
+
     def _prepare_settings(self):
         # Make webapp settings accessible to initialize_settings method
         webapp = self.serverapp.web_app
@@ -280,6 +289,7 @@ def load_jupyter_server_extension(cls, serverapp, argv=None, **kwargs):
         extension.initialize(serverapp, argv=argv)
 
         # Initialize extension template, settings, and handlers.
+        extension._prepare_config()
         extension._prepare_templates()
         extension._prepare_settings()
         extension._prepare_handlers()

jupyter_server/extension/handler.py

@@ -16,6 +16,10 @@ def initialize(self, extension_name, **kwargs):
         self.extension_name = extension_name
         super(ExtensionHandler, self).initialize(**kwargs)
 
+    @property
+    def config(self):
+        return self.settings["{}_config".format(self.extension_name)]
+
     @property
     def static_url_prefix(self):
         return "/static/{extension_name}/".format(