Refactor how XStaticFileHandler interacts with parent class

Hopefully fixes issue gh-2

tornado_xstatic.py

@@ -6,32 +6,20 @@
 
 class XStaticFileHandler(tornado.web.StaticFileHandler):
     _cached_xstatic_data_dirs = {}
+    default_filename = None
 
     def initialize(self, allowed_modules=None, **kwargs):
         if allowed_modules:
             self.allowed_modules = set(allowed_modules)
         else:
             self.allowed_modules = None
 
-        assert 'root' not in kwargs
-        # NOTE: Not wild on passing path=/ , because StaticFileHandler's own
-        # validation will let this serve any file. If this subclass is working
-        # correctly, that shouldn't be an issue, but...
-        super(XStaticFileHandler, self).initialize(path="/")
-
-    def parse_url_path(self, url_path):
-        if '/' not in url_path:
-            raise tornado.web.HTTPError(403, "XStatic module, not a file")
-        if self.allowed_modules is not None:
-            module_name = url_path.split('/', 1)[0]
-            if module_name not in self.allowed_modules:
-                raise tornado.web.HTTPError(
-                    403, 'Access to XStatic module %s denied', module_name)
-
-        return super(XStaticFileHandler, self).parse_url_path(url_path)
+        # Not calling parent initialize() here because there's no root to set.
+        # If SFH ever gains further attributes set in initialize(), we'll need
+        # to copy them here.
 
     @classmethod
-    def _get_xstatic_data_dir(cls, mod_name):
+    def get_xstatic_data_dir(cls, mod_name):
         try:
             return cls._cached_xstatic_data_dirs[mod_name]
         except KeyError:
@@ -43,23 +31,29 @@ def _get_xstatic_data_dir(cls, mod_name):
             cls._cached_xstatic_data_dirs[mod_name] = data_dir
             return data_dir
 
-    @classmethod
-    def get_absolute_path(cls, root, path):
-        mod_name, path = path.split(os.path.sep, 1)
-        root = cls._get_xstatic_data_dir(mod_name)
-        abs_path = os.path.join(root, path)
-        if not abs_path.startswith(root):
+    def get(self, path, include_body=True):
+        if '/' not in path:
+            raise tornado.web.HTTPError(403, "XStatic module, not a file")
+
+        mod, path = path.split('/')
+        if (self.allowed_modules is not None) and (mod not in self.allowed_modules):
             raise tornado.web.HTTPError(
-                403, "Request for file outside XStatic package %s: %s", mod_name, path)
+                403, 'Access to XStatic module %s denied', mod)
 
-        return abs_path
+        # This stateful setting of root seems awkward, but SFH is already stateful
+        # (self.path, self.absolute_path, self.modified), and from examining
+        # the code of SFH, this should work.
+        self.root = self.get_xstatic_data_dir(mod)
+        return super(XStaticFileHandler, self).get(path, include_body=include_body)
 
 
 def url_maker(prefix, include_version=True):
     def make_url(package, path):
         if include_version:
-            fs_style_path = package + os.path.sep + path.replace("/", os.path.sep)
-            version_bit = "?v=" + XStaticFileHandler.get_version({'static_path': ''}, fs_style_path)
+            fs_style_path = path.replace("/", os.path.sep)
+            pkg_dir = XStaticFileHandler.get_xstatic_data_dir(package)
+            version_bit = "?v=" + XStaticFileHandler.get_version(
+                                        {'static_path': pkg_dir}, fs_style_path)
         else:
             version_bit = ""
         return prefix + package + "/" + path + version_bit