fix: allow voila to run a server extension for notebook <5

voila/server_extension.py

@@ -21,6 +21,7 @@
 from .treehandler import VoilaTreeHandler
 from .static_file_handler import MultiStaticFileHandler, WhiteListFileHandler
 from .configuration import VoilaConfiguration
+from .utils import get_server_root_dir
 
 
 def load_jupyter_server_extension(server_app):
@@ -67,7 +68,7 @@ def load_jupyter_server_extension(server_app):
             {
                 'whitelist': voila_configuration.file_whitelist,
                 'blacklist': voila_configuration.file_blacklist,
-                'path': os.path.expanduser(web_app.settings['server_root_dir']),
+                'path': os.path.expanduser(get_server_root_dir(web_app.settings)),
             },
         ),
     ])

voila/treehandler.py

@@ -13,6 +13,8 @@
 from jupyter_server.base.handlers import JupyterHandler
 from jupyter_server.utils import url_path_join, url_escape
 
+from .utils import get_server_root_dir
+
 
 class VoilaTreeHandler(JupyterHandler):
     def initialize(self, **kwargs):
@@ -69,7 +71,7 @@ def allowed_content(content):
                        breadcrumbs=breadcrumbs,
                        contents=contents,
                        terminals_available=False,
-                       server_root=self.settings['server_root_dir']))
+                       server_root=get_server_root_dir(self.settings)))
         elif cm.file_exists(path):
             # it's not a directory, we have redirecting to do
             model = cm.get(path, content=False)

voila/utils.py

@@ -0,0 +1,17 @@
+import os
+
+
+def get_server_root_dir(settings):
+    # notebook >= 5.0.0 has this in the settings
+    if 'server_root_dir' in settings:
+        return settings['server_root_dir']
+
+    # This copies the logic added in the notebook in
+    #  https://github.com/jupyter/notebook/pull/2234
+    contents_manager = settings['contents_manager']
+    root_dir = contents_manager.root_dir
+    home = os.path.expanduser('~')
+    if root_dir.startswith(home + os.path.sep):
+        # collapse $HOME to ~
+        root_dir = '~' + root_dir[len(home):]
+    return root_dir