Allow specifying extra_labextensions_path (#1542)

* Allow specifying extra_labextensions_path

* Add docs

* format

Author: jtpio

docs/customize.md

@@ -768,3 +768,30 @@ Voila will load all extensions under `{PREFIX}/share/jupyter/labextensions` just
 
 It also has its own path for labextensions that you can use: `{PREFIX}/share/jupyter/voila/labextensions`. Installing extensions there will make those extensions only available to Voila. This is really useful if you
 don't want to pollute JupyterLab or Jupyter Notebook with extensions that only work for Voila.
+
+### Configuring extra labextensions paths
+
+You can configure additional paths for Voilà to search for JupyterLab extensions using the `extra_labextensions_path` configuration option:
+
+```bash
+voila --VoilaConfiguration.extra_labextensions_path="['/path/to/custom/extensions', '/another/path']"
+```
+
+Or via the configuration file (`voila.json`):
+
+```json
+{
+  "VoilaConfiguration": {
+    "extra_labextensions_path": ["/path/to/custom/extensions", "/another/path"]
+  }
+}
+```
+
+Or in a Python configuration file (`voila.py`):
+
+```python
+c.VoilaConfiguration.extra_labextensions_path = [
+    '/path/to/custom/extensions',
+    '/another/path'
+]
+```

voila/app.py

@@ -474,7 +474,9 @@ def _default_log_level(self):
 
     @property
     def labextensions_path(self):
-        return get_voila_labextensions_path()
+        return get_voila_labextensions_path(
+            self.voila_configuration.extra_labextensions_path
+        )
 
     @property
     def data_dir(self):
@@ -761,7 +763,9 @@ def init_handlers(self) -> List:
                     {
                         "themes_url": "/voila/api/themes",
                         "path": self.themes_dir,
-                        "labextensions_path": get_voila_labextensions_path(),
+                        "labextensions_path": get_voila_labextensions_path(
+                            self.voila_configuration.extra_labextensions_path
+                        ),
                         "no_cache_paths": ["/"],
                     },
                 ),

voila/configuration.py

@@ -269,3 +269,9 @@ def page_config_hook(
         This option is not compatible with preheat-kernel option.
         """,
     )
+
+    extra_labextensions_path = List(
+        Unicode(),
+        config=True,
+        help="""Extra paths to look for federated JupyterLab extensions""",
+    )

voila/server_extension.py

@@ -125,7 +125,9 @@ def _load_jupyter_server_extension(server_app: ServerApp):
     tree_handler_conf = {"voila_configuration": voila_configuration}
 
     themes_dir = pjoin(get_data_dir(), "themes")
-    labextensions_path = get_voila_labextensions_path()
+    labextensions_path = get_voila_labextensions_path(
+        voila_configuration.extra_labextensions_path
+    )
 
     handlers = [
         (

voila/utils.py

@@ -92,7 +92,7 @@ async def _get_request_info(ws_url: str) -> Awaitable:
         return ri
 
 
-def get_voila_labextensions_path():
+def get_voila_labextensions_path(extra_paths=None):
     labextensions_path = jupyter_path("labextensions")
 
     # Paths to labextensions specific to Voila
@@ -101,6 +101,10 @@ def get_voila_labextensions_path():
     ]
     labextensions_path = labextensions_path + voila_labextensions
 
+    # Add extra labextensions paths if provided
+    if extra_paths:
+        labextensions_path = labextensions_path + extra_paths
+
     return labextensions_path
 
 
@@ -136,7 +140,9 @@ def get_page_config(
     )
     page_config.setdefault("mathjaxConfig", mathjax_config)
     page_config.setdefault("fullMathjaxUrl", mathjax_url)
-    labextensions_path = get_voila_labextensions_path()
+    labextensions_path = get_voila_labextensions_path(
+        voila_configuration.extra_labextensions_path
+    )
 
     recursive_update(
         page_config,