Retrieve Base URL extension for Jupyterlab v4

A JupyterLab extension to retrieve the base URL from the frontend. It was developped as a workaround for current limitation of dash jupyterlab extension that cannot be installed with jupyterlab v4. Code is mostly taken from here and here in the dash project.

Install

Note that this extension requires jupyterlab>=4.0.0.

To install/uninstall the extension, execute:

# Install
pip install jupyterlab-retrieve-base-url

# Uninstall
pip uninstall jupyterlab-retrieve-base-url

Usage

In a jupyterlab notebook:

from jupyterlab_retrieve_base_url import retrieve_base_url

retrieve_base_url()

Some typical results:

# Running locally
{'type': 'base_url_response',
 'server_url': 'http://localhost:8890',
 'base_subpath': '/',
 'frontend': 'jupyterlab'}

# Using jupyterhub
{'type': 'base_url_response',
 'server_url': 'https://my-domain.com',
 'base_subpath': '/user/user@my-domain.com/',
 'frontend': 'jupyterlab'}

Configure dash proxy config

The current jupyter_dash.infer_jupyterlab_proxy_config() method from the dash==2.18.1 library is not working correctly with jupyterlab>=4.0.0 (see plotly/dash#2804 and plotly/dash#2998). If you run into this issue, then you can try the following:

from dash import Dash, jupyter_dash

# Set proxy settings
from dash._jupyter import _jupyter_config
from jupyterlab_retrieve_base_url import retrieve_base_url
_jupyter_config.update(retrieve_base_url())

# Create a dash app
app = dash.Dash()
...

# Run the dash app
jupyter_dash.run_app(app, host=host, port=port, mode="jupyterlab")