jupyterlab/docs/extensions_user.md

Extensions User Guide

JupyterLab extensions add functionality to the JupyterLab application. They can provide new file viewer types, launcher activities, and new Notebook output renderers for example.

Installing Node.js

Installing JupyterLab extensions requires Node.js version 4+.

If you use conda, you can get them with:

conda -c conda-forge install nodejs

If you use Homebrew on Mac OS X:

brew install node

Installing Extensions

The base JupyterLab application comes with core set of extensions, which provide the Notebook, Terminal, Text Editor, etc. New extensions can be installed into the application using the command:

jupyter labextension install <foo>

Where <foo> is a valid JupyterLab extension specifier. This specifier is defined by the extension author in their installation instructions.

The currently installed extensions can be listed by running the command:

jupyter labextension list

An installed extension can be uninstalled by running the command:

jupyter labextension uninstall <bar>

Where <bar> is the name of the extension, as printed in the extension list. Core extensions can also be uninstalled this way (and can later be re-installed).

Extensions can be disabled by running the command:

jupyter labextension disable <foo>

Where <foo> is the name of the extension. This will prevent the extension from loading on the front end, but does not require a rebuild. The extension can be re-enabled using the command:

jupyter labextension enable <foo>

Core plugins can also be disabled (and then re-enabled).

Advanced usage

The JupyterLab application directory (where the application assets are built and the settings reside) can be overridden using --app-dir in any of the JupyterLab commands, or by setting the JUPYTERLAB_DIR environment variable. If not specified, it will default to <sys-prefix/share/jupyter/lab, where sys-prefix is the site-specific directory prefix of the current Python environment. You can query the current application path using jupyter lab path.

To create the app directory without installing any extensions, run jupyter lab build. The install and link commands already run the build, so it typically does not need to be called directly.

Building consists of:

• Populating the staging/ directory using template files
• Handling any linked packages (see jupyter labextension link)
• Ensuring all install assets are available
• Building the assets
• Copying the assets to the static directory

The settings directory contains page_config.json and build_config.json files.

page_config.json

The page_config.json data is used to provide config data to the application environment.

Two important fields in the page_config.json file allow control of which plugins load:

1. disabledExtensions for extensions that should not load at all.
2. deferredExtensions for extensions that do not load until they are required by something, irrespective of whether they set autostart to true.

The values for each are an array of strings. The following sequence of checks are performed against the patterns in disabledExtensions and deferredExtensions.

• If an identical string match occurs between a config value and a package name (e.g., "@jupyterlab/apputils-extension"), then the entire package is disabled (or deferred).
• If the string value is compiled as a regular expression and tests positive against a package name (e.g., "disabledExtensions": ["@jupyterlab/apputils*$"]), then the entire package is disabled (or deferred).
• If an identical string match occurs between a config value and an individual plugin ID within a larger package (e.g., "disabledExtensions": ["@jupyterlab/apputils-extension:settings"]), then that specific plugin is disabled (or deferred).
• If the string value is compiled as a regular expression and tests positive against an individual plugin ID within a larger package (e.g., "disabledExtensions": ["^@jupyterlab/apputils-extension:set.*$"]), then that specific plugin is disabled (or deferred).

build_config.json

The build_config.json file is used to track the folders that have been added using jupyter labextension link <folder>, as well as core extensions that have been explicitly uninstalled. e.g.

$ cat settings/build_config.json
{
    "uninstalled_core_extensions": [
        "@jupyterlab/markdownwidget-extension"
    ],
    "linked_packages": {
        "@jupyterlab/python-tests": "/path/to/my/extension"
    }
}

The other folders in the app directory are: extensions, static, and staging. The extensions folder has the packed tarballs for each of the installed extensions for the app. If the application directory is not the same as the sys-prefix directory, the extensions installed in the sys-prefix directory will be used in the app directory. If an extension is installed in the app directory that exists in the sys-prefix directory, it will shadow the sys-prefix version. Uninstalling an extension will first uninstall the shadowed extension, and then attempt to uninstall the sys-prefix version if called again. If the sys-prefix version cannot be uninstalled, its plugins can still be ignored using ignoredPackages metadata in settings.

The static folder contains the assets that will be loaded by the JuptyerLab application. The staging folder is used to create the build and then populate the static folder.

Running jupyter lab will attempt to run the static assets in the application folder if they exist. You can run jupyter lab --core-mode to load the core JupyterLab application instead.