jupyterlab/docs/source/user/extensions.rst

Extensions
----------

JupyterLab extensions add functionality to the JupyterLab application.
They can provide new file viewer types, launcher activities, and output
renderers, among many other things. JupyterLab extensions are
`npm <https://www.npmjs.com/>`__ packages (the standard package format
in Javascript development). For information about developing extensions,
see the :ref:`developer documentation <developer-guide>`.

In order to install JupyterLab extensions, you need to have Node.js
version 4+ installed.

If you use ``conda``, you can get it with:

.. code:: bash

    conda -c conda-forge install nodejs

If you use `Homebrew <https://brew.sh/>`__ on Mac OS X:

.. code:: bash

    brew install node

Installing Extensions
~~~~~~~~~~~~~~~~~~~~~

The base JupyterLab application includes a core set of extensions, which
provide the features described in this User Guide (Notebook, Terminal,
Text Editor, etc.) You can install new extensions into the application
using the command:

.. code:: bash

    jupyter labextension install <foo>

where ``<foo>`` is the name of a valid JupyterLab extension npm package
on `npm <https://www.npmjs.com>`__. Use the ``<foo>@<foo version>``
syntax to install a specific version of an extension, for example:

.. code:: bash

    jupyter labextension install <foo>@1.2.3

You can also install an extension that is not uploaded to npm, i.e.,
``<foo>`` can be a local directory containing the extension, a gzipped
tarball, or a URL to a gzipped tarball.

We encourage extension authors to add the ``jupyterlab-extensions``
GitHub topic to any repository with a JupyterLab extension to facilitate
discovery. You can see a list of extensions by searching Github for the
`jupyterlab-extensions <https://github.com/search?utf8=%E2%9C%93&q=topic%3Ajupyterlab-extensions&type=Repositories>`__
topic.

You can list the currently installed extensions by running the command:

.. code:: bash

    jupyter labextension list

Uninstall an extension by running the command:

.. code:: bash

    jupyter labextension uninstall <bar>

where ``<bar>`` is the name of the extension, as printed in the
extension list. You can also uninstall core extensions using this
command (which can later be re-installed).

Installing and uninstalling extensions can take some time, as they are
downloaded, bundled with the core extensions, and the whole application
is rebuilt. You can install/uninstall more than one extension in the
same command by listing their names after the ``install`` command.

If you are installing/uninstalling several extensions in several stages,
you may want to defer rebuilding the application by including the flag
``--no-build`` in the install/uninstall step. Once you are ready to
rebuild, you can run the command:

.. code:: bash

    jupyter lab build

Disabling Extensions
~~~~~~~~~~~~~~~~~~~~

You can disable specific JupyterLab extensions (including core
extensions) without rebuilding the application by running the command:

.. code:: bash

    jupyter labextension disable <bar>

where ``<bar>`` is the name of the extension. This will prevent the
extension from loading in the browser, but does not require a rebuild.

You can re-enable an extension using the command:

.. code:: bash

    jupyter labextension enable <foo>

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 by running ``jupyter lab path``.

JupyterLab Build Process
^^^^^^^^^^^^^^^^^^^^^^^^

To rebuild the app directory, run ``jupyter lab build``. By default the
``jupyter lab install`` command builds the application, so you typically
do not need to call ``build`` directly.

Building consists of:

-  Populating the ``staging/`` directory using template files
-  Handling any locally installed packages
-  Ensuring all installed assets are available
-  Bundling the assets
-  Copying the assets to the ``static`` directory

JupyterLab Application Directory
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The JupyterLab application directory contains the subdirectories
``extensions``, ``schemas``, ``settings``, ``staging``, ``static``, and
``themes``.

.. _extensions-1:

extensions
''''''''''

The ``extensions`` directory 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``.

schemas
'''''''

The ``schemas`` directory contains `JSON
Schemas <http://json-schema.org/>`__ that describe the settings used by
individual extensions. Users may edit these settings using the
JupyterLab Settings Editor.

settings
''''''''

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

.. _page_configjson:

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

.. _build_configjson:

build_config.json
                 

The ``build_config.json`` file is used to track the local directories
that have been installed using
``jupyter labextension install <directory>``, as well as core extensions
that have been explicitly uninstalled. An example of a
``build_config.json`` file is:

.. code:: json

    {
        "uninstalled_core_extensions": [
            "@jupyterlab/markdownwidget-extension"
        ],
        "local_extensions": {
            "@jupyterlab/python-tests": "/path/to/my/extension"
        }
    }

staging and static
''''''''''''''''''

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

Running ``jupyter lab`` will attempt to run the ``static`` assets in the
application directory if they exist. You can run
``jupyter lab --core-mode`` to load the core JupyterLab application
(i.e., the application without any extensions) instead.

themes
''''''

The ``themes`` directory contains assets (such as CSS and icons) for
JupyterLab theme extensions.