8. Extending Plone with add-on packages – Mastering Plone 6 development

Extending Plone with add-on packages

8. Extending Plone with add-on packages#

Backend chapter

For frontend add-ons see chapter Using Volto add-ons.

The creation of a custom backend add-on is explained in Roundtrip [The voting story] frontend, backend, and REST

Plone add-ons enrich the CMS by

  • adding content types

  • adding behaviors with new fields, relations and other features for existing and custom content types

  • adding blocks to add elementary content snippets to a page

  • designing the layout

  • customizing the editor experience

  • adding content assembling features for overview pages

Plone 6 knows two groups of add-ons: add-ons for Plone and such for the frontend Volto.

Plone backend add-ons provide

  • content types

  • behaviors to enrich content types

Plone frontend add-ons provide

  • new blocks

  • variations and enhancements of blocks

  • a theme to design the layout of a site

  • components independent of blocks like a dropdown navigation

Both can be coupled, if a frontend feature depends on a new content type, a new behavior or any other change needed in data structure. For example an add-on that has the goal to provide a bookmarking feature depends on a backend add-on that handles the storing of the bookmarks.

Have a look at the curated lists of add-ons:

Awesome Plone: backend add-ons
Awesome Volto: frontend add-ons

8.1. How to find appropriate add-ons#

It can be hard to find the right add-on for your requirements. Here are some tips.

8.2. Installing Plone add-ons#

We have two groups of add-ons: backend and frontend.

The training setup starts without any frontend add-on. Later on we will add features via a frontend add-on. See chapter Using Volto add-ons how to install a frontend add-on.

The training setup starts with one backend add-on ploneconf.site. Let's see how it is installed.

Making a backend add-on package available to Zope#

First, we must make the add-on package available to Zope. This means that Zope can import the code.

A backend add-on is a Python package. Therefore we install it with pip.

Look at the requirements.txt file. You add a package to the configuration by adding a new line containing the package name.

If the add-on is not released on PyPI, we tell Zope where to find the package on Github or another repository platform by including the necessary information in mx.ini.

[training.votable]
url=git@github.com:collective/training.votable.git
branch=main
; tag=volto

Adding the package to instance.yaml causes the generation of the Zope configuration to make the package available in a Zope app.

  zcml_package_includes: training.votable, ploneconf.site

Running make build has three effects:

  • The build installs the python package with pip.

  • The build generates in instance/ a Zope instance configuration that makes the package available in our Zope app.

  • As soon as the Zope app is started via make start, the add-on can be enabled per Plone instance. A Zope app can include multiple Plone instances. So an add-on can be enabled per Plone instance.

See also

Documentation Install Plone add-ons

Enabling add-ons in your Plone site#

An add-on can be enabled per Plone instance.

In your browser, go to Site Setup at http://localhost:3000/controlpanel, and open the Add-ons Panel. You will see a list of available add-ons.

Link to Site Setup

Link to Site Setup#

Enable ploneconf.site now if you haven't done already.

This is what happens: The GenericSetup profile of the product gets loaded. This does things like:

  • Registering new content types

  • Registering behaviors

  • Configuring new actions

  • Create catalog indexes

All this is configured in the default GenericSetup profile, which can be found in backend/sources/<package name>/src/<package name>/profiles/default. In the next chapters we will add here our content type talk, configure a catalog index, and some more.

8.3. Summary#

We have seen in short how to extend a vanilla Plone website with third party add-ons to add new functionality. Even if you do not use many of these, they are nonetheless an inspiration on how to implement features in Plone.

For frontend add-ons see chapter Using Volto add-ons

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