Using extensions

When to use extensions

When you first install Solidus, you will notice that the platform is complete but quite lean. There aren't any toggles to enable shiny additional features. You get what you need to start an online store, and nothing more. This is by design. We know that each brand's business domain and USP are unique, and that they require a unique implementation approach. With that said, we also know that it isn't always smart to reinvent the wheel, especially when you're dealing with a common problem that's already been solved.

The easiest and quickest way to augment the functionality of your store is through extensions. These are gems or full-fledged Rails engines that provide additional functionality for Solidus by extending and overriding parts of the core. The Solidus ecosystem has a lot of extensions for many disparate tasks. There are extensions that add support for new payment providers or 3PL integrations, extensions that enhance your store with social features and many, many more to choose from.

In general, if there's already an extension that solves your problem, you should evaluate it before attempting to roll your own solution. Reusing the work of the community will not only save you the effort of a custom implementation, but will also make the community stronger.

With that said, you're strongly encouraged to customize Solidus on your own if none of the available solutions work for you, and this is exactly where the platform shines. You may then decide whether to keep your implementation private or, if you think the world could benefit from your work, to give back to the community and open-source it.

There's also a third option: if an extension already exists and takes you 90% of the way to solving your problem, consider submitting a patch to improve it and/or make it more flexible. This way, you benefit from the community's efforts while also ending up with a solution that fits your own use case perfectly.

Extension governance

The Solidus community has a strict governance model around extension management and maintenance. Extensions can be split into three big groups:

  • Official extensions: these extensions are hosted in the solidusio GitHub organization. They provide critical pieces of functionality that need to be working at all times (e.g. payment providers, sales tax calculation and a few other categories). They are maintained by the core team and any contribution is reviewed by the core team for correctness and completeness.

  • Community extensions: these extensions are hosted in the solidusio-contrib GitHub organization. They provide common pieces of functionality that, although useful, are usually not mission-critical. They are maintained by the entire Solidus community, with each extension usually having its own maintainer(s). The core team works on tools and automations that make their maintenance easier, but doesn't commit to spending their time actively working on these extensions.

  • Third-party extensions: these are extensions that live "in the wild", and are not hosted in any of Solidus' GitHub organizations. They may be written by organizations or individuals that were interested in Solidus and decided to open-source their efforts. As you may imagine, the Solidus community has no control over the quality of these extensions, so you're encouraged to review them on your own before installing them in your store.

Extensions may be "promoted" from one group to the other by popular demand (e.g. a third-party extension becoming a community extension because it's widely used, or a community extension becoming an official extension because it's become critical for multiple stores). If you want to propose a promotion, ping someone from the core team in Slack.

Finding the right extension

You can find many useful extensions on the Extensions page of the Solidus website, along with their CI status and supported Solidus versions. You can also filter by extension type (official, community or third-party), which is useful if you want your extensions to come with certain guarantees.

If you haven't found what you're looking for, you should still search on Google, GitHub and The Ruby Toolbox: new extensions are born every day and the one you need may be out there!

Installing an extension

As a general rule, you should ALWAYS review any code that goes into your application. While Solidus has strict policies around code reviews, you should go the extra mile and ensure any extensions you're installing are safe and production-ready.

The process for installing a Solidus extension is usually pretty simple and similar to the installation of the platform itself (after all, extensions are also Rails engines). The first step is always adding the extension to your Gemfile:

Gemfile
gem 'solidus'
gem 'solidus_auth_devise'
# ...
gem 'solidus_awesome_extension'

Note that some extensions may have an outdated release on RubyGems or may not have been released yet, in which case you'll want to pull the extensions directly from GitHub:

gem 'solidus'
gem 'solidus_auth_devise'
# ...
gem 'solidus_awesome_extension', github: 'solidusio/solidus_awesome_extension'

Once you have added the gem, install your bundle:

$ bundle install

Once the extension has been installed, simply follow the instructions in the extension's documentation. You may have to run an installation generator and run database migrations if the extension alters the database's schema.

The order gems appear in your Gemfile is important in the case of Solidus extensions. Make sure extensions are always added after the solidus and solidus_auth_devise gems, so that any overrides in the extension are applied correctly.

Staying up-to-date

Just like the core, extensions are constantly updated to add new features, enhance existing functionality, fix bugs and add compatibility with new Solidus versions. It's extremely important to keep your extensions up to date with the same diligence you reserve for the rest of your application. You should have a clear process in place for continuously updating extensions. The easier it is to update extensions, the likelier it is you will be doing it early and often.

The recommended approach is to write automated tests for any functionality added by extensions to your store. While extensions may have their own test suites, you cannot always predict how an extension will interact with your store's customizations or with other extensions. Furthermore, it's always best to test functionality in integration and in the context of your own app.

It's also recommended NOT to add any version constraints to extensions in your Gemfile. Instead, rely on your tests to ensure nothing's broken after an update. Ideally, the update process should be as simple as running the following commands:

$ bundle update
$ bundle exec rspec

Of course, this is not always possible and there may be situations where you need to lock an extension, but we recommend keeping these to a minimum.