Apples and Oranges
Comparing GraphQL and JSON:API is very similar to the never-ending stream of blog posts that compare Drupal and Wordpress. They simply don’t aim to do the same thing.
While REST and JSON:API are built around the HTTP architecture, GraphQL is not concerned with its transportation layer. Sending a GraphQL query over HTTP is one way to use it, and unfortunately, one that got stuck in everybody’s minds, but by far not the only one. This is what we are trying to prove with the GraphQL Twig module. It allows you to separate your Twig templates from Drupal’s internal structures and therefore make them easier to maintain and reuse. No HTTP requests involved. If this sparks your interest, watch our two webinars and the Drupal Europe talk on that topic.
So GraphQL is a way to provide typed, implementation agnostic contracts between systems, and therefore achieve decoupling. REST and JSON:API are about decoupling too, are they not?
What does “decoupling” mean?
The term “decoupling” has been re-purposed for content management systems that don’t necessarily generate the user-facing output themselves (in a “coupled” way) but allow to get the stored information using an API exposed over HTTP.
So when building a website using Drupal with its REST, JSON:API or GraphQL 3.x extension and smash a React frontend on top, you would achieve decoupling in terms of technologies. You swap Drupal’s rendering layer with React. This might bring performance improvements - our friends at Lullabot showed that decoupling is not the only way to achieve that - and allows you to implement more interactive and engaging user interfaces. But it also comes at a cost.
What you don’t achieve, is decoupling, or loose-coupling in the sense of software architecture. Information in Drupal might be accessible to arbitrary clients, but they still have to maintain a deep knowledge about Drupal data structures and conventions (entities, bundles, fields, relations…). You might be able to attach multiple frontends, but you will never be able to replace the Drupal backend. So you reached the identical state of coupling as Drupal had for years by being able to run different themes at the same time.
The real purpose of GraphQL
Back when we finished the automatically generated GraphQL schema for Drupal and this huge relation graph would just pop up after you installed the module, we were very proud of ourselves. After all, anybody was able to query for any kind of entity, field, block, menu item or relation between them, and all that with autocompletion!
The harsh reality is that 99.5% of the world doesn’t care what entities, fields or blocks are. Or even worse, they have a completely different understanding of it. A content management system is just one puzzle piece in our client's business case - technology should not be the focus, it’s just there to help achieve the goal.
The real strength of GraphQL is that it allows us to adapt Drupal to the world around it, instead of having to teach everybody how it thinks of it.
Some of you already noticed that there is a 4.x branch of the GraphQL module lingering, and there have been a lot of questions what this is about. This new version has been developed in parallel over the last year (mainly sponsored by our friendly neighbourhood car manufacturer Daimler) with an emphasis on GraphQL schema definitions.
Instead of just exposing everything Drupal has to offer, it allows us to craft a tailored schema that becomes the single source of truth for all information, operations, and interactions that happen within the system. This contract is not imposed by Drupal, but by the business needs that have to be met.
A bright future
So, GraphQL is not a recommendation for Drupal Core. What does that mean? Not a lot, since there is not even an issue on drupal.org to pursue that. GraphQL is an advanced tool that requires a certain amount of professionalism (and budget) to reap its benefits. Drupal aims to be used by everyone, and Drupal Core should not burden itself with complexity, that is not to the benefit of everyone. That's what contrib space is there for.
The GraphQL module is not going anywhere. Usage statistics are still climbing up and the 3.x branch will remain maintained until we can provide the same out-of-the-box experience and an upgrade path for version 4. If you have questions or opinions you would like to share, please reach out in the #graphql channel on drupal.slack.com or contact us on Twitter.