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Last updated June 4, 2020

Starting with Drupal 8 and continuing in Drupal 9, Drupal has been refactored to use an object-oriented architecture and has adopted Symfony components as 3rd-party dependencies, along with many other changes.

Drupal 7 module and theme developers setting out to update their code to the latest version of Drupal can benefit a lot from mapping what they already know about Drupal 7 to the way that they accomplish the same thing in the latest version of Drupal. This generally involves picking a Drupal 7 pattern and then browsing through change records, and using tools like Drupal Module Upgrader to help identify the Drupal 8 (and 9) equivalent.

We also recommend taking the time to familiarize yourself with Drupal features like events, plugins, and services -- at least enough to recognize which pattern is appropriate for different types of problems. This will help you spot instances where there either isn't a direct Drupal 7 to 8+ path, or where Drupal might provide an updated way of accomplishing something.

Example tasks

  • Update a custom Drupal 7 module so that it works with the latest version of Drupal
  • Convert a PHPTemplate (.tpl.php) file to Twig (.html.twig)
  • Test your site's modules for Drupal 9 readiness

Confidence

Beware of any tutorials or documentation showing before/after comparisons with Drupal 7 code from before Drupal 8 was released. Drupal APIs continued to change up until it was released, though many of these older tutorials are still accurate. We recommend spending some time learning current best practices so that when you encounter specific solutions you'll have a better chance to correctly gauge their accuracy.

Drupalize.Me resources

Upgrade status generates a report that serves as a sort of checklist to help you determine whether or not your site is ready to be upgraded to Drupal 9. It packs a lot of useful information into a single report. It's worth taking the time to install it on a copy of your Drupal 8 site and seeing what it has to say.

Drupal check, and Drupal rector, are two useful command line tools you can use to help jump start the process of updating your Drupal 8 code to ensure it's compatible with Drupal 9. This post includes some notes about the process I went through while testing them out on some of the Drupalize.Me code base.

More Guides

We have guides on many Drupal skills and topics.

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External resources

  • Change Records (drupal.org)
    • If you've got questions about what happened to a specific hook, function, or way of doing things search through the change records for an answer. Most change records show before and after examples of specific code snippets. Make sure to also review those that are still in a draft state.
  • Drupal Module Upgrader (drupal.org)
    • This module works in combination with Drush, and Composer in order to scan your Drupal 7 code and make suggestions on how to upgrade it.
  • Drupal Twig Conversion Instructions (.tpl.php to .html.twig) (drupal.org)
    • Step-by-step instructions that were used for converting core functions, which can also be used by anyone who needs to covert to Twig.
  • Converting Drupal 7 modules to Drupal 8 (drupal.org)
    • This guide contains a number of different walkthroughs showing how to convert various elements in a Drupal 7 module. While you can't always follow it step-by-step and be successful we've found it to be a useful place to start tracking down what is necessary to incorporate some of the bigger and more conceptual changes.