Integrating Devel for module debuggingfor Drupal 8 , 9 , 10 , and 11

Introduction

As a Drupal developer, having the right set of tools can significantly enhance your debugging process. In this installment of our "Module Development" series, we will explore the Devel module, a staple in the toolbox of Drupal developers. This module provides powerful functions for debugging and analyzing your modules to ensure they perform optimally.

What is Devel?

The Devel module is a set of developer utilities and functions that assist with module development, site building, and troubleshooting. Its features include variable dumping, SQL query logging, and more. Devel can significantly streamline your workflow and provide insights into your module's inner workings during development.

Installing Devel

Let's start by adding the Devel module to your Drupal installation. This is typically done using Composer, a dependency manager for PHP. Follow these steps:

Step 1: Add Devel Module

Execute the following command in your Drupal root directory to add the Devel module:

composer require drupal/devel

This command fetches the latest version of the Devel module and places it in your modules/contrib directory.

Step 2: Enable Devel

Once installed, enable the Devel module and its submodules through Drush or the Drupal admin UI:

drush en devel kint -y

Or navigate to Extend in your Drupal admin menu and activate Devel and Kint (a replacement for var_dump()).

Utilizing Devel for Debugging

With Devel installed and enabled, you can start leveraging its features to debug your custom modules:

1. Dumping Variables

Devel's Kint integration allows you to view complex data structures in a human-readable format, which is particularly helpful for examining arrays and objects:

use Kint\Kint;

function my_module_function() {
  $data = [
    'key1' => 'value1',
    'key2' => 'value2',
  ];
  Kint::dump($data);
}

Place Kint::dump($variable) where you need insight into variables, and this will output detailed information on the browser page.

2. Logging SQL Queries

Devel can log SQL queries, showing you what's happening under the hood regarding database interactions. To activate this feature, navigate to Configuration > Development > Devel settings and enable Database query logging.

This is useful for optimizing queries and troubleshooting database-related issues.

3. Accessing Developer Information

With Devel, you gain additional admin menu options to access things like:

• Theme Information: Quick access to view theme hooks and suggestions.
• Module Information: Insights about active modules and dependencies.

These features are accessible under Development in the admin menu.

Best Practices with Devel

• Use Kint sparingly on production environments due to performance and security considerations.
• Regularly check SQL query logs to catch queries that could be optimized for performance improvements.
• Uninstall or disable Devel before deploying to production to avoid inadvertent data exposure.

Conclusion

The Devel module is an empowering extension for Drupal developers, enhancing the ability to debug and refine custom modules effectively. Through its various debugging utilities, Devel assists in identifying bottlenecks and better understanding module operations.

What's Next?

Having mastered the Devel module, our next lesson will introduce you to Webprofiler, a tool for performance analysis in Drupal. Webprofiler provides even deeper insights into performance metrics, helping you optimize your modules further. Stay tuned!