Let’s debug in Drupal 8 !

It has been nearly 7 months since Drupal 8 first release and as a developer, I am still in the learning process. It can be hard sometimes to know what is going wrong with your code and how to solve it. I will tell you about few things to know on how to develop and debug Drupal 8 projects and continue learning, learning and learning !

Disabling cache

First of all, to avoid having a crazy terminal with thousands of drupal cr hits, you can disable Drupal caching during development. You need to copy and rename sites/example.settings.local.php file to sites/default/settings.local.php. Then uncomment/update some values:

• uncomment this line to enable the “null cache service”:

$settings['container_yamls'][] = DRUPAL_ROOT . '/sites/development.services.yml';

• uncomment these lines to disable CSS/JS aggregation:

$config['system.performance']['css']['preprocess'] = FALSE;
$config['system.performance']['js']['preprocess'] = FALSE;

• uncomment these lines to disable the render cache and the dynamic page cache:

$settings['cache']['bins']['render'] = 'cache.backend.null';
$settings['cache']['bins']['dynamic_page_cache'] = 'cache.backend.null';

• you can allow test modules and themes to be installed if needed with:

$settings['extension_discovery_scan_tests'] = TRUE;

To include this file as part of Drupal’s settings file, open sites/default/settings.php file and uncomment these lines:

if (file_exists(__DIR__ . '/settings.local.php')) {
    include __DIR__ . '/settings.local.php';
}

Then, to disable Twig caching, open sites/development.services.yml file and add the following settings:

parameters:
    twig.config:
        debug: true
        auto_reload: true
        cache: false

Finally, rebuild the Drupal cache and it is done !

Displaying errors

As in Drupal 7, you can set different levels of errors display (by visiting this page: /admin/config/development/logging in the administration interface):

• None
• Errors and warnings
• All

In Drupal 8, there is a fourth level called “All messages, with backtrace information”. This is native to Drupal core and it allows to display the error backtrace in the message area.

You can also adjust the level of errors in your local setting file:

$config['system.logging']['error_level'] = 'verbose';

Creating log messages

Developers from Drupal 7 know the Database Logging module that allows to log messages in the database using the famous watchdog() function.

Well, this module still exists in Drupal 8 but the function has a replacement : the Drupal 8 logger class.

It looks like this:

// Logs an error
\Drupal::logger('my_module')->error($message);

Let’s have a look at the different parts of the code:

• \Drupal::logger(‘my_module') is the helper method that quickly creates a copy of the logger service. As a parameter, it takes the module name from where we log the information;
• ->error:this is the severity-level method (it can be debug, info, notice, warning, error, critical, alert, emergency);
• $message is the log message. It can be a simple string or it can contain some placeholders. In this case, you can pass the associative array (placeholders as keys) as a second parameter.

All the messages created with the logger service can be viewed in the reports page of the administration interface in /admin/reports/dblog as it used to be in Drupal 7.

Debugging Twig templates

Drupal core comes with a theming debug mode that is really helpful for local environments. To enable it, copy-and-paste the following code into sites/default/services.yml file (if you haven’t already added these lines in development.services.yml):

parameters:
    twig.config:
        debug: true

Thanks to this mode, it will be easier to find out which portion of HTML code has been written in which templates: in the source code, you will see each part of Twig templates (pages, nodes, blocks, menus etc.) surrounded by HTML comments that contain the matching suggestion templates. The one in current use will be checked.

Bitcoin Blogs 3001
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