How do I enable developer/debugging mode?

Question

I'm installing Drupal 8 core (using the standard profile). Whenever I get an exception/error, I get a blank page with "The website has encountered an error. Please try again later." (As shown in the image below.) This is shown as text and has no details or tracing about the error.

How do I enable developer/debugging mode?

Answer 1

On a development site I would suggest uncommenting the following lines in the settings.php file. emacs sites/default/settings.php

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

and then copying the file example.settings.local.php from /sites folder to /sites/default folder and rename it to settings.local.php

cp sites/example.settings.local.php sites/default/settings.local.php

In addition to adding the following setting

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

it also adds a few other settings which will help you in debugging and making development easier. If you don't want any of them in particular, you can always comment them out.

Note : If you think adding a file_exists call to each page will slow down the site, you can always remove it in the production code.

Answer 2

Add the following line in the settings.php file.

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

See Make developer tricks / tools for D8 more discoverable/obvious for more details.

Answer 3

An easy option, if you have access to Drupal Console, is to enable the development/debugging environment using drupal site:mode dev; when you are ready to change it back to production, use drupal site:mode prod.

Answer 4

Here is the variable with the different values :

$config['system.logging']['error_level'] = 'all'; // hide|some|all|verbose

These error levels are defined in the Drupal Core Bootstrap, here is the details for each one :

/**
 * Error reporting level: display no errors.
 */
const ERROR_REPORTING_HIDE = 'hide';

/**
 * Error reporting level: display errors and warnings.
 */
const ERROR_REPORTING_DISPLAY_SOME = 'some';

/**
 * Error reporting level: display all messages.
 */
const ERROR_REPORTING_DISPLAY_ALL = 'all';

/**
 * Error reporting level: display all messages, plus backtrace information.
 */
const ERROR_REPORTING_DISPLAY_VERBOSE = 'verbose';

Answer 5

To get basic error messages in Drupal 8 you don't need to touch any code at all. Just go to:

/admin/config/development/logging

and set "Error Messages to Display" to an appropriate level.

You can also view your recent errors through the admin interface:

/admin/reports/dblog

That said, other answers about settings files are relevant – you should only ever make errors visible on your development site, not production.

Overwritten $config objects/keys in settings.php won't be written to the sync directory when exporting, so providing your settings.php is in .gitignore, you can continue to safely use the configuration system to sync between clones of the same site.

Answer 6

If you only have access to Drush (no Drupal console) and you are working on a remote server, you can set the config to show all errors:

drush MYSITE.MYENV config-set system.logging error_level all -y

This is useful if you are getting a WSOD on a remote server and can't troubleshoot without more info.

Answer 7

Adding $config['system.logging']['error_level'] = 'verbose'; to the sites/default/settings.php should log the error.

I will rather suggest the following steps.

• Enable Twig debug and disable the cache for development purpose

• Copy the sites/example.settings.local.php file to sites/default/settings.local.php

• Un-comment the $settings['cache']['bins']['render'] = 'cache.backend.null'; line in the settings.local.php file

• On the site/default/settings.php file, un-comment the following lines

  if (file_exists($app_root . '/' . $site_path . '/settings.local.php')) {
    include $app_root . '/' . $site_path . '/settings.local.php';
  }
  

• Add the following lines to the sites/development.services.yml file

  parameters:
    http.response.debug_cacheability_headers: true
    twig.config:
      debug: true
      auto-reload: true
      cache: false
  services:
    cache.backend.null:
      class: Drupal\Core\Cache\NullBackendFactory
  

when all steps completed change directory to root dir and rebuild cache ```

• Run drush cr

You should now see the debug output. Don't forget to undo the changes before deploying to production.

Answer 8

You can also install the the Devel and Devel kint modules. This will let you debug using kint(xyz).

Answer 9

Blank page with "The website has encountered an error. Please try again later." won't take you anywhere. To get more information out of your Drupal 8 site you can enable following configs.

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

For local Drupal 8 development, you should also enable error reporting, display errors and display startup error to help you further debugging and fixing major runtime error.

error_reporting(E_ALL);
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);

You can find more information about TWIG debugging and enabling debugging with Drupal Console in the blog post below.

https://www.drupixels.com/blog/enable-debug-mode-and-error-reporting-local-development-drupal-8