\Drupal\Core\Asset\LibraryDiscoveryParser should use FileCache to cache the parsed YAML

I can't find anything to complain about 🤓

Question, is this a feature we should add test coverage for?

@smustgrave I've added a test - it's not hard to add something small to a unit test for this.

One nit on the MR.

Should we do some profiling or benchmarking here? 🤔 I think it's not really necessary because this only happens in the cold cache scenario, per:

This means that library YAML files have to be re-read on a cache clear even when the files do not change. This is different from info.yml, service.yml and any of the plugin yaml files.

… but it sure wouldn't hurt. We don't want to make the cold cache scenario more expensive/slower. But if anything, this should make it faster/cheaper.

For the given code in test_script.php, Standard profile installed, on PHP 8.2 and APCu installed and enabled on CLI:

use Drupal\Component\Utility\Timer;
$modules = array_keys(\Drupal::getContainer()->getParameter('container.modules'));

foreach($modules as $module) {
  \Drupal::service('library.discovery.parser')->buildByExtension($module);
}


for ($i = 0; $i < 10; $i++) {
  drupal_flush_all_caches();
  Timer::start('library.discovery.parser');
  foreach($modules as $module) {
    \Drupal::service('library.discovery.parser')->buildByExtension($module);
  }
  Timer::stop('library.discovery.parser');
}

$time = Timer::read('library.discovery.parser');
print "Library parsing completed in {$time}ms\n";

With MR using Symfony YAML

$ vendor/bin/drush scr test_script.php
Library parsing completed in 63.54ms

Without patch using Symfony YAML

$ vendor/bin/drush scr test_script.php
Library parsing completed in 117.06ms

Without patch and with PECL YAML installed

$ vendor/bin/drush scr test_script.php
Library parsing completed in 75.47ms

Random failure in https://git.drupalcode.org/project/drupal/-/jobs/662217 because the MySQL DB went away, which made 4 unrelated kernel tests fail. I cannot retest this job 🤷‍♂️

#8 provides the numbers that remove any worries about cold cache scenarios 👍

Committed/pushed to 11.x, thanks!

Automatically closed - issue fixed for 2 weeks with no activity.