hook_library_alter() must be manually invoked by users of LibraryDiscovery, and has no test coverage

Patch looks fine!

1. +++ b/core/lib/Drupal/Core/Asset/LibraryDiscovery.php
   @@ -22,22 +23,51 @@ class LibraryDiscovery implements LibraryDiscoveryInterface {
       * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
       *   The module handler.
   ...
   +  public function __construct(CacheCollectorInterface $library_discovery_collector, ModuleHandlerInterface $module_handler) {
   

   HAHA

2. +++ b/core/lib/Drupal/Core/Asset/LibraryDiscovery.php
   @@ -22,22 +23,51 @@ class LibraryDiscovery implements LibraryDiscoveryInterface {
   -    return $this->collector->get($extension);
   +    if (!isset($this->libraryDefinitions[$extension])) {
   +      $libraries = $this->collector->get($extension);
   +      $this->libraryDefinitions[$extension] = [];
   +      foreach ($libraries as $name => $definition) {
   +        // Allow modules and themes to dynamically attach request and context
   +        // specific data for this library; e.g., localization.
   +        $this->moduleHandler->alter('library', $definition, $name);
   +        $this->libraryDefinitions[$extension][$name] = $definition;
   +      }
   +    }
   +
   +    return $this->libraryDefinitions[$extension];
      }
   

   I know its "out of scope" but can we think about not executing an alter hook for each library but rather once for all? What bout a follow up for both the static and dynamic alter hook?

I attempted to test the patch submitted in #1 to see what was up. Applying the patch to an existing install of 8.0.x immediately broke the site. My attempts to recover by following the procedure at https://www.drupal.org/documentation/rebuild were unsuccessful, as well as attempts to perform a new install after zapping the database, settings.php, etc.

Browsing to /core/install.php at this point gave the following output:

Additional uncaught exception thrown while handling exception.

Original

LogicException: A stray drupal_render() invocation with $is_root_call = TRUE is causing bubbling of attached assets to break. in drupal_render() (line 2857 of /var/www/8.0.x/core/includes/common.inc).

drupal_render(Array, 1)
drupal_render_root(Array)
Drupal\Core\Render\BareHtmlPageRenderer->renderBarePage(Array, 'Error', Array, Array, 'install_page')
Drupal\Core\Render\BareHtmlPageRenderer->renderInstallPage(Array, 'Error', Array)
install_display_output(Array, Array)
_drupal_log_error(Array, 1)
_drupal_error_handler_real(4096, 'Argument 2 passed to Drupal\Core\Asset\LibraryDiscovery::__construct() must implement interface Drupal\Core\Extension\ModuleHandlerInterface, none given', '/var/www/8.0.x/core/lib/Drupal/Core/Asset/LibraryDiscovery.php', 50, Array)
_drupal_error_handler(4096, 'Argument 2 passed to Drupal\Core\Asset\LibraryDiscovery::__construct() must implement interface Drupal\Core\Extension\ModuleHandlerInterface, none given', '/var/www/8.0.x/core/lib/Drupal/Core/Asset/LibraryDiscovery.php', 50, Array)
Drupal\Core\Asset\LibraryDiscovery->__construct(Object)
ReflectionClass->newInstanceArgs(Array)
Symfony\Component\DependencyInjection\ContainerBuilder->createService(Object, 'library.discovery')
Symfony\Component\DependencyInjection\ContainerBuilder->get('library.discovery', 1)
Drupal\Core\DependencyInjection\ContainerBuilder->get('library.discovery')
Drupal::service('library.discovery')
_drupal_add_library('core/html5shiv')
drupal_process_attached(Array)
template_preprocess_html(Array, 'html', Array)
_theme('html', Array)
Drupal\Core\Theme\ThemeManager->render('html', Array)
drupal_render(Array)
Drupal\Core\Render\BareHtmlPageRenderer->renderBarePage(Array, 'Choose language', Array, Array, 'install_page')
Drupal\Core\Render\BareHtmlPageRenderer->renderInstallPage(Array, 'Choose language', Array)
install_display_output(Array, Array)
install_drupal()

Additional

LogicException: A stray drupal_render() invocation with $is_root_call = TRUE is causing bubbling of attached assets to break. in drupal_render() (line 2857 of /var/www/8.0.x/core/includes/common.inc).

drupal_render(Array, 1)
drupal_render_root(Array)
Drupal\Core\Render\BareHtmlPageRenderer->renderBarePage(Array, 'Error', Array, Array, 'install_page')
Drupal\Core\Render\BareHtmlPageRenderer->renderInstallPage(Array, 'Error', Array)
install_display_output(Array, Array)
_drupal_log_error(Array, 1)
_drupal_exception_handler(Object)

Running the patch through simplytest.me produced similar output. I'm guessing the patch that was submitted is in some way incomplete/incorrect.

Blocks #2368797: Optimize ajaxPageState to keep Drupal 8 sites fast on high-latency networks, prevent CSS/JS aggregation from taking down sites and use HTTP GET for AJAX requests, bumping to critical.

Alright!

This issue addresses a critical bug and is allowed per https://www.drupal.org/core/beta-changes. Committed 7d36a7c and pushed to 8.0.x. Thanks!