Remove module check in DrupalKernel

Yes this should be something you can opt-in to for sites that want the fail safe - and there's other ways to accomplish it (like timestamp comparison) than loading the configuration every request.

We already rebuild the container on switches to/from multi-lingual and based on settings.php changes, and this doesn't cover either of those, so it's a false sense of security.

       $this->registerNamespaces($this->container->getParameter('container.namespaces'));

Why do we still need this?

Reroll.

Just an idea: Use two separate flags allowDumping and allowLoading. Forcibly set the latter to FALSE from within updateModules. If we already know that the container on disk is out of date, do not bother trying to load it...

Now that the module-list is not checked anymore during the bootstrap, it is essential that the container is dumped each time it is modified in the simpletest parent site. Therefore we need to prevent WebTestBase::rebuildContainer() from creating a kernel without $allowDumping, or even better remove that method entirely (as per #2033567: Remove TestBase::rebuildContainer()).

Let's not attack #2033567: Remove TestBase::rebuildContainer() and instead try to keep the changes small. Interdiff is against #6 (the reroll of the original patch).

Reintroduce the idea that after DrupalKernel::updateModules(), the container never ever should be loaded from disk anymore during subsequent rebuilds of the kernel. This also leads to the container being dumped (if dumping is enabled) after each DrupalKernel::updateModules().

Fix DrupalKernelTest.

I'm glad that you removed the changes related to #2033567: Remove TestBase::rebuildContainer(), because I strongly disagree with the idea of removing it. — Instead, what we need is an enhancement to PhpStorage that allows it to work in a "single hashed file mode"; i.e., the class name of the dumped file gets a hash appended, which in turn would enable us to actually reload the already dumped container of the test child site from disk (which we cannot do right now, since the class name of the service container is always identical, and PHP does not support to unload code, so rebuildContainer() intends to just reload, but actually has to rebuild, because the class is loaded already).

Aside from that remark, this looks good to me.

As a directly related follow-up, we should get back to #2160091: drupal_rebuild() rebuilds container twice, since drupal_flush_all_caches() also rebuilds it

Lastly, not sure what the consequences of this patch are with regard to #1897468: Kernel rebuilds service container on every request when a module vanishes

Couple of comment issues, otherwise looks great.

1. +++ b/core/lib/Drupal/Core/DrupalKernel.php
   @@ -171,12 +178,16 @@ class DrupalKernel implements DrupalKernelInterface, TerminableInterface {
   +   *   (optional) FALSE to prevent that the kernel is attempted to be read from
   

   'to prevent the kernel attempting to read the dependency injection container from disk'?

2. +++ b/core/lib/Drupal/Core/DrupalKernel.php
   @@ -344,6 +355,12 @@ public function updateModules(array $module_list, array $module_filenames = arra
   +    // disable loading of a dumped kernel from the disk, because it is
   

   Are we dumping the kernel or the container?

Thanks!

Committed/pushed to 8.x, thanks!

The original commit contained #2259275: Rename "DrupalUnitTestBase" to KernelTestBase so I reverted and recommitted see 486e276 (the revert) and 3cc312e (the proper commit)

We should remove even more stuff from initializeContainer(): #2277445: Remove newModuleList instance variable from DrupalKernel and related check in initializeContainer