webform_submission.exporter injects plugin.manager.archiver, which Drupal 12 removes

Problem/Motivation

Core's Archiver subsystem is deprecated in drupal:11.3.0 and removed from drupal:12.0.0 with no replacement (change record 3556927). Webform still injects its plugin manager, so on Drupal 12 the container cannot be built at all:

Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException: The service "webform_submission.exporter" has a dependency on a non-existent service "plugin.manager.archiver"

That is a hard failure rather than a deprecation notice: every kernel test that installs webform dies during container build, and a site on Drupal 12 would not boot with webform enabled.

Steps to reproduce

Install webform 6.3.x against Drupal 12 (core 12.0.x-dev) and boot anything that builds the container, for example run any kernel test that enables webform.

Proposed resolution

Drop the dependency. It appears to be unused: in both places the manager is assigned to a property and no method is ever called on it.

• webform.services.yml line 89 passes @plugin.manager.archiver as the fifth argument to webform_submission.exporter.
• src/WebformSubmissionExporter.php imports Drupal\Core\Archiver\ArchiverManager, type-hints it in the constructor and stores it in $this->archiverManager (line 149). There is no other reference to that property in the class.
• modules/webform_devel/src/Form/WebformDevelEntityFormApiBaseForm.php line 61 does $instance->archiverManager = $container->get('plugin.manager.archiver') and likewise never calls it.

Removing a constructor argument is technically an API change, so 6.3.x may prefer to keep the parameter and default it to NULL rather than drop it outright.

Remaining tasks

Confirm the property really is unused across the branch, then remove the service argument, the constructor parameter or its default, the property and the import.

User interface changes

None.

API changes

The constructor signature of WebformSubmissionExporter changes if the argument is dropped rather than defaulted.

Found while testing another module against core 12: patching webform with the MR from #3618362: Align definitions of getSortedDefinitions and getGroupedDefinitions with core cleared the getGroupedDefinitions() signature fatals and let this one through. Related to #3578701: Remove \Archive_Tar dependency in favor of PharData, which removes the abandoned pear/archive_tar package; this is core's plugin.manager.archiver service, a separate dependency.

AI-Generated: Yes (Claude Code was used to help draft this issue summary. No patch is attached. The failure was observed on a real Drupal 12 pipeline, and I verified the two call sites and the absence of any method call on the property.)