Do not fatal when a shorthand service class cannot be loaded

[mglaman]

Problem

Service map generation calls class_exists() on shorthand service IDs (added in #817). class_exists() autoloads the class, and PHP resolves parent classes at declaration time. A service class extending a class from an unavailable module throws an Error that kills the bootstrap before PHPStan analyzes a single file:

Error thrown in modules/canvas_headless/src/RenderConverter/JsComponentCanvasRenderConverter.php
on line 15 while loading bootstrap file vendor/mglaman/phpstan-drupal/drupal-autoloader.php:
Class "Drupal\custom_elements\RenderConverter\CanvasRenderConverter" not found

Canvas hit this: canvas_headless registers a decorator for a custom_elements service with decoration_on_invalid: ignore, and drupal/custom_elements sits in require-dev. Symfony ignores the decorator at runtime. phpstan-drupal fataled anyway, because the crash happens during class load, not container compilation. See https://git.drupalcode.org/project/canvas/-/merge_requests/1460, which works around it with an explicit class: key.

Fix

Catch Throwable around both shorthand class_exists() calls (DrupalAutoloader, ServiceMap) and skip the service when its class cannot load. ServiceMap::setDrupalServices() also skips decorator registration when the decorating service was dropped — previously an undefined array key.

Tests

• New fixture module service_map_broken with a shorthand service whose class extends a class from a missing module. Every bootstrap-dependent test now exercises the failure path; without the fix, DrupalContainerDynamicReturnTypeTest fatals with the exact error above.
• ServiceMapFactoryTest::testShorthandServiceWithUnloadableClass covers ServiceMap directly: the broken service is skipped and the decorated service survives with zero decorators.

🤖 Generated with Claude Code

[mglaman]

Pushed a second commit that respects decoration_on_invalid: ignore: when the decorated service does not exist and the decorator opts into ignore, the decorating service is dropped from the service map. This matches Symfony's compile-time behavior — the service does not exist in the runtime container either. null and the default exception keep the current behavior.