Issue #3222251 by bbrala, longwave: [November 8, 2021] Replace all isset constructs with the null coalescing operator

Issue #3232110 by daffie: [Symfony 6] Add type hints to the methods Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher::getListeners(), ::getListenerPriority() and ::hasListeners()

Revert "Issue #3161983 by Pooja Ganjage, sanjayk, catch, longwave, daffie, dww, Gábor Hojtsy: [Symfony 6] Update EventDispatcherInterface type hints in constructors"

This reverts commit a9cee683.

Issue #3161983 by Pooja Ganjage, sanjayk, catch, longwave, daffie, dww, Gábor Hojtsy: [Symfony 6] Update EventDispatcherInterface type hints in constructors

Issue #3153803 by catch, Krzysztof Domański, andypost, longwave, kim.pepper, alexpott: [Symfony 5] Update EventDispatcher::dispatch() to make it forward-compatible with Symfony 5

Issue #3055194 by catch, mikelutz, longwave, mkalkbrenner, hchonov: [Symfony 5] The signature of the "Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher::dispatch()" method should be updated to "dispatch($event, string $eventName = null)", not doing so is deprecated since Symfony 4.3

Issue #2927746 by alexpott, catch, slasher13, mpdonadio, martin107, RoSk0, jibran, larowlan, pounard, Mile23, Jo Fitzgerald, deviantintegral, pritish.kumar: Update Symfony components to 3.4.*

Issue #2712647 by slasher13, klausi, catch, jibran, Manuel Garcia, alexpott, mpdonadio, naveenvalecha, neclimdul, timmillwood, webflo, dawehner, Wim Leers, pounard: Update Symfony components to ~3.2

Issue #2776975 by joelpittet, dawehner, tim.plunkett, xjm, pfrenssen: March 3, 2017: Convert core to array syntax coding standards for Drupal 8.3.x RC phase

Revert "Issue #2712647 by klausi, catch, slasher13, jibran, Manuel Garcia, alexpott, naveenvalecha, neclimdul, dawehner, Wim Leers, pounard: Update Symfony components to ~3.1"

This reverts commit a55b8ef1.

Issue #2712647 by klausi, catch, slasher13, jibran, Manuel Garcia, alexpott, naveenvalecha, neclimdul, dawehner, Wim Leers, pounard: Update Symfony components to ~3.1

Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #2602872 by rakesh.gectcr: Wrong @param doc for construct function in class ContainerAwareEventDispatcher

Issue #1392754 by tss, justAChris, jhodgdon: Comply with new documentation standards for @file for namespaced class files