Issue #3109970 by znerol, andypost, Prashant.c, daffie, Wim Leers, dww, catch: Convert uses of $_SESSION in forms and batch

Issue #3245252 by andypost, ranjith_kumar_k_u, Spokje: Fix possibly undefined $finished in _batch_process()

Issue #3319582 by mondrake, Spokje, longwave, mallezie: Fix calls to methods with too many parameters passed in

Issue #3222769 by bbrala, alexpott, longwave, Matroskeen: [November 8, 2021] Replace all list (array destructuring) assignment to the array syntax

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

Issue #3236798 by alexpott: \Drupal\Core\Datetime\DateFormatter::formatInterval() causes deprecations in PHP 8.1

Issue #2664016 by hchonov, gease, DuaelFr, morsok, tstoeckler, Daniele Nicastro, alexpott, plach, larowlan, dawehner, cspitzlay: Adding a new batch set while the batch is running breaks batch order

Issue #2731817 by mikelutz, ashishdalvi, Sonal.Sangale, dbt102, andypost, jhodgdon, martin107, roderik: Replace all calls to the deprecated Drupal::url() function in Core

Issue #2999473 by albertski, dhirendra.mishra, longwave, alexpott: Notice: Undefined variable: label in _batch_process()

Issue #2935254 by kim.pepper: Remove all usages of drupal_get_message and drupal_set_message in core includes

Issue #2851111 by tedbow, tstoeckler, Munavijayalakshmi, dagmar, dawehner, catch, Fabianx, david_garcia, Nebel54, hchonov: fastcgi_finish_request and shutdown functions (e.g. batch) do not play nicely together

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

Issue #2575615 by alexpott, pwolanin, stefan.r, catch, dawehner, effulgentsia, xjm, David_Rothstein, iMiksu, lauriii, joelpittet: Introduce HtmlEscapedText and remove SafeMarkup::setMultiple() and SafeMarkup::getAll() and remove the static safeStrings list

Issue #2426969 by David_Rothstein, joelpittet, dawehner: Dynamic redirects are no longer possible in the batch API (breaks updating existing modules or themes with the Update Manager)

Issue #2351015 by plach, effulgentsia, Wim Leers, dawehner, martin107, damiankloip, cilefen, Fabianx, catch, pwolanin, Damien Tournoud, znerol, YesCT, larowlan: URL generation does not bubble cache contexts

Issue #2407195 by Wim Leers, Fabianx, joelpittet, lauriii, Crell: Move attachment processing to services and per-type response subclasses

Revert "Issue #1986330 by subhojit777, marcelodornelas, wheatpenny, kasperg, timaholt, stefank, AkshayKalose, develCuy, valthebald, moymilo, YesCT, dawehner, tstoeckler: When Batch ID doesn't exist, Drupal should emit a 404"

Somehow broke testbot/HEAD. Reverting for now.

This reverts commit 30432a03.

Issue #1986330 by subhojit777, marcelodornelas, wheatpenny, kasperg, timaholt, stefank, AkshayKalose, develCuy, valthebald, moymilo, YesCT, dawehner, tstoeckler: When Batch ID doesn't exist, Drupal should emit a 404

Issue #2364157 by mpdonadio, dawehner, martin107, Berdir, pcambra, naveenvalecha, tim.plunkett: Replace most existing _url calls with Url objects

Issue #2367743 by rpayanm, Miroling, YesCT, ianthomas_uk, shadik, gaurav.pahuja: Remove usages of drupal_form_submit() and update documentation

Issue #2378095 by Wim Leers, Devin Carlson: Convert all remaining attached individual CSS/JS assets to attached asset libraries

Issue #2362227 by dawehner, mpdonadio, znerol, tim.plunkett, skipyT: Replace all instances of current_path()

Issue #2328111 by dawehner, martin107, neclimdul: Replace most instances of the DRUPAL_ROOT constant with the app.root container parameter.

Issue #2350877 by dawehner, Wim Leers, hussainweb: Deprecate/rename drupal_add_feed(), drupal_add_html_head(), drupal_add_html_head_link(), drupal_add_http_header(), and allow to be set declaratively in #attached.

Issue #2343661 by larowlan, tim.plunkett | xjm: Rename l() to _l() and url() to _url(), and document replacements.

Issue #2343759 by pwolanin, larowlan, dawehner, tim.plunkett, effulgentsia, xjm, Wim Leers: Provide an API function to replace url()/l() for external urls.

Issue #2340251 by iMiksu, alexpott, tim.plunkett, dawehner, Wim Leers: Remove most remaining url() calls.

Issue #2335659 by tim.plunkett, dawehner, effulgentsia, sun: Remove FormState ArrayAccess usage from core.

Issue #2318099 by tim.plunkett: Replace $form_state['complete_form'] with $form_state->getCompleteForm().