Issue #3377570 by catch, Wim Leers, mglaman, marcelovani, Kingdutch: Add PHP Fibers support to BigPipe

Issue #2514960 by Aki Tendo, catch: \Drupal\Core\Theme\Registry->build() does not always return \Drupal\Core\Utility\ThemeRegistry

Issue #3335768 by Berdir, andypost, smustgrave, catch: Manually clear cache keys from plugin managers with finite variations instead of using cache tags

Issue #3304256 by longwave, Spokje, dww, lauriii, catch, quietone, mherchel: Remove Bartik from Drupal core

Issue #3285131 by andregp, daffie, catch, longwave: Fix constructor deprecation in Drupal\Core\Theme\Registry::__construct()

Issue #2616814 by dpi, Xano, geek-merlin, Hardik_Patel_12, jofitz, alexpott, Fabianx, catch, joachim, andypost, dawehner, daffie, cweagans, neclimdul: Delegate all hook invocations to ModuleHandler

Issue #3097889 by longwave, paulocs, anushrikumari, SenthilMohith, andypost, Gábor Hojtsy, catch, lauriii, Wim Leers: Remove deprecated theme functions

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 #2347783 by kim.pepper, andypost, almaudoh, gumanist, aleevas, rodrigoaguilera, Berdir, saurabh-2k17, Spokje, dhirendra.mishra, alexpott, paulocs, izus, Wim Leers, KapilV, naveenvalecha, anmolgoyal74, subson, yo30, harsha012, mrinalini9, daffie, voleger, dww, fietserwin, tim.plunkett, joachim, larowlan: Deprecate drupal_get_path() and drupal_get_filename() and replace with ExtensionList::getPath() and ExtensionList::getPathname()

Issue #2937513 by eltori, longwave, klausi, catch, idebr: Fix 'Drupal.Commenting.DocComment.TagGroupSpacing' coding standard

Issue #3120954 by tim.plunkett, czigor: Add function name to the deprecation message about theme functions

Issue #3109480 by longwave, catch, bnjmnm, xjm, lauriii, Gábor Hojtsy: Properly deprecate theme functions for Drupal 10

Issue #2861840 by tim.plunkett, lauriii: Preprocess functions are not merged when a module registers a theme hook for a theme-provided template

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 #2559825 by tim.plunkett, Antti J. Salminen, lauriii, aspilicious, alexpott: Preprocess functions from base hooks not triggered for theme hooks not using the __  pattern

This reverts commit d189ff05.

This reverts commit 4a95e650.

Issue #2719695 by alexpott, Mile23: Fix 'Drupal.Classes.ClassDeclaration.CloseBraceAfterBody' coding standard

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

Issue #2388247 by pguillard, snehi, joelpittet, sriharsha.uppuluri: Documentation refers to _theme() function, which has been removed

Issue #2493989 by Antti J. Salminen, lauriii, slashrsm: template_preprocess() and other preprocess functions are called even for theme hooks implemented as functions

Issue #2556785 by Antti J. Salminen, lauriii: Specific preprocess functions doesn't support second level without first level

Issue #939462 by lauriii, Antti J. Salminen, NROTC_Webmaster, mbrett5062, tim.plunkett, tostinni, rteijeiro, dvessel, cilefen, barraponto, theapi, joelpittet, Xano, tuutti, drzraf, Fabianx, markcarver, xjm, catch, Cottser, sun, jenlampton, effulgentsia, davidhernandez, kscheirer, akalata, andypost, hass, rooby, jhodgdon, fubhy, becw, MXT, mlncn, lemunet, chriscalip, mike stewart, PavanL, kevinquillen, gleroux02: Specific preprocess functions for theme hook suggestions are not invoked

Issue #1885564 by joelpittet, SebCorbin, Cottser, mpdonadio, David_Rothstein, drupalninja99, jenlampton, lauriii, rteijeiro, mbrett5062, akalata, Devin Carlson, trevorkjorlien, longwave, socketwench, shanethehat, aboros: theme.maintenance.inc (authorize.php) - Convert theme_ functions to Twig

Issue #2191115 by cs_shadow, alexrayu, JacobSanford, jhodgdon, Cottser: Clean up stale references to theme('foo') in documentation

Issue #2448847 by dawehner, arlinsandbulte: [regression] Themes unable to implement hook_theme_registry_alter()