Issue #2935256 by Jo Fitzgerald, voleger, kim.pepper, ibustos, Yogesh Pawar, catch, jibran: Remove all usages of drupal_get_message and drupal_set_message in modules

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

Issue #2572791 by Mile23, andriyun, attiks, RoSk0: Fix 'Drupal.WhiteSpace.OpenBracketSpacing' coding standard

Issue #1862892 by oriol_e9g, joseph.olstad, vaplas, G.I.Joe, leopathu, peterpoe, cilefen, xjm, larowlan: When a theme has a managed_file field and a submit callback, call to undefined function error is thrown

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 #2594937 by Peacog, cilefen, Sagar Ramgade, chgasparoto, aerozeppelin, iStryker, feraline, alvar0hurtad0, Cottser, Wim Leers, xjm, sebas5384, almaudoh, gvso, racarvalho1987: Empty 'libraries:' in theme .info.yml file produces confusing PHP warning

Issue #2687897 by dawehner, jhedstrom, catch, jibran, Berdir, klausi: Convert system module's kernel tests to NG

Issue #2682723 by thpoul, jagjitsingh_drupal, avinashm, maggo: Allow ckeditor_stylesheets to refer to external URL, for e.g. webfonts

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

Issue #304540 by typhonius, BrockBoland, nabiyllin, RobLoach, marcingy, ravi.khetri, jyotisankar, sudhanshug, jaredsmith, nesta_: Disable themes when theme engine or base theme aren't available

Issue #2572643 by alexpott, attiks, Jelle_S, jhodgdon: Fix Drupal.Commenting.FileComment coding standard

Issue #2553553 by burkeker, alvar0hurtad0, meramo: Remove references to system.module.css and system.theme.css in core

Issue #2122087 by rakesh.gectcr, snehi, InternetDevels, Xano, alvar0hurtad0: Remove references to hook_init()

Issue #2575737 by Cottser, davidhernandez: Copy templates, CSS, and related assets to Stable and override core libraries' CSS

Issue #2574975 by alexpott, Cottser, izus: Allow (base-)themes to be excluded from the UI (e.g. blocks, Appearance)

Issue #2513266 by mikeker, joelpittet, lauriii, Cottser, pwolanin, larowlan, Fabianx, stevector, catch, alexpott, dawehner: Twig templates can call delete() on entities and other objects

Issue #2575735 by almaudoh: LibraryDiscoveryCollector::reset() does not properly reset its $cid, resulting in loading wrong library assets if the active theme changes

Issue #2575421 by Cottser, mdrummond, lauriii, davidhernandez, LewisNyman, catch, alexpott, joelpittet, webchick, Bojhan, emma.maria, mortendk: Add a Stable base theme to core and make it the default if a base theme is not specified

Issue #2520540 by alexpott: Enforced configuration dependencies shouldn't have to be repeated in the calculated dependencies

Issue #2497667 by almaudoh, Wim Leers, Cottser, Fabianx, jaxxed: Add libraries-extend to themes' *.info.yml

Issue #2451411 by almaudoh, Shamsher_Alam, lauriii, borisson_, cilefen, davidhernandez, Cottser, Wim Leers, joelpittet: Add libraries-override to themes' *.info.yml

Issue #2574717 by dawehner, hussainweb, lauriii, pwolanin, davidhernandez, xjm, stefan.r, webchick, Wim Leers: Remove PHPTemplate, and add test coverage for multiple theme engine support

Issue #2545972 by alexpott, joelpittet, ericjenkins, stefan.r, Wim Leers, Cottser: Remove all code usages SafeMarkup::checkPlain() and rely more on Twig autoescaping

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 #2489830 by cilefen, davidhernandez, dcmul, Adam Clarey, joshi.rohit100, rpayanm, sqndr, Cottser, lauriii: Improve theme compatibility error message

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

Issue #2349711 by lauriii, mortendk, sqndr, akalata, yannickoo, Manjit.Singh, Jolidog, b0unty, aliyakhan, LewisNyman: Remove all visual from stark

Issue #2465887 by dawehner, amateescu, tim.plunkett: Extract the install/uninstall functionality to a ThemeInstaller

Issue #2432791 by alexpott, vijaycs85, tim.plunkett, joshtaylor, Fabianx, Berdir, yched, bojanz: Skip Config::save schema validation of config data for trusted data.

Issue #2389735 by lauriii, iMiksu, davidhernandez, larowlan, loopduplicate, LewisNyman, Wim Leers, dawehner, Cottser: Core and base theme CSS files in libraries override theme CSS files with the same name