Issue #1493324 by tim.plunkett, dmsmidt, mgifford, bleen18, davidhernandez, crasx, mparker17, stefan.r, YesCT, joelpittet, tstoeckler, larowlan, vijaycs85, swentel, rpayanm, Bojhan, LewisNyman, emma.maria, BarisW, njbarrett, rteijeiro, nod_, sun, joshtaylor, mrjmd, webchick, marcvangend, kattekrab, SKAUGHT, bowersox, andrewmacpherson, Manjit.Singh, RavindraSingh, Wim Leers, BLadwin, aspilicious, mortendk, mausolos, jessebeach, Gábor Hojtsy, anandps, falcon03, franz, andypost, rooby, rootwork, Cottser, Xano: Inline form errors for accessibility and UX

Issue #2463321 by amateescu: Serializing the database connection is dangerous and error-prone, make it unserializable again

Issue #2457887 by prateekMehta, stefan.r, rpayanm, alexpott: Use Utility\SafeMarkup class instead of Utility\String for placeholder(), checkPlain(),format() functions

Issue #2335673 by ashutoshsngh, oenie, rudins, er.pushpinderrana: Remove usage of drupal_process_form()

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

Issue #2030165 by Berdir, tim.plunkett, vijaycs85, tkuldeep17 | rteijeiro: Convert form_test_* functions to classes.

Issue #697760 by sun: Replace getInfo() in tests with native phpDoc + annotations (following PHPUnit).

Issue #2089331 by grom358 | thedavidmeister: [meta] Replace calls to check_plain() with Drupal\Component\Utility\String::checkPlain().

Issue #2152217 by joelpittet, mgifford, vijaycs85, jjcarrion, sun: Remove theme_form_required_marker() from the theme system - use CSS instead.

Issue #2208609 by sun, Jalandhar, damiankloip: Move Json utility class into Drupal\Component\Serialization.

Issue #2093173 by longwave, Cyberschorsch, forbesgraham, sandipmkhairnar, damiankloip, rbayliss, grom358, harijari, InternetDevels, dawehner: Remove all calls to drupal_json_decode(), use \Drupal\Component\Utility\Json::decode().

Issue #2192419 by sun, mgifford: Use a WCAG-compliant fieldset (fieldgroup) for #type radios/checkboxes.

Issue #2191285 by sun, andypost, jibran, Berdir, alexpott: Text module is not required, but is marked as required.

Issue #1987716 by pfrenssen, tim.plunkett, kgoel: Provide a FormTestBase class to allow PHPUnit form tests.

Issue #2143349 by larowlan: Submitting a form as an anonymous user when $form['#token'] = FALSE results in a notice.

Issue #2121775 by jessebeach: Make the markup associated with the required star on field items silent.

Issue #2080391 by johnmcc, Bladedu, chertzog, jeroen12345: Remove Unused local variables from multiple core files.

Issue #2074037 by Wim Leers, effulgentsia: Add drupalPostUrl() — drupalPost()/drupalPostAjax() are for forms only, D8 JS performs non-form HTTP requests.

Issue #2047075 by Caecus, mgifford, jessebeach, larowlan: Mark invalid form field with [aria-invalid=true].