V9.0.0: New features, deprecation removals and bug fixes

Added

• Interface RuleContainer for RuleSet Rule manipulation methods (#1256)
• Partial support for CSS Color Module Level 4:
  • rgb and rgba, and hsl and hsla are now aliases (#797)
  • Parse color functions that use the "modern" syntax (#800)
  • Render RGB functions with "modern" syntax when required (#840)
  • Support none as color function component value (#859)
• Add a class diagram to the README (#482)
• Add more tests (#449)

Changed

• DeclarationBlock no longer extends RuleSet and instead has a RuleSet as
  a property; use getRuleSet() to access it directly (#1194)
• The default line (and column) number is now null (not zero) (#1288)
• setPosition() (in Rule and other classes) now has fluent interface,
  returning itself (#1259)
• RuleSet::removeRule() now only allows Rule as the parameter
  (implementing classes are AtRuleSet and DeclarationBlock);
  use removeMatchingRules() or removeAllRules() for other functions (#1255)
• RuleSet::getRules() and getRulesAssoc() now only allow string or null
  as the parameter (implementing classes are AtRuleSet and DeclarationBlock)
  (#1253)
• Initialize KeyFrame properties to sensible defaults (#1146)
• Make OutputFormat final (#1128)
• Make Selector a Renderable (#1017)
• Only allow string for some OutputFormat properties (#885)
• Use more native type declarations and strict mode
  (#641, #772, #774, #778, #804, #841, #873, #875, #891, #922, #923, #933, #958,
  #964, #967, #1000, #1044, #1134, #1136, #1137, #1139, #1140, #1141, #1145,
  #1162, #1163, #1166, #1172, #1174, #1178, #1179, #1181, #1183, #1184, #1186,
  #1187, #1190, #1192, #1193, #1203)
• Add visibility to all class/interface constants (#469)

Removed

• Remove getLineNo() from these classes (use getLineNumber() instead):
  Comment, CSSList, SourceException, Charset, CSSNamespace, Import,
  Rule, DeclarationBlock, RuleSet, CSSFunction, Value (#1258)
• Remove Rule::getColNo() (use getColumnNumber() instead) (#1287)
• Passing a string as the first argument to getAllValues() is no longer
  supported and will not work;
  the search pattern should now be passed as the second argument (#1243)
• Passing a Boolean as the second argument to getAllValues() is no longer
  supported and will not work; the flag for searching in function arguments
  should now be passed as the third argument (#1243)
• Remove __toString() (#1046)
• Drop magic method forwarding in OutputFormat (#898)
• Drop atRuleArgs() from the AtRule interface (#1141)
• Remove OutputFormat::get() and ::set() (#1108, #1110)
• Drop special support for vendor prefixes (#1083)
• Remove the IE hack in Rule (#995)
• Drop getLineNo() from the Renderable interface (#1038)
• Remove OutputFormat::level() (#874)
• Remove expansion of shorthand properties (#838)
• Remove Parser::setCharset/getCharset (#808)
• Remove Rule::getValues() (#582)
• Remove Rule::setValues() (#562)
• Remove Document::getAllSelectors() (#561)
• Remove DeclarationBlock::getSelector() (#559)
• Remove DeclarationBlock::setSelector() (#560)
• Drop support for PHP < 7.2 (#420)

Fixed

• Remove trailing semicolon from declaration blocks with 'compact'
  OutputFormat (#1345)
• Parse selector functions (like :not) with comma-separated arguments (#1292)
• Parse quoted attribute selector value containing comma (#1323)
• Allow comma in selectors (e.g. :not(html, body)) (#1293)
• Insert Rule before sibling even with different property name
  (in RuleSet::addRule()) (#1270)
• Ensure RuleSet::addRule() sets non-negative column number when sibling
  provided (#1268)
• Don't render rgb colors with percentage values using hex notation (#803)

Documentation

• Add an API and deprecation policy (#720)

@ziegenberg is a new contributor to this release and did a lot of the heavy
lifting. Thanks! ❤️