[BUGFIX] Allow at-rules to be parsed in strict mode

The reverts the change to `CSSList` in
134f4e6
and adds a comment that `null` is an expected return value when the end of
the list (or block) is reached.

It also adds a convention, for now, that a test filename beginning with `=`
should mean that it is initially tested with strict parsing enabled.

Fixes #352

Author: JakeQZ

CHANGELOG.md

@@ -19,6 +19,8 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 
 ### Fixed
 
+Fix (regression) failure to parse at-rules with strict parsing (#456)
+
 ## 8.5.0
 
 ### Added

src/CSSList/CSSList.php

@@ -131,18 +131,15 @@ private static function parseListItem(ParserState $oParserState, CSSList $oList)
             }
             return $oAtRule;
         } elseif ($oParserState->comes('}')) {
-            if (!$oParserState->getSettings()->bLenientParsing) {
-                throw new UnexpectedTokenException('CSS selector', '}', 'identifier', $oParserState->currentLine());
-            } else {
-                if ($bIsRoot) {
-                    if ($oParserState->getSettings()->bLenientParsing) {
-                        return DeclarationBlock::parse($oParserState);
-                    } else {
-                        throw new SourceException("Unopened {", $oParserState->currentLine());
-                    }
+            if ($bIsRoot) {
+                if ($oParserState->getSettings()->bLenientParsing) {
+                    return DeclarationBlock::parse($oParserState);
                 } else {
-                    return null;
+                    throw new SourceException("Unopened {", $oParserState->currentLine());
                 }
+            } else {
+                // End of list
+                return null;
             }
         } else {
             return DeclarationBlock::parse($oParserState, $oList);

tests/ParserTest.php

@@ -74,7 +74,10 @@ public function files()
                     // or a future test of a as-of-now missing feature
                     continue;
                 }
-                $oParser = new Parser(file_get_contents($sDirectory . '/' . $sFileName));
+                $oParser = new Parser(
+                    \file_get_contents($sDirectory . '/' . $sFileName),
+                    Settings::create()->withLenientParsing($sFileName[0] !== '=')
+                );
                 try {
                     self::assertNotEquals('', $oParser->parse()->render());
                 } catch (\Exception $e) {

tests/fixtures/=at-media-min-width.css

@@ -0,0 +1,3 @@
+@media (min-width: 1220px) {
+  div { width:auto; }
+}

tests/fixtures/=at-media.css

@@ -0,0 +1,8 @@
+@media print
+{
+	html
+	{
+		background: white;
+		color: black;
+	}
+}