[FEATURE] Parse simple expressions

config/phpstan-baseline.neon

@@ -48,6 +48,12 @@ parameters:
 			count: 3
 			path: ../src/Value/Color.php
 
+		-
+			message: '#^Parameter \#2 \$arguments of class Sabberworm\\CSS\\Value\\Expression constructor expects array\<Sabberworm\\CSS\\Value\\Value\|string\>\|Sabberworm\\CSS\\Value\\RuleValueList, Sabberworm\\CSS\\Value\\Value\|string given\.$#'
+			identifier: argument.type
+			count: 1
+			path: ../src/Value/Expression.php
+
 		-
 			message: '#^Parameters should have "float" types as the only types passed to this method$#'
 			identifier: typePerfect.narrowPublicClassMethodParamType
@@ -107,3 +113,9 @@ parameters:
 			identifier: argument.type
 			count: 2
 			path: ../tests/Unit/CSSList/CSSListTest.php
+
+		-
+			message: '#^Call to an undefined static method Sabberworm\\CSS\\Tests\\Value\\ExpressionTest\:\:listDelimiterForRule\(\)\.$#'
+			identifier: staticMethod.notFound
+			count: 1
+			path: ../tests/Unit/Value/ExpressionTest.php

src/Value/CSSFunction.php

@@ -17,14 +17,14 @@
 class CSSFunction extends ValueList
 {
     /**
-     * @var non-empty-string
+     * @var string
      *
      * @internal since 8.8.0
      */
     protected $name;
 
     /**
-     * @param non-empty-string $name
+     * @param string $name
      * @param RuleValueList|array<Value|string> $arguments
      * @param non-empty-string $separator
      * @param int<1, max>|null $lineNumber
@@ -76,7 +76,7 @@ private static function parseName(ParserState $parserState, bool $ignoreCase = f
      * @throws UnexpectedEOFException
      * @throws UnexpectedTokenException
      */
-    private static function parseArguments(ParserState $parserState)
+    protected static function parseArguments(ParserState $parserState)
     {
         return Value::parseValue($parserState, ['=', ' ', ',']);
     }

src/Value/Expression.php

@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sabberworm\CSS\Value;
+
+use Sabberworm\CSS\Parsing\ParserState;
+use Sabberworm\CSS\Parsing\SourceException;
+
+/**
+ * An `Expression` represents a special kind of value that is comprised of multiple components wrapped in parenthesis.
+ * Examle `height: (vh - 10);`.
+ */
+class Expression extends CSSFunction
+{
+    /**
+     * @throws SourceException
+     */
+    public static function parse(ParserState $oParserState, bool $bIgnoreCase = false): CSSFunction
+    {
+        $oParserState->consume('(');
+        $aArguments = parent::parseArguments($oParserState);
+        $mResult = new Expression('', $aArguments, ',', $oParserState->currentLine());
+        $oParserState->consume(')');
+        return $mResult;
+    }
+}

src/Value/Value.php

@@ -164,6 +164,8 @@ public static function parsePrimitiveValue(ParserState $parserState)
             $value = LineName::parse($parserState);
         } elseif ($parserState->comes('U+')) {
             $value = self::parseUnicodeRangeValue($parserState);
+        } elseif ($parserState->comes('(')) {
+            $value = Expression::parse($parserState);
         } else {
             $nextCharacter = $parserState->peek(1);
             try {

tests/ParserTest.php

@@ -435,6 +435,20 @@ public function functionSyntax(): void
         self::assertSame($expected, $document->render());
     }
 
+    /**
+     * @test
+     */
+    public function parseExpressions(): void
+    {
+        $oDoc = self::parsedStructureForFile('expressions');
+        $sExpected = 'div {height: (vh - 10);}'
+            . "\n"
+            . 'div {height: (vh - 10)/2;}'
+            . "\n"
+            . 'div {height: max(5,(vh - 10));}';
+        self::assertSame($sExpected, $oDoc->render());
+    }
+
     /**
      * @test
      */
@@ -593,8 +607,8 @@ public function calcNestedInFile(): void
     public function invalidCalcInFile(): void
     {
         $document = self::parsedStructureForFile('calc-invalid', Settings::create()->withMultibyteSupport(true));
-        $expected = 'div {}
-div {}
+        $expected = 'div {height: calc (25% - 1em);}
+div {height: calc (25% - 1em);}
 div {}
 div {height: -moz-calc;}
 div {height: calc;}';
@@ -1177,6 +1191,19 @@ public function lonelyImport(): void
         self::assertSame($expected, $document->render());
     }
 
+    /**
+     * @test
+     */
+    public function functionArithmeticInFile(): void
+    {
+        $oDoc = self::parsedStructureForFile('function-arithmetic', Settings::create()->withMultibyteSupport(true));
+        $sExpected = 'div {height: max(300,vh + 10);}
+div {height: max(300,vh - 10);}
+div {height: max(300,vh * 10);}
+div {height: max(300,vh / 10);}';
+        self::assertSame($sExpected, $oDoc->render());
+    }
+
     public function escapedSpecialCaseTokens(): void
     {
         $document = self::parsedStructureForFile('escaped-tokens');

tests/Unit/Value/ExpressionTest.php

@@ -0,0 +1,69 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sabberworm\CSS\Tests\Value;
+
+use PHPUnit\Framework\TestCase;
+use Sabberworm\CSS\Parsing\ParserState;
+use Sabberworm\CSS\OutputFormat;
+use Sabberworm\CSS\Settings;
+use Sabberworm\CSS\Value\Value;
+use Sabberworm\CSS\Value\ValueList;
+use Sabberworm\CSS\Value\Expression;
+use Sabberworm\CSS\Rule\Rule;
+
+/**
+ * @covers \Sabberworm\CSS\Value\Expression
+ */
+final class ExpressionTest extends TestCase
+{
+    /**
+     * @return list<array{input: non-empty-string, expected_output: non-empty-string, expression_index: int}>
+     */
+    public static function provideExpressions(): array
+    {
+        return [
+            [
+                'input' => '(vh - 10) / 2',
+                'expected_output' => '(vh - 10)/2',
+                'expression_index' => 0,
+            ],
+            [
+                'input' => 'max(5, (vh - 10))',
+                'expected_output' => 'max(5,(vh - 10))',
+                'expression_index' => 1,
+            ],
+        ];
+    }
+
+    /**
+     * @test
+     *
+     * @dataProvider provideExpressions
+     */
+    public function parseExpressions(string $input, string $expected, int $expression_index): void
+    {
+        $val = Value::parseValue(
+            new ParserState($input, Settings::create()),
+            $this->getDelimiters('height')
+        );
+
+        self::assertInstanceOf(ValueList::class, $val);
+        self::assertInstanceOf(Expression::class, $val->getListComponents()[$expression_index]);
+        self::assertSame($expected, $val->render(OutputFormat::createCompact()));
+    }
+
+    /**
+     * @return list<non-empty-string>
+     */
+    private function getDelimiters(string $rule): array
+    {
+        $closure = function ($rule) {
+            return self::listDelimiterForRule($rule);
+        };
+
+        $getter = $closure->bindTo(null, Rule::class);
+        return $getter($rule);
+    }
+}

tests/fixtures/expressions.css

@@ -0,0 +1,11 @@
+div {
+    height: (vh - 10);
+}
+
+div {
+    height: (vh - 10) / 2;
+}
+
+div {
+    height: max(5, (vh - 10));
+}

tests/fixtures/function-arithmetic.css

@@ -0,0 +1,12 @@
+div {
+    height: max(300, vh + 10);
+}
+div {
+    height: max(300, vh - 10);
+}
+div {
+    height: max(300, vh * 10);
+}
+div {
+    height: max(300, vh / 10);
+}