[BUGFIX] Reject selector comprising only whitespace (#1433)

Author: JakeQZ

CHANGELOG.md

@@ -24,6 +24,7 @@ Please also have a look at our
 
 ### Fixed
 
+- Reject selector comprising only whitespace (#1433)
 - Improve recovery parsing when a rogue `}` is encountered (#1425, #1426)
 - Parse comment(s) immediately preceding a selector (#1421)
 - Parse consecutive comments (#1421)

src/RuleSet/DeclarationBlock.php

@@ -354,6 +354,11 @@ private static function parseSelector(ParserState $parserState, array &$comments
             throw new UnexpectedTokenException(')', $nextCharacter);
         }
 
-        return \implode('', $selectorParts);
+        $selector = \trim(\implode('', $selectorParts));
+        if ($selector === '') {
+            throw new UnexpectedTokenException('selector', $nextCharacter, 'literal', $parserState->currentLine());
+        }
+
+        return $selector;
     }
 }

tests/Unit/RuleSet/DeclarationBlockTest.php

@@ -159,20 +159,43 @@ public function parsesTwoCommaSeparatedSelectors(string $firstSelector, string $
     }
 
     /**
-     * @return array<non-empty-string, array{0: non-empty-string}>
+     * @return array<non-empty-string, array{0: string, 1: non-empty-string}>
      */
-    public static function provideInvalidSelector(): array
+    public static function provideInvalidSelectorAndExpectedExceptionMessage(): array
     {
         // TODO: the `parse` method consumes the first character without inspection,
-        // so the 'lone' test strings are prefixed with a space.
+        // so some of the test strings are prefixed with a space.
         return [
-            'lone `(`' => [' ('],
-            'lone `)`' => [' )'],
-            'unclosed `(`' => [':not(#your-mug'],
-            'extra `)`' => [':not(#your-mug))'],
+            'no selector' => [' ', 'Token “selector” (literal) not found. Got “{”. [line no: 1]'],
+            'lone `(`' => [' (', 'Token “)” (literal) not found. Got “{”.'],
+            'lone `)`' => [' )', 'Token “anything but” (literal) not found. Got “)”.'],
+            'lone `,`' => [' ,', 'Token “selector” (literal) not found. Got “,”. [line no: 1]'],
+            'unclosed `(`' => [':not(#your-mug', 'Token “)” (literal) not found. Got “{”.'],
+            'extra `)`' => [':not(#your-mug))', 'Token “anything but” (literal) not found. Got “)”.'],
+            '`,` missing left operand' => [' , a', 'Token “selector” (literal) not found. Got “,”. [line no: 1]'],
+            '`,` missing right operand' => ['a,', 'Token “selector” (literal) not found. Got “{”. [line no: 1]'],
         ];
     }
 
+    /**
+     * @return array<non-empty-string, array{0: string}>
+     */
+    public static function provideInvalidSelector(): array
+    {
+        // Re-use the set of invalid selectors, but remove the expected exception message for tests that don't need it.
+        return \array_map(
+            /**
+             * @param array{0: string, 1: non-empty-string}
+             *
+             * @return array<{0: string}>
+             */
+            static function (array $testData): array {
+                return [$testData[0]];
+            },
+            self::provideInvalidSelectorAndExpectedExceptionMessage()
+        );
+    }
+
     /**
      * @test
      *
@@ -192,6 +215,25 @@ public function parseSkipsBlockWithInvalidSelector(string $selector): void
         self::assertTrue($parserState->comes($nextCss));
     }
 
+    /**
+     * @test
+     *
+     * @param non-empty-string $expectedExceptionMessage
+     *
+     * @dataProvider provideInvalidSelectorAndExpectedExceptionMessage
+     */
+    public function parseInStrictModeThrowsExceptionWithInvalidSelector(
+        string $selector,
+        string $expectedExceptionMessage
+    ): void {
+        $this->expectException(UnexpectedTokenException::class);
+        $this->expectExceptionMessage($expectedExceptionMessage);
+
+        $parserState = new ParserState($selector . ' {}', Settings::create()->beStrict());
+
+        $subject = DeclarationBlock::parse($parserState);
+    }
+
     /**
      * @return array<non-empty-string, array{0: non-empty-string}>
      */
@@ -436,7 +478,7 @@ public static function provideInvalidStandaloneSelector(): array
     public function setSelectorsThrowsExceptionWithInvalidSelector(string $selector): void
     {
         $this->expectException(UnexpectedTokenException::class);
-        $this->expectExceptionMessageMatches('/^Selector\\(s\\) string is not valid. /');
+        $this->expectExceptionMessageMatches('/^Selector\\(s\\) string is not valid./');
 
         $subject = new DeclarationBlock();