Fix counting *scanf() format string placeholders

src/Rules/Functions/PrintfHelper.php

@@ -5,12 +5,14 @@
 use Nette\Utils\Strings;
 use PHPStan\DependencyInjection\AutowiredService;
 use PHPStan\Php\PhpVersion;
+use ValueError;
 use function array_filter;
 use function array_keys;
 use function count;
 use function in_array;
 use function max;
 use function sprintf;
+use function sscanf;
 use function strlen;
 use const PREG_SET_ORDER;
 
@@ -26,24 +28,36 @@ public function __construct(private PhpVersion $phpVersion)
 
 	public function getPrintfPlaceholdersCount(string $format): ?int
 	{
-		return $this->getPlaceholdersCount(self::PRINTF_SPECIFIER_PATTERN, $format, false);
+		return $this->getPlaceholdersCount(self::PRINTF_SPECIFIER_PATTERN, $format);
 	}
 
 	/** @phpstan-return array<int, non-empty-list<PrintfPlaceholder>> parameter index => placeholders */
 	public function getPrintfPlaceholders(string $format): ?array
 	{
-		return $this->parsePlaceholders(self::PRINTF_SPECIFIER_PATTERN, $format, false);
+		return $this->parsePlaceholders(self::PRINTF_SPECIFIER_PATTERN, $format);
 	}
 
 	public function getScanfPlaceholdersCount(string $format): ?int
 	{
-		return $this->getPlaceholdersCount('(?<specifier>[cdDeEfinosuxX%s]|\[[^\]]+\])', $format, true);
+		if ($this->phpVersion->throwsValueErrorForInternalFunctions()) {
+			try {
+				$result = sscanf('', '%*n' . $format);
+			} catch (ValueError) {
+				return null;
+			}
+		} else {
+			$result = @sscanf('', '%*n' . $format);
+		}
+		if ($result === null) {
+			return null;
+		}
+		return count($result);
 	}
 
 	/**
 	 * @phpstan-return array<int, non-empty-list<PrintfPlaceholder>>|null parameter index => placeholders
 	 */
-	private function parsePlaceholders(string $specifiersPattern, string $format, bool $isScanf): ?array
+	private function parsePlaceholders(string $specifiersPattern, string $format): ?array
 	{
 		$addSpecifier = '';
 		if ($this->phpVersion->supportsHhPrintfSpecifier()) {
@@ -72,10 +86,6 @@ private function parsePlaceholders(string $specifiersPattern, string $format, bo
 			$showValueSuffix = false;
 
 			if (isset($placeholder['width']) && $placeholder['width'] !== '') {
-				if ($isScanf) {
-					// In scanf, * means assignment suppression - skip this placeholder entirely
-					continue;
-				}
 				$parsedPlaceholders[] = new PrintfPlaceholder(
 					sprintf('"%s" (width)', $placeholder[0]),
 					$parameterIdx++,
@@ -136,9 +146,9 @@ private function getAcceptingTypeBySpecifier(string $specifier): string
 		return 'mixed';
 	}
 
-	private function getPlaceholdersCount(string $specifiersPattern, string $format, bool $isScanf): ?int
+	private function getPlaceholdersCount(string $specifiersPattern, string $format): ?int
 	{
-		$placeholdersMap = $this->parsePlaceholders($specifiersPattern, $format, $isScanf);
+		$placeholdersMap = $this->parsePlaceholders($specifiersPattern, $format);
 		if ($placeholdersMap === null) {
 			return null;
 		}

tests/PHPStan/Rules/Functions/PrintfParametersRuleTest.php

@@ -84,6 +84,14 @@ public function testFile(): void
 				'Call to sprintf contains 2 placeholders, 1 value given.',
 				29,
 			],
+			[
+				'Call to sscanf contains an invalid placeholder.',
+				38,
+			],
+			[
+				'Call to fscanf contains an invalid placeholder.',
+				39,
+			],
 			[
 				'Call to sprintf contains 2 placeholders, 1 value given.',
 				45,

tests/PHPStan/Rules/Functions/data/printf.php

@@ -35,8 +35,8 @@
 sscanf($str, "%20[^abcde]a%d", $string, $number); // ok
 printf("%.E", 3.14159); // ok
 sprintf("%.E", 3.14159); // ok
-sscanf($str, '%.E', $number); // ok
-fscanf($str, '%.E', $number); // ok
+sscanf($str, '%.E', $number); // bad scan conversion character '.'
+fscanf($resource, '%.E', $number); // bad scan conversion character '.'
 sscanf($str, '%[A-Z]%d', $char, $number); // ok
 sprintf('%s %s %s', ...[1]); // do not detect unpacked arguments
 sprintf('%s %s %s', ...[1, 2, 3]); // ok