RegexArrayShapeMatcher - Fix optional groups with PREG_UNMATCHED_AS_NULL

Author: staabm

src/Type/Php/RegexArrayShapeMatcher.php

@@ -121,10 +121,13 @@ private function matchRegex(string $regex, ?int $flags, TrinaryLogic $wasMatched
 				$flags ?? 0,
 			);
 
-			return TypeCombinator::union(
-				new ConstantArrayType([new ConstantIntegerType(0)], [new StringType()], [0], [], true),
-				$combiType,
-			);
+			if (!$this->containsUnmatchedAsNull($flags ?? 0)) {
+				$combiType = TypeCombinator::union(
+					new ConstantArrayType([new ConstantIntegerType(0)], [new StringType()], [0], [], true),
+					$combiType,
+				);
+			}
+			return $combiType;
 		} elseif (
 			$wasMatched->yes()
 			&& $onlyTopLevelAlternationId !== null

tests/PHPStan/Analyser/nsrt/preg_match_shapes.php

@@ -353,6 +353,17 @@ function bug11277b(string $value): void
 	}
 }
 
+// see https://3v4l.org/VeDob
+function unmatchedAsNullWithOptionalGroup(string $s): void {
+	if (preg_match('/Price: (£|€)?\d+/', $s, $matches, PREG_UNMATCHED_AS_NULL)) {
+		// with PREG_UNMATCHED_AS_NULL the offset 1 will always exist. It is correct that it's nullable because it's optional though
+		assertType('array{string, string|null}', $matches);
+	} else {
+		assertType('array{}', $matches);
+	}
+	assertType('array{}|array{string, string|null}', $matches);
+}
+
 // https://www.pcre.org/current/doc/html/pcre2pattern.html#dupgroupnumber
 // https://3v4l.org/09qdT
 function bug11291(string $s): void {