Fix #13963 with unit tests.

src/Type/Php/FilterFunctionReturnTypeHelper.php

@@ -191,7 +191,11 @@
 			$type = TypeCombinator::intersect($type, $accessory);
 		}
 
-		if ($exactType === null || $hasOptions->maybe() || (!$inputType->equals($type) && $inputType->isSuperTypeOf($type)->yes())) {
+		if (
+			$exactType === null
+			|| $hasOptions->maybe()
+			|| ($this->isValidationFilter($filterValue) && (!$inputType->equals($type) && $inputType->isSuperTypeOf($type)->yes()))
+		) {
 			if (!$defaultType->isSuperTypeOf($type)->yes()) {
 				$type = TypeCombinator::union($type, $defaultType);
 			}
@@ -389,18 +393,46 @@
 		}
 
 		if ($filterValue === $this->getConstant('FILTER_DEFAULT')) {
-			if ($this->canStringBeSanitized($filterValue, $flagsType)->no() && $in->isString()->yes()) {
-				return $in;
-			}
+			$scalarOrNull = new UnionType([
+				new StringType(),
+				new FloatType(),
+				new BooleanType(),
+				new IntegerType(),
+				new NullType(),
+			]);
+
+			if ($scalarOrNull->isSuperTypeOf($in)->yes()) {
+				$canBeSanitized = $this->canStringBeSanitized($filterValue, $flagsType);
+				if ($canBeSanitized->no()) {
+					$stringType = $in->toString();
+				} else {
+					$stringType = $in->isString()->no()
+						? $in->toString()
+						: TypeCombinator::union(TypeCombinator::remove($in, new StringType()), new StringType());
+				}
 
-			if ($in->isBoolean()->yes() || $in->isFloat()->yes() || $in->isInteger()->yes() || $in->isNull()->yes()) {
-				return $in->toString();
+				return $this->handleEmptyStringNullFlag($stringType, $flagsType);
 			}
 		}
 
 		return null;
 	}
 
+	private function handleEmptyStringNullFlag(Type $in, ?Type $flagsType): Type
+	{
+		$hasFlag = $this->hasFlag('FILTER_FLAG_EMPTY_STRING_NULL', $flagsType);
+		if ($hasFlag->no()) {
+			return $in;
+		}
+
+		$hasEmptyString = !$in->isSuperTypeOf(new ConstantStringType(''))->no();
+		if ($hasFlag->maybe()) {
+			return $hasEmptyString ? TypeCombinator::addNull($in) : $in;
+		}
+
+		return $hasEmptyString ? TypeCombinator::remove(TypeCombinator::addNull($in), new ConstantStringType('')) : $in;
+	}
+
 	/** @param array<string, ?Type> $typeOptions */
 	private function applyRangeOptions(Type $type, array $typeOptions, Type $defaultType): Type
 	{
@@ -532,7 +564,7 @@
 	private function canStringBeSanitized(int $filterValue, ?Type $flagsType): TrinaryLogic
 	{
 		// If it is a validation filter, the string will not be changed
-		if (($filterValue & self::VALIDATION_FILTER_BITMASK) !== 0) {
+		if ($this->isValidationFilter($filterValue)) {
 			return TrinaryLogic::createNo();
 		}
 
@@ -547,4 +579,9 @@
 		return TrinaryLogic::createYes();
 	}
 
+	private function isValidationFilter(int $filterValue): bool
+	{
+		return ($filterValue & self::VALIDATION_FILTER_BITMASK) !== 0;
+	}
+
 }

tests/PHPStan/Analyser/nsrt/filter-var-returns-non-empty-string.php

@@ -8,24 +8,55 @@ class Foo
 {
 	/**
 	 * @param non-empty-string $str
+	 * @param string $maybe_empty_string
+	 * @param null|string $nullable_string
+	 * @param null|non-empty-string $nullable_non_empty_string
+	 * @param int $int
 	 * @param positive-int $positive_int
 	 * @param negative-int $negative_int
+	 * @param bool $bool
 	 */
-	public function run(string $str, int $int, int $positive_int, int $negative_int): void
+	public function run(
+		string $str,
+		string $maybe_empty_string,
+		?string $nullable_string,
+		?string $nullable_non_empty_string,
+		int $int,
+		int $positive_int,
+		int $negative_int,
+		bool $bool,
+	): void
 	{
+		$object = (object)[];
+
 		assertType('non-empty-string', $str);
 
 		$return = filter_var($str, FILTER_DEFAULT);
 		assertType('non-empty-string', $return);
 
+		$return = filter_var($str, FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType('non-empty-string', $return);
+
+		$return = filter_var($maybe_empty_string, FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType('non-empty-string|null', $return);
+
+		$return = filter_var($object, FILTER_DEFAULT, FILTER_FLAG_STRIP_LOW);
+		assertType('false', $return);
+
 		$return = filter_var($str, FILTER_DEFAULT, FILTER_FLAG_STRIP_LOW);
-		assertType('string|false', $return);
+		assertType('string', $return);
+
+		$return = filter_var($object, FILTER_DEFAULT, FILTER_FLAG_STRIP_HIGH);
+		assertType('false', $return);
 
 		$return = filter_var($str, FILTER_DEFAULT, FILTER_FLAG_STRIP_HIGH);
-		assertType('string|false', $return);
+		assertType('string', $return);
+
+		$return = filter_var($object, FILTER_DEFAULT, FILTER_FLAG_STRIP_BACKTICK);
+		assertType('false', $return);
 
 		$return = filter_var($str, FILTER_DEFAULT, FILTER_FLAG_STRIP_BACKTICK);
-		assertType('string|false', $return);
+		assertType('string', $return);
 
 		$return = filter_var($str, FILTER_VALIDATE_EMAIL);
 		assertType('non-falsy-string|false', $return);
@@ -51,6 +82,9 @@ public function run(string $str, int $int, int $positive_int, int $negative_int)
 		$return = filter_var($str, FILTER_SANITIZE_STRING);
 		assertType('string|false', $return);
 
+		$return = filter_var($object, FILTER_SANITIZE_STRING);
+		assertType('false', $return);
+
 		$return = filter_var($str, FILTER_VALIDATE_INT);
 		assertType('int|false', $return);
 
@@ -100,6 +134,9 @@ public function run(string $str, int $int, int $positive_int, int $negative_int)
 		$return = filter_var($str2, FILTER_DEFAULT);
 		assertType("''", $return);
 
+		$return = filter_var('', FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType('null', $return);
+
 		$return = filter_var($str2, FILTER_VALIDATE_URL);
 		assertType('non-falsy-string|false', $return);
 
@@ -129,5 +166,53 @@ public function run(string $str, int $int, int $positive_int, int $negative_int)
 
 		$return = filter_var('0x10', FILTER_VALIDATE_INT, FILTER_FLAG_ALLOW_HEX);
 		assertType('16', $return);
+
+		$return = filter_var(true, FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType("'1'", $return);
+
+		$return = filter_var(false, FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType('null', $return);
+
+		$return = filter_var($bool, FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType("'1'|null", $return);
+
+		$return = filter_var(0.0, FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType("'-0'|'0'", $return);
+
+		$return = filter_var(0, FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType("'0'", $return);
+
+		$return = filter_var(null, FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType('null', $return);
+
+		$return = filter_var($nullable_string, FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType('non-empty-string|null', $return);
+
+		$return = filter_var($nullable_non_empty_string, FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType('non-empty-string|null', $return);
+
+		$return = filter_var($object, FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType('false', $return);
+
+		$return = filter_var($this->anyOf(0.0, true), FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType("'-0'|'0'|'1'", $return);
+
+		$return = filter_var($this->anyOf($bool, $maybe_empty_string), FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType("non-empty-string|null", $return);
+
+		$return = filter_var($this->anyOf(0, null), FILTER_DEFAULT, FILTER_FLAG_EMPTY_STRING_NULL);
+		assertType("'0'|null", $return);
+	}
+
+	/**
+	 * @template T
+	 * @template U
+	 * @param T $a
+	 * @param U $b
+	 * @return T|U
+	 */
+	private function anyOf($a, $b)
+	{
+		return random_int(0, 1) ? $a : $b;
 	}
 }