Improve StrSplit returnType

Author: VincentLanglet

src/Type/Php/StrSplitFunctionReturnTypeExtension.php

@@ -9,6 +9,9 @@
 use PHPStan\ShouldNotHappenException;
 use PHPStan\TrinaryLogic;
 use PHPStan\Type\Accessory\AccessoryArrayListType;
+use PHPStan\Type\Accessory\AccessoryLowercaseStringType;
+use PHPStan\Type\Accessory\AccessoryNonEmptyStringType;
+use PHPStan\Type\Accessory\AccessoryUppercaseStringType;
 use PHPStan\Type\Accessory\NonEmptyArrayType;
 use PHPStan\Type\ArrayType;
 use PHPStan\Type\Constant\ConstantArrayType;
@@ -80,32 +83,43 @@ public function getTypeFromFunctionCall(FunctionReflection $functionReflection,
 			}
 		}
 
-		if (!isset($splitLength)) {
-			return null;
-		}
-
 		$stringType = $scope->getType($functionCall->getArgs()[0]->value);
-
-		$constantStrings = $stringType->getConstantStrings();
-		if (count($constantStrings) > 0) {
-			$results = [];
-			foreach ($constantStrings as $constantString) {
-				$items = $encoding === null
-					? str_split($constantString->getValue(), $splitLength)
-					: @mb_str_split($constantString->getValue(), $splitLength, $encoding);
-				if ($items === false) {
-					throw new ShouldNotHappenException();
+		if (isset($splitLength)) {
+			$constantStrings = $stringType->getConstantStrings();
+			if (count($constantStrings) > 0) {
+				$results = [];
+				foreach ($constantStrings as $constantString) {
+					$items = $encoding === null
+						? str_split($constantString->getValue(), $splitLength)
+						: @mb_str_split($constantString->getValue(), $splitLength, $encoding);
+					if ($items === false) {
+						throw new ShouldNotHappenException();
+					}
+
+					$results[] = self::createConstantArrayFrom($items, $scope);
 				}
 
-				$results[] = self::createConstantArrayFrom($items, $scope);
+				return TypeCombinator::union(...$results);
 			}
+		}
+
+		$isInputNonEmptyString = $stringType->isNonEmptyString()->yes();
 
-			return TypeCombinator::union(...$results);
+		$valueTypes = [new StringType()];
+		if ($isInputNonEmptyString || $this->phpVersion->strSplitReturnsEmptyArray()) {
+			$valueTypes[] = new AccessoryNonEmptyStringType();
+		}
+		if ($stringType->isLowercaseString()->yes()) {
+			$valueTypes[] = new AccessoryLowercaseStringType();
+		}
+		if ($stringType->isUppercaseString()->yes()) {
+			$valueTypes[] = new AccessoryUppercaseStringType();
 		}
+		$returnValueType = TypeCombinator::intersect(new StringType(), ...$valueTypes);
 
-		$returnType = AccessoryArrayListType::intersectWith(new ArrayType(new IntegerType(), new StringType()));
+		$returnType = AccessoryArrayListType::intersectWith(TypeCombinator::intersect(new ArrayType(new IntegerType(), $returnValueType)));
 
-		return $encoding === null && !$this->phpVersion->strSplitReturnsEmptyArray()
+		return $isInputNonEmptyString || ($encoding === null && !$this->phpVersion->strSplitReturnsEmptyArray())
 			? TypeCombinator::intersect($returnType, new NonEmptyArrayType())
 			: $returnType;
 	}

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -29,6 +29,12 @@ private static function findTestFiles(): iterable
 			yield $testFile;
 		}
 
+		if (PHP_VERSION_ID >= 80200) {
+			yield __DIR__ . '/data/str-split-php82.php';
+		} else {
+			yield __DIR__ . '/data/str-split.php';
+		}
+
 		if (PHP_VERSION_ID < 80200 && PHP_VERSION_ID >= 80100) {
 			yield __DIR__ . '/data/enum-reflection-php81.php';
 		}

tests/PHPStan/Analyser/data/str-split.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace StrSplit;
+
+use function PHPStan\Testing\assertType;
+
+class Foo {
+	/**
+	 * @param non-empty-string $nonEmptyString
+	 * @param non-falsy-string $nonFalsyString
+	 * @param lowercase-string $lowercaseString
+	 * @param uppercase-string $uppercaseString
+	 */
+	function doFoo(
+		string $string,
+		string $nonEmptyString,
+		string $nonFalsyString,
+		string $lowercaseString,
+		string $uppercaseString,
+		int $integer,
+	):void {
+		assertType('non-empty-list<string>', str_split($string));
+		assertType('non-empty-list<non-empty-string>', str_split($nonEmptyString));
+		assertType('non-empty-list<non-empty-string>', str_split($nonFalsyString));
+		assertType('non-empty-list<lowercase-string>', str_split($lowercaseString));
+		assertType('non-empty-list<uppercase-string>', str_split($uppercaseString));
+
+		assertType('non-empty-list<string>', str_split($string, $integer));
+		assertType('non-empty-list<non-empty-string>', str_split($nonEmptyString, $integer));
+		assertType('non-empty-list<non-empty-string>', str_split($nonFalsyString, $integer));
+		assertType('non-empty-list<lowercase-string>', str_split($lowercaseString, $integer));
+		assertType('non-empty-list<uppercase-string>', str_split($uppercaseString, $integer));
+
+		assertType('list<string>', mb_str_split($string));
+		assertType('non-empty-list<non-empty-string>', mb_str_split($nonEmptyString));
+		assertType('non-empty-list<non-empty-string>', mb_str_split($nonFalsyString));
+		assertType('list<lowercase-string>', mb_str_split($lowercaseString));
+		assertType('list<uppercase-string>', mb_str_split($uppercaseString));
+
+		assertType('list<string>', mb_str_split($string, $integer));
+		assertType('non-empty-list<non-empty-string>', mb_str_split($nonEmptyString, $integer));
+		assertType('non-empty-list<non-empty-string>', mb_str_split($nonFalsyString, $integer));
+		assertType('list<lowercase-string>', mb_str_split($lowercaseString, $integer));
+		assertType('list<uppercase-string>', mb_str_split($uppercaseString, $integer));
+	}
+}