improve result type of mysqli_result::fetch_object using object shapes

Makefile

@@ -19,3 +19,6 @@ cs-fix:
 
 phpstan:
 	php -d memory_limit=256M vendor/bin/phpstan analyse
+
+phpstan-baseline:
+	php -d memory_limit=256M vendor/bin/phpstan analyse --generate-baseline

composer.json

@@ -21,7 +21,7 @@
 	"require": {
 		"php": "^8.1",
 		"ext-mbstring": "*",
-		"phpstan/phpstan": "^1.10"
+		"phpstan/phpstan": "^1.10.12"
 	},
 	"require-dev": {
 		"ext-mysqli": "*",

phpstan-baseline.neon

@@ -1,2 +1,6 @@
 parameters:
-	ignoreErrors: []
+	ignoreErrors:
+		-
+			message: "#^Doing instanceof PHPStan\\\\Type\\\\Constant\\\\ConstantStringType is error\\-prone and deprecated\\. Use Type\\:\\:getConstantStrings\\(\\) instead\\.$#"
+			count: 1
+			path: src/PHPStan/Helper/MySQLi/PHPStanMySQLiHelper.php

src/PHPStan/Helper/MySQLi/PHPStanMySQLiHelper.php

@@ -13,9 +13,14 @@
 use MariaStan\PHPStan\Helper\PHPStanReturnTypeHelper;
 use PHPStan\Type\ArrayType;
 use PHPStan\Type\Constant\ConstantBooleanType;
+use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\ErrorType;
 use PHPStan\Type\IntegerType;
+use PHPStan\Type\NeverType;
 use PHPStan\Type\NullType;
+use PHPStan\Type\ObjectShapeType;
+use PHPStan\Type\ObjectType;
+use PHPStan\Type\ObjectWithoutClassType;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
 use PHPStan\Type\VerbosityLevel;
@@ -193,6 +198,59 @@ public function fetchArray(AnalyserResultPHPStanParams $params, ?int $mode): Typ
 		return TypeCombinator::union($this->getRowType($params, $mode), new NullType(), new ConstantBooleanType(false));
 	}
 
+	public function fetchObject(AnalyserResultPHPStanParams $params, ?string $class): Type
+	{
+		$rowType = $this->getRowType($params, MYSQLI_ASSOC);
+		$baseObjectType = $class !== null
+			? new ObjectType($class)
+			: new ObjectWithoutClassType();
+
+		// Modified from
+		// https://github.com/phpstan/phpstan-src/blob/8cdb5c95fd7a7c1a8f47d07637d5ebbbff0bfb86/src/Analyser/MutatingScope.php#L1375
+		if (count($rowType->getConstantArrays()) > 0) {
+			$objects = [];
+
+			foreach ($rowType->getConstantArrays() as $constantArray) {
+				$properties = [];
+				$optionalProperties = [];
+
+				foreach ($constantArray->getKeyTypes() as $i => $keyType) {
+					if (! $keyType instanceof ConstantStringType) {
+						// an object with integer properties is >weird<
+						continue;
+					}
+
+					$valueType = $constantArray->getValueTypes()[$i];
+					$optional = $constantArray->isOptionalKey($i);
+
+					if ($optional) {
+						$optionalProperties[] = $keyType->getValue();
+					}
+
+					$properties[$keyType->getValue()] = $valueType;
+				}
+
+				$intersectedObject = TypeCombinator::intersect(
+					new ObjectShapeType($properties, $optionalProperties),
+					$baseObjectType,
+				);
+
+				// This happens if the class is not registered in universalObjectCratesClasses.
+				if ($intersectedObject instanceof NeverType) {
+					$intersectedObject = $baseObjectType;
+				}
+
+				$objects[] = $intersectedObject;
+			}
+
+			$objectType = TypeCombinator::union(...$objects);
+		} else {
+			$objectType = $baseObjectType;
+		}
+
+		return TypeCombinator::union($objectType, new NullType(), new ConstantBooleanType(false));
+	}
+
 	public function fetchAll(AnalyserResultPHPStanParams $params, ?int $mode): Type
 	{
 		return new ArrayType(new IntegerType(), $this->getRowType($params, $mode));

src/PHPStan/Type/MySQLi/MySQLiResultDynamicReturnTypeExtension.php

@@ -47,6 +47,7 @@ public function isMethodSupported(MethodReflection $methodReflection): bool
 				'fetch_row',
 				'fetch_array',
 				'fetch_column',
+				'fetch_object',
 			],
 			true,
 		);
@@ -75,6 +76,10 @@ public function getTypeFromMethodCall(
 				$this->extractModeFromFirstArg($methodCall, $scope),
 			),
 			'fetch_row' => $this->phpstanMysqliHelper->fetchArray($params, MYSQLI_NUM),
+			'fetch_object' => $this->phpstanMysqliHelper->fetchObject(
+				$params,
+				$this->extractClassFromFirstArg($methodCall, $scope),
+			),
 			'fetch_array' => $this->phpstanMysqliHelper->fetchArray(
 				$params,
 				$this->extractModeFromFirstArg($methodCall, $scope),
@@ -117,6 +122,22 @@ private function extractModeFromFirstArg(MethodCall $methodCall, Scope $scope):
 		return null;
 	}
 
+	private function extractClassFromFirstArg(MethodCall $methodCall, Scope $scope): ?string
+	{
+		if (count($methodCall->getArgs()) === 0) {
+			return \stdClass::class;
+		}
+
+		$firstArgType = $scope->getType($methodCall->getArgs()[0]->value);
+		$constantStrings = $firstArgType->getConstantStrings();
+
+		if (count($constantStrings) === 1) {
+			return $constantStrings[0]->getValue();
+		}
+
+		return null;
+	}
+
 	private function getFallbackReturnType(
 		MethodReflection $methodReflection,
 		MethodCall $methodCall,

tests/PHPStan/Type/MySQLi/CustomResultClass.php

@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+namespace MariaStan\PHPStan\Type\MySQLi;
+
+class CustomResultClass
+{
+}

tests/PHPStan/Type/MySQLi/CustomUniversalObjectCrate.php

@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+namespace MariaStan\PHPStan\Type\MySQLi;
+
+class CustomUniversalObjectCrate
+{
+}

tests/PHPStan/Type/MySQLi/data/MySQLiTypeInferenceDataTest.php

@@ -4,6 +4,8 @@
 
 namespace MariaStan\PHPStan\Type\MySQLi\data;
 
+use MariaStan\PHPStan\Type\MySQLi\CustomResultClass;
+use MariaStan\PHPStan\Type\MySQLi\CustomUniversalObjectCrate;
 use MariaStan\TestCaseHelper;
 use mysqli;
 use mysqli_result;
@@ -14,6 +16,7 @@
 use function array_keys;
 use function assert;
 use function function_exists;
+use function get_object_vars;
 use function gettype;
 use function implode;
 use function in_array;
@@ -658,6 +661,114 @@ public function testFetchArray(): void
 		} while (true);
 	}
 
+	public function testFetchObject(): void
+	{
+		$db = TestCaseHelper::getDefaultSharedConnection();
+		$result = $db->query('SELECT id FROM mysqli_test');
+
+		do {
+			$row = $result->fetch_object();
+
+			if (function_exists('assertType')) {
+				assertType('(object{id: int}&stdClass)|false|null', $row);
+			}
+
+			if ($row === null) {
+				break;
+			}
+
+			$row = get_object_vars($row);
+			$this->assertSame(['id'], array_keys($row));
+			$this->assertIsInt($row['id']);
+		} while (true);
+
+		$result = $db->query('SELECT id, 5 val, "aa" id FROM mysqli_test');
+
+		do {
+			$row = $result->fetch_object();
+
+			if (function_exists('assertType')) {
+				assertType('(object{id: string, val: int}&stdClass)|false|null', $row);
+			}
+
+			if ($row === null) {
+				break;
+			}
+
+			$row = get_object_vars($row);
+			$this->assertSame(['id', 'val'], array_keys($row));
+			$this->assertIsString($row['id']);
+			$this->assertIsInt($row['val']);
+		} while (true);
+
+		$result = $db->query('SELECT id, 5 val, "aa" id FROM mysqli_test');
+
+		do {
+			$row = $result->fetch_object(CustomUniversalObjectCrate::class);
+
+			if (function_exists('assertType')) {
+				// The class needs to be registered in universalObjectCratesClasses
+				assertType('(' . CustomUniversalObjectCrate::class . '&object{id: string, val: int})|false|null', $row);
+			}
+
+			if ($row === null) {
+				break;
+			}
+
+			$this->assertInstanceOf(CustomUniversalObjectCrate::class, $row);
+			$row = get_object_vars($row);
+			$this->assertSame(['id', 'val'], array_keys($row));
+			$this->assertIsString($row['id']);
+			$this->assertIsInt($row['val']);
+		} while (true);
+
+		$result = $db->query('SELECT id, 5 val, "aa" id FROM mysqli_test');
+
+		do {
+			$row = $result->fetch_object(CustomResultClass::class);
+
+			if (function_exists('assertType')) {
+				// This class is not registered in universalObjectCratesClasses, so we can't intersect it with object
+				// shape.
+				assertType(CustomResultClass::class . '|false|null', $row);
+			}
+
+			if ($row === null) {
+				break;
+			}
+
+			$this->assertInstanceOf(CustomResultClass::class, $row);
+			$row = get_object_vars($row);
+			$this->assertSame(['id', 'val'], array_keys($row));
+			$this->assertIsString($row['id']);
+			$this->assertIsInt($row['val']);
+		} while (true);
+
+		$result = $db->query('SELECT id, 5 val, "aa" id FROM mysqli_test');
+
+		do {
+			$row = $result->fetch_object(
+				$this->hideValueFromPhpstan(true)
+					? CustomUniversalObjectCrate::class
+					: \stdClass::class,
+			);
+
+			if (function_exists('assertType')) {
+				assertType('object{id: string, val: int}|false|null', $row);
+			}
+
+			if ($row === null) {
+				break;
+			}
+
+			$this->assertInstanceOf(CustomUniversalObjectCrate::class, $row);
+			$row = get_object_vars($row);
+			$this->assertSame(['id', 'val'], array_keys($row));
+			$this->assertIsString($row['id']);
+			$this->assertIsInt($row['val']);
+		} while (true);
+	}
+
 	public function testFetchColumn(): void
 	{
 		$db = TestCaseHelper::getDefaultSharedConnection();

tests/PHPStan/Type/MySQLi/test.file-reflection.neon

@@ -2,5 +2,7 @@ parameters:
 	maria-stan:
 		reflection:
 			file: %rootDir%/../../../tests/PHPStan/Type/MySQLi/schema.dump
+	universalObjectCratesClasses:
+		- MariaStan\PHPStan\Type\MySQLi\CustomUniversalObjectCrate
 services:
 	mariaDbReflection: @mariaDbFileDbReflection

tests/PHPStan/test.neon

@@ -6,6 +6,8 @@ parameters:
 			user: 'root'
 			password: 'root'
 			database: 'mariastan_test'
+	universalObjectCratesClasses:
+		- MariaStan\PHPStan\Type\MySQLi\CustomUniversalObjectCrate
 
 services:
 	-