Fix vimeo#9997

- make SimpleXmlElement and SimpleXmlIterator not a universal object crate
- added typed magic __get method to SimpleXmlElement
- 'fixed' code translating `null` to `TNamedObject('null')` instead of `TNull`

src/Psalm/Config.php

@@ -728,8 +728,6 @@ protected function __construct()
         $this->eventDispatcher = new EventDispatcher();
         $this->universal_object_crates = [
             strtolower(stdClass::class),
-            strtolower(SimpleXMLElement::class),
-            strtolower(SimpleXMLIterator::class),
         ];
     }
 
@@ -1030,7 +1028,6 @@ private static function processConfigDeprecations(
 
     /**
      * @param non-empty-string $file_contents
-     * @psalm-suppress MixedMethodCall
      * @psalm-suppress MixedAssignment
      * @psalm-suppress MixedArgument
      * @psalm-suppress MixedPropertyFetch
@@ -1161,12 +1158,13 @@ private static function fromXmlAndPaths(
         }
 
         if (isset($config_xml['autoloader'])) {
-            $autoloader_path = $config->base_dir . DIRECTORY_SEPARATOR . $config_xml['autoloader'];
+            $autoloader = (string) $config_xml['autoloader'];
+            $autoloader_path = $config->base_dir . DIRECTORY_SEPARATOR . $autoloader;
 
             if (!file_exists($autoloader_path)) {
                 // in here for legacy reasons where people put absolute paths but psalm resolved it relative
-                if ($config_xml['autoloader']->__toString()[0] === '/') {
-                    $autoloader_path = $config_xml['autoloader']->__toString();
+                if ($autoloader[0] === '/') {
+                    $autoloader_path = $autoloader;
                 }
 
                 if (!file_exists($autoloader_path)) {
@@ -1312,7 +1310,7 @@ private static function fromXmlAndPaths(
             );
         }
 
-        if (isset($config_xml->fileExtensions)) {
+        if (isset($config_xml->fileExtensions->extension)) {
             $config->file_extensions = [];
 
             $config->loadFileExtensions($config_xml->fileExtensions->extension);
@@ -1336,7 +1334,6 @@ private static function fromXmlAndPaths(
 
         if (isset($config_xml->ignoreExceptions)) {
             if (isset($config_xml->ignoreExceptions->class)) {
-                /** @var SimpleXMLElement $exception_class */
                 foreach ($config_xml->ignoreExceptions->class as $exception_class) {
                     $exception_name = (string) $exception_class['name'];
                     $global_attribute_text = (string) $exception_class['onlyGlobalScope'];
@@ -1347,7 +1344,6 @@ private static function fromXmlAndPaths(
                 }
             }
             if (isset($config_xml->ignoreExceptions->classAndDescendants)) {
-                /** @var SimpleXMLElement $exception_class */
                 foreach ($config_xml->ignoreExceptions->classAndDescendants as $exception_class) {
                     $exception_name = (string) $exception_class['name'];
                     $global_attribute_text = (string) $exception_class['onlyGlobalScope'];
@@ -1401,7 +1397,6 @@ private static function fromXmlAndPaths(
         // this plugin loading system borrows heavily from etsy/phan
         if (isset($config_xml->plugins)) {
             if (isset($config_xml->plugins->plugin)) {
-                /** @var SimpleXMLElement $plugin */
                 foreach ($config_xml->plugins->plugin as $plugin) {
                     $plugin_file_name = (string) $plugin['filename'];
 
@@ -1413,7 +1408,6 @@ private static function fromXmlAndPaths(
                 }
             }
             if (isset($config_xml->plugins->pluginClass)) {
-                /** @var SimpleXMLElement $plugin */
                 foreach ($config_xml->plugins->pluginClass as $plugin) {
                     $plugin_class_name = $plugin['class'];
                     // any child elements are used as plugin configuration
@@ -1429,21 +1423,23 @@ private static function fromXmlAndPaths(
 
         if (isset($config_xml->issueHandlers)) {
             foreach ($config_xml->issueHandlers as $issue_handlers) {
-                /** @var SimpleXMLElement $issue_handler */
-                foreach ($issue_handlers->children() as $key => $issue_handler) {
-                    if ($key === 'PluginIssue') {
-                        $custom_class_name = (string) $issue_handler['name'];
-                        /** @var string $key */
-                        $config->issue_handlers[$custom_class_name] = IssueHandler::loadFromXMLElement(
-                            $issue_handler,
-                            $base_dir,
-                        );
-                    } else {
-                        /** @var string $key */
-                        $config->issue_handlers[$key] = IssueHandler::loadFromXMLElement(
-                            $issue_handler,
-                            $base_dir,
-                        );
+                $issue_handler_children = $issue_handlers->children();
+                if ($issue_handler_children) {
+                    foreach ($issue_handler_children as $key => $issue_handler) {
+                        if ($key === 'PluginIssue') {
+                            $custom_class_name = (string)$issue_handler['name'];
+                            /** @var string $key */
+                            $config->issue_handlers[$custom_class_name] = IssueHandler::loadFromXMLElement(
+                                $issue_handler,
+                                $base_dir,
+                            );
+                        } else {
+                            /** @var string $key */
+                            $config->issue_handlers[$key] = IssueHandler::loadFromXMLElement(
+                                $issue_handler,
+                                $base_dir,
+                            );
+                        }
                     }
                 }
             }

src/Psalm/Config/FileFilter.php

@@ -388,7 +388,6 @@ public static function loadFromXMLElement(
 
         if ($e->directory) {
             $config['directory'] = [];
-            /** @var SimpleXMLElement $directory */
             foreach ($e->directory as $directory) {
                 $config['directory'][] = [
                     'name' => (string) $directory['name'],
@@ -401,56 +400,48 @@ public static function loadFromXMLElement(
 
         if ($e->file) {
             $config['file'] = [];
-            /** @var SimpleXMLElement $file */
             foreach ($e->file as $file) {
                 $config['file'][]['name'] = (string) $file['name'];
             }
         }
 
         if ($e->referencedClass) {
             $config['referencedClass'] = [];
-            /** @var SimpleXMLElement $referenced_class */
             foreach ($e->referencedClass as $referenced_class) {
                 $config['referencedClass'][]['name'] = strtolower((string)$referenced_class['name']);
             }
         }
 
         if ($e->referencedMethod) {
             $config['referencedMethod'] = [];
-            /** @var SimpleXMLElement $referenced_method */
             foreach ($e->referencedMethod as $referenced_method) {
                 $config['referencedMethod'][]['name'] = (string)$referenced_method['name'];
             }
         }
 
         if ($e->referencedFunction) {
             $config['referencedFunction'] = [];
-            /** @var SimpleXMLElement $referenced_function */
             foreach ($e->referencedFunction as $referenced_function) {
                 $config['referencedFunction'][]['name'] = strtolower((string)$referenced_function['name']);
             }
         }
 
         if ($e->referencedProperty) {
             $config['referencedProperty'] = [];
-            /** @var SimpleXMLElement $referenced_property */
             foreach ($e->referencedProperty as $referenced_property) {
                 $config['referencedProperty'][]['name'] = strtolower((string)$referenced_property['name']);
             }
         }
 
         if ($e->referencedConstant) {
             $config['referencedConstant'] = [];
-            /** @var SimpleXMLElement $referenced_constant */
             foreach ($e->referencedConstant as $referenced_constant) {
                 $config['referencedConstant'][]['name'] = strtolower((string)$referenced_constant['name']);
             }
         }
 
         if ($e->referencedVariable) {
             $config['referencedVariable'] = [];
-
-            /** @var SimpleXMLElement $referenced_variable */
             foreach ($e->referencedVariable as $referenced_variable) {
                 $config['referencedVariable'][]['name'] = strtolower((string)$referenced_variable['name']);
             }

src/Psalm/Config/IssueHandler.php

@@ -38,9 +38,10 @@ public static function loadFromXMLElement(SimpleXMLElement $e, string $base_dir)
             }
         }
 
-        /** @var SimpleXMLElement $error_level */
-        foreach ($e->errorLevel as $error_level) {
-            $handler->custom_levels[] = ErrorLevelFileFilter::loadFromXMLElement($error_level, $base_dir, true);
+        if (isset($e->errorLevel)) {
+            foreach ($e->errorLevel as $error_level) {
+                $handler->custom_levels[] = ErrorLevelFileFilter::loadFromXMLElement($error_level, $base_dir, true);
+            }
         }
 
         return $handler;

src/Psalm/Config/ProjectFileFilter.php

@@ -28,7 +28,6 @@ public static function loadFromXMLElement(
                 throw new ConfigException('Cannot nest ignoreFiles inside itself');
             }
 
-            /** @var SimpleXMLElement $e->ignoreFiles */
             $filter->file_filter = static::loadFromXMLElement($e->ignoreFiles, $base_dir, false);
         }
 

src/Psalm/Internal/Analyzer/Statements/Block/ForeachAnalyzer.php

@@ -755,20 +755,6 @@ public static function handleIterable(
 
             $has_valid_iterator = true;
 
-            if ($iterator_atomic_type instanceof TNamedObject
-                && strtolower($iterator_atomic_type->value) === 'simplexmlelement'
-            ) {
-                $value_type = Type::combineUnionTypes(
-                    $value_type,
-                    new Union([$iterator_atomic_type]),
-                );
-
-                $key_type = Type::combineUnionTypes(
-                    $key_type,
-                    Type::getString(),
-                );
-            }
-
             if ($iterator_atomic_type instanceof TIterable
                 || (strtolower($iterator_atomic_type->value) === 'traversable'
                     || $codebase->classImplements(

src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/ArrayFetchAnalyzer.php

@@ -1737,8 +1737,10 @@ private static function handleArrayAccessOnNamedObject(
         ?Union &$array_access_type,
         bool &$has_array_access
     ): void {
-        if (strtolower($type->value) === 'simplexmlelement') {
-            $call_array_access_type = new Union([new TNamedObject('SimpleXMLElement')]);
+        if (strtolower($type->value) === 'simplexmlelement'
+            || $statements_analyzer->getCodebase()->classExtendsOrImplements($type->value, 'SimpleXMLElement')
+        ) {
+            $call_array_access_type = new Union([new TNull(), new TNamedObject('SimpleXMLElement')]);
         } elseif (strtolower($type->value) === 'domnodelist' && $stmt->dim) {
             $old_data_provider = $statements_analyzer->node_data;
 

src/Psalm/Internal/Provider/MethodReturnTypeProvider.php

@@ -11,7 +11,6 @@
 use Psalm\Internal\Provider\ReturnTypeProvider\DomNodeAppendChild;
 use Psalm\Internal\Provider\ReturnTypeProvider\ImagickPixelColorReturnTypeProvider;
 use Psalm\Internal\Provider\ReturnTypeProvider\PdoStatementReturnTypeProvider;
-use Psalm\Internal\Provider\ReturnTypeProvider\SimpleXmlElementAsXml;
 use Psalm\Plugin\EventHandler\Event\MethodReturnTypeProviderEvent;
 use Psalm\Plugin\EventHandler\MethodReturnTypeProviderInterface;
 use Psalm\StatementsSource;
@@ -39,7 +38,6 @@ public function __construct()
 
         $this->registerClass(DomNodeAppendChild::class);
         $this->registerClass(ImagickPixelColorReturnTypeProvider::class);
-        $this->registerClass(SimpleXmlElementAsXml::class);
         $this->registerClass(PdoStatementReturnTypeProvider::class);
         $this->registerClass(ClosureFromCallableReturnTypeProvider::class);
         $this->registerClass(DateTimeModifyReturnTypeProvider::class);

src/Psalm/Type/Atomic.php

@@ -323,11 +323,7 @@ private static function createInner(
                 return $analysis_php_version_id !== null ? new TNamedObject($value) : new TScalar();
 
             case 'null':
-                if ($analysis_php_version_id === null || $analysis_php_version_id >= 8_00_00) {
-                    return new TNull();
-                }
-
-                return new TNamedObject($value);
+                return new TNull();
 
             case 'mixed':
                 if ($analysis_php_version_id === null || $analysis_php_version_id >= 8_00_00) {
@@ -577,7 +573,14 @@ public function isArrayAccessibleWithStringKey(Codebase $codebase): bool
             || $this instanceof TKeyedArray
             || $this instanceof TClassStringMap
             || $this->hasArrayAccessInterface($codebase)
-            || ($this instanceof TNamedObject && $this->value === 'SimpleXMLElement');
+            || ($this instanceof TNamedObject
+                && ($this->value === 'SimpleXMLElement'
+                    || $codebase->classExtendsOrImplements(
+                        $this->value,
+                        'SimpleXMLElement',
+                    )
+                )
+            );
     }
 
     public function isArrayAccessibleWithIntOrStringKey(Codebase $codebase): bool

stubs/extensions/simplexml.phpstub

@@ -25,6 +25,7 @@ function simplexml_import_dom(SimpleXMLElement|DOMNode $node, ?string $class_nam
 
 /**
  * @implements Traversable<string, SimpleXMLElement>
+ * @psalm-no-seal-properties
  */
 class SimpleXMLElement implements Traversable, Countable
 {
@@ -63,6 +64,8 @@ class SimpleXMLElement implements Traversable, Countable
     public function __toString(): string {}
 
     public function count(): int {}
+
+    public function __get(string $name): SimpleXMLElement|SimpleXMLIterator|null {}
 }
 
 /**

tests/ArrayAccessTest.php

@@ -1013,7 +1013,7 @@ public function pop(): void {
             ],
             'simpleXmlArrayFetch' => [
                 'code' => '<?php
-                    function foo(SimpleXMLElement $s) : SimpleXMLElement {
+                    function foo(SimpleXMLElement $s) : ?SimpleXMLElement {
                         return $s["a"];
                     }',
             ],

tests/PropertyTypeTest.php

@@ -1389,6 +1389,16 @@ public function __construct() {
                     '$d->e' => 'mixed',
                 ],
             ],
+            'getPropertiesOfSimpleXmlElement' => [
+                'code' => '<?php
+                    $a = new SimpleXMLElement("<person><child role=\"son\"></child></person>");
+                    $b = $a->b;',
+                'assertions' => [
+                    '$a' => 'SimpleXMLElement',
+                    '$a->b' => 'SimpleXMLElement|null',
+                    '$b' => 'SimpleXMLElement|null',
+                ],
+            ],
             'allowLessSpecificReturnTypeForOverriddenMethod' => [
                 'code' => '<?php
                     class A {

tests/TypeReconciliation/ConditionalTest.php

@@ -2817,7 +2817,6 @@ function getIntOrFalse() {return false;}
                     $lilstring = "";
 
                     $n = new SimpleXMLElement($lilstring);
-                    /** @psalm-suppress MixedAssignment */
                     $n = $n->b;
 
                     if (!$n instanceof SimpleXMLElement) {
@@ -2905,7 +2904,11 @@ function b(B $_b): void {
                     $lilstring = "";
 
                     $n = new SimpleXMLElement($lilstring);
-                    $n = $n->children();
+                    $n = $n->b;
+
+                    if (!$n instanceof SimpleXMLIterator) {
+                        return;
+                    }
 
                     if (!$n) {
                         echo "false";