Fixed false positive about undefined property guarded with property_exists

Author: ondrejmirtes

src/Rules/Properties/AccessPropertiesCheck.php

@@ -2,9 +2,12 @@
 
 namespace PHPStan\Rules\Properties;
 
+use PhpParser\Node\Arg;
 use PhpParser\Node\Expr;
+use PhpParser\Node\Expr\FuncCall;
 use PhpParser\Node\Expr\PropertyFetch;
 use PhpParser\Node\Identifier;
+use PhpParser\Node\Name\FullyQualified;
 use PHPStan\Analyser\NullsafeOperatorHelper;
 use PHPStan\Analyser\Scope;
 use PHPStan\Internal\SprintfHelper;
@@ -143,6 +146,17 @@ private function processSingleProperty(Scope $scope, PropertyFetch $node, string
 				}
 			}
 
+			if ($node->name instanceof Expr) {
+				$propertyExistsExpr = new FuncCall(new FullyQualified('property_exists'), [
+					new Arg($node->var),
+					new Arg($node->name),
+				]);
+
+				if ($scope->getType($propertyExistsExpr)->isTrue()->yes()) {
+					return [];
+				}
+			}
+
 			$ruleErrorBuilder = RuleErrorBuilder::message(sprintf(
 				'Access to an undefined property %s::$%s.',
 				$typeForDescribe->describe(VerbosityLevel::typeOnly()),

src/Type/Php/PropertyExistsTypeSpecifyingExtension.php

@@ -5,6 +5,7 @@
 use PhpParser\Node\Expr\FuncCall;
 use PhpParser\Node\Expr\PropertyFetch;
 use PhpParser\Node\Identifier;
+use PhpParser\Node\Name\FullyQualified;
 use PHPStan\Analyser\Scope;
 use PHPStan\Analyser\SpecifiedTypes;
 use PHPStan\Analyser\TypeSpecifier;
@@ -13,6 +14,7 @@
 use PHPStan\Reflection\FunctionReflection;
 use PHPStan\Rules\Properties\PropertyReflectionFinder;
 use PHPStan\Type\Accessory\HasPropertyType;
+use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\FunctionTypeSpecifyingExtension;
 use PHPStan\Type\IntersectionType;
@@ -53,7 +55,12 @@ public function specifyTypes(
 	{
 		$propertyNameType = $scope->getType($node->getArgs()[1]->value);
 		if (!$propertyNameType instanceof ConstantStringType) {
-			return new SpecifiedTypes([], []);
+			return $this->typeSpecifier->create(
+				new FuncCall(new FullyQualified('property_exists'), $node->getRawArgs()),
+				new ConstantBooleanType(true),
+				$context,
+				$scope,
+			);
 		}
 
 		if ($propertyNameType->getValue() === '') {

tests/PHPStan/Rules/Properties/AccessPropertiesRuleTest.php

@@ -1035,4 +1035,12 @@ public function testNewIsAlwaysFinalClass(): void
 		]);
 	}
 
+	public function testPropertyExists(): void
+	{
+		$this->checkThisOnly = false;
+		$this->checkUnionTypes = true;
+		$this->checkDynamicProperties = true;
+		$this->analyse([__DIR__ . '/data/property-exists.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Properties/data/property-exists.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace PropertyExists;
+
+class Model
+{
+
+}
+
+class Defaults
+{
+	public function defaults(Model $model): void
+	{
+		$columns = [
+			'getCreatedByColumn',
+			'getUpdatedByColumn',
+			'getDeletedByColumn',
+			'getCreatedAtColumn',
+			'getUpdatedAtColumn',
+			'getDeletedAtColumn',
+		];
+
+		foreach ($columns as $column) {
+			if (property_exists($model, $column)) {
+				echo $model->{$column};
+			}
+		}
+	}
+}