NullsafePropertyFetchRule to check nullsafe operator on non-nullable expression

ondrejmirtes · ondrejmirtes · commit a72aea6cd1b1 · 2020-11-12T09:41:24.000+01:00
diff --git a/conf/config.level4.neon b/conf/config.level4.neon
@@ -12,6 +12,7 @@ rules:
 	- PHPStan\Rules\Methods\CallToMethodStamentWithoutSideEffectsRule
 	- PHPStan\Rules\Methods\CallToStaticMethodStamentWithoutSideEffectsRule
 	- PHPStan\Rules\Methods\NullsafeMethodCallRule
+	- PHPStan\Rules\Properties\NullsafePropertyFetchRule
 	- PHPStan\Rules\TooWideTypehints\TooWideArrowFunctionReturnTypehintRule
 	- PHPStan\Rules\TooWideTypehints\TooWideClosureReturnTypehintRule
 	- PHPStan\Rules\TooWideTypehints\TooWideFunctionReturnTypehintRule
diff --git a/src/Rules/Properties/NullsafePropertyFetchRule.php b/src/Rules/Properties/NullsafePropertyFetchRule.php
@@ -0,0 +1,40 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Properties;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use PHPStan\Type\NullType;
+use PHPStan\Type\VerbosityLevel;
+
+/**
+ * @implements Rule<Node\Expr\NullsafePropertyFetch>
+ */
+class NullsafePropertyFetchRule implements Rule
+{
+
+	public function getNodeType(): string
+	{
+		return Node\Expr\NullsafePropertyFetch::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		$nullType = new NullType();
+		$calledOnType = $scope->getType($node->var);
+		if ($calledOnType->equals($nullType)) {
+			return [];
+		}
+
+		if (!$calledOnType->isSuperTypeOf($nullType)->no()) {
+			return [];
+		}
+
+		return [
+			RuleErrorBuilder::message(sprintf('Using nullsafe property access on non-nullable type %s. Use -> instead.', $calledOnType->describe(VerbosityLevel::typeOnly())))->build(),
+		];
+	}
+
+}
diff --git a/tests/PHPStan/Rules/Properties/NullsafePropertyFetchRuleTest.php b/tests/PHPStan/Rules/Properties/NullsafePropertyFetchRuleTest.php
@@ -0,0 +1,33 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Properties;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<NullsafePropertyFetchRule>
+ */
+class NullsafePropertyFetchRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new NullsafePropertyFetchRule();
+	}
+
+	public function testRule(): void
+	{
+		if (PHP_VERSION_ID < 80000 && !self::$useStaticReflectionProvider) {
+			$this->markTestSkipped('Test requires PHP 8.0.');
+		}
+
+		$this->analyse([__DIR__ . '/data/nullsafe-property-fetch-rule.php'], [
+			[
+				'Using nullsafe property access on non-nullable type Exception. Use -> instead.',
+				16,
+			],
+		]);
+	}
+
+}
diff --git a/tests/PHPStan/Rules/Properties/data/nullsafe-property-fetch-rule.php b/tests/PHPStan/Rules/Properties/data/nullsafe-property-fetch-rule.php
@@ -0,0 +1,20 @@
+<?php // lint >= 8.0
+
+namespace NullsafePropertyFetchRule;
+
+class Foo
+{
+
+	public function doFoo(
+		$mixed,
+		?\Exception $nullable,
+		\Exception $nonNullable
+	): void
+	{
+		$mixed?->foo;
+		$nullable?->foo;
+		$nonNullable?->foo;
+		(null)?->foo; // reported by a different rule
+	}
+
+}
