Automated Code Refactoring with Rector

Lighthouse provides Rector (opens new window) rules to automate code migrations and enforce conventions.

RootResolverSignatureRector

Ensures that root resolver __invoke methods match the Lighthouse calling convention.

Root resolvers receive null as their first argument because they have no parent value. This rule normalizes signatures to explicitly reflect that.

Setup

Add the rule to your rector.php configuration:

use Nuwave\Lighthouse\Rector\RootResolverSignatureRector;
use Rector\Config\RectorConfig;

return static function (RectorConfig $rectorConfig): void {
    $rectorConfig->rule(RootResolverSignatureRector::class);

    // Required: Larastan bootstrap makes config() available
    $rectorConfig->bootstrapFiles([
        __DIR__ . '/vendor/larastan/larastan/bootstrap.php',
    ]);
};

What it does

The examples below use null $root (PHP 8.2+). On PHP 8.0/8.1, the rule produces mixed $root instead.

Adds the missing $root parameter when only array $args is present:

// Before
public function __invoke(array $args): mixed {}

// After
public function __invoke(null $root, array $args): mixed {}

Fixes the root parameter type when it is typed incorrectly:

// Before
public function __invoke(User $root, array $args): mixed {}

// After
public function __invoke(null $root, array $args): mixed {}

Removes a useless single root parameter when only a non-array root is passed:

// Before
public function __invoke(mixed $root): mixed {}

// After
public function __invoke(): mixed {}

Normalizes parameter names via the paramNames option (see Configuration).

Configuration

Optionally configure preferred parameter names:

$rectorConfig->ruleWithConfiguration(RootResolverSignatureRector::class, [
    'paramNames' => ['_', 'args', 'context', 'resolveInfo'],
]);

Use null at any position to skip renaming that parameter:

$rectorConfig->ruleWithConfiguration(RootResolverSignatureRector::class, [
    'paramNames' => [null, null, 'context', 'resolveInfo'],
]);

Known Limitation

The rule assumes every class with an __invoke method found under the resolver directories (e.g. App\GraphQL\Queries, App\GraphQL\Mutations) is a root resolver.

Classes that are not root resolvers — such as nested field resolvers that receive a parent model as their first argument — will be incorrectly rewritten.

Mitigations:

• Move non-root-resolver classes out of the resolver directories (preferred — they do not belong there).
• Add the affected files to the Rector skip list (opens new window).