Simple direct-injection of custom requests with validation rules.

AppServiceProvider.php

<?php declare(strict_types=1);

namespace App\Providers;

use Illuminate\Contracts\Validation\ValidatesWhenResolved;
use Illuminate\Http\Request;
use Illuminate\Support\ServiceProvider;

/**
 * Class AppServiceProvider.
 */
class AppServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     *
     * @return void
     */
    public function register(): void
    {
    }

    /**
     * Bootstrap the application events.
     *
     * @return void
     */
    public function boot(): void
    {
        // Validate "validatable" injected objects
        $this->app->afterResolving(ValidatesWhenResolved::class, function (ValidatesWhenResolved $resolved): void {
            // Translate injected requests
            if ($resolved instanceof Request) {
                Request::createFrom($this->app->get('request'), $resolved);
            }

            $resolved->validateResolved();
        });
    }
}

MyController.php

<?php declare(strict_types=1);

namespace App\Http\Controllers;

use App\Http\Requests\MyRequest; // Subclass of App\Http\Requests\Request
...

final class MyController extends Controller
{
    ...
    public function myAction(MyRequest $request): JsonResponse
    {
        // The injected MyRequest object has already been populated,
        // validated against what's returned by `$request->rules()`
        // and property hinting like `$request->myfield` works.
        ...
    }
    ...
}

Request.php

<?php declare(strict_types=1);

namespace App\Http\Requests;

use Illuminate\Http\Request as BaseRequest;
use Illuminate\Contracts\Validation\ValidatesWhenResolved;
use Illuminate\Contracts\Validation\Validator;
use Illuminate\Support\Facades\Validator as ValidatorFacade;
use Illuminate\Validation\ValidatesWhenResolvedTrait;

/**
 * Common request class.
 */
abstract class Request extends BaseRequest implements ValidatesWhenResolved
{
    use ValidatesWhenResolvedTrait;

    /**
     * Build a validator instance for the request.
     *
     * @return Validator
     */
    protected function getValidatorInstance(): Validator
    {
        return ValidatorFacade::make($this->all(), $this->rules(), $this->messages());
    }

    /**
     * Return the validation rules that apply to this request.
     *
     * @return array
     */
    protected function rules(): array
    {
        return [];
    }

    /**
     * Return any custom error messages for validation of this request.
     *
     * @return array
     */
    protected function messages(): array
    {
        return [];
    }
}