To ensure that the custom validation rule uses the attribute labels defined in the attributes() method of the FormRequest class, you can leverage Laravel's trans() helper or use __() for translating the attribute name dynamically.

Updated FullWidth Rule

Modify the FullWidth rule to use Laravel's translation system or a validation attribute resolver. Here's how you can adjust the rule:

Option 1: Use the Validation Attribute Resolver

Laravel provides access to the Validator instance where attribute names are already resolved. You can utilize this resolver:

namespace App\Rules;

use Closure;
use Illuminate\Contracts\Validation\ValidationRule;
use Illuminate\Support\Facades\Validator;

class FullWidth implements ValidationRule
{
    /**
     * Run the validation rule.
     *
     * @param  \Closure(string, ?string=): \Illuminate\Translation\PotentiallyTranslatedString  $fail
     */
    public function validate(string $attribute, mixed $value, Closure $fail): void
    {
        /** @phpstan-ignore argument.type */
        if (preg_match('/[^\x01-\x7E\xA1-\xDF]/', $value)) {
            // Resolve the human-readable attribute name
            $validator = Validator::make([], []);
            $translatedAttribute = $validator->getTranslator()->get("validation.attributes.$attribute") ?? $attribute;

            // Fail with the resolved attribute name
            $fail($translatedAttribute . ' に、全角が含まれています。');
        }
    }
}

Option 2: Pass the Attribute in the Rule Constructor

If you prefer a simpler approach without accessing the validator, pass the translated attribute when creating the rule instance:

namespace App\Rules;

use Closure;
use Illuminate\Contracts\Validation\ValidationRule;

class FullWidth implements ValidationRule
{
    protected string $attributeName;

    public function __construct(string $attributeName)
    {
        $this->attributeName = $attributeName;
    }

    /**
     * Run the validation rule.
     *
     * @param  \Closure(string, ?string=): \Illuminate\Translation\PotentiallyTranslatedString  $fail
     */
    public function validate(string $attribute, mixed $value, Closure $fail): void
    {
        if (preg_match('/[^\x01-\x7E\xA1-\xDF]/', $value)) {
            $fail($this->attributeName . ' に、全角が含まれています。');
        }
    }
}

Then use the rule in your request:

'login_id' => [ 'required', 'string', 'min:6', 'max:40', new FullWidth(__('ログインID'))],
'password' => [ 'required', 'string', 'min:8', 'max:100', new FullWidth(__('パスワード'))],

Option 3: Combine with Laravel's Built-in trans() Helper

For a more global solution, dynamically resolve the translated attribute name using Laravel's trans() or __() helper. Modify the rule to:

public function validate(string $attribute, mixed $value, Closure $fail): void
{
    if (preg_match('/[^\x01-\x7E\xA1-\xDF]/', $value)) {
        $translatedAttribute = trans("validation.attributes.$attribute", [], 'ja');
        $fail(($translatedAttribute ?: $attribute) . ' に、全角が含まれています。');
    }
}

Ensure your lang/ja/validation.php file contains the attributes key:

'attributes' => [
    'login_id' => 'ログインID',
    'password' => 'パスワード',
],

Recommended Approach

The Option 1 (using the Validator instance to resolve attributes dynamically) is the most reusable and cleanest solution, as it avoids passing the attribute explicitly in the constructor and works seamlessly with Laravel's translation system.

This method ensures that your rule respects the attributes() definition in the FormRequest class without extra manual effort. Let me know if you need further clarification! 🚀