snipe-it/app/Http/Requests/UpdateAssetRequest.php

<?php

namespace App\Http\Requests;

use App\Http\Requests\Traits\MayContainCustomFields;
use App\Models\Asset;
use Illuminate\Support\Facades\Gate;
use Illuminate\Validation\Rule;

class UpdateAssetRequest extends ImageUploadRequest
{
    use MayContainCustomFields;
    /**
     * Determine if the user is authorized to make this request.
     *
     * @return bool
     */
    public function authorize()
    {
        return Gate::allows('update', $this->asset);
    }

    /**
     * Get the validation rules that apply to the request.
     *
     * @return array
     */
    public function rules()
    {
        $rules = array_merge(
            parent::rules(),
            (new Asset)->getRules(),
            // this is to overwrite rulesets that include required, and rewrite unique_undeleted
            [
                'model_id'  => ['integer', 'exists:models,id,deleted_at,NULL', 'not_array'],
                'status_id' => ['integer', 'exists:status_labels,id'],
                'asset_tag' => [
                    'min:1', 'max:255', 'not_array',
                    Rule::unique('assets', 'asset_tag')->ignore($this->asset)->withoutTrashed()
                ],
            ],
        );

        return $rules;
    }
}