ldc-legaulois/app/Http/Requests/UpdateSubRange.php

<?php

namespace App\Http\Requests;

use App\Models\SubRange;

class UpdateSubRange extends StoreSubRange
{
    /**
     * Get the validation rules that apply to the request.
     *
     * @return array
     */
    public function rules()
    {
        return \array_merge(parent::rules(), [
            'slug' => [
                'required',
                //phpcs:ignore Generic.CodeAnalysis.UnusedFunctionParameter.FoundInExtendedClassBeforeLastUsed
                function ($attribute, $value, $fail) {
                    if ($this->subrange->slug !== $value and SubRange::where('slug', $value)->exists()) {
                        $fail("Le champ Nom est déjà utilisé");
                    }
                }
            ]
        ]);
    }
}