In this repo, I'm using the Shield plugin for the user roles/permissions in my Filament panel. The user resource has the following select field with relationship-sourced options for the role assignement. The issue isn't specific to the Shield plugin, that's just where I initially noticed the issue and the code I have on-hand.

Forms\Components\Select::make('roles')
    ->label('Role')
    ->preload()
    ->relationship(titleAttribute: 'name')
    ->required()
    ->searchable(),

Since Filament 3.2.79, setting the role causes the following error when saving:

array_diff(): Argument #2 must be of type array, string given

Downgrading to 3.2.78 fixes the issue. The issue isn't present when using options() with the select. The error appears to originate on Select.php#L994-L1000. It seems to be expecting an array but the select is returning a single value.

Steps to reproduce the issue

1. Clone the repo git clone <url>

2. CD into the project cd filament-select-relationship-issue

3. Composer composer install

4. Create the .env config cp .env.example .env

5. Generate the application key php artisan key:generate

6. Serve the project php artisan serve

7. Login Vist http://127.0.0.1:8000 and log in - the user/pass is preconfigured.

8. Create a user Navigate to the user resource and create a new user. The user will be created but the selected role will not be assigned. The application will error with the following:

array_diff(): Argument #2 must be of type array, string given

9. Edit a user The same will happen if you edit a user and assign a new role.