How to express Larvel subqueries to use within a whereIn - laravel

Question

I'm sorry for asking somthing so simple, but I can't get the docs (https://laravel.com/docs/9.x/queries#subquery-where-clauses)
I'm writting something like a social network functionality, so I have my messages table and my users table, there's another pivot table where I store the users the user follows, and they work pretty well.
I want to represent the following SQL in Laravel's ORM
SELECT * FROM mensajes
WHERE user_id=1
OR user_id IN (SELECT seguido_id FROM seguidos WHERE user_id=1)
The idea is I'll get the user's posts, and also the posts from the users that the user follows.
My following solution works, but I feel it's quite dirty, and should be solved with a Subquery
// this relation returns the users the user is following, ans works correctly
$seguidos = auth()->user()->seguidos;
// I store in an array the ids of the followed users
$seg = [];
foreach ($seguidos as $s) {
array_push($seg, $s->id);
}
array_push($seg, auth()->user()->id);
// Then I retrieve all the messages from the users ids (including self user)
$this->mensajes = Mensaje::whereIn('user_id', $seg)
->orderBy('created_at', 'desc')
->get();
I'd like to change everything to use subqueries, but I don't get it
$this->mensajes = Mensaje::where('user_id', auth()->user()->id)
->orWhereIn('user_id', function($query) {
// ... what goes here?
// $query = auth()->user()->seguidos->select('id');
// ???? This doesn't work, of course
}
->orderBy('created_at', 'desc')
->get();

Answer 1

You can simply construct the raw query as you have done with the SQL.
->orWhereIn('user_id', function($query) {
$query->select('seguido_id')
->from('seguidos')
->where('seguidos.user_id', auth()->user()->id);
});
But normally sub queries have a relationship between the primary SQL query with the sub query, you don't have this here and instead of doing one query with a sub query, you can quite simply write it as two queries. If you are not calling this multiple times in a single request, one vs two queries is insignificant performance optimization in my opinion.
Mensaje::where('user_id', auth()->user()->id)
->orWhereIn(
'user_id',
Seguidos::where('user_id', auth()->user()->id)->pluck('seguido_id'),
);