Laravel Eloquent正在获取嵌套紧急加载的属性，该属性可能存在也可能不存在

$posts = Post::with('user')->get();

$comments = Comment::with(['user', 'attachment' => function ($query) {
    $query->whereNotNull('path');
}])->get();

class Post extends Model
{
    public function user()
    {
        return $this->belongsTo(User::class);
    }

    public function comments()
    {
        return $this->hasMany(Comment::class);
    }
}

class Comment extends Model
{
    public function user()
    {
        return $this->belongsTo(User::class);
    }

    public function attachment()
    {
        return $this->hasOne(Attachment::class);
    }
}

class Attachment extends Model
{
    // ...
}

$posts = Post::with([
    'user',
    'comments.user',
    'comments.attachment' => function ($query) {
        $query->whereNotNull('path');
    }
])->get();