public function role()
    {
        return $this->belongsToMany(Role::class, Access::class, 'role_id', 'auth_id');
    }

这样取不到中间表数据

AuthModel::find(2)->role

解决

\vendor\topthink\think-orm\src\model\relation\BelongsToMany.php 中 getRelation 替换成旧版本的

     /**
     * 延迟获取关联数据
     * @access public
     * @param  array    $subRelation 子关联名
     * @param  Closure  $closure     闭包查询条件
     * @return Collection
     */
    public function getRelation(array $subRelation = [], Closure $closure = null): Collection
    {
        if ($closure) {
            $closure($this->getClosureType($closure));
        }
 
        $result = $this->buildQuery()
            ->relation($subRelation)
            ->select()
            ->setParent(clone $this->parent);
 
        $this->hydratePivot($result);
 
        return $result;
    }
 
 
 
 
    /**
     * 创建关联查询Query对象
     * @access protected
     * @return Query
     */
    protected function buildQuery(): Query
    {
        $foreignKey = $this->foreignKey;
        $localKey   = $this->localKey;
 
        // 关联查询
        $condition = ['pivot.' . $localKey, '=', $this->parent->getKey()];
 
        return $this->belongsToManyQuery($foreignKey, $localKey, [$condition]);
    }

拓展知识

laravel中可以通过在后面追加withPivot(['role_id','auth_id']) 来添加中间表字段

tp6默认取出中间表字段，可以通过 hiden(['pivot']) 隐藏整个中间表字段数据，或者隐藏指定字段
hiden(['pivot.role_id']);

参考地址：
https://blog.csdn.net/bluebird2/article/details/115106936