A Assumption about the classic problem: OnTriggerEnter2D called twice

Questions & Answers
1 
public bool test = false;
void OnTriggerEnter2D(Collider2D other)
{
    if (test == true && (gameObject.activeSelf == false || _collider2D.enabled == false))
    {
        Debug.Log("Error");
    }

    gameObject.SetActive(false);
    _collider2D.enabled = false;
    test = true;
    Destroy(gameObject);
}

Codes above will print Error, like so many other questions.So I had a assume,maybe unity run collider events like this:after a physic update,unity create a delegate for every collider event then execute them one by one(all in a fixedupdate).So the problem occured when A is triggerred with B,and C in the same physic update,and it sames like a unactived collider can still be triggerred.

This is just my assumption.Thx a lot If someone can confirm it ,like checking unity source code.

2

Yea, it should be working the way you described.