I think it's complicated and it probably depends on the person we tell. In some ways- I'd say it could actually be seen as more ethical to tell someone. A suicide is such a shocking event for those left behind. By forewarning them, they get the time to expect it. They also get the chance to discuss it with us and, to say goodbye.
But then- that's the thing. We have to suspect they will accept our decision. That they will realise there's nothing they can do to 'save' us. That it isn't necessarily their responsibility to try and 'save' us.
I think a lot of peoole simply won't accept such a decision and, they likely will feel obliged to try to stop us. So- then, I think it becomes difficult. I'm sure it can be a very large burden, worry and a dilema really for some who find out.
Should they respect our wish to die or, should they intervene? Will they be in legal trouble if they know about an actual attempt and don't intervene? If not legal trouble- will the parents/ family of the deceased be after them? I think to know about an actual attempt may be the most difficult for people.
But yeah- I've also thought about the dilema with ideation itself. If my friends know how close I am to the edge- it gives them the opportunity to do more to support me. If they do or don't and then I still suicide- will they not feel more guilt because they knew and did nothing or, may feel they didn't do enough?
Surely better in a way to know nothing and be able to tell themselves- they would have done more if they'd known. I suppose also- if we know they can't help- no matter how much they give, it does somehow seem kinder just not to tell them.
I tend to be careful in who I do talk to now. It's usually someone who is also suicidal. My reasoning being that they are more likely to understand and, be pro- choice.