AllowTopLevelPaidExecutionFrom incorrectly checks Limited weight in BuyExecution

[Dinonard]

Hi,

In AllowTopLevelPaidExecutionFrom (here), when processing BuyExecution we do it like this:

BuyExecution { weight_limit: Limited(ref mut weight), .. } if *weight >= max_weight => {   <==== THIS CHECK
		*weight = max_weight;
		Ok(())
	},
	BuyExecution { ref mut weight_limit, .. } if weight_limit == &Unlimited => {
		*weight_limit = Limited(max_weight);
		Ok(())
	},
	_ => Err(()),
}

Regarding the first arm, should we also be Ok(()) in case weight is below max_weight?

It seems like an error to me but I'm skeptical of my own understanding since it hasn't been noticed by now 😅

[KiChjang]

No, because recall that whatever you specify as weight in BuyExecution is the total amount of weight that your XCM is willing to pay for. If it's any less than max_weight (which I know is a misnomer, but it means what the executing chain thinks is fair price for the message), then we should definitely throw an error and refuse to execute said XCM, as it did not pay enough weight.

[Dinonard]

You are right, my mistake! This makes total sense, I switched the order in which Transact and BuyExecution are evaluated when thinking about it.

Following everything that happens can get confusing 😅

Closing the issue.