`#[callback_vec]` argument includes other args with `#[callback_unwrap]`

[dj8yfo]

A sample contract method

near-sdk-rs/examples/adder/src/lib.rs

Lines 40 to 49 in 3bdbdd3

	pub fn handle_callbacks(
	&self,
	#[callback_unwrap] a: Pair,
	#[callback_unwrap] b: Pair,
	#[callback_vec] others: Vec<Pair>,
	) -> CompositeCallbacksResult {
	log!("a : {:#?}", a);
	log!("b : {:#?}", b);
	log!("others : {:#?}", others);
	CompositeCallbacksResult { a, b, others }

behaves very strange with respect to handling arguments: an argument annotated with #[callback_vec]
comprises the values of previous arguments annotated with #[callback_unwrap]:

near-sdk-rs/examples/adder/src/lib.rs

Lines 112 to 123 in 3bdbdd3

	let res = contract
	.call("call_all")
	.args_json(())
	.gas(near_sdk::Gas::from_tgas(300))
	.transact()
	.await?;
	println!("res: {:#?}", res);
	let composite_result = res.json::<CompositeCallbacksResult>()?;
	assert_eq!(composite_result.a, Pair(0, 0));
	assert_eq!(composite_result.b, Pair(2, 2));
	assert_eq!(composite_result.others, vec![Pair(0, 0), Pair(2, 2), Pair(3, 3), Pair(4, 4),]);

One would probably expect this argument to behave as a var-arg parameter with respect to Promise-s:

// pseudo-code
fn handle_callbacks(a_promise, b_promise, *rest_of_the_promises)

=>

assert_eq!(composite_result.others, vec![Pair(3, 3), Pair(4, 4),]);

---

Possible changes/fixes:

1. Simple
   1. disallow using #[callback_vec] with #[callback_unwrap]/#[callback_result] on other arguments
   2. disallow using #[callback_vec] more that once on all of the arguments
2. Less simple
   1. adjust starting promise idx computing for #[callback_vec]
   2. disallow using #[callback_vec] more that once on all of the arguments
   3. require #[callback_vec] to be used after all of the #[callback_unwrap]/#[callback_result]-s

[0xscharki]

I’d like to work on this.