`contract invoke` silently drops or accepts missing values in a tuple struct array argument

[leighmcculloch]

What version are you using?

stellar-cli 28.0.0.

What did you do?

I deployed a small contract with a function that takes a tuple struct argument, and passed that argument as a JSON array: once with the right number of values, and then with too many and too few.

#![no_std]
use soroban_sdk::{contract, contractimpl, contracttype, Env};

#[contracttype]
pub struct Point(u32, u32);

#[contract]
pub struct Contract;

#[contractimpl]
impl Contract {
    pub fn tuple_arg(_env: Env, point: Point) -> Point {
        point
    }
}

stellar contract build
stellar keys generate demo --network testnet --fund
stellar contract deploy \
  --wasm target/wasm32v1-none/release/repro_contract.wasm \
  --source demo --network testnet --alias repro_demo

Correct call:

stellar contract invoke --id repro_demo --source demo --network testnet --send no -- \
  tuple_arg --point '[1,2]'

Mis-sized calls — same command, but with three values, one value, or none:

stellar contract invoke --id repro_demo --source demo --network testnet --send no -- \
  tuple_arg --point '[1,2,3]'

stellar contract invoke --id repro_demo --source demo --network testnet --send no -- \
  tuple_arg --point '[1]'

stellar contract invoke --id repro_demo --source demo --network testnet --send no -- \
  tuple_arg --point '[]'

What did you expect to see?

A normal CLI error telling me the --point argument has the wrong number of values, the same way the CLI rejects --point '{"0":1}' with a missing key error.

What did you see instead?

The CLI accepts all three mis-sized arguments. With [1,2,3] the extra value is silently dropped and the contract is called with Point(1, 2), so the invocation succeeds with an argument I didn't pass. With [1] and [] the CLI builds a one-element and an empty vector and sends them on, so the mistake only surfaces later, from simulation or the contract, rather than as an argument error.