stellar contract invoke with `--arg-file-path` silently ignored for `Option<T>` contract parameters

[leighmcculloch]

What version are you using?

25.1.0

What did you do?

Given a contract with both a required and an optional parameter:

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

#[contract]
pub struct Contract;

#[contractimpl]
impl Contract {
    pub fn req(i: u32) -> u32 {
        i
    }
    pub fn opt(i: Option<u32>) -> u32 {
        i.unwrap_or(123)
    }
}

Invoked both functions using --arg-file-path.

What did you expect to see?

Both invocations should return 127, since the file contains 127 and both functions are given the value via --i-file-path.

Expected for the opt function:

127

What did you see instead?

The function with the required parameter accepts the --arg-file-path as expected:

$ stellar contract invoke --id c -- req --i-file-path =(echo 127)
127

The function with the optional parameter ignores the --arg-file-path:

$ stellar contract invoke --id c -- opt --i-file-path =(echo 127)
123

Note that passing the value directly on the command line works as expected:

$ stellar contract invoke --id c -- opt --i 127
127