fix(ts): support nested option serialization

[abhinavgautam01]

Fixes #2435

Summary

Adds an explicit borsh.some(value) helper so TypeScript clients can serialize nested options where the outer option is Some and the inner option is None.

Previously, null always encoded as None, so Option<Option<T>> could encode:

• None
• Some(Some(value))

but could not represent:

• Some(None)

With this change, callers can now encode Some(None) using:

borsh.some(null)

Testing

• yarn build in ts/packages/borsh
• yarn jest tests/coder-instructions.spec.ts --runInBand
• yarn build:node in ts/packages/anchor
• yarn test --runInBand in ts/packages/anchor

[jamie-osec]

I'm not super happy with this approach, as the decode change means a small breaking change and it just papers over an API design issue. I'm going to close this for now, but consider a PR to anchor-next which makes this API more intuitive

[abhinavgautam01]

I'm not super happy with this approach, as the decode change means a small breaking change and it just papers over an API design issue. I'm going to close this for now, but consider a PR to anchor-next which makes this API more intuitive

thanks, that makes sense... i agree this is better handled as an API design change rather than trying to patch the current v1 behavior with a wrapper...

i will leave this PR closed and, if i pick this back up, i will target anchor-next with a cleaner nested option API instead of changing decode semantics in v1...