How to treat additional fields in RPC responses: feature for `serde(deny_unknown_fields)`?

[0xB10C]

I ran into a situation where a getpeerinfo RPC call returned an additional, not-yet-merged last_block_announcement field from bitcoin/bitcoin#27052 in 0xB10C/peer-observer#260 (comment). Since I plan to and do run Bitcoin Core PRs, master, and release candidates, I think this is something I'll hit again in the future.

This happens because this crate uses #[serde(deny_unknown_fields)] to ensure all existing fields are covered (see #241 (comment)). This makes sense to have as a default, but I was wondering if a feature flag to disable this for users would make sense.

edit: an alternative would be for me to run a patched version of this crate and I'd be fine with that, but I was looking for a more general solution

[jamillambert]

Interesting. We had not planned for this situation, but it makes sense.

I'll get on it.

[tcharding]

Concept ack but off the top of my head I don't know how we can cfg attributes without duplicating the types. It would be nice to find some sort of solution though.

EDIT: Gee wiz, I guess off-the-top-of-my-head wasn't of much value today ... I just saw the solution in #396.