Update to prost 0.9

[rubdos]

Prost 0.9 contains some performance improvement for varint, and allows developers to work on Apple silicon.

https://github.com/tokio-rs/prost/releases/tag/v0.9.0

Technically this is a breaking change (because prost::DecodeError is exposed through SignalProtocolError), so you'll want to bump to 0.12 after this.

[jrose-signal]

Thank you! As an aside, the version numbers are more for Signal-internal use, so they track the stability of the Java, Swift, and TypeScript interfaces rather than the Rust crate (which is why that's stuck at 0.1.0).

[rubdos]

Thank you! As an aside, the version numbers are more for Signal-internal use, so they track the stability of the Java, Swift, and TypeScript interfaces rather than the Rust crate (which is why that's stuck at 0.1.0).

Aha, I see. Maybe I should make a separate issue about this, but would it at a certain point be possible to start versioning the crate as well?

[jrose-signal]

Circling back to this: after some discussion we're going to do best-effort versioning for the (non-bridge) Rust APIs as well, though for now I think we'll continue treating the version number as a workspace version number rather than tracking things on a per-crate level. (That is, a change in signal-crypto's API would bump the overall version number, even if libsignal-protocol didn't change.)

[rubdos]

That sounds very usable to me already :-)