pb-rust: codegen via prost + prost-reflect

[tnytown]

Summary

Generate Protobuf structs via prost, handling the Protobuf JSON mapping with prost-reflect.

This approach has a few benefits:

• Handles base64 encoding of the bytes type automatically.
• Converts i64 correctly.
• Better struct naming and module structure.

Unfortunately, prost doesn't handle required fields, so we're still stuck with unwrapping Option manually.

I also took the liberty of generating the structs JIT with build.rs rather than using a separate codegen step. This slows down CI for Rust significantly since we have to run everything through the Docker container, but this approach is more idiomatic and won't clutter the tree with generated files. We may want to look into caching the build container somehow.

Release Note

Documentation

[tnytown]

CC @woodruffw

[kommendorkapten]

Thanks!

[jleightcap]

Fantastic, this helps clean up uses of protobuf specs in e.g. sigstore/sigstore-rs#311 a lot 🙂

[woodruffw]

LGTM, thank you @tnytown!

JIT generation is indeed more idiomatic, although it's slightly out-of-sync with what the rest of this repo does. I have no strong opinion here, though, so I'm happy to merge with this approach assuming @kommendorkapten and @haydentherapper have no objections.

[woodruffw]

(Planning note: once merged, I'll do another RC release to crates.io.)

[woodruffw]

@tnytown You'll need to rebase here 🙂

[tnytown]

@woodruffw rebased!

[tnytown]

Hmm, tests are failing. Taking a look ...

[woodruffw]

Let's get this in following #213. That way we can do a 0.3.0 release of the crate with these new APIs.

[tnytown]

This should be ready for merge again, modulo the bump to 0.3 in gen/pb-rust/sigstore-protobuf-specs/Cargo.toml.

[haydentherapper]

protobuf-specs/gen/pb-rust/Cargo.toml

Line 3 in 1ef5b8e

version = "0.3.0"

has been updated, do we need to update under the generated code too?

Edit: From the failing test, I think you just need to regenerate the generated code

[tnytown]

Oops! I bumped the version and reran cargo update.