prost-canonical-serde

Canonical JSON encoding for Prost-generated protobuf bindings.

Why this exists

Protobuf has a canonical JSON mapping that differs from plain Serde JSON (for example, int64/uint64 are encoded as strings and bytes use base64). Prost provides efficient Rust bindings, but it does not implement canonical JSON on its own. This project fills that gap by generating serde::Serialize and serde::Deserialize implementations that follow the protobuf canonical JSON spec, while keeping the normal serde_json API surface.

Highlights

• Seamless Prost integration: derive macros and build helpers work with prost-generated message types.
• Well-known types support: prost-types (Timestamp, Duration, Any, Struct, etc.) are handled with their canonical JSON mappings.
• no_std friendly: the core crate works without std (alloc required).
• High conformance: validated against the upstream protobuf conformance test suite. Remaining non-conformance aligns with limitations in Prost itself (for example, unknown field preservation and MessageSet support).

Quick start

Use the derive macros for prost-generated types and keep using serde_json. See the crate documentation on docs.rs for a full end-to-end example with a .proto, build.rs, and a runnable usage snippet.

License

Apache-2.0. See LICENSE.