grpc-forge

Generate typed Rust tonic gRPC servers from OpenAPI specs. The gRPC sibling of mcp-forge in the forge-gen ecosystem.

One OpenAPI spec is the single source of truth; forge-gen emits REST, gRPC, GraphQL, MCP, SDKs, and docs from it. grpc-forge is the gRPC half: it maps the spec to a typed .proto (component schemas → messages/enums; operations → a service with one rpc each, over synthesized request/response messages) plus a compilable tonic crate scaffold (Cargo.toml + build.rs + tonic::include_proto!

• the service trait + a ready-to-run handler stub the author fills over their data layer).

Usage

grpc-forge proto    --spec api.yaml --package myapi.v1     # print the typed .proto
grpc-forge generate --spec api.yaml --output ./gen --package myapi.v1
grpc-forge generate --spec api.yaml --output ./gen --no-serde   # minimal prost-only crate

The JSON↔typed bridge (serde, default-on)

By default the generated messages are serde-(de)serializable via pbjson (the proto3 JSON mapping). This is the high-leverage mode for the pleme-io fleet: a service whose data layer returns serde_json::Value (the universal facade shape shared across REST/GraphQL/MCP) bridges to typed gRPC for free —

let v: serde_json::Value = facade.get_band(kind, ns, name).await?;   // CRD JSON
let band: pb::Band = serde_json::from_value(v)?;                      // typed, no hand-mapping
Ok(tonic::Response::new(band))

Well-known types (google.protobuf.Struct/Empty) come from pbjson-types (prost + serde), so open CRD-JSON sub-objects (metadata, free-form spec) round-trip cleanly.

Empirically verified against breathe's real spec + a full Kubernetes CRD JSON (apiVersion/kind/rich metadata/spec/status):

• ✅ faithful CRD JSON deserializes into the typed message; rich metadata (uid/resourceVersion/managedFields) is absorbed by the Struct field.
• ✅ both camelCase (growAbove) and snake_case (grow_above) field names are accepted.
• ⚠️ pbjson is strict: unknown fields are rejected. The typed bridge is a strict contract — keep the spec faithful to the data shape (the spec-first standard already mandates this); drift surfaces as a typed error, never a silent wrong answer.

--no-serde emits a minimal prost-only crate (Empty → (), no pbjson deps).

Mapping

Built on sekkei (the canonical pleme-io OpenAPI 3.0 model). MIT.