#Go JSON-RPC code generation

moonrockz/smithy-codegen-go writes a Go module for one JSON-RPC peer. Register plugin as go-jsonrpc-codegen in a Smithy build runner. The Smithy CLI registers this name. The generator works on native, wasm, wasm-gc, and JS. It returns text files and does not access files, processes, or the network.

{
  "version": "1.0",
  "plugins": {
    "go-jsonrpc-codegen": {
      "service": "example.payments#PaymentTerminal",
      "protocol": "example.payments#TerminalProtocol",
      "peer": "terminal",
      "module": "example/payments/terminal",
      "package": "payments",
      "transports": ["stdio", "http", "websocket"]
    }
  }
}

service is required. protocol selects a two-peer protocol. Without it, the service has implicit client and server peers. peer defaults to client. module defaults to example/generated. package defaults to generated. version defaults to 2.0, the supported version. transports checks the selected transport names. The generated module includes all three transport adapters. Unknown settings fail in lexical name order.

Use run(PluginContext) for an existing plugin context. Use generate(model, description, peer, module_name~, package_name~) when a caller already has a prepared smithy-codegen-jsonrpc.Description. generate does not read RPC traits. The model supplies value shapes and service renames. The description supplies methods, wire names, required members, unknown-member policies, result and error selectors, and session rules.

#Generated API

The root package has types.go, peer.go, contract.go, and errors.go. NewPeer(Handlers, rpc.Options) returns a peer. Handlers has one typed function field for each accepted operation. A nil field leaves that handler unregistered. The peer has a typed method for each operation that the other peer accepts. Call Serve(ctx, transport) on the peer to start it. The embedded rpc.Peer also supplies Ready, Close, State, and HasCapability.

An operation with input has an input argument. A unit input has no argument. A notification or a null result returns error. Another request returns its typed result and error. A selected result member returns that member's target type. An operation that permits both kinds also has a Notify method with the operation name as its suffix.

Structures have JSON tags. Optional members are pointers. Required members keep their value type. Sparse lists and maps use pointer values to keep null entries. Decoders check required members and apply the prepared policy for unknown members. Union types are sealed interfaces. Each variant has a Value field, for example EntryMethodSwipe{Value: card}. Generated decoders read union members in structures, lists, maps, results, and error data.

Modeled error structures implement error and RPCError() *rpc.Error. Return them from a handler to send the prepared code and data. Typed calls convert a mapped error back to its modeled type. Use errors.As to inspect the result. An unmapped error stays an *rpc.Error. An absent optional selected error member omits the error data. A required document member keeps JSON null as present data.

Custom simple types are aliases. bigDecimal uses rpc.Number; bigInteger uses rpc.Integer. These types preserve exact JSON number text. No float carries a big number. Documents use json.RawMessage. The default timestamp type is rpc.Number, for epoch seconds. A prepared DateTime default uses string. Core timestampFormat on a member has priority over its target's format. The target format has priority over the prepared default. This rule also applies to list and map members, union members, selected results, and error data. Blobs use []byte and JSON base64 encoding. Decoders reject null for an optional primitive or enum member. A document member can hold null. Enums reject unknown values on input and output. Maps with enum keys check each key against its enum target on input and result validation. Maps with string keys keep ordinary string keys. All maps check entries in lexical key order to keep their first diagnostic stable.

The runtime applies the prepared lifecycle, capability, cancellation, and active call rules. rpc.RequestID(ctx) reads a handler's exact request ID. rpc.PeerFromContext(ctx) returns the runtime peer for a callback. Contract() returns a fresh copy of the prepared runtime contract.

#Names and dependencies

The shared ServiceNames helper applies the rename maps of both protocol services before Go casing. Exported names start with an uppercase letter. An underscore starts the next word. An all-uppercase word becomes title case. For example, paymentId becomes PaymentId, and INSERT_CARD becomes InsertCard. The generator reports declaration and member name conflicts. It does not change a rendered symbol name. $T and the shared package import policy select the import aliases. Text order uses lexical_compare.

The generated rpc/ package contains the real runtime source from runtimes/go. Every runtime reference uses <module>/rpc. The runtime's go.mod and go.sum supply the exact dependency pins. The generator changes only the module line. The embedding check maintained with the runtime detects source drift.

Run gofmt -w on the generated Go files before a Go build. Then run go build./..., go vet ./..., and go test ./.... Generation does not require Go. The package golden fixture records generator output before Go formatting.

The fixture config at fixtures/smithy-build.json generates a separate value codec module. Its Go tests check sparse entries, nested policies, null values, and enum output. The payment codec fixture checks exact decimals, sealed unions, modeled errors, and the prepared session contract.

generate

source

fn generate(model : @moonrockz/smithy.Model
Model, description : @moonrockz/smithy-codegen-jsonrpc.Description
Description, peer : @moonrockz/smithy-validation/rpc.PeerName
PeerName, module_name? : String, package_name? : String) -> Map[String, String] raise @moonrockz/smithy-codegen.CodegenError
CodegenError

Generate one peer from a prepared description. This function does not read RPC traits. The semantic model supplies value shapes and service names.

plugin

source

fn plugin(model : @moonrockz/smithy.Model
Model, raw : Json) -> Map[String, String] raise @moonrockz/smithy-build.BuildError
BuildError

run

source

fn run(plugin : @moonrockz/smithy-codegen.PluginContext
PluginContext) -> Map[String, String] raise @moonrockz/smithy-codegen.CodegenError
CodegenError