Smithy to OpenRPC#

moonrockz/smithy-openrpc converts an assembled JSON-RPC 2.0 service to an OpenRPC 1.3.2 document using JSON Schema draft-07. These are three separate versions. The service's own version becomes info.version.

Load models with moonrockz/smithy-validation/rpc.loader() to opt into the smithy.rpc traits. Select a validated ServiceId, construct Config, and call convert_result(model, config). The result contains the document and structured, shape-linked warnings. convert returns the document directly.

Methods reuse the prepared runtime contract, including explicit positional order, named parameter policy, direct result selectors and application errors. The converter never fetches references or executes model-controlled code. The library has no Ion, WIT, WAC or wasm-devkit dependency.

The document itself is built with the published moonrockz/openrpc library at 0.2.0. Its checked constructors build the typed OpenRPC model. Its draft-07 model holds every generated schema, and its exact JSON keeps numeric tokens. Before returning, the converter validates the document with the MetaschemaCompatibility profile against the model, schema-document, reference, OpenRPC 1.3.2 normative and official-metaschema checks. That profile reports only an optional parameter before a required one as a warning, because Smithy keeps the explicit positional order. Any other finding fails conversion with the operation of the affected method, or the service, as its shape. Smithy-specific mapping, extension loss policies and warnings stay in this package.

Conversion.document is the library's JSON for that document. Object members follow the library's field order, not the order of earlier releases; values are unchanged. The library checks each schema graph within fixed bounds (moonrockz/moon-lander#56). When a very large component graph exceeds them, the unchecked part does not fail conversion.

///|
test {
  let loaded = @rpc.loader()
    .add_idl(
      "api.smithy",
      (
        #|$version: "2"
        #|namespace example
        #|use smithy.rpc#jsonRpc
        #|use smithy.rpc#method
        #|@jsonRpc(versions: ["2.0"])
        #|service Api { version: "1", operations: [Ping] }
        #|@method(name: "ping", params: "named", nullResult: true)
        #|operation Ping {}
      ),
    )
    .assemble()
  let config = @openrpc.Config::new(
    @openrpc.ServiceId::parse("example#Api").unwrap(),
  )
  let result = @openrpc.convert_result(loaded.model.unwrap(), config)
  assert_true(result.document is { "openrpc": String("1.3.2"), .. })
}

The complete standalone library example uses pinned imports. In a source checkout, mise run test:openrpc packages the working modules and runs that example in an isolated registry on all four targets. Its dependency audit checks the full resolved module graph.

For the built CLI, the calculator model and build configuration provide a working conversion:

moon run apps/smithy -- build --config examples/openrpc/smithy-build.json

The default artifact is build/smithy/source/openrpc/openrpc.json relative to the build configuration. Plugin aliases and projections follow Smithy build rules, for example openrpc::description writes under description/.

Build settings are service, version, protocolVersion, useJsonName, timestampFormat, extensions, title and apiVersion. Unknown keys fail. version accepts only 1.3.2; protocolVersion accepts only 2.0. apiVersion overrides info.version, independently of both. useJsonName defaults to false. Timestamp defaults to epoch-seconds, matching the runtime validator; date-time is an explicit alternative. Config::new uses typed versions, naming, timestamp and extension policies.

Methods sort by wire name. Named-only descriptors sort by wire member name; positional and either descriptors follow the complete explicit positional member list. Optional parameters retain required:false, even before required ones. Interior omissions require an explicit valid positional value. Either-mode examples that omit an interior position carry x-smithy-param-structure:by-name. Results are always present in a successful JSON-RPC response, even when the selected output member is optional in the enclosing Smithy structure.

The default extension policy preserves error-data schemas on methods in x-smithy-error-data. OpenRPC error objects' data is a value, not a schema. Root x-smithy-protocol records notification, batch and exchange boundaries. An explicit null result describes a successful payload, not a notification-only operation. Method value schemas do not establish envelope or exchange validity. x-smithy-error-examples carries examples of application errors because standard example pairings describe successful results. Modeled examples are checked against the same prepared runtime contract before emission. Invalid examples fail conversion with the operation's semantic shape ID. Ordinary success examples use standard OpenRPC example pairings. extensions=omit reports structured losses; extensions=fail rejects mappings that need extensions. JSON-RPC 1.0 is supported by the separate runtime validator and cannot be exported as standard OpenRPC.

The converter preserves exact numeric tokens and does not insert defaults. Downstream validators that round numbers through binary floating point cannot prove the runtime engine's exact decimal/large-integer semantics. Draft-07 formats and content encodings can be annotations in downstream tools; timestamp and decoded blob-length checks need their documented runtime policies.

mise run test:openrpc checks the pinned official metaschema digest, standard document conformance, embedded draft-07 schemas, every component reference, determinism, aliases, failing build status, and representative parameter/result/ error-data agreement with the actual RPC CLI. It also runs the isolated library consumer across native, wasm, JS and wasm-gc. Tool installation for these tests uses the network; library/build conversion uses no network or model execution.