Swift based AWS Smithy loader

What's New


  • Create unique set of prelude shapes for each model, to avoid them be accessed from multiple threads

Soto Smithy

Library for loading AWS Smithy files and their JSON AST models. The Smithy interface definition language (IDL) defines services and documentation for any protocol.

Smithy IDL

Smithy models define a service as a collection of resources, operations and shapes. This library loads Smithy IDL and the isomorphic JSON abstract syntax tree (AST) representation.

For example the following Smithy IDL example represents a service TimeService with one operation GetServerTime which returns a structure GetServerTimeOutput that contains a timestamp.

namespace soto.example

service TimeService {
    version: "2020-10-01",
    operations: [GetServerTime],

operation GetServerTime {
    output: GetServerTimeOutput

structure GetServerTimeOutput {
    time: Timestamp

It can be represented in Smithy JSON AST as

    "smithy": "1.0",
    "shapes": {
        "soto.example#TimeService": {
            "type": "service",
            "version": "2020-10-01"
            "operations": [
                    "target": "soto.example#GetServerTime"
        "soto.example#GetServerTime": {
            "type": "operation",
            "output": {
                "target": "soto.example#GetServerTimeOutput"
        "soto.example#GetServerTimeOutput": {
            "type": "structure",
            "members": {
                "time": {
                    "target": "smithy.api#Timestamp",
                    "traits": {
                        "smithy.api#required": {}


SotoSmithy supports all the standard shapes and traits defined in the Smithy 1.0 spec. It supports a limited number of selectors including shape and shape with trait eg

string [trait|sensitive]


This library can be used for reading any Smithy files but was written specifically for parsing the AWS service Smithy files. There is an additional library SotoSmithyAWS that includes the traits required to load AWS service Smithy. If you want to use the AWS traits library you need to register these traits with SotoSmithy by calling the following before you load any files.



  • Swift Tools 5.3.0
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Last updated: Thu Jan 12 2023 21:22:30 GMT-0500 (GMT-05:00)