OpenAPI Nexus

OpenAPI 3.0 / 3.1 / 3.2 to multi-language code generator

OpenAPI Nexus transforms OpenAPI specifications into type-safe client libraries. Generated output is deterministic, compile-checked in CI, and tested byte-for-byte via golden tests.

Language Support

Language	Generator	HTTP Client	Status
TypeScript	typescript-fetch	fetch	Beta
Go	go-http	net/http	Beta
Rust	rust-reqwest	reqwest	Beta
Rust	rust-ureq	ureq	Beta
Rust	rust-aioduct	aioduct	Beta
Python	python-httpx	httpx	Beta
Python	python-requests	requests	Beta
Java	java-okhttp	OkHttp	Beta
Kotlin	kotlin-okhttp	OkHttp	Beta

Quick Start

Install

Shell installer (no Rust toolchain needed):

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/adamcavendish/openapi-nexus/releases/download/0.1.13/openapi-nexus-installer.sh | sh

Nightly build (latest master):

curl --proto '=https' --tlsv1.2 -LsSf https://github.com/adamcavendish/openapi-nexus/releases/download/nightly/openapi-nexus-installer.sh | sh

Build from source:

cargo install openapi-nexus

Requires Rust 1.90+.

Generate

# TypeScript client
openapi-nexus generate -i spec.yaml -o output -g typescript-fetch

# Go client
openapi-nexus generate -i spec.yaml -o output -g go-http

# Rust client (reqwest)
openapi-nexus generate -i spec.yaml -o output -g rust-reqwest

# Python client (httpx)
openapi-nexus generate -i spec.yaml -o output -g python-httpx

# Java client
openapi-nexus generate -i spec.yaml -o output -g java-okhttp

# Multiple generators at once
openapi-nexus generate -i spec.yaml -o output -g typescript-fetch,go-http,rust-reqwest

Configuration

Configuration resolves in order: CLI args > environment variables (OPENAPI_NEXUS_*) > config file (openapi-nexus-config.toml) > defaults.

# Environment variables
export OPENAPI_NEXUS_INPUT="spec.yaml"
export OPENAPI_NEXUS_OUTPUT="generated"
export OPENAPI_NEXUS_GENERATOR="typescript-fetch"

Generator-specific options go in the config file:

[generators.go-http]
module_path = "github.com/myorg/myproject/sdk"

[generators.rust-reqwest]
workspace_mode = true
workspace_deps = "workspace_version"

[generators.rust-reqwest.extra_derives.structs]
derives = ["PartialEq"]

[generators.rust-reqwest.extra_derives.enums]
derives = ["Hash"]

[generators.rust-reqwest.utoipa]
enabled = true
dependency = '{ version = "5" }'

[generators.rust-aioduct.aioduct]
compression = ["gzip", "zstd"]
features = ["tracing"]

[generators.typescript-fetch]
emit_enum_constants = true
emit_type_guards = true
property_naming = "camelCase"

How It Works

OpenAPI YAML/JSON → parse → lower to IR → CodeGenerator::generate(&IrSpec) → write

Parsing auto-detects OAS version (3.0, 3.1, 3.2). Lowering produces a version-agnostic IrSpec. Each generator receives the pre-lowered IR and uses sigil-stitch for type-safe code emission.

Documentation

Full documentation is available at the project docs site.

Development

# Run all tests
cargo test

# Clippy (required before commit)
cargo clippy --all-targets --all-features -- -D warnings

# Update golden files after intentional output changes
UPDATE_GOLDEN=1 cargo test

# Compile-check generated output for all languages
just golden-build-all

License

Dual-licensed under MIT or Apache-2.0 at your option.