create-pure-module

Fills in an existing react-native-builder-bob / create-react-native-library turbo-module project with the op-sqlite architecture: a TurboModule used only as a thin, blocking-synchronous install() entry point that hands the JSI Runtime and CallInvoker to hand-written C++. The actual API surface is plain JSI — HostObjects and HostFunctions — not codegen'd TurboModule methods. This avoids the serialization overhead and per-method codegen boilerplate of a normal TurboModule, at the cost of writing the JSI glue by hand.

This tool does not scaffold a new npm package from scratch — it replaces the default example TurboModule inside a project that create-react-native-library already generated. Create that project first:

npx create-react-native-library@latest react-native-acme-kit \
  --type turbo-module --languages kotlin-objc

This is a tool for pure C++ modules only — no Swift/Kotlin API surface, no Nitro/Expo module conventions. If you want a "normal" TurboModule or Nitro module, this isn't the tool for that.

What you get

• A per-HostObject ThreadPool + promisify() helper for async work: background thread does the blocking work, CallInvoker::invokeAsync hops back to the JS thread to resolve/reject the Promise.
• HFN/HFN2/HFN3 HostFunction-creation macros, prefixed with your module's chosen prefix so they can't collide with another native module's macros in the same translation unit.
• iOS (Objective-C++ TurboModule + podspec) and Android (fbjni JNI bridge + Kotlin TurboModule + CMake/prefab build.gradle) wiring, with no codegen required for anything beyond the single install() call.
• Every generated identifier — C++ namespace, class/file names, the JNI class descriptor, the global.__{Prefix}Proxy JS bridge object, the Android log tag — is stamped with a prefix you choose, so the generated module can't collide with another native module's symbols in the same app.
• to_jsi()/to_variant() in {Prefix}Utils.hpp: the single place every JSI <-> C++ conversion goes through, built on a JSVariant type (in {Prefix}Types.hpp) you extend as needed, instead of hand-rolled jsi::Value reads/writes scattered across HostFunctions. Prefixed so it can't collide with another pure-C++ module's own types.hpp/utils.hpp in the same app.
• create_object_array(): builds an array of same-shaped objects (e.g. query-result rows) by creating each column's jsi::PropNameID once, outside the row loop, instead of re-interning the same property name once per cell — a real performance win once you're returning more than a handful of rows.
• An ExampleHostObject showing all three patterns: a synchronous method (add), an async method (computeAsync) built with promisify(), and a method returning an object array (labelItems) built with to_string_vec() + create_object_array().

Usage

Inside the react-native-acme-kit directory create-react-native-library just created:

npx create-pure-module \
  --prefix Acme \
  --package com.acme.kit

--dir defaults to .; pass it to point at a different existing project. The command refuses to run (unless you pass --force) if the target directory doesn't have a package.json with a react-native-builder-bob or create-react-native-library key — that's the signal it uses to confirm there's an existing scaffold to fill in rather than an empty directory.

Omit --prefix/--package and it'll prompt for them interactively (as long as stdin is a TTY); --package defaults to whatever codegenConfig.android.javaPackageName is already in the project's package.json. See SKILL.md for the full list of files it generates and removes.

As a Claude Code skill

This repo is also a Claude Code skill (skills/create-pure-module/SKILL.md). Install it into a project with the skills CLI:

npx skills add OP-Engineering/pure-module-skill

This copies skills/create-pure-module/ into .claude/skills/ (or the equivalent directory for your agent) and Claude can drive the scaffolding interactively via /create-pure-module. You can also drop the skills/create-pure-module/ directory in by hand into .claude/skills/ in a project (or a personal ~/.claude/skills/).

After running it

create-react-native-library already bundled an example/ app that depends on the library locally, so there's no separate test app to wire up:

1. yarn install at the project root (picks up the codegenConfig change).
2. iOS: cd example/ios && pod install (or yarn pods from the root, if create-react-native-library set that script up).
3. Android: build normally — prefab headers are wired up already.

Extend it by adding new HostObjects under cpp/ (copy ExampleHostObject as a starting point) and registering them in {Prefix}Module.cpp's install(). No codegen changes needed for new methods.

License

MIT