Contributing

The repository is a yarn workspace: the library at the root, the example app under example/, one package per language under languages/ and this site under website/. You need Node 24 and yarn 4 through corepack, JDK 17, the Android SDK with an emulator, and Xcode 16 with an iOS 17 simulator.

git clone https://github.com/SectionTN/react-native-codepad
cd react-native-codepad
yarn

JavaScript

Command	Does
yarn lint, yarn format	Runs the Biome check, with fixes for format
yarn typecheck	Runs tsc over the library, the example, the generator and the tests
yarn test	Runs jest for the wrapper and node --test for the generator, the theme coverage and the docs drift tests
yarn nitrogen	Regenerates nitrogen/generated after a change to a *.nitro.ts file. The output is committed
yarn prepare	Builds the library

Android

The Kotlin core, the keyboard protocol and the syntax engine are tested on the JVM, so no device is needed. The syntax tests use a host build of tree-sitter, built once:

yarn host:treesitter
yarn test:android

For the device loop, start Metro and install the example on a running emulator:

yarn example start --port 8081
adb reverse tcp:8081 tcp:8081
yarn example android

Every build, bench and instrumented run uses the debugOptimized variant: a debuggable app over release library modules, so the numbers mean something.

Command	Does
yarn test:device [-e class codepad.example.X]	Installs both APKs and runs the instrumented tests
yarn bench:scroll [swipes]	Prints the frame times and the janky count over flings of the benchmark document
yarn bench:memory	Prints the Java and native heaps and the PSS
yarn bench:typing [chars]	Types through adb shell input and prints the key handler, key to paint and parse percentiles
yarn ime:record <name>	Records the keyboard's input connection calls into tests/ime/<name>.json, which yarn test:android replays

Languages

Command	Does
yarn gen:languages [id...]	Regenerates the packages from languages/grammars.json and the language packages page
yarn gen:report	Lists every predicate each language's queries use, with counts

Generated files are never edited by hand: CI regenerates them and fails on a diff. Adding a language has the steps.

iOS

The Swift core, input, syntax and layout layers build as a Swift package at the root and are tested on macOS, so no simulator is needed:

yarn test:swift
swift test --filter CodepadTests.DocumentTests

For the simulator loop, start Metro and run the example on an iOS 17 simulator. Run bundle exec pod install in example/ios after a podspec, a Nitro spec or a dependency changed.

yarn example start --port 8081
yarn example ios --udid <udid>

Command	Does
yarn test:ios [-only-testing:CodepadTests/<Class>]	Runs the view and input suites on the simulator. CODEPAD_IOS_UDID picks the device
yarn bench:ios scroll, memory, typing	Collects the same measures as Android on the simulator, for regressions only
yarn ime:record:ios <name>	Records the keyboard's UITextInput calls into tests/ime-ios/<name>.json, which yarn test:swift replays

This site

yarn docs serves the site with live reload and yarn docs:build builds it. The pages live under website/docs. The reference pages are written by hand, and a test under tests/docs fails when a prop, method or type of src/types.ts is missing from them. A push to main that touches website/ deploys the site to Cloudflare Pages.

Conventions

• The layers are the ones on the architecture page: core and input are pure Kotlin and pure Swift, and Nitro code lives only in com.margelo.nitro.codepad, ios/Codepad/nitro and src/specs.
• UTF-16 offsets, half open ranges and 0 based lines and columns, everywhere.
• Tests first: a vector or a JUnit and XCTest case for engine behavior, a jest case for the wrapper, and a keyboard recording for a keyboard bug.
• Biome formatting, conventional commits with an imperative subject under 72 characters, and comments of one to three lines for platform quirks and invariants only.
• Pull requests run lint, test, test-swift, docs, build-library, build-android and build-ios in CI.

CONTRIBUTING in the repository is the short version of this page.