Languages

Each language is a compiled tree-sitter grammar plus the nvim-treesitter queries, shipped as its own npm package. The core has no language built in, so without a package every document is plain text.

Packages and ids

language	Package
c	react-native-codepad-lang-c
css	react-native-codepad-lang-css
go	react-native-codepad-lang-go
html	react-native-codepad-lang-html
java	react-native-codepad-lang-java
javascript	react-native-codepad-lang-javascript
json	react-native-codepad-lang-json
kotlin	react-native-codepad-lang-kotlin
markdown	react-native-codepad-lang-markdown
python	react-native-codepad-lang-python
rust	react-native-codepad-lang-rust
swift	react-native-codepad-lang-swift
tsx	react-native-codepad-lang-tsx
typescript	react-native-codepad-lang-typescript
yaml	react-native-codepad-lang-yaml

Pass the id as language. The reference lists each grammar's revision and capture names.

Use markdown, not markdown_inline: the inline grammar is reached through injection.

Codepad.availableLanguages() lists the installed packages:

import { Codepad } from 'react-native-codepad';

const installed = Codepad.availableLanguages();
// ['javascript', 'markdown', 'markdown_inline', ...]

Plain text fallback

A language with no installed package renders as plain text in foreground and logs one warning. Nothing throws. Switching language on a live editor reparses the document.

Injections

A grammar's injection query hands ranges to another language: fenced blocks in markdown, <script> and <style> in html, css and html tagged templates in javascript, markdown front matter. The name comes from the document or from the query, is lowercased, and goes through this table before the registry looks for a package:

Name in the source	Resolves to
js, jsx, mjs, cjs	javascript
ts, mts, cts	typescript
py, python3	python
kt, kts	kotlin
rs	rust
golang	go
yml	yaml
jsonc, json5	json
htm, xhtml	html
md	markdown
h	c

A name with no package keeps the host language's colors. cpp, bash, sh, sql, graphql, text and the rest of nvim-treesitter's list stay silent, and any other name logs the fallback warning once.

• Injections go one level deep: a javascript block inside markdown highlights, an html template inside that block does not.
• ${...} substitutions inside a tagged template are parsed by the injected language.
• Injected trees survive edits and reparse only when their own range changed. The performance guide has the numbers.

Size

One native library per ABI, loaded on first use. On arm64-v8a in a release build:

Package	Library
kotlin	5.5 MB
swift	4.0 MB
tsx, typescript	1.4 MB each
rust	1.1 MB
markdown	0.7 MB
c	0.6 MB
java, javascript, python	0.4 MB each
go, yaml	0.2 MB each
css	0.1 MB
html, json	under 0.1 MB

An app bundle splits libraries per ABI, so a device downloads one set.

Adding a language

Packages are generated from languages/grammars.json in the repository, never written by hand:

1. Add an entry: the id (it must match the nvim-treesitter query directory), the grammar repository and commit, and the grammar directories.
2. Run yarn gen:languages <id>. It fetches the grammar and the queries, translates the predicates and writes the package. Patterns it cannot translate are dropped with a warning each, and yarn gen:report lists every predicate per language.
3. Run yarn host:treesitter && yarn test:android to compile the queries against the parser on the JVM.
4. Run yarn test:device -e class codepad.example.LanguagesTest to load the package through the real view on an emulator.

CI regenerates every package and fails on any diff. A grammar bump is a rev change followed by the same steps.

A third party package works when it follows the convention: the npm name react-native-codepad-lang-<id>, a Kotlin LanguageProvider at me.sectiontn.codepad.lang.<id> with a keep rule, an asset marker at codepad-languages/<id>, and a parser built against tree-sitter 0.26 (ABI 13 to 15).