@fazelstudio/codemirror-lang-luau

This package implements Luau (.luau) language support for the CodeMirror code editor: a full Lezer grammar covering Luau syntax including all Lua 5.1 features plus Luau-specific additions: gradual typing with type annotations (: Type), type aliases, generic types with variadic packs (T...), union/intersection/optional types (|, &, ?), type casts (:: Type), export type, typeof types, compound assignments (+=, -=, *=, /=, //=, %=, ^=, ..=), continue statement (context-sensitive), string interpolation (backtick `...{expr}...`), if expressions (if cond then a else b with elseif chains), bitwise operators (&, |, ~, <<, >>), extended string escapes (\x, \u, \z), extended numeric literals (hex 0x, binary 0b, underscore separators), and function attributes (@[attribute]).

This code is released under an MIT license.

Features

• Full Lua 5.1 compatibility (all valid Lua 5.1 code works)
• Gradual typing: type annotations, export type, typeof, generic types with packs (T...), union/intersection/optional types, named function types ((a: number) -> string), type casts (::), variadic packs (...T, T...)
• Compound assignment operators (8 variants)
• continue statement (context-sensitive keyword, disambiguated vs continue = 5 / continue())
• String interpolation with backticks (`Hello {name} {expr}`) with escapes
• If expressions with elseif chains (if c then a elseif d then b else c)
• Correct operator precedence (or < and < if < cmp < .. right < + - < * / // % < & < ~ < | < << >> < ^ right < unary)
• Bitwise operators, extended literals, function attributes, --!strict directives
• Syntax highlighting, auto-indent and code folding for all blocks

Usage

import { EditorView, basicSetup } from "codemirror"
import { luau } from "@fazelstudio/codemirror-lang-luau"

new EditorView({
  parent: document.body,
  doc: `local name: string = "World"\nprint(\`Hello, {name}!\`)`,
  extensions: [basicSetup, luau()],
})

API

luau() → LanguageSupport

Create a language support extension for Luau.

import {EditorView, basicSetup} from "codemirror"
import {luau} from "@fazelstudio/codemirror-lang-luau"

new EditorView({
  parent: document.body,
  extensions: [basicSetup, luau()],
  doc: `export type User = { name: string }\nlocal x: number | string = 42`
})

luauLanguage: LRLanguage

The Luau language object. Can be used for custom configuration:

import {luauLanguage} from "@fazelstudio/codemirror-lang-luau"
luauLanguage.data.of({ autocomplete: myCompletions })

Testing

npm run build:grammar  # generate parser from src/luau.grammar
npm run build          # build ESM + CJS + .d.ts via rollup
npm test               # run 104 fixture tests (mocha)
npm pack --dry-run     # verify only dist/ is published

Grammar highlights

• External tokenizer (src/tokens.js) for block comments (--[=[ ... ]=]), long strings ([=[ ... ]=]), and interpolated strings (backtick, {expr}, escapes) — contextual (stack.canShift) to avoid conflict with normal strings.
• continue disambiguation via GLR ~cont split: continue is VariableName when followed by =, ,, (, [, ., : and ContinueStatement otherwise.
• type / export / typeof treated as contextual keywords via ~type GLR, allowing local type = 10 and type{} call vs type Foo = number.
• String interpolation: `a {b} c {d+e} f` → InterpolatedString with InterpContent + Interpolation{ "{" Expression "}" }.
• Types: UnionType, IntersectionType, OptionalType (?), ParenType ((A, B)), TableType, FunctionType ((a: number) -> string with FuncParam), GenericType (Foo<T>), TypeofType (typeof(x)), TypeParams (<T...>).

Known limitations

• Type analysis/inference is out of scope — this package only provides syntax highlighting and parsing, not semantic type checking.
• goto and labels are not supported (Luau doesn't have them).
• Module/package system (require) is runtime-level, not part of the grammar.
• Autocomplete for Roblox APIs is out of scope (use a separate language server).