Luwu is a fast, small, safe, gradually typed embeddable scripting language based on Luau.
Luwu is a community-led fork intended to provide a more featureful and helpful experience for general-purpose, open-source language development. It will evolve with features, syntax, and semantics that may not align with upstream Luau.
Luwu is backwards compatible with Luau up to and including version 0.730, with possible exceptions for export local and Luau's unreleased integer feature as those areas are improved in Luwu.
For more information about Luwu and how to contribute, please join our Discord server hina & ferris. Credit for the name goes to @Crazyblox!
For RFCs and changes to the language, please see the RFCs folder. To propose new features, discuss them in our #features channel on Discord.
Luwu is an embeddable programming language, but it also comes with two command-line tools by default, luau and luau-analyze.
luau is a command-line REPL and can also run input files. Note that REPL runs in a sandboxed environment and as such doesn't have access to the underlying file system except for ability to require modules.
luau-analyze is a command-line type checker and linter; given a set of input files, it produces errors/warnings according to the file configuration, which can be customized by using --! comments in the files or .luaurc files. For details, please refer to our type checking and linting documentation. Our community maintains a language server frontend for luau-analyze called luau-lsp for use with text editors.
You can install and run Luwu by downloading the compiled binaries from a recent release; note that luau and luau-analyze binaries from the archives will need to be added to PATH or copied to a directory like /usr/local/bin on Linux/macOS.
Alternatively, upstream Luau is available from the packaged distributions below. These packages are not maintained by the Luwu development team and may not match Luwu's Luau 0.730 compatibility baseline:
- macOS: Install Homebrew and run
brew install luau - Arch Linux: Luau has been added to the official Arch Linux packages repository under the extras repository (see
luau), simply install usingpacman:pacman -Syu luau - Alpine Linux: Enable community repositories and run
apk add luau - Gentoo Linux: Luau is officially packaged by Gentoo and can be installed using
emerge dev-lang/luau. You may have to unmask the package first before installing it (which can be done by including the--autounmask=yoption in theemergecommand).
After installing, you will want to validate the installation was successful by running the test case here.
On all platforms, you can use CMake to run the following commands to build Luwu binaries from source:
mkdir cmake && cd cmake
cmake .. -DCMAKE_BUILD_TYPE=RelWithDebInfo
cmake --build . --target Luau.Repl.CLI --config RelWithDebInfo
cmake --build . --target Luau.Analyze.CLI --config RelWithDebInfoAlternatively, on Linux and macOS, you can also use make:
make config=release luau luau-analyzeTo integrate Luwu into your CMake application projects as a library, at the minimum, you'll need to depend on the Luau.Compiler and Luau.VM projects. From there you need to create a new state (using a Lua 5.x API such as lua_newstate), compile source to bytecode, and load it into the VM like this:
// needs lua.h and luacode.h
size_t bytecodeSize = 0;
char* bytecode = luau_compile(source, strlen(source), NULL, &bytecodeSize);
int result = luau_load(L, chunkname, bytecode, bytecodeSize, 0);
free(bytecode);
if (result == 0)
return 1; /* return chunk main function */For more details about the use of the host API, you currently need to consult the Lua 5.x API. Luwu inherits Luau's close alignment with that API, including a few deviations such as the need to compile source separately (which is important for deploying the VM without a compiler) and the lack of __gc support (use lua_newuserdatadtor instead).
To gain advantage of many performance improvements, it's highly recommended to use the safeenv feature, which sandboxes individual scripts' global tables from each other, and protects builtin libraries from monkey-patching. For this to work, you must call luaL_sandbox on the global state and luaL_sandboxthread for each new script's execution thread.
Luwu has an internal test suite; in CMake builds, it is split into two targets, Luau.UnitTest (for the bytecode compiler and type checker/linter tests) and Luau.Conformance (for the VM tests). The unit tests are written in C++, whereas the conformance tests are largely written in Luwu (see tests/conformance).
Makefile builds combine both into a single target that can be run via make test.
Luwu uses C++ as its implementation language. The runtime requires C++11, while the compiler and analysis components require C++17. It should build without issues using Microsoft Visual Studio 2017 or later, or gcc-7 or clang-7 or later.
Other than the STL/CRT, Luwu library components don't have external dependencies. The test suite depends on the doctest testing framework, and the REPL command-line depends on isocline.
The Luwu implementation is distributed under the terms of the MIT License. It is based on Luau, which is based on the Lua 5.x implementation; both are also distributed under the MIT License.
When Luwu is integrated into external projects, please honor the included license notices and preserve attribution to Luwu, Luau, and Lua.