luau/prototyping/README.md

# Prototyping Luau

![prototyping workflow](https://github.com/Roblox/luau/actions/workflows/prototyping.yml/badge.svg)

An experimental prototyping system for the Luau type system. This is
intended to allow core language features to be tested quickly, without
having to interact with all the features of production Lua.

## Building

First install Haskell and Agda.

Install dependencies:
```
  cabal update
  cabal install --lib aeson scientific vector
```

Then compile
```
  agda --compile PrettyPrinter.agda
```

and run!
```
  luau-ast Examples/SmokeTest.lua | ./PrettyPrinter
```

## Testing

We have a series of snapshot tests in the `Tests/` directory. You interact with the tests using the `tests` Python script in the `prototyping` directory. To simply run the tests, run:

```sh
tests --luau-cli ../build/luau-ast --build
```

This will build the test targets and run them. Run `tests --help` for information about all the command-line options.

### Adding a new test

To add a new test, add it to `Tests/{SUITE_NAME}/{CASE_NAME}`. You'll need an `in.lua` file and an `out.txt` file. The `in.lua` file is the input Luau source code, while the `out.txt` file is the expected output after running `luau-ast in.lua | test_executable`.

### Updating a test

If you make a change to the prototype that results in an expected change in behavior, you might want to update the test cases automatically. To do this, run `tests` with the `--accept-new-output` (`-a` for short) flag. Rather than diffing the output, this will overwrite the `out.txt` files for each test case with the actual result. Commit the resulting changes with your PR.