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https://github.com/facebookexperimental/starlark-rust

A Rust implementation of the Starlark language
https://github.com/facebookexperimental/starlark-rust

Last synced: about 2 months ago
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A Rust implementation of the Starlark language

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README 

        
# Starlark in Rust



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There are several copies of this repo on GitHub,

[facebook/starlark-rust](https://github.com/facebook/starlark-rust) is the

canonical one.



This project provides a Rust implementation of the

[Starlark language](https://github.com/bazelbuild/starlark/blob/master/spec.md).

Starlark (formerly codenamed Skylark) is a deterministic language inspired by

Python3, used for configuration in the build systems

[Bazel](https://bazel.build), [Buck](https://buck.build) and

[Buck2](https://buck2.build), of which Buck2 depends on this library. This

project was originally developed

[in this repo](https://github.com/google/starlark-rust), which contains a more

extensive history.



There are at least three implementations of Starlark,

[one in Java](https://github.com/bazelbuild/starlark),

[one in Go](https://github.com/google/starlark-go), and this one in Rust. We

mostly follow the Starlark standard. If you are interested in trying out Rust

Starlark, you can clone this repo and run:



```shell

$ curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

$ cargo run

$> 1+2

3

```



This project was started by

[Damien Martin-Guillerez](https://github.com/damienmg). Version 0.4.0 of this

library changed ownership [from Google](https://github.com/google/starlark-rust)

to Facebook.



## Learn More



Read

[this blog post](https://developers.facebook.com/blog/post/2021/04/08/rust-starlark-library/)

for an overview of the library, the reasons behind Starlark, and how it might

fit in to your project. There is also a

[2 minute introductory video](https://www.youtube.com/watch?v=3kHER3KIPj4).



## Features



This project features:



- Easy interoperability between Rust types and Starlark.

- Rust-friendly types, so frozen values are `Send`/`Sync`, while non-frozen

  values aren't.

- [Garbage collected](docs/gc.md) values allocated on [a heap](docs/heaps.md).

- Optional runtime-checked [types](docs/types.md).

- A linter, to detect code issues in Starlark.

- IDE integration in the form of

  [LSP](https://microsoft.github.io/language-server-protocol/).

- Extensive testing, including

  [fuzz testing](https://github.com/google/oss-fuzz/tree/master/projects/starlark-rust).

- [DAP](https://microsoft.github.io/debug-adapter-protocol/) support.



This project also has three non-goals:



- We do _not_ aim for API stability between releases, preferring to iterate

  quickly and refine the API as much as possible. But we do

  [follow SemVer](https://doc.rust-lang.org/cargo/reference/semver.html).

- We do _not_ aim for minimal dependencies, preferring to keep one package with

  lots of power. But if some dependencies prove tricky, we might add feature

  flags.



## Components



There are six components:



- `starlark_derive`, a proc-macro crate that defines the necessary macros for

  Starlark. This library is a dependency of `starlark` the library, which

  reexports all the relevant pieces, and should not be used directly.

- `starlark_map`, a library with memory-efficient ordered/unordered maps/sets

  and various other data structures useful in Starlark.

- `starlark_syntax`, a library with the AST of Starlark and parsing functions.

  Only use if you want to manipulate the AST directly.

- `starlark` the main library, with evaluator, standard library, debugger

  support and lots of other pieces. Projects wishing to embed Starlark in their

  environment (with additional types, library functions and features) will make

  use of this library. This library reexports the relevant pieces of

  `starlark_derive`, `starlark_map` and most of `starlark_syntax`.

- `starlark_lsp`, a library providing an

  [LSP](https://microsoft.github.io/language-server-protocol/).

- `starlark_bin` the binary, which provides interactive evaluation, IDE features

  and linter, exposed through a command line. Useful if you want to use vanilla

  Starlark (but if you do, consider Python3 instead) or as a test-bed for

  experimenting. Most projects will end up implementing some of this

  functionality themselves over the `starlark` and `starlark_lsp` libraries,

  incorporating their specific extra types etc.



In particular the `starlark_bin` binary _can_ be effectively used as a linter.

But for the REPL, evaluator and IDE features the `starlark_bin` binary is only

aware of standard Starlark. Most Starlark embeddings supply extra functions and

data types to work with domain-specific concerns, and the lack of these bindings

will cause the REPL/evaluator to fail if they are used, and will give a subpar

IDE experience. In most cases you should write your own binary depending on the

`starlark` library, integrating your domain-specific pieces, and then using the

bundled LSP functions to produce your own IDE/REPL/evaluator on top of those.

You should still be able to use the [VS Code extension](vscode/README.md).



## Compatibility



In this section we outline where we don't comply with the

[Starlark spec](https://github.com/bazelbuild/starlark/blob/master/spec.md).



- We have plenty of extensions, e.g. type annotations, recursion, top-level

  `for`.

- We don't yet support later additions to Starlark, such as

  [bytes](https://github.com/facebook/starlark-rust/issues/4).

- In some cases creating circular data structures may lead to stack overflows.



## Making a release



1. Check the [GitHub Actions](https://github.com/facebook/starlark-rust/actions)

   are green.

2. Update `CHANGELOG.md` with the changes since the last release.

   [This link](https://github.com/facebook/starlark-rust/compare/v0.4.0...main)

   can help (update to compare against the last release).

3. Update the version numbers of the two `Cargo.toml` files. Bump them by 0.0.1

   if there are no incompatible changes, or 0.1.0 if there are. Bump the

   dependency in `starlark` to point at the latest `starlark_derive` version.

4. Copy the files `CHANGELOG.md`, `LICENSE` and `README.md` into each

   subdirectory.

5. Run `cargo publish --allow-dirty --dry-run`, then without the `--dry-run`, in

   each of the component directories in the [order above](#components).

6. Create a

   [GitHub release](https://github.com/facebook/starlark-rust/releases/new) with

   `v0.X.Y`, using the `starlark` version as the name.



## License



Starlark Rust is Apache License, Version 2.0 licensed, as found in the

[LICENSE](LICENSE) file.