Rhai - Embedded Scripting for Rust

Rhai is an embedded scripting language and evaluation engine for Rust that gives a safe and easy way to add scripting to any application.

Supported targets and builds

• All common CPU targets for Windows, Linux and MacOS.
• WebAssembly (WASM)
• no-std
• Minimum Rust version 1.45

Standard features

• Easy-to-use language similar to JavaScript+Rust with dynamic typing.
• Fairly low compile-time overhead.
• Fairly efficient evaluation (1 million iterations in 0.3 sec on a single core, 2.3 GHz Linux VM).
• Tight integration with native Rust functions and types, including getters/setters, methods and indexers.
• Freely pass Rust variables/constants into a script via an external Scope.
• Easily call a script-defined function from Rust.
• Relatively little unsafe code (yes there are some for performance reasons).
• Few dependencies (currently only smallvec).
• Re-entrant scripting engine can be made Send + Sync (via the sync feature).
• Scripts are optimized (useful for template-based machine-generated scripts) for repeated evaluations.
• Easy custom API development via plugins system powered by procedural macros.
• Function overloading and operator overloading.
• Dynamic dispatch via function pointers with additional support for currying.
• Closures (anonymous functions) that can capture shared values.
• Some syntactic support for object-oriented programming (OOP).
• Organize code base with dynamically-loadable modules.
• Serialization/deserialization support via serde (requires the serde feature).
• Support for minimal builds by excluding unneeded language features.

Protection against attacks

• Sand-boxed - the scripting engine, if declared immutable, cannot mutate the containing environment unless explicitly permitted.
• Rugged - protected against malicious attacks (such as stack-overflow, over-sized data, and runaway scripts etc.) that may come from untrusted third-party user-land scripts.
• Track script evaluation progress and manually terminate a script run.

For those who actually want their own language

• Use as a DSL.
• Restrict the language by surgically disabling keywords and operators.
• Define custom operators.
• Extend the language with custom syntax.

Documentation

See The Rhai Book for details on the Rhai scripting engine and language.

To build The Book, first install mdbook and mdbook-tera (for templating). Running mdbook build builds it.

Playground

An Online Playground is available with syntax-highlighting editor. Scripts can be evaluated directly from the editor.

License

Licensed under either of the following, at your choice:

• Apache License, Version 2.0, or
• MIT license

Unless explicitly stated otherwise, any contribution intentionally submitted for inclusion in this crate, as defined in the Apache-2.0 license, shall be dual-licensed as above, without any additional terms or conditions.