meow-meow-script 0.6.0

A host-neutral parser, runtime, and evaluator for Meow Meow Script
Documentation
  • Coverage
  • 13.99%
    75 out of 536 items documented0 out of 168 items with examples
  • Size
  • Source code size: 186.47 kB This is the summed size of all the files inside the crates.io package for this release.
  • Documentation size: 5.47 MB This is the summed size of all files generated by rustdoc for all configured targets
  • Ø build duration
  • this release: 5s Average build duration of successful builds.
  • all releases: 5s Average build duration of successful builds in releases after 2024-10-23.
  • Links
  • rei-kurzweil/mittens
    3 1 0
  • crates.io
  • Dependencies
    • —
  • Versions
  • Owners
  • rei-kurzweil

meow-meow-script

The host-neutral Meow Meow Script language crate. It owns syntax, parsing, runtime values, evaluation, and the synchronous host protocol. Engine-specific component construction is provided by mittens-engine.

Configurable runtime

Embedders create a Runtime with Runtime::builder() and register the script surface they want to expose:

  • ComponentSpec declares the canonical component name, aliases, constructors, builder calls, named properties, positional values, instance methods, and optional normalize/validate callbacks.
  • HostApiSpec declares free functions or namespace methods such as telemetry.record(...).
  • Language builtins are tracked separately from host APIs so component names, namespaces, and builtins cannot collide.

Parsing is catalog-driven in a configured session. Registered component names are matched case-insensitively, aliases are canonicalized before host dispatch, and unknown constructors, methods, properties, APIs, or conflicting catalog entries produce typed diagnostics with known-name suggestions.

Sessions and hosts

Runtime::session(host) checks the host capabilities before evaluating any script. A Session then owns its lexical scopes, heap-backed table objects, and callback registry across repeated eval(...) calls. Hosts are selected per session and are not hot-swapped.

The host boundary is the Host trait. New hosts usually implement dispatch_with_context(...), receive HostRequest values, and return HostResponse values. Component handles identify host-owned resources, so a host may return handles derived from native IDs; HostContext can allocate synthetic component handles for simple logging hosts. Callback handles identify MMS-owned closures and are allocated by the runtime.

Component expressions can also be parsed and materialized without attaching a host by using Runtime::materialize_component(...). A host is only required for effects such as emit/register, query, component methods, and host APIs.

Tables are heap-backed inside MMS, so aliases observe mutation across evaluations. When a table crosses into a host API, it is converted into an owned TransportValue::Table snapshot. Cycles or non-transferable values fail with a typed conversion error.

Example hosts

The crate includes two generic hosts:

  • EventStreamHost records ordered in-memory events suitable for forwarding to a socket, broker, or test harness.
  • JsonLinesHost records the same events as JSON-lines.

Run them with:

cargo run -p meow-meow-script --example event_stream_host
cargo run -p meow-meow-script --example json_lines_host

These examples intentionally do not provide a socket implementation, filesystem host, or standalone CLI. A future standalone REPL should be built on Runtime plus persistent Session.