tree-sitter-moo

Tree-sitter grammar for MOO verb code. The grammar targets ToastStunt as the initial superset dialect while keeping LambdaMOO compatibility in view.

Install

Install the parser with the core Tree-sitter runtime:

npm install tree-sitter@^0.25.0 tree-sitter-moo

Parse MOO code from Node:

const Parser = require("tree-sitter");
const MOO = require("tree-sitter-moo");

const parser = new Parser();
parser.setLanguage(MOO);

const source = 'player:tell("Hello from MOO.");';
const tree = parser.parse(source);

console.log(tree.rootNode.toString());

The package exports the native Node binding at tree-sitter-moo, a browser-loadable Wasm parser at tree-sitter-moo/wasm, and query files for editor integrations.

Supported Syntax

This parser currently validates against 446 checked-in valid MOO verb fixtures imported from moo-for-llms, with no ERROR or MISSING nodes.

Supported language surface includes:

• raw verb bodies in .moo files
• assignments, assignment expressions, scatter assignment, and list splicing
• if / elseif / else, while, for, try / except, and fork
• function calls, verb calls, pass(...), property access, computed properties
• list literals, list indexing/ranges, numeric range literals
• ToastStunt map literals and map indexing
• inline error-catching expressions
• object refs, system objects, error constants, and type constants
• durable MOO string-literal comments, exposed as comment nodes

Version 1 parses raw verb bodies as provided by a MOO server. .moo files are treated as plain verb code with no wrapper metadata, object declarations, or database-dump syntax.

Stored verb code uses standalone string-literal statements for durable comments. Parser-discarded forms such as // ... and /* ... */ are not treated as MOO comments by this grammar because they are not portable stored verb code.

ToastStunt-only forms such as maps, MAP, WAIF, ANON, and BOOL are accepted by default. A future dialect mode can distinguish ToastStunt from LambdaMOO when tooling needs that distinction.

Documentation

• Usage: Node API, Wasm parser, CLI usage, and package exports
• Language bindings: Node, Wasm, Go, Rust, Python, C, and Swift examples
• Editor setup: Neovim, Emacs, Helix, and extension notes
• Testing: local test tiers, fixture validation, and CI expectations
• Contributing: development and pull request workflow
• Fixtures: fixture provenance and validation policy
• Release process: npm release workflow and checklist
• Security: security reporting policy
• Roadmap: planned follow-up work
• Changelog: release notes and known gaps

License

MIT. See LICENSE.