treegrep-query-lang

A tiny, Lisp-like query language intended for tree-grep style matching of parse trees.

This package includes:

• src/query.grammar: a Lezer grammar for the query language itself
• a small library that parses query strings into a compact AST

Install

npm i treegrep-query-lang

Build / publish

This repo is set up so that publishing runs:

npm run generate
npm run build

• generate uses lezer-generator to write src/generated/parser.js
• build runs TypeScript and (with allowJs) copies the generated JS into dist/

Main API

parseQuery(query: string): Promise<ParseResult>

Parses a query into an AST.

• If a generated Lezer parser is present (after npm run generate), it uses that.
• Otherwise it falls back to the built-in manual parser.

parseQuerySync(query: string): ParseResult

Always uses the manual parser.

Query language summary

• (Kind P*) — structural match (head + ordered children)
• [P] — capture
• $P — capture prefix (captures whatever P matches)
• #A — kind-variable (unification by kind, for match engines)
• _ — wildcard node
• ... — sibling wildcard (0+)
• (@op P*) — operator form (operator names start with @)

Operator semantics are implemented by your matching engine; this library only parses.

Output types

export type ParseResult =
  | { ok: true; ast: Pattern }
  | { ok: false; error: string };

export type Pattern =
  | { type: "list"; head: Pattern; args: Pattern[] }
  | { type: "symbol"; name: string }
  | { type: "kvar"; name: string }
  | { type: "string"; value: string }
  | { type: "wild" }
  | { type: "many" }
  | { type: "capture"; inner: Pattern };

Autocomplete

See AUTOCOMPLETE.md.