ts-dsl-tree-sitter

This repo contains a port of the current tree-sitter DSL to typescript and a new typescript-based DSL. The typescript port and the test suite are inteded to make refactoring the DSL easier.

Development

#!/usr/bin/env bash
pnpm install --dev # set up dev-dependencies
pnpm run test # build && test that the new dsl implementation generates the same output as the old one

Usage

typescript port of the tree-sitter DSL

Compile a grammar.ts file into a grammar.js file, then use the tree-sitter cli as you would normally.

New DSL

The new typescript DSL has two notable differences from the current tree-sitter DSL. First, rules are functions that can reference each other by name. This works due to the distinction between named and anonymous functions; in typescript, a named function's type is something like

type Function<Args, Return> = {
  name: string,
  (...args: Args) => Return,
}

Second, the new DSL also exposes the DSL as importable functions. Combined, these features let your js/ts language server should enable quick and easy jump-to-definition, documentation-on-hover, and type-checking, same as it would for any other typescript code.

This means you can write grammars that use imports and look like normal typescript:

// foobar.ts
import { seq } from "./src/functional"
export const foobar = () => seq(foo, bar)
export const foo = () => "foo"
export const bar = () => "bar"

// grammar.ts
import {grammar} from "./src/functional"
import * as rules from "./foobar.ts"

console.log(
  JSON.stringify(
    grammar({ name: "foolang", rules })
  )
)

esbuild --bundle --format=iife ./grammar.ts | node > ./src/grammar.json
tree-sitter generate ./src/grammar.json

Design, trade-offs, and downsides.

Dropping $ => $.rule_name in favor of direct function references means typescript can't check for rules to referencing other rules that aren't part of the rules object in a grammar defintion. Instead, that check happens at JS runtime, prior to invoking the tree-sitter cli.

Also, ts => js compilation can mangle function names if minification is configured.

SKalt / ts-dsl-tree-sitter