lezer-template-json

A Lezer grammar for parsing template JSON (JSON with {{variable}} holes) with incremental parsing support and TypeScript definitions.

Install

npm i lezer-template-json

Features

• Supports parsing template JSON with {{variable}} syntax

Usage

Basic

import { parser } from "lezer-template-json";

const tree = parser.parse(`{
  "name": {{name}},
  "age": {{age}},
  "nested": {
    "value": {{value}}
  }
}`);
console.log(tree.toString());

With CodeMirror

import { parser, templateJsonHighlighting } from "lezer-template-json";
import { LRLanguage } from "@codemirror/language";
import { HighlightStyle, syntaxHighlighting } from "@codemirror/language";

const templateJsonLanguage = LRLanguage.define({
  parser,
  languageData: { name: "template-json" },
});

const highlightStyle = HighlightStyle.define([templateJsonHighlighting]);
const extensions = [templateJsonLanguage, syntaxHighlighting(highlightStyle)];

Tree Navigation

import { parser } from "lezer-template-json";
import * as terms from "lezer-template-json";

const tree = parser.parse(`{
  "name": {{name}},
  "age": {{age}}
}`);
const cursor = tree.cursor();
while (cursor.next()) {
  if (cursor.type.id === terms.Variable) {
    console.log(`Found variable: ${cursor.node.name}`);
  }
}

Error Handling

import { parser } from "lezer-template-json";

function parseWithErrors(pattern: string) {
  const tree = parser.parse(pattern);
  const errors: any[] = [];

  tree.cursor().iterate((node) => {
    if (node.type.isError) {
      errors.push({
        from: node.from,
        to: node.to,
        message: `Syntax error at ${node.from}-${node.to}`,
      });
    }
  });

  return { tree, errors };
}

API

Exports

• parser - Lezer parser instance
• templateJsonHighlighting - CodeMirror syntax highlighting
• Grammar terms - Node type constants for tree navigation

Types

parser.parse(input: string, fragments?: TreeFragment[], ranges?: {from: number, to: number}[]): Tree

Development

git clone https://github.com/Sec-ant/lezer-template-json
cd lezer-template-json
pnpm install
pnpm build
pnpm test

Commands:

• pnpm test:run - Run all tests
• pnpm test:ui - Interactive test UI

Contributing

1. Fork the repository
2. Create a feature branch
3. Add tests in tests/fixtures/
4. Ensure tests pass
5. Submit a pull request

License

MIT