lezer-loader

0.3.0 verified Sat Apr 25 auth: no javascript

A webpack loader for Lezer grammar files (.grammar). Currently at version 0.3.0 with a stable API. It enables importing .grammar files as parser modules, supporting external token imports. No configuration options are supported yet. @external imports in grammar files are not tracked as webpack dependencies, requiring manual rebuild triggers. Best paired with @lezer/generator and @lezer/lr for TypeScript usage.

Common errors

error Module parse failed: Unexpected token (1:0) in file.grammar ↓

cause Webpack is not configured to handle .grammar files with lezer-loader.

fix

Add rule { test: /\.grammar$/, use: 'lezer-loader' } to webpack config.

error Cannot find module './tokens' from 'syntax.grammar' ↓

cause External token import path is incorrect or tokens.js is not in webpack's resolution scope.

fix

Ensure the @external tokens import path in the grammar file is correct and the module is accessible.

Warnings

gotcha @external imports in grammar files are not tracked as webpack dependencies. Edit the grammar file to trigger a rebuild. ↓

fix Manually edit the .grammar file (e.g., add a comment or change whitespace) to force webpack to recompile.

breaking No options are supported yet. Attempting to pass options to the loader may break silently. ↓

fix Do not pass any options to the loader in webpack config.

Install

npm install lezer-loader

yarn add lezer-loader

pnpm add lezer-loader

Imports

default (parser)
wrong
```
const parser = require('./syntax.grammar')
```
correct
```
import parser from './syntax.grammar'
```
Default export is the LRParser instance. Use ESM syntax for webpack.
named (external tokens)
```
import { insertSemi } from './syntax.grammar'
```
Named exports only exist for external tokens defined in the grammar with @external tokens.
type (TypeScript)
wrong
```
import { LRParser } from '@lezer/lr'
```
correct
```
import type { LRParser } from '@lezer/lr'
```
Use type-only imports for TypeScript declarations to avoid runtime overhead.

Quickstart

Configures webpack to handle .grammar files with lezer-loader, enabling import of Lezer parsers.

// webpack.config.js
module.exports = {
  module: {
    rules: [
      {
        test: /\.grammar$/,
        use: 'lezer-loader',
      },
    ],
  },
};