pegjs-loader/README.md

PEG.js loader for webpack

# [PEG.js](https://github.com/pegjs/pegjs) loader for [webpack](http://webpack.github.io/)

[![npm version](https://img.shields.io/npm/v/pegjs-loader.svg?style=flat-square)](https://www.npmjs.com/package/pegjs-loader)
[![npm downloads](https://img.shields.io/npm/dm/pegjs-loader.svg?style=flat-square)](https://www.npmjs.com/package/pegjs-loader)

## Install

`npm install --save-dev pegjs-loader pegjs webpack`

The pegjs-loader requires [PEG.js](https://github.com/pegjs/pegjs) and [webpack](https://github.com/webpack/webpack)
as [`peerDependency`](https://docs.npmjs.com/files/package.json#peerdependencies). Thus you are able to specify the required versions accurately.

## Usage

[Documentation: Using loaders](http://webpack.github.io/docs/using-loaders.html)

``` js
var parser = require("!pegjs!./parser.pegjs");
// => returns compiled PEG.js parser
```

### Apply via webpack config

It's recommended to adjust your `webpack.config` so `pegjs!` is applied automatically on all files ending with `.pegjs`:

``` js
module.exports = {
  ...
  module: {
    loaders: [
      {
        test: /\.pegjs$/,
        loader: 'pegjs-loader'
      }
    ]
  }
};
```

Then you only need to write: `require("./parser.pegjs")`.

### PEG.js options

You can pass options to PEG.js as [query parameters](http://webpack.github.io/docs/using-loaders.html#query-parameters). The following options are supported:

  * `allowedStartRules` - The rules the built parser will be allowed to start
    parsing from (default: the first rule in the grammar).

  * `cache` — If `true`, makes the parser cache results, avoiding exponential
    parsing time in pathological cases but making the parser slower (default:
    `false`).

  * `dependencies` - Parser dependencies, the value is an object which maps variables used to access the
    dependencies in the parser to module IDs used to load them (default: `{}`).

  * `optimize` - Whether to optimize the built parser either for `speed` or
    `size` (default: `speed`).

  * `trace` - If `true`, the tracing support in the built parser is enabled
    (default: `false`).

``` js
module.exports = {
  ...
  module: {
    loaders: [
      {
        test: /\.pegjs$/,
        loader: 'pegjs-loader?cache=true&optimize=size&allowedStartRules[]=RuleA,allowedStartRules[]=RuleB&trace=true'
      }
    ]
  }
};
```

## Change Log

This project adheres to [Semantic Versioning](http://semver.org/).  
Every release, along with the migration instructions, if any, is documented on the Github [Releases](https://github.com/eploko/pegjs-loader/releases) page.

## Thanks

* [Victor Homyakov](https://github.com/victor-homyakov) for the propagation of the `cache` option.
* [VladimirTechMan](https://github.com/VladimirTechMan) for the propagation of the `optimize` option and updating things to be compatible with PEG.js 0.10.0.
* [ragtime](https://github.com/ragtime) for the propagation of the `allowedStartRules` and `trace` options.
* [Jan Varwig](https://github.com/janv) for the Webpack 2 compatibility fix.
* [retorquere](https://github.com/retorquere) for the propagation of the `dependencies` option.

## License

MIT (http://www.opensource.org/licenses/mit-license.php)