Add troubleshooting "Error spawn ENOENT"

[github/fretlink/purs-loader.git] / README.md

# purs-loader

> [PureScript](http://www.purescript.org) loader for [webpack](http://webpack.github.io)

- Supports hot-reloading and rebuilding of single source files
- Dead code elimination using the `bundle` option
- Colorized build output using `purescript-psa` and the `psc: "psa"` option

## Install

Install with [npm](https://npmjs.org/package/purs-loader).

```
// For PureScript 0.9 and newer
npm install purs-loader --save-dev

// For PureScript 0.8
npm install purs-loader@purescript-0.8 --save-dev
```

## Example

```javascript
const webpackConfig = {
  // ...
  loaders: [
    // ...
    {
      test: /\.purs$/,
      loader: 'purs-loader',
      exclude: /node_modules/,
      query: {
        psc: 'psa',
        src: ['bower_components/purescript-*/src/**/*.purs', 'src/**/*.purs']
      }
    }
    // ...
  ]
  // ...
}
```

Refer to the [purescript-webpack-example](https://github.com/ethul/purescript-webpack-example) for a more detailed example.

### Options

Default options:

```javascript
const loaderConfig = {
  psc: 'psc',
  pscArgs: {},
  pscBundle: 'psc-bundle',
  pscBundleArgs: {},
  pscIde: false, // instant rebuilds using psc-ide-server (experimental)
  pscIdeArgs: {}, // for example, to use different psc-ide-server port: {port: 4088}
  pscIdeServerArgs: {}, // for example, to change the port { port: 4088 }
  pscIdeColors: false, // defaults to true if psc === 'psa'
  pscPackage: false,
  bundleOutput: 'output/bundle.js',
  bundleNamespace: 'PS',
  bundle: false,
  warnings: true,
  watch: false, // indicates if webpack is in watch mode
  output: 'output',
  src: [
    path.join('src', '**', '*.purs'),
    // if pscPackage = false
    path.join('bower_components', 'purescript-*', 'src', '**', '*.purs')
    // if pscPackage = true
    // source paths reported by `psc-package sources`
  ]
}
```

### `psc-ide` support (experimental)

Experimental support for instant rebuilds using `psc-ide-server` can be enabled
via the `pscIde: true` option.
You can use an already running `psc-ide-server` instance by specifying the port in `pscIdeArgs`,
if there is no server running this loader will start one for you.

### `psc-package` support (experimental)

Set `pscPackage` query parameter to `true` to enable `psc-package` support. The `psc-package`-supplied source paths
will be appended to `src` parameter.

### Troubleshooting

#### Slower webpack startup after enabling psc-ide support?

By default, the psc-ide-server will be passed the globs from query.src, this is
helpful for other tools using psc-ide-server (for example IDE plugins), however
it might result in a slower initial webpack startup time (rebuilds are not
affected). To override the default behaviour, add:
`pscIdeServerArgs: { "_": ['your/*globs/here'] }` to the loader config

#### Errors not being displayed in watch mode?

When the `watch` option is set to `true`, psc errors are appended to
webpack's compilation instance errors array and not passed back as an
error to the loader's callback. This may result in the error not being
reported by webpack. To display errors, the following plugin may be added
to the webpack config.

```javascript
const webpackConfig = {
  // ...
  plugins: [
    function(){
      this.plugin('done', function(stats){
        process.stderr.write(stats.toString('errors-only'));
      });
    }
  ]
  // ...
}
```

#### Error `spawn ENOENT`

This is caused when the loader tries to spawn a binary that does not exists
(`file or directory not found`). If you call webpack like `webpack` or
`webpack --watch`, then you need to ensure that all required binaries that the
loader depends on are available in your `$PATH`. 

If you use `npm run` and `npm start` on NixOS, then it will first attempt to find 
binaries in `node_packages/.bin`. If you have the compiler installed through `npm` 
and it finds it there, this will cause `ENOENT`on Nix, because 
[the binary needs to be patched first, because npm will install the binary that is 
linked with /lib64/ld-linux-x86-64.so.2 - a file that will not exist at that path in 
NixOS](https://github.com/ethul/purescript-webpack-example/issues/5#issuecomment-282492131).
The solution is to simply use the compiler from `haskellPackages.purescript` and
make sure that it's available in `$PATH`. For more information about how to make 
it work on Nix, see [Purescript Webpack Example](https://github.com/ethul/purescript-webpack-example#using-globally-installed-binaries)