## Usage

```js
var Config = require('./');
var config = new Config();
console.log(config.expand(require('./package')));
```

## Schema

Values are parsed using a [schema](lib/schema.js) that is passed to [map-schema][] (builds on the schema from [normalize-pkg][] as a starting point):

- only properties that have a corresponding field on the schema will be parsed.
- any properties that do not have a corresponding field are returned unmodified.

See the [.field docs](#field) to learn how to add or overwrite a field on the schema.

## Defaults

A `default` value may optionally be defined when a `.field` is registered. When `.expand` is run and a property that is required or recommended by npm is missing, `expand-pkg` attempts to create the field if valid data can be found in the repository. 

The following fields are the only built-in fields with default values:

- `version`: `'0.1.0'`
- `license`: `'MIT'`
- `engines`: `{node: '>= 0.10.0'}`

## API
{%= apidocs("index.js") %}

## Options

### options.knownOnly

**Type**: `boolean`

**Default**: `undefined`

Omit properties from package.json that do not have a field registered on the schema.

```js
var Config = require('{%= name %}');
var config = new Config({knownOnly: true});

console.log(config.expand({author: 'Brian Woodward', foo: 'bar'}));
//=> {author: {name: 'Brian Woodward'}}
```

### options.pick

**Type**: `array`

**Default**: `undefined`

Filter the resulting object to contain only the specified keys.

### options.omit

**Type**: `array`

**Default**: `undefined`

Remove the specified keys from the resulting object.

### options.fields

Pass a `fields` object on the options to customize any fields on the schema (also see [options.extend](#options-extend)):

```js
var pkg = config.expand(require('./package'), {
  extend: true,
  fields: {
    name: {
      normalize: function() {
        return 'bar'
      }
    }
  }
});

console.log(pkg.name);
//=> 'bar'
```

### options.extend

**Type**: `boolean`

**Default**: `undefined`

Used with [options.field](#options-field), pass ` true` if you want to extend a field that is already defined on the schema.

```js
var pkg = config.expand(require('./package'), {
  extend: true,
  fields: {
    name: {
      normalize: function() {
        return 'bar'
      }
    }
  }
});

console.log(pkg.name);
//=> 'bar'
```