steal-tools/lib/process_babel_plugins.js

var _ = require("lodash");
var path = require("path");
var babel = require("babel-standalone");

/**
 * A Babel plugin as defined in `babelOptions.plugins`
 * @typedef {string|Function|<string, Object>[]|<Function, Object>[]} BabelPlugin
 */

/**
 * The options needed to load the babel plugins not bundled in babel-standalone
 * @typedef {Object} LoadCustomPluginsOptions
 * @property {string} baseURL The loader baseURL value
 * @property {string} loaderEnv The loader env value
 * @property {Object} babelOptions The babel configuration options
 */

/**
 * Returns a list of babel plugins to be used by transpile
 * @param {LoadCustomPluginsOptions} opts The options object
 * @return {BabelPlugin[]} The list of plugins to be used by transpile
 */
module.exports = function(opts) {
	var processed = [];
	var babelOptions = opts.babelOptions || {};
	var babelEnvConfig = babelOptions.env || {};

	var babelEnv = process.env.BABEL_ENV ||
		process.env.NODE_ENV ||
		opts.loaderEnv;

	// process plugins in babelOptions.plugins
	processed = processed.concat(processPlugins(opts.baseURL, babelOptions.plugins));

	// process environment dependant plugins
	_.keys(babelEnvConfig).forEach(function(envName) {
		if (envName === babelEnv) {
			var plugins = babelEnvConfig[envName].plugins || [];
			processed = processed.concat(processPlugins(opts.baseURL, plugins));
		}
	});

	return processed;
};

/**
 * Collect builtin plugin names and non builtin plugin functions
 * @param {string} baseURL The loader baseURL value
 * @param {BabelPlugin[]} plugins An array of babel plugins
 * @return {BabelPlugin[]} An array of babel plugins filtered by the babel
 *                         environment name and with non-builtins replaced
 *                         by their respective functions
 */
function processPlugins(baseURL, plugins) {
	var normalized = [];

	// path.resolve does not work correctly if baseURL starts with "file:"
	baseURL = baseURL.replace("file:", "");
	plugins = plugins || [];

	plugins.forEach(function(plugin) {
		var name = getPluginName(plugin);

		if (isPluginFunction(plugin) || isBuiltinPlugin(name)) {
			normalized.push(plugin);
		}
		else if (!isBuiltinPlugin(name)) {
			var npmPluginNameOrPath = getNpmPluginNameOrPath(baseURL, name);

			// load the plugin!
			var pluginFn = require(npmPluginNameOrPath);

			if (_.isString(plugin)) {
				normalized.push(pluginFn);
			}
			else if (_.isArray(plugin)) {
				// [ pluginName, pluginOptions ]
				normalized.push([pluginFn, plugin[1]]);
			}
		}
	});

	return normalized;
}

/**
 * Whether the plugin function was provided instead of the plugin name
 * @param {BabelPlugin} plugin
 * @return {boolean} `true` if a plugin function was provided, `false` otherwise
 */
function isPluginFunction(plugin) {
	return _.isFunction(plugin) || _.isFunction(_.head(plugin));
}

function getNpmPluginNameOrPath(baseURL, name) {
	var isPath = /\//;
	var isNpmPluginName = /^(?:babel-plugin-)/;

	if (isPath.test(name)) {
		return path.resolve(baseURL, name);
	}
	else if (!isNpmPluginName.test(name)) {
		return "babel-plugin-" + name;
	}

	return name;
}

/**
 * Gets the plugin name
 * @param {BabelPlugin} plugin An item inside of `babelOptions.plugins`
 * @return {?string} The plugin name
 */
function getPluginName(plugin) {
	if (isPluginFunction(plugin)) return null;

	return _.isString(plugin) ? plugin : _.head(plugin);
}

/**
 * Whether the plugin is built in babel-standalone
 *
 * @param {string} name A plugin path or shorthand name.
 * @return {boolean} `true` if plugin is bundled, `false` otherwise
 *
 * Babel plugins can be set using the following variations:
 *
 * 1) the npm plugin name, which by convention starts with `babel-plugin-`
 *    (e.g babel-plugin-transform-decorators).
 * 2) A shorthand name, which is the npm name without the `babel-plugin-` prefix
 * 3) A path to where the plugin function is defined
 *
 * babel-standalone registers the plugins bundled with it using the shorthand
 * version.
 */
function isBuiltinPlugin(name) {
	var isNpmPluginName = /^(?:babel-plugin-)/;
	var availablePlugins = babel.availablePlugins;

	// if the full npm plugin name was set in `babelOptions.plugins`, use the
	// shorthand to check whether the plugin is included in babel-standalone;
	// shorthand plugin names are used internally by babel-standalone
	var shorthand = isNpmPluginName.test(name) ?
		name.replace("babel-plugin-", "") :
		name;

	return !!availablePlugins[shorthand];
}