webpack/lib/OptionsDefaulter.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/
"use strict";

/**
 * Gets the value at path of object
 * @param {object} obj object to query
 * @param {string} path query path
 * @returns {any} - if {@param path} requests element from array, then `undefined` will be returned
 */
const getProperty = (obj, path) => {
	let name = path.split(".");
	for (let i = 0; i < name.length - 1; i++) {
		obj = obj[name[i]];
		if (typeof obj !== "object" || !obj || Array.isArray(obj)) return;
	}
	return obj[name.pop()];
};

/**
 * Sets the value at path of object. Stops execution, if {@param path} requests element from array to be set
 * @param {object} obj object to query
 * @param {string} path query path
 * @param {any} value value to be set
 * @returns {void}
 */
const setProperty = (obj, path, value) => {
	let name = path.split(".");
	for (let i = 0; i < name.length - 1; i++) {
		if (typeof obj[name[i]] !== "object" && obj[name[i]] !== undefined) return;
		if (Array.isArray(obj[name[i]])) return;
		if (!obj[name[i]]) obj[name[i]] = {};
		obj = obj[name[i]];
	}
	obj[name.pop()] = value;
};

/**
 * @typedef {'call' | 'make' | 'append'} ConfigType
 */
/**
 * @typedef {(options: object) => any} MakeConfigHandler
 */
/**
 * @typedef {(value: any, options: object) => any} CallConfigHandler
 */
/**
 * @typedef {any[]} AppendConfigValues
 */

class OptionsDefaulter {
	constructor() {
		/**
		 * Stores default options settings or functions for computing them
		 */
		this.defaults = {};
		/**
		 * Stores configuration for options
		 * @type {{[key: string]: ConfigType}}
		 */
		this.config = {};
	}

	/**
	 * Enhancing {@param options} with default values
	 * @param {object} options provided options
	 * @returns {object} - enhanced options
	 * @throws {Error} - will throw error, if configuration value is other then `undefined` or {@link ConfigType}
	 */
	process(options) {
		options = Object.assign({}, options);
		for (let name in this.defaults) {
			switch (this.config[name]) {
				/**
				 * If {@link ConfigType} doesn't specified and current value is `undefined`, then default value will be assigned
				 */
				case undefined:
					if (getProperty(options, name) === undefined) {
						setProperty(options, name, this.defaults[name]);
					}
					break;
				/**
				 * Assign result of {@link CallConfigHandler}
				 */
				case "call":
					setProperty(
						options,
						name,
						this.defaults[name].call(this, getProperty(options, name), options)
					);
					break;
				/**
				 * Assign result of {@link MakeConfigHandler}, if current value is `undefined`
				 */
				case "make":
					if (getProperty(options, name) === undefined) {
						setProperty(options, name, this.defaults[name].call(this, options));
					}
					break;
				/**
				 * Adding {@link AppendConfigValues} at the end of the current array
				 */
				case "append": {
					let oldValue = getProperty(options, name);
					if (!Array.isArray(oldValue)) {
						oldValue = [];
					}
					oldValue.push(...this.defaults[name]);
					setProperty(options, name, oldValue);
					break;
				}
				default:
					throw new Error(
						"OptionsDefaulter cannot process " + this.config[name]
					);
			}
		}
		return options;
	}

	/**
	 * Builds up default values
	 * @param {string} name option path
	 * @param {ConfigType | any} config if {@param def} is provided, then only {@link ConfigType} is allowed
	 * @param {MakeConfigHandler | CallConfigHandler | AppendConfigValues} [def] defaults
	 * @returns {void}
	 */
	set(name, config, def) {
		if (def !== undefined) {
			this.defaults[name] = def;
			this.config[name] = config;
		} else {
			this.defaults[name] = config;
			delete this.config[name];
		}
	}
}

module.exports = OptionsDefaulter;