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Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.
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/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Joel Denning @joeldenning
*/

"use strict";

const { ConcatSource } = require("webpack-sources");
const { UsageState } = require("../ExportsInfo");
const ExternalModule = require("../ExternalModule");
const Template = require("../Template");
const propertyAccess = require("../util/propertyAccess");
const AbstractLibraryPlugin = require("./AbstractLibraryPlugin");

/** @typedef {import("webpack-sources").Source} Source */
/** @typedef {import("../../declarations/WebpackOptions").LibraryOptions} LibraryOptions */
/** @typedef {import("../../declarations/WebpackOptions").LibraryType} LibraryType */
/** @typedef {import("../Chunk")} Chunk */
/** @typedef {import("../Compilation").ChunkHashContext} ChunkHashContext */
/** @typedef {import("../Compiler")} Compiler */
/** @typedef {import("../javascript/JavascriptModulesPlugin").RenderContext} RenderContext */
/** @typedef {import("../util/Hash")} Hash */
/** @template T @typedef {import("./AbstractLibraryPlugin").LibraryContext} LibraryContext */

/**
 * @typedef {object} SystemLibraryPluginOptions
 * @property {LibraryType} type
 */

/**
 * @typedef {object} SystemLibraryPluginParsed
 * @property {string} name
 */

/**
 * @typedef {SystemLibraryPluginParsed} T
 * @extends {AbstractLibraryPlugin}
 */
class SystemLibraryPlugin extends AbstractLibraryPlugin {
	/**
	 * @param {SystemLibraryPluginOptions} options the plugin options
	 */
	constructor(options) {
		super({
			pluginName: "SystemLibraryPlugin",
			type: options.type
		});
	}

	/**
	 * @param {LibraryOptions} library normalized library option
	 * @returns {T | false} preprocess as needed by overriding
	 */
	parseOptions(library) {
		const { name } = library;
		if (name && typeof name !== "string") {
			throw new Error(
				`System.js library name must be a simple string or unset. ${AbstractLibraryPlugin.COMMON_LIBRARY_NAME_MESSAGE}`
			);
		}
		return {
			name: /** @type {string} */ (name)
		};
	}

	/**
	 * @param {Source} source source
	 * @param {RenderContext} renderContext render context
	 * @param {LibraryContext} libraryContext context
	 * @returns {Source} source with library export
	 */
	render(source, { chunkGraph, moduleGraph, chunk }, { options, compilation }) {
		const modules = chunkGraph
			.getChunkModules(chunk)
			.filter(m => m instanceof ExternalModule && m.externalType === "system");
		const externals = /** @type {ExternalModule[]} */ (modules);

		// The name this bundle should be registered as with System
		const name = options.name
			? `${JSON.stringify(compilation.getPath(options.name, { chunk }))}, `
			: "";

		// The array of dependencies that are external to webpack and will be provided by System
		const systemDependencies = JSON.stringify(
			externals.map(m =>
				typeof m.request === "object" && !Array.isArray(m.request)
					? m.request.amd
					: m.request
			)
		);

		// The name of the variable provided by System for exporting
		const dynamicExport = "__WEBPACK_DYNAMIC_EXPORT__";

		// An array of the internal variable names for the webpack externals
		const externalWebpackNames = externals.map(
			m =>
				`__WEBPACK_EXTERNAL_MODULE_${Template.toIdentifier(
					`${chunkGraph.getModuleId(m)}`
				)}__`
		);

		// Declaring variables for the internal variable names for the webpack externals
		const externalVarDeclarations = externalWebpackNames
			.map(name => `var ${name} = {};`)
			.join("\n");

		// Define __esModule flag on all internal variables and helpers
		/** @type {string[]} */
		const externalVarInitialization = [];

		// The system.register format requires an array of setter functions for externals.
		const setters =
			externalWebpackNames.length === 0
				? ""
				: Template.asString([
						"setters: [",
						Template.indent(
							externals
								.map((module, i) => {
									const external = externalWebpackNames[i];
									const exportsInfo = moduleGraph.getExportsInfo(module);
									const otherUnused =
										exportsInfo.otherExportsInfo.getUsed(chunk.runtime) ===
										UsageState.Unused;
									const instructions = [];
									const handledNames = [];
									for (const exportInfo of exportsInfo.orderedExports) {
										const used = exportInfo.getUsedName(
											undefined,
											chunk.runtime
										);
										if (used) {
											if (otherUnused || used !== exportInfo.name) {
												instructions.push(
													`${external}${propertyAccess([
														used
													])} = module${propertyAccess([exportInfo.name])};`
												);
												handledNames.push(exportInfo.name);
											}
										} else {
											handledNames.push(exportInfo.name);
										}
									}
									if (!otherUnused) {
										if (
											!Array.isArray(module.request) ||
											module.request.length === 1
										) {
											externalVarInitialization.push(
												`Object.defineProperty(${external}, "__esModule", { value: true });`
											);
										}
										if (handledNames.length > 0) {
											const name = `${external}handledNames`;
											externalVarInitialization.push(
												`var ${name} = ${JSON.stringify(handledNames)};`
											);
											instructions.push(
												Template.asString([
													"Object.keys(module).forEach(function(key) {",
													Template.indent([
														`if(${name}.indexOf(key) >= 0)`,
														Template.indent(`${external}[key] = module[key];`)
													]),
													"});"
												])
											);
										} else {
											instructions.push(
												Template.asString([
													"Object.keys(module).forEach(function(key) {",
													Template.indent([`${external}[key] = module[key];`]),
													"});"
												])
											);
										}
									}
									if (instructions.length === 0) return "function() {}";
									return Template.asString([
										"function(module) {",
										Template.indent(instructions),
										"}"
									]);
								})
								.join(",\n")
						),
						"],"
					]);

		return new ConcatSource(
			Template.asString([
				`System.register(${name}${systemDependencies}, function(${dynamicExport}, __system_context__) {`,
				Template.indent([
					externalVarDeclarations,
					Template.asString(externalVarInitialization),
					"return {",
					Template.indent([
						setters,
						"execute: function() {",
						Template.indent(`${dynamicExport}(`)
					])
				]),
				""
			]),
			source,
			Template.asString([
				"",
				Template.indent([
					Template.indent([Template.indent([");"]), "}"]),
					"};"
				]),
				"})"
			])
		);
	}

	/**
	 * @param {Chunk} chunk the chunk
	 * @param {Hash} hash hash
	 * @param {ChunkHashContext} chunkHashContext chunk hash context
	 * @param {LibraryContext} libraryContext context
	 * @returns {void}
	 */
	chunkHash(chunk, hash, chunkHashContext, { options, compilation }) {
		hash.update("SystemLibraryPlugin");
		if (options.name) {
			hash.update(compilation.getPath(options.name, { chunk }));
		}
	}
}

module.exports = SystemLibraryPlugin;