webpack/lib/runtime/ConcatenationWrapRuntimeModule.js

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.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
*/

"use strict";

const RuntimeGlobals = require("../RuntimeGlobals");
const Template = require("../Template");
const HelperRuntimeModule = require("./HelperRuntimeModule");

/** @import Compilation from "../Compilation" */

class ConcatenationWrapRuntimeModule extends HelperRuntimeModule {
	constructor() {
		super("concatenation wrap");
	}

	/**
	 * Returns true, if the runtime module should get it's own scope.
	 * When false, `generate()` must emit complete statements ending with `;`
	 * so a following runtime IIFE is not parsed as a call (ASI).
	 * @returns {boolean} true, if the runtime module should get it's own scope
	 */
	shouldIsolate() {
		return false;
	}

	/**
	 * Generates runtime code for this runtime module.
	 * @returns {string | null} runtime code
	 */
	generate() {
		const compilation = /** @type {Compilation} */ (this.compilation);
		const { runtimeTemplate, outputOptions } = compilation;
		const { strictModuleErrorHandling, strictModuleExceptionHandling } =
			outputOptions;
		const fn = RuntimeGlobals.concatenationWrap;
		/** @type {string[]} */
		const runBody = [];
		if (strictModuleErrorHandling) {
			// mirrors the module cache: the error is remembered and rethrown
			runBody.push(
				"try {",
				Template.indent("fn.call(mod.exports, mod, mod.exports);"),
				"} catch (e) {",
				Template.indent(["mod.error = e;", "throw e;"]),
				"}"
			);
		} else if (strictModuleExceptionHandling) {
			// mirrors deleting the cache entry: a later call runs the body again
			runBody.push(
				"var threw = true;",
				"try {",
				Template.indent([
					"fn.call(mod.exports, mod, mod.exports);",
					"threw = false;"
				]),
				"} finally {",
				Template.indent(["if (threw) { body = fn; mod = undefined; }"]),
				"}"
			);
		} else {
			runBody.push("fn.call(mod.exports, mod, mod.exports);");
		}
		return Template.asString([
			"// wrap a concatenated module body as a lazy, memoized accessor; mod is",
			"// set before the body runs so re-entrant calls (require cycles) observe",
			"// the partial exports like Node.js",
			`${fn} = ${runtimeTemplate.basicFunction("body", [
				"var mod;",
				`return ${runtimeTemplate.basicFunction("", [
					"if (body) {",
					Template.indent([
						"var fn = body;",
						"body = 0;",
						"mod = { exports: {} };",
						...runBody
					]),
					"}",
					...(strictModuleErrorHandling
						? ["if (mod.error !== undefined) throw mod.error;"]
						: []),
					"return mod.exports;"
				])};`
			])};`
		]);
	}
}

module.exports = ConcatenationWrapRuntimeModule;