webpack/lib/UseStrictPlugin.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
	Author Tobias Koppers @sokra
*/

"use strict";

const {
	JAVASCRIPT_MODULE_TYPE_AUTO,
	JAVASCRIPT_MODULE_TYPE_DYNAMIC,
	JAVASCRIPT_MODULE_TYPE_ESM
} = require("./ModuleTypeConstants");
const ConstDependency = require("./dependencies/ConstDependency");

/** @typedef {import("../declarations/WebpackOptions").JavascriptParserOptions} JavascriptParserOptions */
/** @typedef {import("./Compiler")} Compiler */
/** @typedef {import("./Dependency").DependencyLocation} DependencyLocation */
/** @typedef {import("./Module").BuildInfo} BuildInfo */
/** @typedef {import("./javascript/JavascriptParser")} JavascriptParser */
/** @typedef {import("./javascript/JavascriptParser").Range} Range */

const PLUGIN_NAME = "UseStrictPlugin";

class UseStrictPlugin {
	/**
	 * Applies the plugin by registering its hooks on the compiler.
	 * @param {Compiler} compiler the compiler instance
	 * @returns {void}
	 */
	apply(compiler) {
		compiler.hooks.compilation.tap(
			PLUGIN_NAME,
			(compilation, { normalModuleFactory }) => {
				/**
				 * Handles the hook callback for this code path.
				 * @param {JavascriptParser} parser the parser
				 * @param {JavascriptParserOptions} parserOptions the javascript parser options
				 */
				const handler = (parser, parserOptions) => {
					parser.hooks.program.tap(PLUGIN_NAME, (ast) => {
						const firstNode = ast.body[0];
						if (
							firstNode &&
							firstNode.type === "ExpressionStatement" &&
							firstNode.expression.type === "Literal" &&
							firstNode.expression.value === "use strict"
						) {
							// Remove "use strict" expression. It will be added later by the renderer again.
							// This is necessary in order to not break the strict mode when webpack prepends code.
							// @see https://github.com/webpack/webpack/issues/1970
							const dep = new ConstDependency(
								"",
								/** @type {Range} */ (firstNode.range)
							);
							dep.loc = /** @type {DependencyLocation} */ (firstNode.loc);
							parser.state.module.addPresentationalDependency(dep);
							/** @type {BuildInfo} */
							(parser.state.module.buildInfo).strict = true;
						}
						if (parserOptions.overrideStrict) {
							/** @type {BuildInfo} */
							(parser.state.module.buildInfo).strict =
								parserOptions.overrideStrict === "strict";
						}
					});
				};

				normalModuleFactory.hooks.parser
					.for(JAVASCRIPT_MODULE_TYPE_AUTO)
					.tap(PLUGIN_NAME, handler);
				normalModuleFactory.hooks.parser
					.for(JAVASCRIPT_MODULE_TYPE_DYNAMIC)
					.tap(PLUGIN_NAME, handler);
				normalModuleFactory.hooks.parser
					.for(JAVASCRIPT_MODULE_TYPE_ESM)
					.tap(PLUGIN_NAME, handler);
			}
		);
	}
}

module.exports = UseStrictPlugin;