webpack/lib/UseStrictPlugin.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";

const ConstDependency = require("./dependencies/ConstDependency");

/** @typedef {import("./Compiler")} Compiler */

class UseStrictPlugin {
	/**
	 * Apply the plugin
	 * @param {Compiler} compiler the compiler instance
	 * @returns {void}
	 */
	apply(compiler) {
		compiler.hooks.compilation.tap(
			"UseStrictPlugin",
			(compilation, { normalModuleFactory }) => {
				const handler = parser => {
					parser.hooks.program.tap("UseStrictPlugin", 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("", firstNode.range);
							dep.loc = firstNode.loc;
							parser.state.module.addPresentationalDependency(dep);
							parser.state.module.buildInfo.strict = true;
						}
					});
				};

				normalModuleFactory.hooks.parser
					.for("javascript/auto")
					.tap("UseStrictPlugin", handler);
				normalModuleFactory.hooks.parser
					.for("javascript/dynamic")
					.tap("UseStrictPlugin", handler);
				normalModuleFactory.hooks.parser
					.for("javascript/esm")
					.tap("UseStrictPlugin", handler);
			}
		);
	}
}

module.exports = UseStrictPlugin;