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node_modules/webpack/lib/UseStrictPlugin.js

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+/*
+	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;