feat: handle import.meta.main (#20065)

alexander-akait · web-flow · commit 8651ffc23a13 · 2025-10-31T16:51:41.000+03:00
diff --git a/lib/dependencies/CommonJsImportsParserPlugin.js b/lib/dependencies/CommonJsImportsParserPlugin.js
@@ -126,15 +126,6 @@ class CommonJsImportsParserPlugin {
 		});
 
 		// #region Unsupported
-		parser.hooks.expression
-			.for("require.main")
-			.tap(
-				PLUGIN_NAME,
-				expressionIsUnsupported(
-					parser,
-					"require.main is not supported by webpack."
-				)
-			);
 		parser.hooks.call
 			.for("require.main.require")
 			.tap(
diff --git a/lib/dependencies/ImportMetaPlugin.js b/lib/dependencies/ImportMetaPlugin.js
@@ -13,6 +13,7 @@ const {
 	JAVASCRIPT_MODULE_TYPE_AUTO,
 	JAVASCRIPT_MODULE_TYPE_ESM
 } = require("../ModuleTypeConstants");
+const RuntimeGlobals = require("../RuntimeGlobals");
 const Template = require("../Template");
 const BasicEvaluatedExpression = require("../javascript/BasicEvaluatedExpression");
 const {
@@ -34,6 +35,7 @@ const ConstDependency = require("./ConstDependency");
 /** @typedef {import("../javascript/JavascriptParser").Range} Range */
 /** @typedef {import("../javascript/JavascriptParser").Members} Members */
 /** @typedef {import("../javascript/JavascriptParser").DestructuringAssignmentProperty} DestructuringAssignmentProperty */
+/** @typedef {import("./ConstDependency").RawRuntimeRequirements} RawRuntimeRequirements */
 
 const getCriticalDependencyWarning = memoize(() =>
 	require("./CriticalDependencyWarning")
@@ -168,6 +170,9 @@ class ImportMetaPlugin {
 								return true;
 							}
 
+							/** @type {RawRuntimeRequirements} */
+							const runtimeRequirements = [];
+
 							let str = "";
 							for (const prop of referencedPropertiesInDestructuring) {
 								const value = hooks.propertyInDestructuring.call(prop);
@@ -184,6 +189,14 @@ class ImportMetaPlugin {
 									case "webpack":
 										str += `webpack: ${importMetaWebpackVersion()},`;
 										break;
+									case "main":
+										str += `main: ${RuntimeGlobals.moduleCache}[${RuntimeGlobals.entryModuleId}] === ${RuntimeGlobals.module},`;
+										runtimeRequirements.push(
+											RuntimeGlobals.moduleCache,
+											RuntimeGlobals.entryModuleId,
+											RuntimeGlobals.module
+										);
+										break;
 									default:
 										str += `[${JSON.stringify(
 											prop.id
@@ -193,7 +206,8 @@ class ImportMetaPlugin {
 							}
 							const dep = new ConstDependency(
 								`({${str}})`,
-								/** @type {Range} */ (metaProperty.range)
+								/** @type {Range} */ (metaProperty.range),
+								runtimeRequirements
 							);
 							dep.loc = /** @type {DependencyLocation} */ (metaProperty.loc);
 							parser.state.module.addPresentationalDependency(dep);
@@ -237,17 +251,17 @@ class ImportMetaPlugin {
 						);
 
 					// import.meta.webpack
-					parser.hooks.typeof
+					parser.hooks.expression
 						.for("import.meta.webpack")
 						.tap(
 							PLUGIN_NAME,
-							toConstantDependency(parser, JSON.stringify("number"))
+							toConstantDependency(parser, importMetaWebpackVersion())
 						);
-					parser.hooks.expression
+					parser.hooks.typeof
 						.for("import.meta.webpack")
 						.tap(
 							PLUGIN_NAME,
-							toConstantDependency(parser, importMetaWebpackVersion())
+							toConstantDependency(parser, JSON.stringify("number"))
 						);
 					parser.hooks.evaluateTypeof
 						.for("import.meta.webpack")
@@ -256,6 +270,30 @@ class ImportMetaPlugin {
 						.for("import.meta.webpack")
 						.tap(PLUGIN_NAME, evaluateToNumber(webpackVersion));
 
+					parser.hooks.expression
+						.for("import.meta.main")
+						.tap(
+							PLUGIN_NAME,
+							toConstantDependency(
+								parser,
+								`${RuntimeGlobals.moduleCache}[${RuntimeGlobals.entryModuleId}] === ${RuntimeGlobals.module}`,
+								[
+									RuntimeGlobals.moduleCache,
+									RuntimeGlobals.entryModuleId,
+									RuntimeGlobals.module
+								]
+							)
+						);
+					parser.hooks.typeof
+						.for("import.meta.main")
+						.tap(
+							PLUGIN_NAME,
+							toConstantDependency(parser, JSON.stringify("boolean"))
+						);
+					parser.hooks.evaluateTypeof
+						.for("import.meta.main")
+						.tap(PLUGIN_NAME, evaluateToString("boolean"));
+
 					// Unknown properties
 					parser.hooks.unhandledExpressionMemberChain
 						.for("import.meta")
diff --git a/test/configCases/parsing/import-meta-main/boolean.js b/test/configCases/parsing/import-meta-main/boolean.js
@@ -0,0 +1 @@
+export default "1";
diff --git a/test/configCases/parsing/import-meta-main/index.js b/test/configCases/parsing/import-meta-main/index.js
@@ -0,0 +1,14 @@
+import { main } from "./module.js";
+
+it("should handle import.meta.main", async () => {
+	expect(import.meta.main).toBe(true);
+	expect(typeof import.meta.main).toBe("boolean");
+
+	// Just for test, nobody uses this in real code
+	await import(`./${typeof import.meta.main}.js`);
+
+	const { main: myMain } = import.meta;
+	expect(myMain).toBe(true);
+
+	expect(main).toBe(false);
+});
diff --git a/test/configCases/parsing/import-meta-main/module.js b/test/configCases/parsing/import-meta-main/module.js
@@ -0,0 +1,3 @@
+const main = import.meta.main;
+
+export { main };
diff --git a/test/configCases/parsing/import-meta-main/webpack.config.js b/test/configCases/parsing/import-meta-main/webpack.config.js
@@ -0,0 +1,9 @@
+"use strict";
+
+/** @type {import("../../../../").Configuration} */
+module.exports = {
+	target: "node",
+	optimization: {
+		concatenateModules: false
+	}
+};
diff --git a/test/configCases/parsing/require-main/index.js b/test/configCases/parsing/require-main/index.js
@@ -0,0 +1,7 @@
+const { main } = require("./module");
+
+it("should handle require.main", async () => {
+	expect(require.main === module).toBe(true);
+
+	expect(main).toBe(false);
+});
diff --git a/test/configCases/parsing/require-main/module.js b/test/configCases/parsing/require-main/module.js
@@ -0,0 +1,3 @@
+const main = require.main === module;
+
+module.exports = { main };
diff --git a/test/configCases/parsing/require-main/webpack.config.js b/test/configCases/parsing/require-main/webpack.config.js
@@ -0,0 +1,9 @@
+"use strict";
+
+/** @type {import("../../../../").Configuration} */
+module.exports = {
+	target: "node",
+	optimization: {
+		concatenateModules: false
+	}
+};

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+const main = import.meta.main;`
	`2`	`+`
	`3`	`+export { main };`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+const main = require.main === module;`
	`2`	`+`
	`3`	`+module.exports = { main };`