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fix(javascript): wrap an inlined entry that returns at its top level in an IIFE
A script parse accepts a top-level `return`, as CommonJS does, but an inlined entry rendered without a wrapper (`output.iife: false`, module output, or the `avoidEntryIife` rename) put it outside any function, and the bundle did not parse. test262's top-level `return` cases now pass minified too, so they leave MINIFIED_FAILURES. Claude-Session: https://claude.ai/code/session_019cRZoHW2M4sCbrLFgrAc6b
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9 files changed

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‎.changeset/039-entry-top-level-return-iife.md‎

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---
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"webpack": patch
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---
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Wrap an inlined entry module that returns at its top level in an IIFE.

‎lib/javascript/JavascriptModulesPlugin.js‎

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@@ -430,6 +430,24 @@ const renameInlinedModuleVariable = (
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const PLUGIN_NAME = "JavascriptModulesPlugin";
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/**
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* Marks a module whose top level holds a `return`, which a script parse allows
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* as CommonJS does. Rendered outside a function, that statement does not parse.
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* @param {JavascriptParser} parser the parser
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* @returns {void}
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*/
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const recordTopLevelReturn = (parser) => {
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parser.hooks.statement.tap(PLUGIN_NAME, (statement) => {
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if (
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statement.type === "ReturnStatement" &&
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parser.scope.topLevelScope === true
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) {
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/** @type {BuildInfo} */
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(parser.state.module.buildInfo).topLevelReturn = true;
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}
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});
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};
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// Drops the redundant string/buffer copy of a source, keeping its map: a
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// parsed map is far more expensive to rebuild than a `toString`.
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const CLEAR_SOURCE_COPIES = { maps: false, source: true };
@@ -519,6 +537,12 @@ class JavascriptModulesPlugin {
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}
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}
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});
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// Only a module parse rejects a `return` outside a function.
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if (type !== JAVASCRIPT_MODULE_TYPE_ESM) {
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normalModuleFactory.hooks.parser
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.for(type)
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.tap(PLUGIN_NAME, recordTopLevelReturn);
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}
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normalModuleFactory.hooks.createGenerator
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.for(type)
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.tap(PLUGIN_NAME, () => new JavascriptGenerator());
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? "it needs to be isolated against other modules in the chunk."
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: exports && !webpackExports
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? `it uses a non-standard name for the exports (${m.exportsArgument}).`
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: hooks.embedInRuntimeBailout.call(m, renderContext);
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: /** @type {BuildInfo} */ (m.buildInfo).topLevelReturn
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? "it returns at its top level."
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: hooks.embedInRuntimeBailout.call(m, renderContext);
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if (iife) {
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inlinedInIIFE = true;

‎lib/module/Module.js‎

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* @property {boolean=} isCircular true when the module is in a synchronous circular dependency chain
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* @property {number=} circularKind CircularKind bit flags from CircularModulesPlugin; unset when the plugin did not run
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* @property {boolean=} usesTopLevelAwaitForOf module uses top-level `for await…of` or `await using`, which can't be lowered to a generator
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* @property {boolean=} topLevelReturn module returns at its top level, as a CommonJS module may, so it can only be rendered inside a function
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* @property {BuildDiagnostics=} diagnostics what the build recorded for stats and the performance hints to report
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*/
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‎test/configCases/module/iife-top-level-return/index.js‎

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let reached = false;
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it("should stop the entry at its top-level return", () => {
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expect(reached).toBe(false);
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});
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if (typeof it === "function") return;
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reached = true;

‎test/configCases/module/iife-top-level-return/test.config.js‎

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"use strict";
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module.exports = {
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findBundle() {
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return ["script.js", "module.mjs", "test.js"];
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}
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};

‎test/configCases/module/iife-top-level-return/test.js‎

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const fs = require("fs");
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const path = require("path");
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const vm = require("vm");
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it("should wrap an entry returning at its top level in an IIFE", () => {
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for (const file of ["script.js", "module.mjs"]) {
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const source = fs.readFileSync(path.join(__dirname, file), "utf-8");
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expect(source).toContain(
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"This entry needs to be wrapped in an IIFE because it returns at its top level."
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);
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}
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const script = fs.readFileSync(path.join(__dirname, "script.js"), "utf-8");
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expect(() => new vm.Script(script)).not.toThrow();
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});

‎test/configCases/module/iife-top-level-return/webpack.config.js‎

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"use strict";
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/** @type {import("../../../../").Configuration[]} */
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module.exports = [
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{
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name: "script",
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output: {
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iife: false,
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filename: "script.js"
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}
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},
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{
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name: "module",
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output: {
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module: true,
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filename: "module.mjs"
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},
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target: "es2020"
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},
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{
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name: "test-output",
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entry: "./test.js",
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output: {
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filename: "test.js"
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}
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}
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];

‎test/specCases/test262.spectest.js‎

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"terser writes a program that no longer parses",
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minifiers: ["terser", "printer"],
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tests: [
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"global-code/return.js (sloppy)",
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"global-code/return.js (strict)",
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"statements/class/elements/fields-hash-constructor-is-a-valid-name.js (sloppy)",
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"statements/class/elements/fields-hash-constructor-is-a-valid-name.js (strict)",
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"statements/return/S12.9_A1_T1.js (sloppy)",
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"statements/return/S12.9_A1_T1.js (strict)",
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"statements/return/S12.9_A1_T10.js (sloppy)",
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"statements/return/S12.9_A1_T10.js (strict)",
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"statements/return/S12.9_A1_T2.js (sloppy)",
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"statements/return/S12.9_A1_T2.js (strict)",
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"statements/return/S12.9_A1_T3.js (sloppy)",
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"statements/return/S12.9_A1_T3.js (strict)",
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"statements/return/S12.9_A1_T4.js (sloppy)",
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"statements/return/S12.9_A1_T4.js (strict)",
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"statements/return/S12.9_A1_T5.js (sloppy)",
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"statements/return/S12.9_A1_T5.js (strict)",
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"statements/return/S12.9_A1_T6.js (sloppy)",
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"statements/return/S12.9_A1_T6.js (strict)",
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"statements/return/S12.9_A1_T7.js (sloppy)",
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"statements/return/S12.9_A1_T7.js (strict)",
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"statements/return/S12.9_A1_T8.js (sloppy)",
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"statements/return/S12.9_A1_T8.js (strict)",
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"statements/return/S12.9_A1_T9.js (sloppy)",
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"statements/return/S12.9_A1_T9.js (strict)"
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"statements/class/elements/fields-hash-constructor-is-a-valid-name.js (strict)"
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]
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},
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{

‎types.d.ts‎

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*/
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usesTopLevelAwaitForOf?: boolean;
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/**
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* module returns at its top level, as a CommonJS module may, so it can only be rendered inside a function
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*/
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topLevelReturn?: boolean;
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/**
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* what the build recorded for stats and the performance hints to report
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*/

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