fix: separately export __proto__ for compatibility with CJS Transpiler Re-exports

cli/help.md

@@ -65,6 +65,7 @@ Basic options:
 --preserveModules           Preserve module structure
 --preserveModulesRoot       Put preserved modules under this path at root level
 --preserveSymlinks          Do not follow symlinks when resolving files
+--no-reexportProtoFromExternal Ignore `__proto__` in star re-exports
 --no-sanitizeFileName       Do not replace invalid characters in file names
 --shimMissingExports        Create shim variables for missing exports
 --silent                    Don't print warnings

docs/command-line-interface/index.md

@@ -416,6 +416,7 @@ Many options have command line equivalents. In those cases, any arguments passed
 --preserveModules           Preserve module structure
 --preserveModulesRoot       Put preserved modules under this path at root level
 --preserveSymlinks          Do not follow symlinks when resolving files
+--no-reexportProtoFromExternal Ignore `__proto__` in star re-exports
 --no-sanitizeFileName       Do not replace invalid characters in file names
 --shimMissingExports        Create shim variables for missing exports
 --silent                    Don't print warnings

docs/configuration-options/index.md

@@ -1959,6 +1959,51 @@ export default {
 
 This will generate an additional `noConflict` export to UMD bundles. When called in an IIFE scenario, this method will return the bundle exports while restoring the corresponding global variable to its previous value.
 
+### output.reexportProtoFromExternal
+
+|  |  |
+| --: | :-- |
+| Type: | `boolean` |
+| CLI: | `--reexportProtoFromExternal`/`--no-reexportProtoFromExternal` |
+| Default: | `true` |
+
+This option is only effective when [`output.format`](#output-format) is set to one of `['amd', 'cjs', 'iife', 'umd']` and [`output.externalLiveBindings`](#output-externallivebindings) is set to false.
+
+For maximum compatibility, Rollup reexports `__proto__` from an external module by default. However, for common use cases, it is strongly recommended to set this value to false as it effectively reduces the output size.
+
+```js
+// the input file
+export * from 'rollup';
+```
+
+```js
+// the output file if the output.format is cjs
+'use strict';
+
+// reexportProtoFromExternal is true
+var rollup = require('rollup');
+
+Object.prototype.hasOwnProperty.call(rollup, '__proto__') &&
+	!Object.prototype.hasOwnProperty.call(exports, '__proto__') &&
+	Object.defineProperty(exports, '__proto__', {
+		enumerable: true,
+		value: rollup['__proto__']
+	});
+
+Object.keys(rollup).forEach(function (k) {
+	if (k !== 'default' && !Object.prototype.hasOwnProperty.call(exports, k))
+		exports[k] = rollup[k];
+});
+
+// reexportProtoFromExternal is false
+var rollup = require('rollup');
+
+Object.keys(rollup).forEach(function (k) {
+	if (k !== 'default' && !Object.prototype.hasOwnProperty.call(exports, k))
+		exports[k] = rollup[k];
+});
+```
+
 ### output.sanitizeFileName
 
 |          |                                            |

docs/javascript-api/index.md

@@ -193,6 +193,7 @@ const outputOptions = {
 	freeze,
 	indent,
 	noConflict,
+	reexportProtoFromExternal,
 	sanitizeFileName,
 	strict,
 	systemNullSetters,

docs/repl/stores/options.ts

@@ -319,6 +319,12 @@ export const useOptions = defineStore('options2', () => {
 		available: optionOutputPreserveModules.value,
 		name: 'output.preserveModulesRoot'
 	});
+	const optionOutputReexportProtoFromExternal = getBoolean({
+		available: () =>
+			isInteropFormat.value && optionOutputExternalLiveBindings.value.value === false,
+		defaultValue: true,
+		name: 'output.reexportProtoFromExternal'
+	});
 	const optionOutputSanitizeFileName = getBoolean({
 		available: alwaysTrue,
 		defaultValue: true,
@@ -450,6 +456,7 @@ export const useOptions = defineStore('options2', () => {
 		optionOutputPaths,
 		optionOutputPreserveModules,
 		optionOutputPreserveModulesRoot,
+		optionOutputReexportProtoFromExternal,
 		optionOutputSourcemap,
 		optionOutputSourcemapFileNames,
 		optionOutputSanitizeFileName,

src/finalisers/amd.ts

@@ -32,6 +32,7 @@ export default function amd(
 		freeze,
 		generatedCode: { symbols },
 		interop,
+		reexportProtoFromExternal,
 		strict
 	}: NormalizedOutputOptions
 ): void {
@@ -83,7 +84,8 @@ export default function amd(
 		interop,
 		snippets,
 		t,
-		externalLiveBindings
+		externalLiveBindings,
+		reexportProtoFromExternal
 	);
 	let namespaceMarkers = getNamespaceMarkers(
 		namedExportsMode && hasExports,

src/finalisers/cjs.ts

@@ -29,6 +29,7 @@ export default function cjs(
 		freeze,
 		interop,
 		generatedCode: { symbols },
+		reexportProtoFromExternal,
 		strict
 	}: NormalizedOutputOptions
 ): void {
@@ -66,6 +67,7 @@ export default function cjs(
 		snippets,
 		t,
 		externalLiveBindings,
+		reexportProtoFromExternal,
 		`module.exports${_}=${_}`
 	);
 

src/finalisers/iife.ts

@@ -36,6 +36,7 @@ export default function iife(
 		extend,
 		freeze,
 		externalLiveBindings,
+		reexportProtoFromExternal,
 		globals,
 		interop,
 		name,
@@ -116,7 +117,8 @@ export default function iife(
 		interop,
 		snippets,
 		t,
-		externalLiveBindings
+		externalLiveBindings,
+		reexportProtoFromExternal
 	);
 	let namespaceMarkers = getNamespaceMarkers(
 		namedExportsMode && hasExports,

src/finalisers/shared/getExportBlock.ts

@@ -16,6 +16,7 @@ export function getExportBlock(
 	snippets: GenerateCodeSnippets,
 	t: string,
 	externalLiveBindings: boolean,
+	reexportProtoFromExternal: boolean,
 	mechanism = 'return '
 ): string {
 	const { _, getDirectReturnFunction, getFunctionIntro, getPropertyAccess, n, s } = snippets;
@@ -102,6 +103,16 @@ export function getExportBlock(
 			for (const specifier of reexports) {
 				if (specifier.reexported === '*') {
 					if (exportBlock) exportBlock += n;
+					if (!specifier.needsLiveBinding && reexportProtoFromExternal) {
+						const protoString = "'__proto__'";
+						exportBlock +=
+							`Object.prototype.hasOwnProperty.call(${name},${_}${protoString})${_}&&${n}` +
+							`${t}!Object.prototype.hasOwnProperty.call(exports,${_}${protoString})${_}&&${n}` +
+							`${t}Object.defineProperty(exports,${_}${protoString},${_}{${n}` +
+							`${t}${t}enumerable:${_}true,${n}` +
+							`${t}${t}value:${_}${name}[${protoString}]${n}` +
+							`${t}});${n}${n}`;
+					}
 					const copyPropertyIfNecessary = `{${n}${t}if${_}(k${_}!==${_}'default'${_}&&${_}!Object.prototype.hasOwnProperty.call(exports,${_}k))${_}${getDefineProperty(
 						name,
 						specifier.needsLiveBinding,
@@ -251,9 +262,5 @@ const getDefineProperty = (
 			`${t}${t}get:${_}${left}${name}[k]${right}${n}${t}})`
 		);
 	}
-	return (
-		`k${_}===${_}'__proto__'${_}?${_}Object.defineProperty(exports,${_}k,${_}{${n}` +
-		`${t}${t}enumerable:${_}true,${n}` +
-		`${t}${t}value:${_}${name}[k]${n}${t}})${_}:${_}exports[k]${_}=${_}${name}[k]`
-	);
+	return `exports[k]${_}=${_}${name}[k]`;
 };

src/finalisers/umd.ts

@@ -61,6 +61,7 @@ export default function umd(
 		generatedCode: { symbols },
 		globals,
 		noConflict,
+		reexportProtoFromExternal,
 		strict
 	}: NormalizedOutputOptions
 ): void {
@@ -202,7 +203,8 @@ export default function umd(
 		interop,
 		snippets,
 		t,
-		externalLiveBindings
+		externalLiveBindings,
+		reexportProtoFromExternal
 	);
 	let namespaceMarkers = getNamespaceMarkers(
 		namedExportsMode && hasExports,

src/rollup/types.d.ts

@@ -725,6 +725,7 @@ export interface OutputOptions {
 	plugins?: OutputPluginOption;
 	preserveModules?: boolean;
 	preserveModulesRoot?: string;
+	reexportProtoFromExternal?: boolean;
 	sanitizeFileName?: boolean | ((fileName: string) => string);
 	sourcemap?: boolean | 'inline' | 'hidden';
 	sourcemapBaseUrl?: string;
@@ -776,6 +777,7 @@ export interface NormalizedOutputOptions {
 	plugins: OutputPlugin[];
 	preserveModules: boolean;
 	preserveModulesRoot: string | undefined;
+	reexportProtoFromExternal: boolean;
 	sanitizeFileName: (fileName: string) => string;
 	sourcemap: boolean | 'inline' | 'hidden';
 	sourcemapBaseUrl: string | undefined;

src/utils/options/mergeOptions.ts

@@ -267,6 +267,7 @@ async function mergeOutputOptions(
 		plugins: await normalizePluginOption(config.plugins),
 		preserveModules: getOption('preserveModules'),
 		preserveModulesRoot: getOption('preserveModulesRoot'),
+		reexportProtoFromExternal: getOption('reexportProtoFromExternal'),
 		sanitizeFileName: getOption('sanitizeFileName'),
 		sourcemap: getOption('sourcemap'),
 		sourcemapBaseUrl: getOption('sourcemapBaseUrl'),

src/utils/options/normalizeOutputOptions.ts

@@ -84,6 +84,7 @@ export async function normalizeOutputOptions(
 		plugins: await normalizePluginOption(config.plugins),
 		preserveModules,
 		preserveModulesRoot: getPreserveModulesRoot(config),
+		reexportProtoFromExternal: config.reexportProtoFromExternal ?? true,
 		sanitizeFileName:
 			typeof config.sanitizeFileName === 'function'
 				? config.sanitizeFileName

test/form/samples/cjs-transpiler-re-exports-1/_config.js

@@ -0,0 +1,50 @@
+const { execSync } = require('node:child_process');
+
+module.exports = defineTest({
+	description:
+		'Disable reexporting the __proto__ from the external module if both output.externalLiveBindings and output.reExportProtoFromExternal are false',
+	formats: ['cjs'],
+	options: {
+		output: {
+			externalLiveBindings: false,
+			reexportProtoFromExternal: false
+		},
+		plugins: [
+			{
+				resolveId(id) {
+					if (id.endsWith('main.js')) {
+						return { id };
+					}
+					return {
+						id,
+						external: true
+					};
+				},
+				buildEnd() {
+					this.emitFile({
+						type: 'prebuilt-chunk',
+						fileName: 'foo.js',
+						code:
+							'exports.foo = 1;\n' +
+							'Object.defineProperty(exports, "__proto__", {\n' +
+							'	enumerable: true,\n' +
+							'	value: 2\n' +
+							'});'
+					});
+					this.emitFile({
+						type: 'prebuilt-chunk',
+						fileName: 'execute.mjs',
+						code:
+							'import assert from "node:assert";\n' +
+							'import { foo, __proto__ } from "./cjs.js";\n' +
+							'assert.strictEqual(foo, 1);\n' +
+							'assert.strictEqual(__proto__, undefined);'
+					});
+				}
+			}
+		]
+	},
+	after() {
+		execSync('node _actual/execute.mjs', { cwd: __dirname });
+	}
+});

test/form/samples/cjs-transpiler-re-exports-1/_expected/cjs.js

@@ -0,0 +1,9 @@
+'use strict';
+
+var foo_js = require('./foo.js');
+
+
+
+Object.keys(foo_js).forEach(function (k) {
+	if (k !== 'default' && !Object.prototype.hasOwnProperty.call(exports, k)) exports[k] = foo_js[k];
+});

test/form/samples/cjs-transpiler-re-exports-1/main.js

@@ -0,0 +1 @@
+export * from './foo.js';

test/form/samples/cjs-transpiler-re-exports/_config.js

@@ -0,0 +1,49 @@
+const { execSync } = require('node:child_process');
+
+module.exports = defineTest({
+	description:
+		'Compatibility with CJS Transpiler Re-exports if output.externalLiveBindings is false',
+	formats: ['cjs'],
+	options: {
+		output: {
+			externalLiveBindings: false
+		},
+		plugins: [
+			{
+				resolveId(id) {
+					if (id.endsWith('main.js')) {
+						return { id };
+					}
+					return {
+						id,
+						external: true
+					};
+				},
+				buildEnd() {
+					this.emitFile({
+						type: 'prebuilt-chunk',
+						fileName: 'foo.js',
+						code:
+							'exports.foo = 1;\n' +
+							'Object.defineProperty(exports, "__proto__", {\n' +
+							'	enumerable: true,\n' +
+							'	value: 2\n' +
+							'});'
+					});
+					this.emitFile({
+						type: 'prebuilt-chunk',
+						fileName: 'execute.mjs',
+						code:
+							'import assert from "node:assert";\n' +
+							'import { foo, __proto__ } from "./cjs.js";\n' +
+							'assert.strictEqual(foo, 1);\n' +
+							'assert.strictEqual(__proto__, 2);'
+					});
+				}
+			}
+		]
+	},
+	after() {
+		execSync('node _actual/execute.mjs', { cwd: __dirname });
+	}
+});

test/form/samples/cjs-transpiler-re-exports/_expected/cjs.js

@@ -0,0 +1,16 @@
+'use strict';
+
+var foo_js = require('./foo.js');
+
+
+
+Object.prototype.hasOwnProperty.call(foo_js, '__proto__') &&
+	!Object.prototype.hasOwnProperty.call(exports, '__proto__') &&
+	Object.defineProperty(exports, '__proto__', {
+		enumerable: true,
+		value: foo_js['__proto__']
+	});
+
+Object.keys(foo_js).forEach(function (k) {
+	if (k !== 'default' && !Object.prototype.hasOwnProperty.call(exports, k)) exports[k] = foo_js[k];
+});

test/form/samples/cjs-transpiler-re-exports/main.js

@@ -0,0 +1 @@
+export * from './foo.js';

test/form/samples/export-__proto__/_expected/amd.js

@@ -12,11 +12,15 @@ define(['exports', 'x'], (function (exports, x$1) { 'use strict';
 		value: __proto__
 	});
 	exports.x = x;
-	Object.keys(x$1).forEach(function (k) {
-		if (k !== 'default' && !Object.prototype.hasOwnProperty.call(exports, k)) k === '__proto__' ? Object.defineProperty(exports, k, {
+	Object.prototype.hasOwnProperty.call(x$1, '__proto__') &&
+		!Object.prototype.hasOwnProperty.call(exports, '__proto__') &&
+		Object.defineProperty(exports, '__proto__', {
 			enumerable: true,
-			value: x$1[k]
-		}) : exports[k] = x$1[k];
+			value: x$1['__proto__']
+		});
+
+	Object.keys(x$1).forEach(function (k) {
+		if (k !== 'default' && !Object.prototype.hasOwnProperty.call(exports, k)) exports[k] = x$1[k];
 	});
 
 }));