Add module toStringTag to entries and interop namespaces

src/Chunk.ts

@@ -716,9 +716,10 @@ export default class Chunk {
 				hasExports,
 				indentString: this.indentString,
 				intro: addons.intro!,
-				isEntryModuleFacade:
+				isEntryFacade:
 					this.outputOptions.preserveModules ||
 					(this.facadeModule !== null && this.facadeModule.info.isEntry),
+				isModuleFacade: this.facadeModule !== null,
 				namedExportsMode: this.exportMode !== 'default',
 				outro: addons.outro!,
 				usesTopLevelAwait,

src/finalisers/amd.ts

@@ -1,8 +1,7 @@
 import { Bundle as MagicStringBundle } from 'magic-string';
 import { NormalizedOutputOptions } from '../rollup/types';
 import { FinaliserOptions } from './index';
-import { compactEsModuleExport, esModuleExport } from './shared/esModuleExport';
-import getExportBlock from './shared/getExportBlock';
+import { getExportBlock, getNamespaceMarkers } from './shared/getExportBlock';
 import getInteropBlock from './shared/getInteropBlock';
 import warnOnBuiltins from './shared/warnOnBuiltins';
 
@@ -25,7 +24,8 @@ export default function amd(
 		hasExports,
 		indentString: t,
 		intro,
-		isEntryModuleFacade,
+		isEntryFacade,
+		isModuleFacade,
 		namedExportsMode,
 		outro,
 		varOrConst,
@@ -38,6 +38,7 @@ export default function amd(
 		externalLiveBindings,
 		freeze,
 		interop,
+		namespaceToStringTag,
 		strict
 	}: NormalizedOutputOptions
 ) {
@@ -74,6 +75,7 @@ export default function amd(
 			interop,
 			externalLiveBindings,
 			freeze,
+			namespaceToStringTag,
 			accessedGlobals,
 			_,
 			n,
@@ -91,11 +93,17 @@ export default function amd(
 		t,
 		externalLiveBindings
 	);
-	if (exportBlock) magicString.append(exportBlock);
-	if (namedExportsMode && hasExports && isEntryModuleFacade && esModule)
-		magicString.append(`${n}${n}${compact ? compactEsModuleExport : esModuleExport}`);
-	if (outro) magicString.append(outro);
-
+	let namespaceMarkers = getNamespaceMarkers(
+		namedExportsMode && hasExports,
+		isEntryFacade && esModule,
+		isModuleFacade && namespaceToStringTag,
+		_,
+		n
+	);
+	if (namespaceMarkers) {
+		namespaceMarkers = n + n + namespaceMarkers;
+	}
+	magicString.append(`${exportBlock}${namespaceMarkers}${outro}`);
 	return magicString
 		.indent(t)
 		.prepend(`${amdDefine}(${params}function${_}(${args.join(`,${_}`)})${_}{${useStrict}${n}${n}`)

src/finalisers/cjs.ts

@@ -2,8 +2,7 @@ import { Bundle as MagicStringBundle } from 'magic-string';
 import { ChunkDependencies } from '../Chunk';
 import { NormalizedOutputOptions } from '../rollup/types';
 import { FinaliserOptions } from './index';
-import { compactEsModuleExport, esModuleExport } from './shared/esModuleExport';
-import getExportBlock from './shared/getExportBlock';
+import { getExportBlock, getNamespaceMarkers } from './shared/getExportBlock';
 import getInteropBlock from './shared/getInteropBlock';
 
 export default function cjs(
@@ -15,37 +14,53 @@ export default function cjs(
 		hasExports,
 		indentString: t,
 		intro,
-		isEntryModuleFacade,
+		isEntryFacade,
+		isModuleFacade,
 		namedExportsMode,
 		outro,
 		varOrConst
 	}: FinaliserOptions,
-	{ compact, esModule, externalLiveBindings, freeze, interop, strict }: NormalizedOutputOptions
+	{
+		compact,
+		esModule,
+		externalLiveBindings,
+		freeze,
+		interop,
+		namespaceToStringTag,
+		strict
+	}: NormalizedOutputOptions
 ) {
 	const n = compact ? '' : '\n';
 	const s = compact ? '' : ';';
 	const _ = compact ? '' : ' ';
 
 	const useStrict = strict ? `'use strict';${n}${n}` : '';
-	const esModuleProp =
-		namedExportsMode && hasExports && isEntryModuleFacade && esModule
-			? `${compact ? compactEsModuleExport : esModuleExport}${n}${n}`
-			: '';
+	let namespaceMarkers = getNamespaceMarkers(
+		namedExportsMode && hasExports,
+		isEntryFacade && esModule,
+		isModuleFacade && namespaceToStringTag,
+		_,
+		n
+	);
+	if (namespaceMarkers) {
+		namespaceMarkers += n + n;
+	}
 	const importBlock = getImportBlock(dependencies, compact, varOrConst, n, _);
 	const interopBlock = getInteropBlock(
 		dependencies,
 		varOrConst,
 		interop,
 		externalLiveBindings,
 		freeze,
+		namespaceToStringTag,
 		accessedGlobals,
 		_,
 		n,
 		s,
 		t
 	);
 
-	magicString.prepend(`${useStrict}${intro}${esModuleProp}${importBlock}${interopBlock}`);
+	magicString.prepend(`${useStrict}${intro}${namespaceMarkers}${importBlock}${interopBlock}`);
 
 	const exportBlock = getExportBlock(
 		exports,

src/finalisers/iife.ts

@@ -3,7 +3,7 @@ import { NormalizedOutputOptions } from '../rollup/types';
 import { error } from '../utils/error';
 import { isLegal } from '../utils/identifierHelpers';
 import { FinaliserOptions } from './index';
-import getExportBlock from './shared/getExportBlock';
+import { getExportBlock, getNamespaceMarkers } from './shared/getExportBlock';
 import getInteropBlock from './shared/getInteropBlock';
 import { keypath } from './shared/sanitize';
 import setupNamespace from './shared/setupNamespace';
@@ -28,12 +28,14 @@ export default function iife(
 	}: FinaliserOptions,
 	{
 		compact,
+		esModule,
 		extend,
 		freeze,
 		externalLiveBindings,
 		globals,
 		interop,
 		name,
+		namespaceToStringTag,
 		strict
 	}: NormalizedOutputOptions
 ) {
@@ -81,6 +83,7 @@ export default function iife(
 		interop,
 		externalLiveBindings,
 		freeze,
+		namespaceToStringTag,
 		accessedGlobals,
 		_,
 		n,
@@ -115,6 +118,16 @@ export default function iife(
 		t,
 		externalLiveBindings
 	);
-	magicString.append(`${exportBlock}${outro}`);
+	let namespaceMarkers = getNamespaceMarkers(
+		namedExportsMode && hasExports,
+		esModule,
+		namespaceToStringTag,
+		_,
+		n
+	);
+	if (namespaceMarkers) {
+		namespaceMarkers = n + n + namespaceMarkers;
+	}
+	magicString.append(`${exportBlock}${namespaceMarkers}${outro}`);
 	return magicString.indent(t).prepend(wrapperIntro).append(wrapperOutro);
 }

src/finalisers/index.ts

@@ -15,7 +15,8 @@ export interface FinaliserOptions {
 	hasExports: boolean;
 	indentString: string;
 	intro: string;
-	isEntryModuleFacade: boolean;
+	isEntryFacade: boolean;
+	isModuleFacade: boolean;
 	namedExportsMode: boolean;
 	outro: string;
 	usesTopLevelAwait: boolean;

src/finalisers/shared/getExportBlock.ts

@@ -6,7 +6,7 @@ import {
 	namespaceInteropHelpersByInteropType
 } from '../../utils/interopHelpers';
 
-export default function getExportBlock(
+export function getExportBlock(
 	exports: ChunkExports,
 	dependencies: ChunkDependencies,
 	namedExportsMode: boolean,
@@ -174,3 +174,33 @@ function getReexportedImportName(
 	}
 	return `${moduleVariableName}.${imported}`;
 }
+
+function getEsModuleExport(_: string): string {
+	return `Object.defineProperty(exports,${_}'__esModule',${_}{${_}value:${_}true${_}});`;
+}
+
+function getNamespaceToStringExport(_: string): string {
+	return `exports[Symbol.toStringTag]${_}=${_}'Module';`;
+}
+
+export function getNamespaceMarkers(
+	hasNamedExports: boolean,
+	addEsModule: boolean,
+	addNamespaceToStringTag: boolean,
+	_: string,
+	n: string
+): string {
+	let namespaceMarkers = '';
+	if (hasNamedExports) {
+		if (addEsModule) {
+			namespaceMarkers += getEsModuleExport(_);
+		}
+		if (addNamespaceToStringTag) {
+			if (namespaceMarkers) {
+				namespaceMarkers += n;
+			}
+			namespaceMarkers += getNamespaceToStringExport(_);
+		}
+	}
+	return namespaceMarkers;
+}

src/finalisers/shared/getInteropBlock.ts

@@ -13,6 +13,7 @@ export default function getInteropBlock(
 	interop: GetInterop,
 	externalLiveBindings: boolean,
 	freeze: boolean,
+	namespaceToStringTag: boolean,
 	accessedGlobals: Set<string>,
 	_: string,
 	n: string,
@@ -92,6 +93,7 @@ export default function getInteropBlock(
 		s,
 		t,
 		externalLiveBindings,
-		freeze
+		freeze,
+		namespaceToStringTag
 	)}${interopStatements.length > 0 ? `${interopStatements.join(n)}${n}${n}` : ''}`;
 }

src/finalisers/umd.ts

@@ -2,8 +2,7 @@ import { Bundle as MagicStringBundle } from 'magic-string';
 import { NormalizedOutputOptions } from '../rollup/types';
 import { error } from '../utils/error';
 import { FinaliserOptions } from './index';
-import { compactEsModuleExport, esModuleExport } from './shared/esModuleExport';
-import getExportBlock from './shared/getExportBlock';
+import { getExportBlock, getNamespaceMarkers } from './shared/getExportBlock';
 import getInteropBlock from './shared/getInteropBlock';
 import { keypath, property } from './shared/sanitize';
 import { assignToDeepVariable } from './shared/setupNamespace';
@@ -45,6 +44,7 @@ export default function umd(
 		freeze,
 		interop,
 		name,
+		namespaceToStringTag,
 		globals,
 		noConflict,
 		strict
@@ -161,6 +161,7 @@ export default function umd(
 			interop,
 			externalLiveBindings,
 			freeze,
+			namespaceToStringTag,
 			accessedGlobals,
 			_,
 			n,
@@ -178,10 +179,16 @@ export default function umd(
 		t,
 		externalLiveBindings
 	);
-	if (exportBlock) magicString.append(exportBlock);
-	if (namedExportsMode && hasExports && esModule)
-		magicString.append(n + n + (compact ? compactEsModuleExport : esModuleExport));
-	if (outro) magicString.append(outro);
-
+	let namespaceMarkers = getNamespaceMarkers(
+		namedExportsMode && hasExports,
+		esModule,
+		namespaceToStringTag,
+		_,
+		n
+	);
+	if (namespaceMarkers) {
+		namespaceMarkers = n + n + namespaceMarkers;
+	}
+	magicString.append(`${exportBlock}${namespaceMarkers}${outro}`);
 	return magicString.trim().indent(t).append(wrapperOutro).prepend(wrapperIntro);
 }