Revert #4939 for now

src/finalisers/es.ts

@@ -3,12 +3,8 @@ import type { ChunkDependency, ChunkExports, ImportSpecifier, ReexportSpecifier
 import type { NormalizedOutputOptions } from '../rollup/types';
 import type { GenerateCodeSnippets } from '../utils/generateCodeSnippets';
 import { getHelpersBlock } from '../utils/interopHelpers';
-import { isValidIdentifier } from '../utils/isValidIdentifier';
 import type { FinaliserOptions } from './index';
 
-const safeExportName = (name: string): string =>
-	isValidIdentifier(name) ? name : JSON.stringify(name);
-
 export default function es(
 	magicString: MagicStringBundle,
 	{ accessedGlobals, indent: t, intro, outro, dependencies, exports, snippets }: FinaliserOptions,
@@ -72,7 +68,7 @@ function getImportBlock(
 						.map(specifier =>
 							specifier.imported === specifier.local
 								? specifier.imported
-								: `${safeExportName(specifier.imported)} as ${specifier.local}`
+								: `${specifier.imported} as ${specifier.local}`
 						)
 						.join(`,${_}`)}${_}}${_}from${_}${pathWithAssertion}`
 				);
@@ -104,9 +100,7 @@ function getImportBlock(
 				for (const specifier of namespaceReexports) {
 					importBlock.push(
 						`export${_}{${_}${
-							name === specifier.reexported
-								? name
-								: `${name} as ${safeExportName(specifier.reexported)}`
+							name === specifier.reexported ? name : `${name} as ${specifier.reexported}`
 						} };`
 					);
 				}
@@ -116,8 +110,8 @@ function getImportBlock(
 					`export${_}{${_}${namedReexports
 						.map(specifier =>
 							specifier.imported === specifier.reexported
-								? safeExportName(specifier.imported)
-								: `${safeExportName(specifier.imported)} as ${safeExportName(specifier.reexported)}`
+								? specifier.imported
+								: `${specifier.imported} as ${specifier.reexported}`
 						)
 						.join(`,${_}`)}${_}}${_}from${_}${pathWithAssertion}`
 				);
@@ -137,7 +131,7 @@ function getExportBlock(exports: ChunkExports, { _, cnst }: GenerateCodeSnippets
 		exportDeclaration.push(
 			specifier.exported === specifier.local
 				? specifier.local
-				: `${specifier.local} as ${safeExportName(specifier.exported)}`
+				: `${specifier.local} as ${specifier.exported}`
 		);
 	}
 	if (exportDeclaration.length > 0) {

src/utils/generateCodeSnippets.ts

@@ -1,6 +1,5 @@
 import type { NormalizedOutputOptions } from '../rollup/types';
 import RESERVED_NAMES from './RESERVED_NAMES';
-import { isValidIdentifier } from './isValidIdentifier';
 
 export interface GenerateCodeSnippets {
 	_: string;
@@ -84,8 +83,8 @@ export function getGenerateCodeSnippets({
 	];
 
 	const isValidPropertyName = reservedNamesAsProps
-		? isValidIdentifier
-		: (name: string): boolean => !RESERVED_NAMES.has(name) && isValidIdentifier(name);
+		? (name: string): boolean => validPropertyName.test(name)
+		: (name: string): boolean => !RESERVED_NAMES.has(name) && validPropertyName.test(name);
 
 	return {
 		_,
@@ -131,3 +130,5 @@ export function getGenerateCodeSnippets({
 
 const wrapIfNeeded = (code: string, needsParens: boolean | undefined): string =>
 	needsParens ? `(${code})` : code;
+
+const validPropertyName = /^(?!\d)[\w$]+$/;

src/utils/safeName.ts

@@ -1,17 +1,15 @@
 import RESERVED_NAMES from './RESERVED_NAMES';
 import { toBase64 } from './base64';
-import { isValidIdentifier } from './isValidIdentifier';
 
 export function getSafeName(
 	baseName: string,
 	usedNames: Set<string>,
 	forbiddenNames: Set<string> | null
 ): string {
-	const safeBase = isValidIdentifier(baseName) ? baseName : '_safe';
-	let safeName = safeBase;
+	let safeName = baseName;
 	let count = 1;
 	while (usedNames.has(safeName) || RESERVED_NAMES.has(safeName) || forbiddenNames?.has(safeName)) {
-		safeName = `${safeBase}$${toBase64(count++)}`;
+		safeName = `${baseName}$${toBase64(count++)}`;
 	}
 	usedNames.add(safeName);
 	return safeName;