From 533d54ad1e43616e02707e88a9bf40680183c2d3 Mon Sep 17 00:00:00 2001
From: weixiaoing <1537476031@qq.com>
Date: Sat, 22 Aug 2026 09:06:22 +0800
Subject: [PATCH] fix(esm-shim): avoid duplicate declarations

close #921
---
 src/plugins/esmShim.ts | 112 ++++++++++++++++++++++++++++++++---------
 1 file changed, 88 insertions(+), 24 deletions(-)

diff --git a/src/plugins/esmShim.ts b/src/plugins/esmShim.ts
index 3829846..3643d4b 100644
--- a/src/plugins/esmShim.ts
+++ b/src/plugins/esmShim.ts
@@ -6,29 +6,14 @@
 
 import MagicString from 'magic-string'
 import type { SourceMapInput } from 'rollup'
-import type { Plugin } from 'vite'
+import type { ESTree, Plugin } from 'vite'
 
 import { supportImportMetaPaths } from '../electron'
 
-const CJSyntaxRe = /__filename|__dirname|require\(|require\.resolve\(/
-
-const CJSShim_normal = `
-// -- CommonJS Shims --
-import __cjs_url__ from 'node:url';
-import __cjs_path__ from 'node:path';
-import __cjs_mod__ from 'node:module';
-const __filename = __cjs_url__.fileURLToPath(import.meta.url);
-const __dirname = __cjs_path__.dirname(__filename);
-const require = __cjs_mod__.createRequire(import.meta.url);
-`
-
-const CJSShim_node_20_11 = `
-// -- CommonJS Shims --
-import __cjs_mod__ from 'node:module';
-const __filename = import.meta.filename;
-const __dirname = import.meta.dirname;
-const require = __cjs_mod__.createRequire(import.meta.url);
-`
+const CJSShimMarker = '// -- CommonJS Shims --'
+const CJSFilenameRe = /__filename/
+const CJSDirnameRe = /__dirname/
+const CJSRequireRe = /require\(|require\.resolve\(/
 
 const ESMStaticImportRe =
   /(?<=\s|^|;)import\s*([\s"']*(?<imports>[\p{L}\p{M}\w\t\n\r $*,/{}@.]+)from\s*)?["']\s*(?<specifier>(?<="\s*)[^"]*[^\s"](?=\s*")|(?<='\s*)[^']*[^\s'](?=\s*'))\s*["'][\s;]*/gmu
@@ -45,19 +30,98 @@ function findStaticImports(code: string): StaticImport[] {
   return matches
 }
 
-export default function esmShimPlugin(): Plugin {
-  const CJSShim = supportImportMetaPaths() ? CJSShim_node_20_11 : CJSShim_normal
+function addBindingIdentifiers(pattern: ESTree.BindingPattern, bindings: Set<string>): void {
+  if (pattern.type === 'Identifier') {
+    bindings.add(pattern.name)
+  } else if (pattern.type === 'ObjectPattern') {
+    for (const property of pattern.properties) {
+      addBindingIdentifiers(property.type === 'RestElement' ? property.argument : property.value, bindings)
+    }
+  } else if (pattern.type === 'ArrayPattern') {
+    for (const element of pattern.elements) {
+      if (element) addBindingIdentifiers(element.type === 'RestElement' ? element.argument : element, bindings)
+    }
+  } else {
+    addBindingIdentifiers(pattern.left, bindings)
+  }
+}
 
+function getUniqueBindingName(base: string, bindings: Set<string>): string {
+  let name = base
+  let index = 1
+  while (bindings.has(name)) name = `${base}${index++}`
+  bindings.add(name)
+  return name
+}
+
+function createCJSShim(code: string, bindings: Set<string>): string | null {
+  const needsFilename = !bindings.has('__filename') && CJSFilenameRe.test(code)
+  const needsDirname = !bindings.has('__dirname') && CJSDirnameRe.test(code)
+  const needsRequire = !bindings.has('require') && CJSRequireRe.test(code)
+
+  if (!needsFilename && !needsDirname && !needsRequire) {
+    return null
+  }
+
+  const imports: string[] = []
+  const declarations: string[] = []
+
+  if (supportImportMetaPaths()) {
+    if (needsFilename) declarations.push('const __filename = import.meta.filename;')
+    if (needsDirname) declarations.push('const __dirname = import.meta.dirname;')
+  } else if (needsFilename || needsDirname) {
+    const urlBinding = getUniqueBindingName('__cjs_url__', bindings)
+    imports.push(`import ${urlBinding} from 'node:url';`)
+    if (needsFilename) declarations.push(`const __filename = ${urlBinding}.fileURLToPath(import.meta.url);`)
+    if (needsDirname) {
+      const pathBinding = getUniqueBindingName('__cjs_path__', bindings)
+      imports.push(`import ${pathBinding} from 'node:path';`)
+      declarations.push(`const __dirname = ${pathBinding}.dirname(${urlBinding}.fileURLToPath(import.meta.url));`)
+    }
+  }
+
+  if (needsRequire) {
+    const moduleBinding = getUniqueBindingName('__cjs_mod__', bindings)
+    imports.push(`import ${moduleBinding} from 'node:module';`)
+    declarations.push(`const require = ${moduleBinding}.createRequire(import.meta.url);`)
+  }
+
+  return `\n${CJSShimMarker}\n${imports.join('\n')}\n${declarations.join('\n')}\n`
+}
+
+export default function esmShimPlugin(): Plugin {
   return {
     name: 'vite:esm-shim',
     apply: 'build',
     enforce: 'post',
     renderChunk(code, _chunk, { format, sourcemap }): { code: string; map?: SourceMapInput } | null {
       if (format === 'es') {
-        if (code.includes(CJSShim) || !CJSyntaxRe.test(code)) {
-          return null
+        const bindings = new Set<string>()
+        for (const node of this.parse(code).body) {
+          if (node.type === 'ImportDeclaration') {
+            for (const specifier of node.specifiers) {
+              bindings.add(specifier.local.name)
+            }
+            continue
+          }
+
+          const declaration =
+            node.type === 'ExportNamedDeclaration' || node.type === 'ExportDefaultDeclaration' ? node.declaration : node
+          if (declaration?.type === 'VariableDeclaration') {
+            for (const declarator of declaration.declarations) {
+              addBindingIdentifiers(declarator.id, bindings)
+            }
+          } else if (
+            (declaration?.type === 'FunctionDeclaration' || declaration?.type === 'ClassDeclaration') &&
+            declaration.id
+          ) {
+            bindings.add(declaration.id.name)
+          }
         }
 
+        const CJSShim = createCJSShim(code, bindings)
+        if (!CJSShim) return null
+
         const lastESMImport = findStaticImports(code).pop()
         const indexToAppend = lastESMImport ? lastESMImport.end : 0
         const s = new MagicString(code)