rollup · rtritto · Feb 14, 2026
@@ -63,6 +63,7 @@
   },
   "dependencies": {
     "@rollup/pluginutils": "^5.0.1",
+    "cjs-module-lexer": "^2.2.0",
     "commondir": "^1.0.1",
     "estree-walker": "^2.0.2",
     "fdir": "^6.2.0",

@@ -0,0 +1,80 @@
+import { init, parse } from 'cjs-module-lexer';
+
+let initialized = false;
+
+/**
+ * Ensure cjs-module-lexer WASM is initialized.
+ * Safe to call multiple times — will only init once.
+ */
+export async function ensureInit() {
+  if (!initialized) {
+    await init();
+    initialized = true;
+  }
+}
+
+/**
+ * Analyze a CommonJS module source to detect named exports.
+ *
+ * @param {string} code — The raw CJS source code.
+ * @param {string} id — The module ID (for error reporting).
+ * @returns {Promise<{
+ *   exports: string[]
+ *   reexports: string[]
+ *   hasDefaultExport: boolean
+ * }>}
+ */
+export async function analyzeExports(code, id) {
+  await ensureInit();
+  try {
+    const result = parse(code);
+    // Deduplicate and filter out "default" — handled separately
+    const namedExports = [...new Set(result.exports)].filter(e => e !== 'default');
+    const reexports = [...new Set(result.reexports)];
+    return {
+      exports: namedExports,
+      reexports,
+      hasDefaultExport: result.exports.includes('default'),
+    };
+  } catch (err) {
+    // If lexer fails (e.g. WASM issue), fall back gracefully
+    console.warn(
+      `[commonjs] cjs-module-lexer failed for ${id}: ${err.message}. ` +
+        'Falling back to no named exports.'
+    );
+
+    return { exports: [], reexports: [], hasDefaultExport: true };
+  }
+}
+
+/**
+ * Given a list of reexport sources, recursively resolve
+ * their named exports using the provided resolver.
+ *
+ * @param {string[]} reexportSources
+ * @param {(source: string) => Promise<string|null>} resolve
+ * @param {(id: string) => Promise<string>} loadCode
+ * @param {Set<string>} [seen]
+ * @returns {Promise<string[]>}
+ */
+export async function resolveReexports(reexportSources, resolve, loadCode, seen = new Set()) {
+  const allExports = [];
+  for (const source of reexportSources) {
+    const resolved = await resolve(source);
+    if (!resolved || seen.has(resolved)) continue;
+    seen.add(resolved);
+    try {
+      const code = await loadCode(resolved);
+      const { exports: childExports, reexports: childReexports } = await analyzeExports(code, resolved);
+      allExports.push(...childExports);
+      if (childReexports.length > 0) {
+        const nested = await resolveReexports(childReexports, resolve, loadCode, seen);
+        allExports.push(...nested);
+      }
+    } catch {
+      // skip unresolvable reexports
+    }
+  }
+
+  return [...new Set(allExports)];
+}
@@ -4,6 +4,7 @@ import { createFilter } from '@rollup/pluginutils';
 
 import { peerDependencies, version } from '../package.json';
 
+import { analyzeExports, ensureInit as ensureLexerInit } from './analyze-exports-lexer';
 import analyzeTopLevelStatements from './analyze-top-level-statements';
 import { getDynamicModuleRegistry, getDynamicRequireModules } from './dynamic-modules';
 
@@ -113,7 +114,7 @@ export default function commonjs(options = {}) {
   // Initialized in buildStart
   let requireResolver;
 
-  function transformAndCheckExports(code, id) {
+  async function transformAndCheckExports(code, id) {
     const normalizedId = normalizePathSlashes(id);
     const { isEsModule, hasDefaultExport, hasNamedExports, ast } = analyzeTopLevelStatements(
       this.parse,
@@ -138,6 +139,16 @@ export default function commonjs(options = {}) {
       return { meta: { commonjs: commonjsMeta } };
     }
 
+    // Use cjs-module-lexer for named export detection on CJS modules
+    if (!isEsModule) {
+      const lexerResult = await analyzeExports(code, id);
+      commonjsMeta.lexerExports = lexerResult.exports;
+      commonjsMeta.lexerReexports = lexerResult.reexports;
+      if (lexerResult.hasDefaultExport && !commonjsMeta.hasDefaultExport) {
+        commonjsMeta.hasDefaultExport = true;
+      }
+    }
+
     const needsRequireWrapper =
       !isEsModule && (dynamicRequireModules.has(normalizedId) || strictRequiresFilter(id));
 
@@ -202,8 +213,9 @@ export default function commonjs(options = {}) {
       return { ...rawOptions, plugins };
     },
 
-    buildStart({ plugins }) {
+    async buildStart({ plugins }) {
       validateVersion(this.meta.rollupVersion, peerDependencies.rollup, 'rollup');
+      await ensureLexerInit();
       const nodeResolve = plugins.find(({ name }) => name === 'node-resolve');
       if (nodeResolve) {
         validateVersion(nodeResolve.version, '^13.0.6', '@rollup/plugin-node-resolve');
@@ -291,10 +303,12 @@ export default function commonjs(options = {}) {
 
       if (isWrappedId(id, ES_IMPORT_SUFFIX)) {
         const actualId = unwrapId(id, ES_IMPORT_SUFFIX);
+        const loadedModule = await this.load({ id: actualId });
         return getEsImportProxy(
           actualId,
           getDefaultIsModuleExports(actualId),
-          (await this.load({ id: actualId })).moduleSideEffects
+          loadedModule.moduleSideEffects,
+          loadedModule.meta?.commonjs?.lexerExports || []
         );
       }
 
@@ -319,11 +333,11 @@ export default function commonjs(options = {}) {
       return requireResolver.shouldTransformCachedModule.call(this, ...args);
     },
 
-    transform(code, id) {
+    async transform(code, id) {
       if (!isPossibleCjsId(id)) return null;
 
       try {
-        return transformAndCheckExports.call(this, code, id);
+        return await transformAndCheckExports.call(this, code, id);
       } catch (err) {
         return this.error(err, err.pos);
       }

@@ -57,14 +57,15 @@ export function getEntryProxy(id, defaultIsModuleExports, getModuleInfo, shebang
     }
     return shebang + code;
   }
-  const result = getEsImportProxy(id, defaultIsModuleExports, true);
+  const lexerExports = commonjsMeta?.lexerExports || [];
+  const result = getEsImportProxy(id, defaultIsModuleExports, true, lexerExports);
   return {
     ...result,
     code: shebang + result.code
   };
 }
 
-export function getEsImportProxy(id, defaultIsModuleExports, moduleSideEffects) {
+export function getEsImportProxy(id, defaultIsModuleExports, moduleSideEffects, lexerExports = []) {
   const name = getName(id);
   const exportsName = `${name}Exports`;
   const requireModule = `require${capitalize(name)}`;
@@ -80,6 +81,17 @@ export function getEsImportProxy(id, defaultIsModuleExports, moduleSideEffects)
   } else {
     code += `\nexport default /*@__PURE__*/getDefaultExportFromCjs(${exportsName});`;
   }
+
+  // Add explicit named re-exports detected by cjs-module-lexer
+  const namedExports = lexerExports.filter(
+    (e) => e !== 'default' && e !== '__esModule' && /^[$_a-zA-Z][$_a-zA-Z0-9]*$/.test(e)
+  );
+  if (namedExports.length > 0) {
+    for (const exportName of namedExports) {
+      code += `\nvar _cjsExport_${exportName} = ${exportsName}["${exportName}"];\nexport { _cjsExport_${exportName} as ${exportName} };`;
+    }
+  }
+
   return {
     code,
     syntheticNamedExports: '__moduleExports'

@@ -531,7 +531,7 @@ export default async function transformCommonjs(
     commonjsMeta
   );
   const usesRequireWrapper = commonjsMeta.isCommonJS === IS_WRAPPED_COMMONJS;
-  const exportBlock = isEsModule
+  let exportBlock = isEsModule
     ? ''
     : rewriteExportsAndGetExportsBlock(
         magicString,
@@ -553,6 +553,29 @@ export default async function transformCommonjs(
         requireName
       );
 
+  // Enhance export block with cjs-module-lexer detected exports
+  // that were not already found by the AST walk
+  if (!isEsModule && !usesRequireWrapper) {
+    const lexerExports = commonjsMeta.lexerExports || [];
+    const astDetectedExports = new Set(exportsAssignmentsByName.keys());
+    const additionalExports = lexerExports.filter(
+      (name) =>
+        !astDetectedExports.has(name) &&
+        name !== 'default' &&
+        name !== '__esModule' &&
+        /^[$_a-zA-Z][$_a-zA-Z0-9]*$/.test(name)
+    );
+    if (additionalExports.length > 0) {
+      const sourceObj = exportMode === 'module' ? exportedExportsName : exportsName;
+      for (const name of additionalExports) {
+        const deconflictedName = deconflict([scope], globals, name);
+        exportBlock += `\nvar ${deconflictedName} = ${sourceObj}["${name}"];\nexport { ${
+          deconflictedName === name ? name : `${deconflictedName} as ${name}`
+        } };`;
+      }
+    }
+  }
+
   if (shouldWrap) {
     wrapCode(magicString, uses, moduleName, exportsName, indentExclusionRanges);
   }