Change option

packages/commonjs/README.md

@@ -34,9 +34,9 @@ export default {
   input: 'src/index.js',
   output: {
     dir: 'output',
-    format: 'cjs'
+    format: 'cjs',
   },
-  plugins: [commonjs()]
+  plugins: [commonjs()],
 };
 ```
 
@@ -66,8 +66,8 @@ commonjs({
     '!node_modules/logform/index.js',
     '!node_modules/logform/format.js',
     '!node_modules/logform/levels.js',
-    '!node_modules/logform/browser.js'
-  ]
+    '!node_modules/logform/browser.js',
+  ],
 });
 ```
 
@@ -174,12 +174,48 @@ If you set `esmExternals` to `true`, this plugins assumes that all external depe
 
 You can also supply an array of ids to be treated as ES modules, or a function that will be passed each external id to determine if it is an ES module.
 
-### `nodeDefaultImport`
+### `defaultIsModuleExports`
 
-Type: `boolean`<br>
-Default: `false`
+Type: `boolean | "auto"`<br>
+Default: `"auto"`
+
+Controls what is the default export when importing a CommonJS file from an ES module.
 
-When `true`, match the Node.js behavior when importing the `default` import from a CommonJS module, making it return the value of `module.exports`.
+- `true`: The value of the default export is `module.exports`. This currently matches the behavior of Node.js when importing a CommonJS file.
+  ```js
+  // mod.cjs
+  exports.default = 3;
+  ```
+  ```js
+  import foo from './mod.cjs';
+  console.log(foo); // { default: 3 }
+  ```
+- `false`: The value of the default export is `exports.default`.
+  ```js
+  // mod.cjs
+  exports.default = 3;
+  ```
+  ```js
+  import foo from './mod.cjs';
+  console.log(foo); // 3
+  ```
+- `"auto"`: The value of the default export is `exports.default` if the CommonJS file has an `exports.__esModule === true` property; otherwise it's `module.exports`. This makes it possible to import
+  the default export of ES modules compiled to CommonJS as if they were not compiled.
+  ```js
+  // mod.cjs
+  exports.default = 3;
+  ```
+  ```js
+  // mod-compiled.cjs
+  exports.__esModule = true;
+  exports.default = 3;
+  ```
+  ```js
+  import foo from './mod.cjs';
+  import bar from './mod-compiled.cjs';
+  console.log(foo); // { default: 3 }
+  console.log(bar); // 3
+  ```
 
 ### `requireReturnsDefault`
 
@@ -214,7 +250,7 @@ This is in line with how other bundlers handle this situation and is also the mo
 
   var dep$1 = /*#__PURE__*/ Object.freeze({
     __proto__: null,
-    default: dep
+    default: dep,
   });
 
   console.log(dep$1.default);
@@ -245,7 +281,7 @@ For these situations, you can change Rollup's behaviour either globally or per m
               enumerable: true,
               get: function () {
                 return n[k];
-              }
+              },
             }
       );
     });
@@ -321,9 +357,9 @@ export default {
   output: {
     file: 'bundle.js',
     format: 'iife',
-    name: 'MyModule'
+    name: 'MyModule',
   },
-  plugins: [resolve(), commonjs()]
+  plugins: [resolve(), commonjs()],
 };
 ```
 
@@ -333,7 +369,7 @@ Symlinks are common in monorepos and are also created by the `npm link` command.
 
 ```js
 commonjs({
-  include: /node_modules/
+  include: /node_modules/,
 });
 ```
 
@@ -356,11 +392,11 @@ function cjsDetectionPlugin() {
     moduleParsed({
       id,
       meta: {
-        commonjs: { isCommonJS }
-      }
+        commonjs: { isCommonJS },
+      },
     }) {
       console.log(`File ${id} is CommonJS: ${isCommonJS}`);
-    }
+    },
   };
 }
 ```

packages/commonjs/src/generate-exports.js

@@ -21,7 +21,7 @@ export function rewriteExportsAndGetExportsBlock(
   code,
   uses,
   HELPERS_NAME,
-  nodeDefaultImport
+  defaultIsModuleExports
 ) {
   const namedExportDeclarations = [`export { ${moduleName} as __moduleExports };`];
   const moduleExportsPropertyAssignments = [];
@@ -76,20 +76,29 @@ export function rewriteExportsAndGetExportsBlock(
 
   // Generate default export
   const defaultExport = [];
-  if (isRestorableCompiledEsm) {
-    defaultExport.push(`export default ${deconflictedDefaultExportName || moduleName};`);
-  } else if (
-    (wrapped || deconflictedDefaultExportName) &&
-    (defineCompiledEsmExpressions.length > 0 ||
-      (!nodeDefaultImport && code.indexOf('__esModule') >= 0))
-  ) {
-    // eslint-disable-next-line no-param-reassign
-    uses.commonjsHelpers = true;
-    defaultExport.push(
-      `export default /*@__PURE__*/${HELPERS_NAME}.getDefaultExportFromCjs(${moduleName});`
-    );
-  } else {
+  if (defaultIsModuleExports === 'auto') {
+    if (isRestorableCompiledEsm) {
+      defaultExport.push(`export default ${deconflictedDefaultExportName || moduleName};`);
+    } else if (
+      (wrapped || deconflictedDefaultExportName) &&
+      (defineCompiledEsmExpressions.length > 0 || code.includes('__esModule'))
+    ) {
+      // eslint-disable-next-line no-param-reassign
+      uses.commonjsHelpers = true;
+      defaultExport.push(
+        `export default /*@__PURE__*/${HELPERS_NAME}.getDefaultExportFromCjs(${moduleName});`
+      );
+    } else {
+      defaultExport.push(`export default ${moduleName};`);
+    }
+  } else if (defaultIsModuleExports === true) {
     defaultExport.push(`export default ${moduleName};`);
+  } else if (defaultIsModuleExports === false) {
+    if (deconflictedDefaultExportName) {
+      defaultExport.push(`export default ${deconflictedDefaultExportName};`);
+    } else {
+      defaultExport.push(`export default ${moduleName}.default;`);
+    }
   }
 
   return `\n\n${defaultExport

packages/commonjs/src/index.js

@@ -59,6 +59,8 @@ export default function commonjs(options = {}) {
       : Array.isArray(esmExternals)
       ? ((esmExternalIds = new Set(esmExternals)), (id) => esmExternalIds.has(id))
       : () => esmExternals;
+  const defaultIsModuleExports =
+    typeof options.defaultIsModuleExports === 'boolean' ? options.defaultIsModuleExports : 'auto';
 
   const { dynamicRequireModuleSet, dynamicRequireModuleDirPaths } = getDynamicRequirePaths(
     options.dynamicRequireTargets
@@ -146,7 +148,7 @@ export default function commonjs(options = {}) {
       disableWrap,
       commonDir,
       ast,
-      options.nodeDefaultImport
+      defaultIsModuleExports
     );
   }
 

packages/commonjs/src/transform-commonjs.js

@@ -54,7 +54,7 @@ export default function transformCommonjs(
   disableWrap,
   commonDir,
   astCache,
-  nodeDefaultImport
+  defaultIsModuleExports
 ) {
   const ast = astCache || tryParse(parse, code, id);
   const magicString = new MagicString(code);
@@ -138,7 +138,7 @@ export default function transformCommonjs(
             // we're dealing with `module.exports = ...` or `[module.]exports.foo = ...` –
             if (programDepth > 3) {
               shouldWrap = true;
-            } else if (!nodeDefaultImport && exportName === KEY_COMPILED_ESM) {
+            } else if (exportName === KEY_COMPILED_ESM) {
               defineCompiledEsmExpressions.push(parent);
             } else if (flattened.keypath === 'module.exports') {
               topLevelModuleExportsAssignments.push(node);
@@ -472,7 +472,7 @@ export default function transformCommonjs(
         code,
         uses,
         HELPERS_NAME,
-        nodeDefaultImport
+        defaultIsModuleExports
       );
 
   const importBlock = rewriteRequireExpressionsAndGetImportBlock(

packages/commonjs/test/fixtures/form/defaultIsModuleExports-auto-__esModule/_config.js

@@ -0,0 +1,5 @@
+module.exports = {
+  options: {
+    defaultIsModuleExports: 'auto'
+  }
+};

packages/commonjs/test/fixtures/form/defaultIsModuleExports-auto-__esModule/output.js

@@ -0,0 +1,15 @@
+const _default = 2;
+const named = 3;
+
+const input = /*#__PURE__*/ Object.defineProperty(
+  {
+    default: _default,
+    named
+  },
+  '__esModule',
+  { value: true }
+);
+
+export default _default;
+export { input as __moduleExports };
+export { named };

packages/commonjs/test/fixtures/form/defaultIsModuleExports-auto-no-__esModule/_config.js

@@ -0,0 +1,5 @@
+module.exports = {
+  options: {
+    defaultIsModuleExports: 'auto'
+  }
+};

packages/commonjs/test/fixtures/form/defaultIsModuleExports-auto-no-__esModule/output.js

@@ -0,0 +1,11 @@
+const _default = 2;
+const named = 3;
+
+const input = {
+  default: _default,
+  named
+};
+
+export default input;
+export { input as __moduleExports };
+export { named };

packages/commonjs/test/fixtures/form/defaultIsModuleExports-false-__esModule/_config.js

@@ -0,0 +1,5 @@
+module.exports = {
+  options: {
+    defaultIsModuleExports: false
+  }
+};

packages/commonjs/test/fixtures/form/defaultIsModuleExports-false-__esModule/input.js

@@ -0,0 +1,3 @@
+exports.__esModule = true;
+exports.default = 2;
+exports.named = 3;

packages/commonjs/test/fixtures/form/defaultIsModuleExports-false-__esModule/output.js

@@ -0,0 +1,15 @@
+const _default = 2;
+const named = 3;
+
+const input = /*#__PURE__*/ Object.defineProperty(
+  {
+    default: _default,
+    named
+  },
+  '__esModule',
+  { value: true }
+);
+
+export default _default;
+export { input as __moduleExports };
+export { named };

packages/commonjs/test/fixtures/form/defaultIsModuleExports-false-no-__esModule/_config.js

@@ -0,0 +1,5 @@
+module.exports = {
+  options: {
+    defaultIsModuleExports: false
+  }
+};

packages/commonjs/test/fixtures/form/defaultIsModuleExports-false-no-__esModule/input.js

@@ -0,0 +1,2 @@
+exports.default = 2;
+exports.named = 3;

packages/commonjs/test/fixtures/form/defaultIsModuleExports-false-no-__esModule/output.js

@@ -0,0 +1,11 @@
+const _default = 2;
+const named = 3;
+
+const input = {
+  default: _default,
+  named
+};
+
+export default _default;
+export { input as __moduleExports };
+export { named };

packages/commonjs/test/fixtures/form/defaultIsModuleExports-false-no-default/_config.js

@@ -0,0 +1,5 @@
+module.exports = {
+  options: {
+    defaultIsModuleExports: false
+  }
+};

packages/commonjs/test/fixtures/form/defaultIsModuleExports-false-no-default/input.js

@@ -0,0 +1 @@
+exports.named = 3;

packages/commonjs/test/fixtures/form/defaultIsModuleExports-false-no-default/output.js

@@ -0,0 +1,9 @@
+const named = 3;
+
+const input = {
+  named
+};
+
+export default input.default;
+export { input as __moduleExports };
+export { named };

packages/commonjs/test/fixtures/form/nodeDefaultImport-__esModule/_config.js → packages/commonjs/test/fixtures/form/defaultIsModuleExports-true-__esModule/_config.js

@@ -1,5 +1,5 @@
 module.exports = {
   options: {
-    nodeDefaultImport: true
+    defaultIsModuleExports: true
   }
 };

packages/commonjs/test/fixtures/form/defaultIsModuleExports-true-__esModule/input.js

@@ -0,0 +1,3 @@
+exports.__esModule = true;
+exports.default = 2;
+exports.named = 3;

packages/commonjs/test/fixtures/form/defaultIsModuleExports-true-__esModule/output.js

@@ -0,0 +1,15 @@
+const _default = 2;
+const named = 3;
+
+const input = /*#__PURE__*/ Object.defineProperty(
+  {
+    default: _default,
+    named
+  },
+  '__esModule',
+  { value: true }
+);
+
+export default input;
+export { input as __moduleExports };
+export { named };

packages/commonjs/test/fixtures/form/nodeDefaultImport-no-__esModule/_config.js → packages/commonjs/test/fixtures/form/defaultIsModuleExports-true-no-__esModule/_config.js

@@ -1,5 +1,5 @@
 module.exports = {
   options: {
-    nodeDefaultImport: true
+    defaultIsModuleExports: true
   }
 };

packages/commonjs/test/fixtures/form/defaultIsModuleExports-true-no-__esModule/input.js

@@ -0,0 +1,2 @@
+exports.default = 2;
+exports.named = 3;

packages/commonjs/test/fixtures/form/defaultIsModuleExports-true-no-__esModule/output.js

@@ -0,0 +1,11 @@
+const _default = 2;
+const named = 3;
+
+const input = {
+  default: _default,
+  named
+};
+
+export default input;
+export { input as __moduleExports };
+export { named };