esm: add pjson.importInterop to support __esModule

doc/api/esm.md

@@ -364,6 +364,21 @@ When importing [CommonJS modules](#commonjs-namespaces), the
 available, provided by static analysis as a convenience for better ecosystem
 compatibility.
 
+You can change the behavior of default imports by adding `importInterop` option
+to your `package.json`:
+
+```json
+{
+  "importInterop": true
+}
+```
+
+All `import` statements in that package will check the value of the imported
+module's `module.exports.__esModule` value.
+If `__esModule` is true, `module.exports.default` value is used as the default
+export instead of `module.exports`.
+This is useful when you are importing modules generated by Babel or TypeScript.
+
 ### `require`
 
 The CommonJS module `require` always treats the files it references as CommonJS.

lib/internal/modules/esm/loader.js

@@ -280,7 +280,14 @@ class ESMLoader {
         throw new ERR_UNKNOWN_MODULE_FORMAT(finalFormat);
       }
 
-      return FunctionPrototypeCall(translator, this, url, source, isMain);
+      return FunctionPrototypeCall(
+        translator,
+        this,
+        url,
+        source,
+        isMain,
+        parentURL
+      );
     };
 
     const inspectBrk = (

lib/internal/modules/esm/resolve.js

@@ -180,6 +180,7 @@ function getPackageConfig(path, specifier, base) {
       type: 'none',
       exports: undefined,
       imports: undefined,
+      cjsImportInterop: undefined,
     };
     packageJSONCache.set(path, packageConfig);
     return packageConfig;
@@ -197,7 +198,7 @@ function getPackageConfig(path, specifier, base) {
   }
 
   let { imports, main, name, type } = packageJSON;
-  const { exports } = packageJSON;
+  const { exports, cjsImportInterop } = packageJSON;
   if (typeof imports !== 'object' || imports === null) imports = undefined;
   if (typeof main !== 'string') main = undefined;
   if (typeof name !== 'string') name = undefined;
@@ -212,6 +213,7 @@ function getPackageConfig(path, specifier, base) {
     type,
     exports,
     imports,
+    cjsImportInterop,
   };
   packageJSONCache.set(path, packageConfig);
   return packageConfig;
@@ -247,6 +249,7 @@ function getPackageScopeConfig(resolved) {
     type: 'none',
     exports: undefined,
     imports: undefined,
+    cjsImportInterop: undefined,
   };
   packageJSONCache.set(packageJSONPath, packageConfig);
   return packageConfig;

lib/internal/modules/esm/translators.js

@@ -58,6 +58,7 @@ const experimentalImportMetaResolve =
 const asyncESM = require('internal/process/esm_loader');
 const { emitWarningSync } = require('internal/process/warning');
 const { TextDecoder } = require('internal/encoding');
+const { getPackageScopeConfig } = require('internal/modules/esm/resolve');
 
 let cjsParse;
 async function initCJSParse() {
@@ -166,9 +167,17 @@ function enrichCJSError(err, content, filename) {
 const isWindows = process.platform === 'win32';
 const winSepRegEx = /\//g;
 translators.set('commonjs', async function commonjsStrategy(url, source,
-                                                            isMain) {
+                                                            isMain,
+                                                            parentURL) {
   debug(`Translating CJSModule ${url}`);
 
+  let importInterop = false;
+  if (parentURL) {
+    const parentPackageConfig = getPackageScopeConfig(parentURL);
+    importInterop =
+      parentPackageConfig && parentPackageConfig.cjsImportInterop;
+  }
+
   let filename = internalURLModule.fileURLToPath(new URL(url));
   if (isWindows)
     filename = StringPrototypeReplace(filename, winSepRegEx, '\\');
@@ -194,6 +203,14 @@ translators.set('commonjs', async function commonjsStrategy(url, source,
       }
     }
 
+    // We might trigger a getter -> dont fail.
+    let esModule = false;
+    if (importInterop) {
+      try {
+        esModule = !!exports.__esModule;
+      } catch {}
+    }
+
     for (const exportName of exportNames) {
       if (!ObjectPrototypeHasOwnProperty(exports, exportName) ||
           exportName === 'default')
@@ -205,7 +222,7 @@ translators.set('commonjs', async function commonjsStrategy(url, source,
       } catch {}
       this.setExport(exportName, value);
     }
-    this.setExport('default', exports);
+    this.setExport('default', esModule ? exports.default : exports);
   });
 });
 

test/es-module/test-esm-cjs-import-interop.js

@@ -0,0 +1,40 @@
+'use strict';
+
+const common = require('../common');
+const fixtures = require('../common/fixtures');
+const { spawn } = require('child_process');
+const assert = require('assert');
+
+const entry = fixtures.path(
+  '/es-modules/package-cjs-import-interop/cjs-exports.mjs'
+);
+
+const child = spawn(process.execPath, [entry]);
+child.stderr.setEncoding('utf8');
+let stdout = '';
+child.stdout.setEncoding('utf8');
+child.stdout.on('data', (data) => {
+  stdout += data;
+});
+child.on('close', common.mustCall((code, signal) => {
+  assert.strictEqual(code, 0);
+  assert.strictEqual(signal, null);
+  assert.strictEqual(stdout, 'ok\n');
+}));
+
+const entryCjs = fixtures.path(
+  '/es-modules/package-cjs-import-interop/cjs-exports-dynamic.cjs'
+);
+
+const childCjs = spawn(process.execPath, [entryCjs]);
+childCjs.stderr.setEncoding('utf8');
+let stdoutCjs = '';
+childCjs.stdout.setEncoding('utf8');
+childCjs.stdout.on('data', (data) => {
+  stdoutCjs += data;
+});
+childCjs.on('close', common.mustCall((code, signal) => {
+  assert.strictEqual(code, 0);
+  assert.strictEqual(signal, null);
+  assert.strictEqual(stdoutCjs, 'ok\n');
+}));

test/fixtures/es-modules/package-cjs-import-interop/cjs-exports-dynamic.cjs

@@ -0,0 +1,30 @@
+'use strict';
+const assert = require('assert');
+
+(async () => {
+  const ns = await import('../exports-cases.js');
+  assert.deepEqual(Object.keys(ns), ['?invalid', 'default', 'invalid identifier', 'isObject', 'package', 'z', 'π', '\u{d83c}\u{df10}']);
+  assert.strictEqual(ns.π, 'yes');
+  assert.strictEqual(typeof ns.default.isObject, 'undefined');
+  assert.strictEqual(ns.default.π, 'yes');
+  assert.strictEqual(ns.default.z, 'yes');
+  assert.strictEqual(ns.default.package, 10);
+  assert.strictEqual(ns.default['invalid identifier'], 'yes');
+  assert.strictEqual(ns.default['?invalid'], 'yes');
+
+  const ns2 = await import('../exports-cases2.js');
+  assert.strictEqual(typeof ns2, 'object');
+  assert.strictEqual(ns2.default, 'the default');
+  assert.strictEqual(ns2.__esModule, true);
+  assert.strictEqual(ns2.name, 'name');
+  assert.deepEqual(Object.keys(ns2), ['__esModule', 'case2', 'default', 'name', 'pi']);
+
+  const ns3 = await import('../exports-cases3.js')
+  assert.deepEqual(Object.keys(ns3), ['__esModule', 'case2', 'default', 'name', 'pi']);
+  assert.strictEqual(ns3.default, 'the default');
+  assert.strictEqual(ns3.__esModule, true);
+  assert.strictEqual(ns3.name, 'name');
+  assert.strictEqual(ns3.case2, 'case2');
+
+  console.log('ok');
+})();

test/fixtures/es-modules/package-cjs-import-interop/cjs-exports.mjs

@@ -0,0 +1,37 @@
+import { strictEqual, deepEqual } from 'assert';
+
+import m, { π } from '../exports-cases.js';
+import * as ns from '../exports-cases.js';
+
+deepEqual(Object.keys(ns), ['?invalid', 'default', 'invalid identifier', 'isObject', 'package', 'z', 'π', '\u{d83c}\u{df10}']);
+strictEqual(π, 'yes');
+strictEqual(typeof m.isObject, 'undefined');
+strictEqual(m.π, 'yes');
+strictEqual(m.z, 'yes');
+strictEqual(m.package, 10);
+strictEqual(m['invalid identifier'], 'yes');
+strictEqual(m['?invalid'], 'yes');
+
+import m2, { __esModule as __esModule2, name as name2 } from '../exports-cases2.js';
+import * as ns2 from '../exports-cases2.js';
+
+strictEqual(__esModule2, true);
+strictEqual(name2, 'name');
+strictEqual(typeof ns2, 'object');
+strictEqual(m2, 'the default');
+strictEqual(ns2.__esModule, true);
+strictEqual(ns2.name, 'name');
+deepEqual(Object.keys(ns2), ['__esModule', 'case2', 'default', 'name', 'pi']);
+
+import m3, { __esModule as __esModule3, name as name3 } from '../exports-cases3.js';
+import * as ns3 from '../exports-cases3.js';
+
+strictEqual(__esModule3, true);
+strictEqual(name3, 'name');
+deepEqual(Object.keys(ns3), ['__esModule', 'case2', 'default', 'name', 'pi']);
+strictEqual(m3, 'the default');
+strictEqual(ns3.__esModule, true);
+strictEqual(ns3.name, 'name');
+strictEqual(ns3.case2, 'case2');
+
+console.log('ok');

test/fixtures/es-modules/package-cjs-import-interop/package.json

@@ -0,0 +1,6 @@
+{
+  "name": "package-cjs-import-interop",
+  "main": "index.mjs",
+  "type": "module",
+  "cjsImportInterop": true
+}