Node.js compatible ESM wrapper for CJS with cjs marker for distinguishing CJS transpiled to ESM

test/fixtures/requireesm-brand-nowrap/expected.js

@@ -1,13 +1,13 @@
 import * as _nobinding2 from "nobinding";
-var _nobinding = _nobinding2;
-try {
-  if ("default" in _nobinding2) _nobinding = _nobinding2.default;
-} catch (e) {}
+var _nobinding = _nobinding2.__cjsModule ? _nobinding2.default : "default" in _nobinding2 && !("__esModule" in _nobinding2) ? new Proxy(_nobinding2, {
+  get: (t, k, r) => k === "__esModule" || Reflect.get(t, k, r),
+  has: (t, k) => k === "__esModule" || Reflect.has(t, k)
+}) : _nobinding2;
 import * as _fs2 from "fs";
-var _fs = _fs2;
-try {
-  if ("default" in _fs2) _fs = _fs2.default;
-} catch (e) {}
+var _fs = _fs2.__cjsModule ? _fs2.default : "default" in _fs2 && !("__esModule" in _fs2) ? new Proxy(_fs2, {
+  get: (t, k, r) => k === "__esModule" || Reflect.get(t, k, r),
+  has: (t, k) => k === "__esModule" || Reflect.has(t, k)
+}) : _fs2;
 import * as _thing from "thing";
 _nobinding;
 const {
@@ -17,4 +17,5 @@ const {
   thing
 } = _thing;
 readFileSync("asdf");
-export default {};
+export default {};
+export const __cjsModule = true;

test/fixtures/requireesm-brand-nowrap/options.js

@@ -1,5 +1,6 @@
 module.exports = {
   nowrap: true,
+  cjsMarker: true,
   esmDependencies (x) {
     if (x === 'thing')
       return 'namespace';

test/fixtures/requireesm-brand/expected.js

@@ -1,19 +1,19 @@
 import * as _nobinding2 from "nobinding";
-var _nobinding = _nobinding2;
-try {
-  if ("default" in _nobinding2) _nobinding = _nobinding2.default;
-} catch (e) {}
 import * as _fs2 from "fs";
-var _fs = _fs2;
-try {
-  if ("default" in _fs2) _fs = _fs2.default;
-} catch (e) {}
 import * as _thing from "thing";
 var exports = {},
   _dewExec = false;
 export function dew() {
   if (_dewExec) return exports;
   _dewExec = true;
+  var _nobinding = _nobinding2.__cjsModule ? _nobinding2.default : "default" in _nobinding2 && !("__esModule" in _nobinding2) ? new Proxy(_nobinding2, {
+    get: (t, k, r) => k === "__esModule" || Reflect.get(t, k, r),
+    has: (t, k) => k === "__esModule" || Reflect.has(t, k)
+  }) : _nobinding2;
+  var _fs = _fs2.__cjsModule ? _fs2.default : "default" in _fs2 && !("__esModule" in _fs2) ? new Proxy(_fs2, {
+    get: (t, k, r) => k === "__esModule" || Reflect.get(t, k, r),
+    has: (t, k) => k === "__esModule" || Reflect.has(t, k)
+  }) : _fs2;
   _nobinding;
   const {
     readFileSync

transform-cjs-dew.js

@@ -54,6 +54,7 @@ module.exports = function ({ types: t }) {
   const dewInterop = t.identifier('__dew');
   const defaultIdentifier = t.identifier('default');
 
+  const esModuleLiteral = t.stringLiteral('__esModule');
   const globalThis = t.identifier('globalThis');
   const globalThisPredicate = t.binaryExpression('!==', t.unaryExpression('typeof', globalThis), t.stringLiteral('undefined'));
   const selfIdentifier = t.identifier('self');
@@ -789,13 +790,26 @@ module.exports = function ({ types: t }) {
             for (let i = state.deps.length - 1; i >= 0; i--) {
               const dep = state.deps[i];
               if (dep.ns && dep.mid.name !== dep.id.name) {
-                unshiftBody(path, t.tryStatement(t.blockStatement([
-                  t.ifStatement(
-                    t.binaryExpression('in', t.stringLiteral('default'), dep.mid),
-                    t.expressionStatement(t.assignmentExpression('=', dep.id, t.memberExpression(dep.mid, defaultIdentifier)))
-                  )
-                ]), t.catchClause(t.identifier('e'), t.blockStatement([]))));
-                unshiftBody(path, t.variableDeclaration('var', [t.variableDeclarator(dep.id, dep.mid)]));
+                unshiftBody(path, t.variableDeclaration('var', [
+                  t.variableDeclarator(dep.id, t.conditionalExpression(
+                    t.memberExpression(dep.mid, t.identifier('__cjsModule')),
+                    t.memberExpression(dep.mid, t.identifier('default')),
+                    t.conditionalExpression(
+                      t.logicalExpression('&&', t.binaryExpression('in', t.stringLiteral('default'), dep.mid), t.unaryExpression('!', t.binaryExpression('in', t.stringLiteral('__esModule'), dep.mid))),
+                      t.newExpression(t.identifier('Proxy'), [dep.mid, t.objectExpression([
+                        t.objectProperty(t.identifier('get'), t.arrowFunctionExpression([t.identifier('t'), t.identifier('k'), t.identifier('r')], t.logicalExpression('||',
+                          t.binaryExpression('===', t.identifier('k'), esModuleLiteral),
+                          t.callExpression(t.memberExpression(t.identifier('Reflect'), t.identifier('get')), [t.identifier('t'), t.identifier('k'), t.identifier('r')])
+                        ))),
+                        t.objectProperty(t.identifier('has'), t.arrowFunctionExpression([t.identifier('t'), t.identifier('k')], t.logicalExpression('||',
+                          t.binaryExpression('===', t.identifier('k'), esModuleLiteral),
+                          t.callExpression(t.memberExpression(t.identifier('Reflect'), t.identifier('has')), [t.identifier('t'), t.identifier('k')])
+                        )))
+                      ])]),
+                      dep.mid
+                    )
+                  ))
+                ]));
               }
               unshiftBody(path, 
                 t.importDeclaration([
@@ -817,11 +831,11 @@ module.exports = function ({ types: t }) {
                 t.exportDefaultDeclaration(exportsReturn)
               );
 
-            if (state.opts.namedExports && state.opts.namedExports.length) {
+            if (state.opts.namedExports && state.opts.namedExports.length || state.opts.cjsMarker) {
               const exportDeclarations = [];
               const namedExports = [];
               const varDeclarations = [];
-              for (const name of state.opts.namedExports) {
+              for (const name of state.opts.namedExports || []) {
                 const id = t.identifier(name);
                 if (name === 'default') {
                   if (exportsReturn)
@@ -836,6 +850,11 @@ module.exports = function ({ types: t }) {
                   namedExports.push(t.exportSpecifier(uid, id));
                 }
               }
+
+              if (state.opts.cjsMarker) {
+                exportDeclarations.push(t.variableDeclarator(t.identifier('__cjsModule'), t.booleanLiteral(true)));
+              }
+
               if (exportDeclarations.length)
                 pushBody(path, t.exportNamedDeclaration(t.variableDeclaration('const', exportDeclarations), []));
               if (varDeclarations.length)
@@ -848,22 +867,37 @@ module.exports = function ({ types: t }) {
 
           let dewBodyWrapper = [];
 
+          const innerWrapper = [];
+
           state.deps.forEach(dep => {
             dewBodyWrapper.push(
               t.importDeclaration([
                 dep.dew && !dep.ns ? t.importSpecifier(dep.mid, dewIdentifier) : (dep.ns ? t.importNamespaceSpecifier : t.importDefaultSpecifier)(dep.mid)
               ], dep.literal)
             );
             if (dep.ns && dep.mid.name !== dep.id.name) {
-              dewBodyWrapper.push(
-                t.variableDeclaration('var', [t.variableDeclarator(dep.id, dep.mid)])
+              innerWrapper.push(
+                t.variableDeclaration('var', [
+                  t.variableDeclarator(dep.id, t.conditionalExpression(
+                    t.memberExpression(dep.mid, t.identifier('__cjsModule')),
+                    t.memberExpression(dep.mid, t.identifier('default')),
+                    t.conditionalExpression(
+                      t.logicalExpression('&&', t.binaryExpression('in', t.stringLiteral('default'), dep.mid), t.unaryExpression('!', t.binaryExpression('in', t.stringLiteral('__esModule'), dep.mid))),
+                      t.newExpression(t.identifier('Proxy'), [dep.mid, t.objectExpression([
+                        t.objectProperty(t.identifier('get'), t.arrowFunctionExpression([t.identifier('t'), t.identifier('k'), t.identifier('r')], t.logicalExpression('||',
+                          t.binaryExpression('===', t.identifier('k'), esModuleLiteral),
+                          t.callExpression(t.memberExpression(t.identifier('Reflect'), t.identifier('get')), [t.identifier('t'), t.identifier('k'), t.identifier('r')])
+                        ))),
+                        t.objectProperty(t.identifier('has'), t.arrowFunctionExpression([t.identifier('t'), t.identifier('k')], t.logicalExpression('||',
+                          t.binaryExpression('===', t.identifier('k'), esModuleLiteral),
+                          t.callExpression(t.memberExpression(t.identifier('Reflect'), t.identifier('has')), [t.identifier('t'), t.identifier('k')])
+                        )))
+                      ])]),
+                      dep.mid
+                    )
+                  ))
+                ])
               );
-              dewBodyWrapper.push(t.tryStatement(t.blockStatement([
-                t.ifStatement(
-                  t.binaryExpression('in', t.stringLiteral('default'), dep.mid),
-                  t.expressionStatement(t.assignmentExpression('=', dep.id, t.memberExpression(dep.mid, defaultIdentifier)))
-                )
-              ]), t.catchClause(t.identifier('e'), t.blockStatement([]))));
             }
           });
 
@@ -888,6 +922,7 @@ module.exports = function ({ types: t }) {
               t.functionDeclaration(dewIdentifier, [], t.blockStatement([
                 t.ifStatement(execIdentifier, t.returnStatement(exportsReturn)),
                 t.expressionStatement(t.assignmentExpression('=', execIdentifier, t.booleanLiteral(true))),
+                ...innerWrapper,
                 ...path.node.body,
                 t.returnStatement(exportsReturn)
               ])),