[tsgen] Make commonjs module output compatible with tsc. (#22988)

This enables commonjs modules to be imported into TypeScript using the
same syntax as ESM modules e.g.

`import moduleFactory from './embind_tsgen.js';`

Author: brendandahl

test/other/embind_tsgen_main.ts

@@ -1,30 +1,39 @@
 // Example TS program that consumes the emscripten-generated module to to
 // illustrate how the type definitions are used and test they are workings as
 // expected.
-import moduleFactory from './embind_tsgen.mjs';
 
-const module = await moduleFactory();
+// The imported file will either be an ES module or a CommonJS module depending
+// on the test.
+import moduleFactory from './embind_tsgen.js';
 
-// Test a few variations of passing value_objects with strings.
-module.setValObj({
-  bar: module.Bar.valueOne,
-  string: "ABCD",
-  callback: () => {}
-});
+// Async IIFE is required for TSC with commonjs modules. This is not needed for
+// ESM output since top level await can be used.
+(async function() {
 
-module.setValObj({
-  bar: module.Bar.valueOne,
-  string: new Int8Array([65, 66, 67, 68]),
-  callback: () => {}
-});
+  const module = await moduleFactory();
 
-const valObj = module.getValObj();
-// TODO: remove the cast below when better definitions are generated for value
-// objects.
-const valString : string = valObj.string as string;
+  // Test a few variations of passing value_objects with strings.
+  module.setValObj({
+    bar: module.Bar.valueOne,
+    string: "ABCD",
+    callback: () => {}
+  });
 
-// Ensure nonnull pointers do no need a cast or nullptr check to use.
-const obj = module.getNonnullPointer();
-obj.delete();
+  module.setValObj({
+    bar: module.Bar.valueOne,
+    string: new Int8Array([65, 66, 67, 68]),
+    callback: () => {}
+  });
 
-console.log('ts ran');
+  const valObj = module.getValObj();
+  // TODO: remove the cast below when better definitions are generated for value
+  // objects.
+  const valString : string = valObj.string as string;
+
+  // Ensure nonnull pointers do no need a cast or nullptr check to use.
+  const obj = module.getNonnullPointer();
+  obj.delete();
+
+  console.log('ts ran');
+
+})();

test/test_other.py

@@ -3397,21 +3397,24 @@ def test_jspi_add_function(self):
     self.do_runf('other/test_jspi_add_function.c', 'done')
 
   @parameterized({
-    '': [[]],
-    'with_jsgen': [['-sEMBIND_AOT']]
+    'commonjs': [['-sMODULARIZE'], ['--module', 'commonjs', '--moduleResolution', 'node']],
+    'esm': [['-sEXPORT_ES6'], ['--module', 'NodeNext', '--moduleResolution', 'nodenext']],
+    'esm_with_jsgen': [['-sEXPORT_ES6', '-sEMBIND_AOT'], ['--module', 'NodeNext', '--moduleResolution', 'nodenext']]
   })
-  def test_embind_tsgen(self, opts):
+  def test_embind_tsgen_end_to_end(self, opts, tsc_opts):
     # Check that TypeScript generation works and that the program is runs as
     # expected.
     self.emcc(test_file('other/embind_tsgen.cpp'),
-              ['-o', 'embind_tsgen.mjs', '-lembind', '--emit-tsd', 'embind_tsgen.d.ts'] + opts)
+              ['-o', 'embind_tsgen.js', '-lembind', '--emit-tsd', 'embind_tsgen.d.ts'] + opts)
 
     # Test that the output compiles with a TS file that uses the defintions.
     shutil.copyfile(test_file('other/embind_tsgen_main.ts'), 'main.ts')
-    # A package file with type=module is needed to enabled ES modules in TSC and
-    # also run the output JS file as a module in node.
-    shutil.copyfile(test_file('other/embind_tsgen_package.json'), 'package.json')
-    cmd = shared.get_npm_cmd('tsc') + ['embind_tsgen.d.ts', 'main.ts', '--module', 'NodeNext', '--moduleResolution', 'nodenext']
+    if '-sEXPORT_ES6' in opts:
+      # A package file with type=module is needed to enabled ES modules in TSC and
+      # also run the output JS file as a module in node.
+      shutil.copyfile(test_file('other/embind_tsgen_package.json'), 'package.json')
+
+    cmd = shared.get_npm_cmd('tsc') + ['embind_tsgen.d.ts', 'main.ts', '--target', 'es2021'] + tsc_opts
     shared.check_call(cmd)
     actual = read_file('embind_tsgen.d.ts')
     self.assertFileContents(test_file('other/embind_tsgen_module.d.ts'), actual)

tools/link.py

@@ -2486,9 +2486,12 @@ def modularize():
       src += 'export default %s;\n' % settings.EXPORT_NAME
   elif not settings.MINIMAL_RUNTIME:
     src += '''\
-if (typeof exports === 'object' && typeof module === 'object')
+if (typeof exports === 'object' && typeof module === 'object') {
   module.exports = %(EXPORT_NAME)s;
-else if (typeof define === 'function' && define['amd'])
+  // This default export looks redundant, but it allows TS to import this
+  // commonjs style module.
+  module.exports.default = %(EXPORT_NAME)s;
+} else if (typeof define === 'function' && define['amd'])
   define([], () => %(EXPORT_NAME)s);
 ''' % {'EXPORT_NAME': settings.EXPORT_NAME}