module: implement the "module" exports condition

The "module" exports condition has been used by bundlers in
the wild to support require(esm) in bundles targeting the
Node.js environment. This patch implements the same condition
for the native require(esm) implementation in Node.js to match
bundler behaviors in the ecosystem.

The tests added in this patch match the output from webpack
bundles.

Refs: https://gist.github.com/sokra/e032a0f17c1721c71cfced6f14516c62

lib/internal/modules/esm/utils.js

@@ -79,6 +79,7 @@ function initializeDefaultConditions() {
   defaultConditions = ObjectFreeze([
     'node',
     'import',
+    'module',
     ...addonConditions,
     ...userConditions,
   ]);

lib/internal/modules/helpers.js

@@ -81,6 +81,9 @@ function initializeCjsConditions() {
     ...addonConditions,
     ...userConditions,
   ]);
+  if (getOptionValue('--experimental-require-module')) {
+    cjsConditions.add('module');
+  }
 }
 
 /**

test/es-module/test-import-module-conditional-exports-module.mjs

@@ -0,0 +1,27 @@
+import '../common/index.mjs';
+import assert from 'node:assert';
+import * as staticImport from '../fixtures/es-modules/module-condition/import.mjs';
+import { import as _import } from '../fixtures/es-modules/module-condition/dynamic_import.js';
+
+async function dynamicImport(id) {
+  const result = await _import(id);
+  return result.resolved;
+}
+
+assert.deepStrictEqual({ ...staticImport }, {
+  import_module_require: 'import',
+  module_and_import: 'module',
+  module_and_require: 'module',
+  module_import_require: 'module',
+  module_only: 'module',
+  module_require_import: 'module',
+  require_module_import: 'module',
+});
+
+assert.strictEqual(await dynamicImport('import-module-require'), 'import');
+assert.strictEqual(await dynamicImport('module-and-import'), 'module');
+assert.strictEqual(await dynamicImport('module-and-require'), 'module');
+assert.strictEqual(await dynamicImport('module-import-require'), 'module');
+assert.strictEqual(await dynamicImport('module-only'), 'module');
+assert.strictEqual(await dynamicImport('module-require-import'), 'module');
+assert.strictEqual(await dynamicImport('require-module-import'), 'module');

test/es-module/test-require-module-conditional-exports-module.js

@@ -0,0 +1,15 @@
+// Flags: --experimental-require-module
+'use strict';
+
+require('../common');
+const assert = require('assert');
+
+const loader = require('../fixtures/es-modules/module-condition/require.cjs');
+
+assert.strictEqual(loader.require('import-module-require').resolved, 'module');
+assert.strictEqual(loader.require('module-and-import').resolved, 'module');
+assert.strictEqual(loader.require('module-and-require').resolved, 'module');
+assert.strictEqual(loader.require('module-import-require').resolved, 'module');
+assert.strictEqual(loader.require('module-only').resolved, 'module');
+assert.strictEqual(loader.require('module-require-import').resolved, 'module');
+assert.strictEqual(loader.require('require-module-import').resolved, 'require');

test/fixtures/es-module-loaders/loader-with-custom-condition.mjs

@@ -5,6 +5,7 @@ export async function resolve(specifier, context, defaultResolve) {
 
   deepStrictEqual([...context.conditions].sort(), [
     'import',
+    'module',
     'node',
     'node-addons',
   ]);

test/fixtures/es-modules/module-condition/dynamic_import.js

@@ -0,0 +1,5 @@
+function load(id) {
+  return import(id);
+}
+
+export { load as import };

test/fixtures/es-modules/module-condition/import.mjs

@@ -0,0 +1,7 @@
+export { resolved as import_module_require } from 'import-module-require';
+export { resolved as module_and_import } from 'module-and-import';
+export { resolved as module_and_require } from 'module-and-require';
+export { resolved as module_import_require } from 'module-import-require';
+export { resolved as module_only } from 'module-only';
+export { resolved as module_require_import } from 'module-require-import';
+export { resolved as require_module_import } from 'require-module-import';

test/fixtures/es-modules/module-condition/require.cjs

@@ -0,0 +1 @@
+exports.require = require;