fix: add default exports to lwc @W-13710298 (#3997)

* fix: include default exports in lwc re-exports

* test(lwc): validate default exports are re-exported; fixes #3605

* fix: remove stub test

oops

* test(lwc): skip testing index file; it's not a package

* fix: make tsconfig consistent with other packages

* chore: add comment explaining .cjs

* test(lwc): validate that all dependencies have an export declared

* test(lwc): use JSDOM so browser packages work

* fix(tests): detect "default" default export and skip it

* chore: use better test description

* chore: clarify comment

packages/lwc/__tests__/default-exports.spec.ts

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2024, Salesforce, Inc.
+ * All rights reserved.
+ * SPDX-License-Identifier: MIT
+ * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
+ */
+import * as fs from 'node:fs';
+import * as path from 'node:path';
+
+const PACKAGE_ROOT = path.join(__dirname, '..');
+
+const expectExportDefaultFromPackageInFile = (pkgName: string, ext: string) => {
+    const filename = path.join(PACKAGE_ROOT, pkgName + ext);
+    const contents = fs.readFileSync(filename, 'utf8');
+    const exportDefaultFromPackage = new RegExp(
+        `^export \\{ default \\} from '@lwc/${pkgName}';$`,
+        'm'
+    );
+    expect(contents).toMatch(exportDefaultFromPackage);
+};
+
+/**
+ * Jest uses CommonJS, which means that packages with no explicit export statements actually export
+ * the default `module.exports` empty object. That export is an empty object with the prototype set
+ * to an empty object with null prototype.
+ */
+const hasExplicitDefaultExport = (mod: object) => {
+    // No default export = self explanatory
+    if (!('default' in mod)) return false;
+    // If we have more than one export, then we must have explicitly declared them
+    if (Object.keys(mod).length > 1) return true;
+    const def = mod.default;
+    // If it's not an object, it must be an explicit export
+    if (typeof def !== 'object' || def === null) return true;
+    // If it's not an empty object, it's not the placeholder object
+    if (Object.keys(def).length > 0) return true;
+    const proto = Object.getPrototypeOf(def);
+    // If the prototype isn't an empty null-prototype object, it's not the placeholder object
+    if (Object.keys(proto).length > 0 || Object.getPrototypeOf(proto) !== null) return true;
+    // It must be the placeholder object!
+    return false;
+};
+
+describe('default exports are not forgotten', () => {
+    const allFiles = fs.readdirSync(PACKAGE_ROOT);
+    const packages = allFiles
+        .filter((f) => f.endsWith('.js') && f !== 'index.js')
+        .map((f) => f.slice(0, -3));
+    test.each(packages)('@lwc/%s', async (pkg) => {
+        const realModule = await import(`@lwc/${pkg}`);
+        // When jest properly supports ESM, this will be a lot simpler
+        // const aliasedModule = await import(`lwc/${pkg}`);
+        // expect(aliasedModule.default).toBe(realModule.default);
+        if (hasExplicitDefaultExport(realModule)) {
+            expectExportDefaultFromPackageInFile(pkg, '.d.ts');
+            expectExportDefaultFromPackageInFile(pkg, '.js');
+        }
+    });
+});

packages/lwc/__tests__/package-exports.spec.ts

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2024, Salesforce, Inc.
+ * All rights reserved.
+ * SPDX-License-Identifier: MIT
+ * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
+ */
+import { readFileSync } from 'node:fs';
+import { join } from 'node:path';
+
+describe('packaged dependencies are re-exported', () => {
+    const pkg = JSON.parse(readFileSync(join(__dirname, '../package.json'), 'utf8'));
+    test.each(Object.keys(pkg.dependencies))(`%s is exported`, (name) => {
+        const relative = name.replace('@lwc', '.');
+        expect(pkg.exports[relative]).toBe(`${relative}.js`);
+    });
+});

packages/lwc/babel-plugin-component.d.ts

@@ -1,7 +1,8 @@
 /*
- * Copyright (c) 2023, salesforce.com, inc.
+ * Copyright (c) 2024, salesforce.com, inc.
  * All rights reserved.
  * SPDX-License-Identifier: MIT
  * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
  */
 export type * from '@lwc/babel-plugin-component';
+export { default } from '@lwc/babel-plugin-component';

packages/lwc/babel-plugin-component.js

@@ -1,7 +1,8 @@
 /*
- * Copyright (c) 2023, salesforce.com, inc.
+ * Copyright (c) 2024, salesforce.com, inc.
  * All rights reserved.
  * SPDX-License-Identifier: MIT
  * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
  */
 export * from '@lwc/babel-plugin-component';
+export { default } from '@lwc/babel-plugin-component';

packages/lwc/features.d.ts

@@ -1,7 +1,8 @@
 /*
- * Copyright (c) 2023, salesforce.com, inc.
+ * Copyright (c) 2024, salesforce.com, inc.
  * All rights reserved.
  * SPDX-License-Identifier: MIT
  * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
  */
 export type * from '@lwc/features';
+export { default } from '@lwc/features';

packages/lwc/features.js

@@ -1,7 +1,8 @@
 /*
- * Copyright (c) 2023, salesforce.com, inc.
+ * Copyright (c) 2024, salesforce.com, inc.
  * All rights reserved.
  * SPDX-License-Identifier: MIT
  * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
  */
 export * from '@lwc/features';
+export { default } from '@lwc/features';

packages/lwc/jest.config.cjs

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2024, Salesforce, Inc.
+ * All rights reserved.
+ * SPDX-License-Identifier: MIT
+ * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
+ */
+/* eslint-env node */
+
+/**
+ * This is a .cjs file because this package is an ESM package, but jest needs CJS to work.
+ * If this file is ever changed to a .js file, add an exclusion to the package.json "files" list,
+ * so that this is not shipped as part of the package.
+ */
+
+// eslint-disable-next-line @typescript-eslint/no-var-requires
+const BASE_CONFIG = require('../../scripts/jest/base.config');
+
+module.exports = {
+    ...BASE_CONFIG,
+    displayName: 'lwc',
+    testEnvironment: 'jsdom',
+};

packages/lwc/rollup-plugin.d.ts

@@ -1,7 +1,8 @@
 /*
- * Copyright (c) 2023, salesforce.com, inc.
+ * Copyright (c) 2024, salesforce.com, inc.
  * All rights reserved.
  * SPDX-License-Identifier: MIT
  * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
  */
 export type * from '@lwc/rollup-plugin';
+export { default } from '@lwc/rollup-plugin';

packages/lwc/rollup-plugin.js

@@ -1,7 +1,8 @@
 /*
- * Copyright (c) 2023, salesforce.com, inc.
+ * Copyright (c) 2024, salesforce.com, inc.
  * All rights reserved.
  * SPDX-License-Identifier: MIT
  * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
  */
 export * from '@lwc/rollup-plugin';
+export { default } from '@lwc/rollup-plugin';

packages/lwc/template-compiler.d.ts

@@ -1,7 +1,8 @@
 /*
- * Copyright (c) 2023, salesforce.com, inc.
+ * Copyright (c) 2024, salesforce.com, inc.
  * All rights reserved.
  * SPDX-License-Identifier: MIT
  * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
  */
 export type * from '@lwc/template-compiler';
+export { default } from '@lwc/template-compiler';

packages/lwc/template-compiler.js

@@ -1,7 +1,8 @@
 /*
- * Copyright (c) 2023, salesforce.com, inc.
+ * Copyright (c) 2024, salesforce.com, inc.
  * All rights reserved.
  * SPDX-License-Identifier: MIT
  * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
  */
 export * from '@lwc/template-compiler';
+export { default } from '@lwc/template-compiler';

packages/lwc/tsconfig.json

@@ -1,5 +1,7 @@
 {
+    "extends": "../../tsconfig.json",
+
     "compilerOptions": {
-        "lib": ["dom"]
+        "lib": ["dom", "es2021"]
     }
 }

scripts/jest/root.config.js

@@ -23,6 +23,7 @@ module.exports = {
         '<rootDir>/packages/@lwc/synthetic-shadow',
         '<rootDir>/packages/@lwc/template-compiler',
         '<rootDir>/packages/@lwc/wire-service',
+        '<rootDir>/packages/lwc',
     ],
     coverageThreshold: {
         global: {