feat(commonjs)!: return the namespace by default when requiring ESM (#507)

* feat(commonjs): require ESM namespace by default, allow configuration

BREAKING CHANGES: By default, require expressions will return the namespace of internal and external modules

* chore(commonjs): refactor and clean up code

* chore(commonjs): add documentation

* feat(commonjs): add esmExternals option

* fix(commonjs): handle requiring mixed ES modules

* chore(commonjs): adapt to updated dependencies

Author: lukastaegert

codecov.yml

@@ -5,6 +5,6 @@ coverage:
   round: down
   range: 70...100
   status:
-    project: 'no'
-    patch: 'yes'
-comment: 'off'
+    project: "no"
+    patch: "yes"
+comment: "off"

package.json

@@ -7,7 +7,7 @@
     "ci:lint": "node scripts/run-changed.js ci:lint",
     "ci:test": "node scripts/run-changed.js ci:test",
     "lint": "pnpm run lint:docs && npm run lint:json && pnpm run lint:package && node scripts/run-changed.js lint",
-    "lint:docs": "prettier --single-quote --arrow-parens avoid --write README.md",
+    "lint:docs": "prettier --single-quote --arrow-parens avoid --trailing-comma none --write README.md",
     "lint:js": "eslint scripts util",
     "lint:json": "prettier --write tsconfig.*.json codecov.yml pnpm-workspace.yaml",
     "lint:package": "prettier --write package.json --plugin=prettier-plugin-package",

packages/alias/package.json

@@ -22,7 +22,7 @@
     "ci:lint:commits": "commitlint --from=${CIRCLE_BRANCH} --to=${CIRCLE_SHA1}",
     "ci:test": "pnpm run test -- --verbose",
     "lint": "pnpm run lint:js && pnpm run lint:docs && pnpm run lint:package",
-    "lint:docs": "prettier --single-quote --arrow-parens avoid --write README.md",
+    "lint:docs": "prettier --single-quote --arrow-parens avoid --trailing-comma none --write README.md",
     "lint:js": "eslint --fix --cache src test types --ext .js,.ts",
     "lint:package": "prettier --write package.json --plugin=prettier-plugin-package",
     "prebuild": "del-cli dist",

packages/auto-install/package.json

@@ -19,7 +19,7 @@
     "ci:lint:commits": "commitlint --from=${CIRCLE_BRANCH} --to=${CIRCLE_SHA1}",
     "ci:test": "pnpm run test -- --verbose",
     "lint": "pnpm run lint:js && pnpm run lint:docs && pnpm run lint:package",
-    "lint:docs": "prettier --single-quote --arrow-parens avoid --write README.md",
+    "lint:docs": "prettier --single-quote --arrow-parens avoid --trailing-comma none --write README.md",
     "lint:js": "eslint --fix --cache src test --ext .js,.ts",
     "lint:package": "prettier --write package.json --plugin=prettier-plugin-package",
     "prebuild": "del-cli dist",
@@ -54,9 +54,7 @@
   },
   "types": "types/index.d.ts",
   "ava": {
-    "babel": {
-      "compileEnhancements": false
-    },
+    "babel": true,
     "extensions": [
       "ts"
     ],

packages/auto-install/test/npm-bare.js

@@ -15,7 +15,7 @@ const input = join(cwd, '../input.js');
 process.chdir(cwd);
 
 test('npm, bare', async (t) => {
-  t.timeout(30000);
+  t.timeout(50000);
   await rollup({
     input,
     output: {

packages/auto-install/test/npm.js

@@ -17,7 +17,7 @@ const pkgFile = join(cwd, 'package.json');
 process.chdir(cwd);
 
 test('invalid manager', (t) => {
-  t.timeout(30000);
+  t.timeout(50000);
   const error = t.throws(
     () =>
       rollup({
@@ -36,7 +36,7 @@ test('invalid manager', (t) => {
 });
 
 test('npm', async (t) => {
-  t.timeout(30000);
+  t.timeout(50000);
   await rollup({
     input,
     output: {

packages/auto-install/test/yarn-bare.js

@@ -15,7 +15,7 @@ const input = join(cwd, '../input.js');
 process.chdir(cwd);
 
 test('yarn, bare', async (t) => {
-  t.timeout(30000);
+  t.timeout(50000);
   await rollup({
     input,
     output: {

packages/auto-install/test/yarn.js

@@ -15,7 +15,7 @@ const input = join(cwd, '../input.js');
 process.chdir(cwd);
 
 test('yarn', async (t) => {
-  t.timeout(30000);
+  t.timeout(50000);
   await rollup({
     input,
     output: {

packages/babel/package.json

@@ -22,7 +22,7 @@
     "ci:lint:commits": "commitlint --from=${CIRCLE_BRANCH} --to=${CIRCLE_SHA1}",
     "ci:test": "pnpm run test -- --verbose",
     "lint": "pnpm run lint:js && pnpm run lint:docs && pnpm run lint:package",
-    "lint:docs": "prettier --single-quote --arrow-parens avoid --write README.md",
+    "lint:docs": "prettier --single-quote --arrow-parens avoid --trailing-comma none --write README.md",
     "lint:js": "eslint --fix --cache src test",
     "lint:package": "prettier --write package.json --plugin=prettier-plugin-package",
     "prebuild": "del-cli dist",

packages/beep/package.json

@@ -20,7 +20,7 @@
     "ci:lint:commits": "commitlint --from=${CIRCLE_BRANCH} --to=${CIRCLE_SHA1}",
     "ci:test": "ava --verbose",
     "lint": "pnpm run lint:js && pnpm run lint:docs && pnpm run lint:package",
-    "lint:docs": "prettier --single-quote --arrow-parens avoid --write README.md",
+    "lint:docs": "prettier --single-quote --arrow-parens avoid --trailing-comma none --write README.md",
     "lint:js": "eslint --fix --cache lib test types --ext .js,.ts",
     "lint:package": "prettier --write package.json --plugin=prettier-plugin-package",
     "test": "ava"

packages/buble/package.json

@@ -22,7 +22,7 @@
     "ci:lint:commits": "commitlint --from=${CIRCLE_BRANCH} --to=${CIRCLE_SHA1}",
     "ci:test": "pnpm run test -- --verbose",
     "lint": "pnpm run lint:js && pnpm run lint:docs && pnpm run lint:package",
-    "lint:docs": "prettier --single-quote --arrow-parens avoid --write README.md",
+    "lint:docs": "prettier --single-quote --arrow-parens avoid --trailing-comma none --write README.md",
     "lint:js": "eslint --fix --cache src test types --ext .js,.ts",
     "lint:package": "prettier --write package.json --plugin=prettier-plugin-package",
     "prebuild": "del-cli dist",

packages/commonjs/README.md

@@ -34,9 +34,9 @@ export default {
   input: 'src/index.js',
   output: {
     dir: 'output',
-    format: 'cjs'
+    format: 'cjs',
   },
-  plugins: [commonjs()]
+  plugins: [commonjs()],
 };
 ```
 
@@ -46,7 +46,7 @@ Then call `rollup` either via the [CLI](https://www.rollupjs.org/guide/en/#comma
 
 ### `dynamicRequireTargets`
 
-Type: `String|Array[String]`<br>
+Type: `string | string[]`<br>
 Default: `[]`
 
 Some modules contain dynamic `require` calls, or require modules that contain circular dependencies, which are not handled well by static imports.
@@ -66,60 +66,182 @@ commonjs({
     '!node_modules/logform/index.js',
     '!node_modules/logform/format.js',
     '!node_modules/logform/levels.js',
-    '!node_modules/logform/browser.js'
-  ]
+    '!node_modules/logform/browser.js',
+  ],
 });
 ```
 
 ### `exclude`
 
-Type: `String` | `Array[...String]`<br>
+Type: `string | string[]`<br>
 Default: `null`
 
 A [minimatch pattern](https://github.com/isaacs/minimatch), or array of patterns, which specifies the files in the build the plugin should _ignore_. By default non-CommonJS modules are ignored.
 
 ### `include`
 
-Type: `String` | `Array[...String]`<br>
+Type: `string | string[]`<br>
 Default: `null`
 
 A [minimatch pattern](https://github.com/isaacs/minimatch), or array of patterns, which specifies the files in the build the plugin should operate on. By default CommonJS modules are targeted.
 
 ### `extensions`
 
-Type: `Array[...String]`<br>
+Type: `string[]`<br>
 Default: `['.js']`
 
 Search for extensions other than .js in the order specified.
 
 ### `ignoreGlobal`
 
-Type: `Boolean`<br>
+Type: `boolean`<br>
 Default: `false`
 
 If true, uses of `global` won't be dealt with by this plugin.
 
 ### `sourceMap`
 
-Type: `Boolean`<br>
+Type: `boolean`<br>
 Default: `true`
 
 If false, skips source map generation for CommonJS modules.
 
 ### `transformMixedEsModules`
 
-Type: `Boolean`<br>
+Type: `boolean`<br>
 Default: `false`
 
 Instructs the plugin whether or not to enable mixed module transformations. This is useful in scenarios with mixed ES and CommonJS modules. Set to `true` if it's known that `require` calls should be transformed, or `false` if the code contains env detection and the `require` should survive a transformation.
 
 ### `ignore`
 
-Type: `Array[...String | (String) => Boolean]`<br>
+Type: `string[] | ((id: string) => boolean)`<br>
 Default: `[]`
 
 Sometimes you have to leave require statements unconverted. Pass an array containing the IDs or an `id => boolean` function. Only use this option if you know what you're doing!
 
+### `esmExternals`
+
+Type: `boolean | string[] || ((id: string) => boolean)`
+Default: `false`
+
+Controls how imports from external dependencies are rendered. By default, all external dependencies are assumed to be CommonJS. This means they are rendered as default imports to be compatible with e.g. NodeJS where ES modules can only import a default export from a CommonJS dependency:
+
+```js
+// input
+const foo = require('foo');
+
+// output
+import foo from 'foo';
+```
+
+This is likely not desired for ES module dependencies: Here `require` should usually return the namespace to be compatible with how bundled modules are handled.
+
+If you set `esmExternals` to `true`, all external dependencies are assumed to be ES modules and will adhere to the `requireReturnsDefault` option. If that option is not set, they will be rendered as namespace imports.
+
+You can also supply an array of ids that are to be treated as ES modules, or a function that will be passed each external id to determine if it is an ES module.
+
+### `requireReturnsDefault`
+
+Type: `boolean | "auto" | "preferred" | ((id: string) => boolean | "auto" | "preferred")`<br>
+Default: `false`
+
+Controls what is returned when requiring an ES module or external dependency from a CommonJS file. By default, this plugin will render it as a namespace import, i.e.
+
+```js
+// input
+const foo = require('foo');
+
+// output
+import * as foo from 'foo';
+```
+
+This is in line with how other bundlers handle this situation and is also the most likely behaviour in case Node should ever support this. However there are some situations where this may not be desired:
+
+- There is code in an external dependency that cannot be changed where a `require` statement expects the default export to be returned from an ES module.
+- If the imported module is in the same bundle, Rollup will generate a namespace object for the imported module which can increase bundle size unnecessarily:
+
+  ```js
+  // input: main.js
+  const dep = require('./dep.js');
+  console.log(dep.default);
+
+  // input: dep.js
+  export default 'foo';
+
+  // output
+  var dep = 'foo';
+
+  var dep$1 = /*#__PURE__*/ Object.freeze({
+    __proto__: null,
+    default: dep,
+  });
+
+  console.log(dep$1.default);
+  ```
+
+For these situations, you can change Rollup's behaviour either globally or per module. To change it globally, set the `requireReturnsDefault` option to one of the following values:
+
+- `false`: This is the default, requiring an ES module returns its namespace. For external dependencies when using `esmExternals: true`, no additional interop code is generated:
+
+  ```js
+  // input
+  const dep = require('dep');
+  console.log(dep);
+
+  // output
+  import * as dep from 'dep';
+
+  console.log(dep);
+  ```
+
+- `"auto"`: This is complementary to how [`output.exports`](https://rollupjs.org/guide/en/#outputexports): `"auto"` works in Rollup: If a module has a default export and no named exports, requiring that module returns the default export. In all other cases, the namespace is returned. For external dependencies when using `esmExternals: true`, a corresponding interop helper is added:
+
+  ```js
+  // output
+  import * as dep$1 from 'dep';
+
+  function getDefaultExportFromNamespaceIfNotNamed(n) {
+    return n &&
+      Object.prototype.hasOwnProperty.call(n, 'default') &&
+      Object.keys(n).length === 1
+      ? n['default']
+      : n;
+  }
+
+  var dep = getDefaultExportFromNamespaceIfNotNamed(dep$1);
+
+  console.log(dep);
+  ```
+
+- `"preferred"`: If a module has a default export, requiring that module always returns the default export, no matter whether additional named exports exist. This is similar to how previous versions of this plugin worked. Again for external dependencies when using `esmExternals: true`, an interop helper is added:
+
+  ```js
+  // output
+  import * as dep$1 from 'dep';
+
+  function getDefaultExportFromNamespaceIfPresent(n) {
+    return n && Object.prototype.hasOwnProperty.call(n, 'default')
+      ? n['default']
+      : n;
+  }
+
+  var dep = getDefaultExportFromNamespaceIfPresent(dep$1);
+
+  console.log(dep);
+  ```
+
+- `true`: This will always try to return the default export on require without checking if it actually exists. This can throw at build time if there is no default export. This is how external dependencies are handled when `esmExternals` is not used. The advantage over the other options is that, like `false`, this does not add an interop helper for external dependencies, keeping the code lean:
+
+  ```js
+  // output
+  import dep from 'dep';
+
+  console.log(dep);
+  ```
+
+To change this for individual modules, you can supply a function for `requireReturnsDefault` instead. This function will then be called once for each required ES module or external dependency with the corresponding id and allows you to return different values for different modules.
+
 ## Using with @rollup/plugin-node-resolve
 
 Since most CommonJS packages you are importing are probably dependencies in `node_modules`, you may need to use [@rollup/plugin-node-resolve](https://github.com/rollup/plugins/tree/master/packages/node-resolve):
@@ -134,9 +256,9 @@ export default {
   output: {
     file: 'bundle.js',
     format: 'iife',
-    name: 'MyModule'
+    name: 'MyModule',
   },
-  plugins: [resolve(), commonjs()]
+  plugins: [resolve(), commonjs()],
 };
 ```
 
@@ -146,7 +268,7 @@ Symlinks are common in monorepos and are also created by the `npm link` command.
 
 ```js
 commonjs({
-  include: /node_modules/
+  include: /node_modules/,
 });
 ```
 

packages/commonjs/package.json

@@ -22,7 +22,7 @@
     "ci:lint:commits": "commitlint --from=${CIRCLE_BRANCH} --to=${CIRCLE_SHA1}",
     "ci:test": "pnpm run test -- --verbose && pnpm run test:ts",
     "lint": "pnpm run lint:js && pnpm run lint:docs && pnpm run lint:package",
-    "lint:docs": "prettier --single-quote --arrow-parens avoid --write README.md",
+    "lint:docs": "prettier --single-quote --arrow-parens avoid --trailing-comma none --write README.md",
     "lint:js": "eslint --fix --cache src test types --ext .js,.ts",
     "lint:package": "prettier --write package.json --plugin=prettier-plugin-package",
     "prebuild": "del-cli dist",
@@ -61,7 +61,6 @@
   "devDependencies": {
     "@rollup/plugin-json": "^4.1.0",
     "@rollup/plugin-node-resolve": "^8.4.0",
-    "acorn": "^7.3.1",
     "locate-character": "^2.0.5",
     "require-relative": "^0.8.7",
     "rollup": "^2.23.0",