Add option to prevent code for external live bindings

docs/01-command-line-reference.md

@@ -89,6 +89,7 @@ export default { // can be an array (for multiple inputs)
     dynamicImportFunction,
     esModule,
     exports,
+    externalLiveBindings,
     freeze,
     indent,
     namespaceToStringTag,
@@ -214,6 +215,7 @@ Many options have command line equivalents. In those cases, any arguments passed
 --no-esModule               Do not add __esModule property
 --exports <mode>            Specify export mode (auto, default, named, none)
 --extend                    Extend global variable defined by --name
+--no-externalLiveBindings   Do not generate code to support live bindings
 --footer <text>             Code to insert at end of bundle (outside wrapper)
 --no-freeze                 Do not freeze namespace objects
 --no-indent                 Don't indent result

docs/02-javascript-api.md

@@ -109,41 +109,42 @@ The `outputOptions` object can contain the following properties (see the [big li
 
 ```js
 const outputOptions = {
-    // core output options
-    dir,
-    file,
-    format, // required
-    globals,
-    name,
-
-    // advanced output options
-    assetFileNames,
-    banner,
-    chunkFileNames,
-    compact,
-    entryFileNames,
-    extend,
-    footer,
-    interop,
-    intro,
-    outro,
-    paths,
-    sourcemap,
-    sourcemapExcludeSources,
-    sourcemapFile,
-    sourcemapPathTransform,
-
-    // danger zone
-    amd,
-    dynamicImportFunction,
-    esModule,
-    exports,
-    freeze,
-    indent,
-    namespaceToStringTag,
-    noConflict,
-    preferConst,
-    strict
+  // core output options
+  dir,
+  file,
+  format, // required
+  globals,
+  name,
+
+  // advanced output options
+  assetFileNames,
+  banner,
+  chunkFileNames,
+  compact,
+  entryFileNames,
+  extend,
+  externalLiveBindings,
+  footer,
+  interop,
+  intro,
+  outro,
+  paths,
+  sourcemap,
+  sourcemapExcludeSources,
+  sourcemapFile,
+  sourcemapPathTransform,
+
+  // danger zone
+  amd,
+  dynamicImportFunction,
+  esModule,
+  exports,
+  freeze,
+  indent,
+  namespaceToStringTag,
+  noConflict,
+  preferConst,
+  strict
 };
 ```
 

docs/999-big-list-of-options.md

@@ -661,6 +661,45 @@ const yourMethod = require( 'your-lib' ).yourMethod;
 const yourLib = require( 'your-lib' ).default;
 ```
 
+#### output.externalLiveBindings
+Type: `boolean`<br>
+CLI: `--externalLiveBindings`/`--no-externalLiveBindings`<br>
+Default: `true`
+
+When set to `false`, Rollup will not generate code to support live bindings for external imports but instead assume that exports do not change over time. This will enable Rollup to generate more optimized code. Note that this can cause issues when there are circular dependencies involving an external dependency. 
+
+This will avoid most cases where Rollup generates getters in the code and can therefore be used to make code IE8 compatible in many cases.
+
+Example:
+
+```js
+// input
+export {x} from 'external';
+
+// CJS output with externalLiveBindings: true
+'use strict';
+
+Object.defineProperty(exports, '__esModule', { value: true });
+
+var external = require('external');
+
+Object.defineProperty(exports, 'x', {
+	enumerable: true,
+	get: function () {
+		return external.x;
+	}
+});
+
+// CJS output with externalLiveBindings: false
+'use strict';
+
+Object.defineProperty(exports, '__esModule', { value: true });
+
+var external = require('external');
+
+exports.x = external.x;
+```
+
 #### output.freeze
 Type: `boolean`<br>
 CLI: `--freeze`/`--no-freeze`<br>

src/Chunk.ts

@@ -851,6 +851,7 @@ export default class Chunk {
 			let importName: string;
 			let needsLiveBinding = false;
 			if (exportName[0] === '*') {
+				needsLiveBinding = options.externalLiveBindings !== false;
 				exportChunk = this.graph.moduleById.get(exportName.substr(1)) as ExternalModule;
 				importName = exportName = '*';
 			} else {
@@ -865,7 +866,7 @@ export default class Chunk {
 				} else {
 					exportChunk = module;
 					importName = variable.name;
-					needsLiveBinding = true;
+					needsLiveBinding = options.externalLiveBindings !== false;
 				}
 			}
 			let reexportDeclaration = reexportDeclarations.get(exportChunk);

src/finalisers/amd.ts

@@ -75,7 +75,7 @@ export default function amd(
 		magicString.prepend(interopBlock + n + n);
 	}
 	if (accessedGlobals.has(INTEROP_NAMESPACE_VARIABLE)) {
-		magicString.prepend(getInteropNamespace(_, n, t));
+		magicString.prepend(getInteropNamespace(_, n, t, options.externalLiveBindings !== false));
 	}
 
 	if (intro) magicString.prepend(intro);

src/finalisers/cjs.ts

@@ -80,7 +80,7 @@ export default function cjs(
 			`?${_}${ex}['default']${_}:${_}${ex}${options.compact ? '' : '; '}}${n}${n}`;
 	}
 	if (accessedGlobals.has(INTEROP_NAMESPACE_VARIABLE)) {
-		intro += getInteropNamespace(_, n, t);
+		intro += getInteropNamespace(_, n, t, options.externalLiveBindings !== false);
 	}
 
 	if (importBlock) intro += importBlock + n + n;

src/finalisers/shared/getExportBlock.ts

@@ -45,13 +45,19 @@ export default function getExportBlock(
 			reexports.forEach(specifier => {
 				if (specifier.reexported === '*') {
 					if (!compact && exportBlock) exportBlock += '\n';
-					exportBlock +=
-						`Object.keys(${name}).forEach(function${_}(k)${_}{${n}` +
-						`${t}if${_}(k${_}!==${_}'default')${_}Object.defineProperty(exports,${_}k,${_}{${n}` +
-						`${t}${t}enumerable:${_}true,${n}` +
-						`${t}${t}get:${_}function${_}()${_}{${n}` +
-						`${t}${t}${t}return ${name}[k];${n}` +
-						`${t}${t}}${n}${t}});${n}});`;
+					if (specifier.needsLiveBinding) {
+						exportBlock +=
+							`Object.keys(${name}).forEach(function${_}(k)${_}{${n}` +
+							`${t}if${_}(k${_}!==${_}'default')${_}Object.defineProperty(exports,${_}k,${_}{${n}` +
+							`${t}${t}enumerable:${_}true,${n}` +
+							`${t}${t}get:${_}function${_}()${_}{${n}` +
+							`${t}${t}${t}return ${name}[k];${n}` +
+							`${t}${t}}${n}${t}});${n}});`;
+					} else {
+						exportBlock +=
+							`Object.keys(${name}).forEach(function${_}(k)${_}{${n}` +
+							`${t}if${_}(k${_}!==${_}'default')${_}exports[k]${_}=${_}${name}[k];${n}});`;
+					}
 				}
 			});
 		}

src/finalisers/shared/getInteropNamespace.ts

@@ -1,22 +1,34 @@
 import { INTEROP_NAMESPACE_VARIABLE } from '../../utils/variableNames';
 
-export function getInteropNamespace(_: string, n: string, t: string) {
-	return `function ${INTEROP_NAMESPACE_VARIABLE}(e)${_}{${n}` +
-`${t}if${_}(e${_}&&${_}e.__esModule)${_}{${_}return e;${_}}${_}else${_}{${n}` +
-`${t}${t}var n${_}=${_}{};${n}` +
-`${t}${t}if${_}(e)${_}{${n}` +
-`${t}${t}${t}Object.keys(e).forEach(function${_}(k)${_}{${n}` +
-`${t}${t}${t}${t}var d${_}=${_}Object.getOwnPropertyDescriptor(e,${_}k);${n}` +
-`${t}${t}${t}${t}Object.defineProperty(n,${_}k,${_}d.get${_}?${_}d${_}:${_}{${n}` +
-`${t}${t}${t}${t}${t}enumerable:${_}true,${n}` +
-`${t}${t}${t}${t}${t}get:${_}function${_}()${_}{${n}` +
-`${t}${t}${t}${t}${t}${t}return e[k];${n}` +
-`${t}${t}${t}${t}${t}}${n}` +
-`${t}${t}${t}${t}});${n}` +
-`${t}${t}${t}});${n}` +
-`${t}${t}}${n}` +
-`${t}${t}n['default']${_}=${_}e;${n}` +
-`${t}${t}return n;${n}` +
-`${t}}${n}` +
-`}${n}${n}`;
+function copyPropertyLiveBinding(_: string, n: string, t: string, i: string) {
+	return (
+		`${i}var d${_}=${_}Object.getOwnPropertyDescriptor(e,${_}k);${n}` +
+		`${i}Object.defineProperty(n,${_}k,${_}d.get${_}?${_}d${_}:${_}{${n}` +
+		`${i}${t}enumerable:${_}true,${n}` +
+		`${i}${t}get:${_}function${_}()${_}{${n}` +
+		`${i}${t}${t}return e[k];${n}` +
+		`${i}${t}}${n}` +
+		`${i}});${n}`
+	);
+}
+
+function copyPropertyStatic(_: string, n: string, _t: string, i: string) {
+	return `${i}n[k]${_}=e${_}[k];${n}`;
+}
+
+export function getInteropNamespace(_: string, n: string, t: string, liveBindings: boolean) {
+	return (
+		`function ${INTEROP_NAMESPACE_VARIABLE}(e)${_}{${n}` +
+		`${t}if${_}(e${_}&&${_}e.__esModule)${_}{${_}return e;${_}}${_}else${_}{${n}` +
+		`${t}${t}var n${_}=${_}{};${n}` +
+		`${t}${t}if${_}(e)${_}{${n}` +
+		`${t}${t}${t}Object.keys(e).forEach(function${_}(k)${_}{${n}` +
+		(liveBindings ? copyPropertyLiveBinding : copyPropertyStatic)(_, n, t, t + t + t + t) +
+		`${t}${t}${t}});${n}` +
+		`${t}${t}}${n}` +
+		`${t}${t}n['default']${_}=${_}e;${n}` +
+		`${t}${t}return n;${n}` +
+		`${t}}${n}` +
+		`}${n}${n}`
+	);
 }

src/rollup/types.d.ts

@@ -431,6 +431,7 @@ export interface OutputOptions {
 	esModule?: boolean;
 	exports?: 'default' | 'named' | 'none' | 'auto';
 	extend?: boolean;
+	externalLiveBindings?: boolean;
 	// only required for bundle.write
 	file?: string;
 	footer?: string | (() => string | Promise<string>);

src/utils/mergeOptions.ts

@@ -269,6 +269,7 @@ function getOutputOptions(
 		esModule: getOption('esModule', true),
 		exports: getOption('exports'),
 		extend: getOption('extend'),
+		externalLiveBindings: getOption('externalLiveBindings', true),
 		file: getOption('file'),
 		footer: getOption('footer'),
 		format: format === 'esm' ? 'es' : format,

test/cli/index.js

@@ -25,7 +25,7 @@ runTestSuiteWithSamples(
 
 				const command = 'node ' + path.resolve(__dirname, '../../bin') + path.sep + config.command;
 
-				const childProcess = exec(command, { timeout: 25000 }, (err, code, stderr) => {
+				const childProcess = exec(command, { timeout: 40000 }, (err, code, stderr) => {
 					if (err && !err.killed) {
 						if (config.error) {
 							const shouldContinue = config.error(err);
@@ -118,7 +118,7 @@ runTestSuiteWithSamples(
 					}
 				});
 			}
-		).timeout(30000);
+		).timeout(50000);
 	},
 	() => process.chdir(cwd)
 );

test/form/samples/no-external-live-bindings-compact/_config.js

@@ -0,0 +1,11 @@
+module.exports = {
+	description: 'Allows omitting the code that handles external live bindings in compact mode',
+	options: {
+		external: () => true,
+		output: {
+			compact: true,
+			externalLiveBindings: false,
+			name: 'bundle'
+		}
+	}
+};

test/form/samples/no-external-live-bindings-compact/_expected/es.js

@@ -0,0 +1 @@
+export{external1}from'external1';export*from'external2';const dynamic = import('external3');export{dynamic};

test/form/samples/no-external-live-bindings-compact/main.js

@@ -0,0 +1,3 @@
+export { external1 } from 'external1';
+export * from 'external2';
+export const dynamic = import('external3');

test/form/samples/no-external-live-bindings/_config.js

@@ -0,0 +1,10 @@
+module.exports = {
+	description: 'Allows omitting the code that handles external live bindings',
+	options: {
+		external: () => true,
+		output: {
+			externalLiveBindings: false,
+			name: 'bundle'
+		}
+	}
+};

test/form/samples/no-external-live-bindings/_expected/amd.js

@@ -0,0 +1,26 @@
+define(['require', 'exports', 'external1', 'external2'], function (require, exports, external1, external2) { 'use strict';
+
+	function _interopNamespace(e) {
+		if (e && e.__esModule) { return e; } else {
+			var n = {};
+			if (e) {
+				Object.keys(e).forEach(function (k) {
+					n[k] =e [k];
+				});
+			}
+			n['default'] = e;
+			return n;
+		}
+	}
+
+	const dynamic = new Promise(function (resolve, reject) { require(['external3'], function (m) { resolve(_interopNamespace(m)); }, reject) });
+
+	Object.keys(external2).forEach(function (k) {
+		if (k !== 'default') exports[k] = external2[k];
+	});
+	exports.external1 = external1.external1;
+	exports.dynamic = dynamic;
+
+	Object.defineProperty(exports, '__esModule', { value: true });
+
+});

test/form/samples/no-external-live-bindings/_expected/cjs.js

@@ -0,0 +1,27 @@
+'use strict';
+
+Object.defineProperty(exports, '__esModule', { value: true });
+
+function _interopNamespace(e) {
+	if (e && e.__esModule) { return e; } else {
+		var n = {};
+		if (e) {
+			Object.keys(e).forEach(function (k) {
+				n[k] =e [k];
+			});
+		}
+		n['default'] = e;
+		return n;
+	}
+}
+
+var external1 = require('external1');
+var external2 = require('external2');
+
+const dynamic = new Promise(function (resolve) { resolve(_interopNamespace(require('external3'))); });
+
+Object.keys(external2).forEach(function (k) {
+	if (k !== 'default') exports[k] = external2[k];
+});
+exports.external1 = external1.external1;
+exports.dynamic = dynamic;

test/form/samples/no-external-live-bindings/_expected/es.js

@@ -0,0 +1,6 @@
+export { external1 } from 'external1';
+export * from 'external2';
+
+const dynamic = import('external3');
+
+export { dynamic };