Add hasDefaultExport to ModuleInfo

docs/05-plugin-development.md

@@ -164,27 +164,42 @@ The `importer` is the fully resolved id of the importing module. When resolving
 
 For those cases, the `isEntry` option will tell you if we are resolving a user defined entry point, an emitted chunk, or if the `isEntry` parameter was provided for the [`this.resolve`](guide/en/#thisresolve) context function.
 
-You can use this for instance as a mechanism to define custom proxy modules for entry points. The following plugin will only expose the default export from entry points while still keeping named exports available for internal usage:
+You can use this for instance as a mechanism to define custom proxy modules for entry points. The following plugin will proxy all entry points to inject a polyfill import.
 
 ```js
-function onlyDefaultForEntriesPlugin() {
+function injectPolyfillPlugin() {
   return {
-    name: 'only-default-for-entries',
+    name: 'inject-polyfill',
     async resolveId(source, importer, options) {
       if (options.isEntry) {
         // We need to skip this plugin to avoid an infinite loop
         const resolution = await this.resolve(source, importer, { skipSelf: true, ...options });
-        // If it cannot be resolved, return `null` so that Rollup displays an error
-        if (!resolution) return null;
+        // If it cannot be resolved or is external, just return it so that
+        // Rollup can display an error
+        if (!resolution || resolution.external) return resolution;
+        // In the load hook of the proxy, we want to use this.load to find out
+        // if the entry has a default export. In the load hook, however, we no
+        // longer have the full "resolution" object that may contain meta-data
+        // from other plugins that is only added on first load. Therefore we
+        // trigger loading here without waiting for it.
+        this.load(resolution);
         return `${resolution.id}?entry-proxy`;
       }
       return null;
     },
-    load(id) {
+    async load(id) {
       if (id.endsWith('?entry-proxy')) {
-        const importee = id.slice(0, -'?entry-proxy'.length);
-        // Note that this will throw if there is no default export
-        return `export {default} from '${importee}';`;
+        const entryId = id.slice(0, -'?entry-proxy'.length);
+        // We need to load and parse the original entry first because we need
+        // to know if it has a default export
+        const { hasDefaultExport } = await this.load({ id: entryId });
+        let code = `import 'polyfill';export * from ${JSON.stringify(entryId)};`;
+        // Namespace reexports do not reexport default, so we need special
+        // handling here
+        if (hasDefaultExport) {
+          code += `export { default } from ${JSON.stringify(entryId)};`;
+        }
+        return code;
       }
       return null;
     }
@@ -673,6 +688,7 @@ type ModuleInfo = {
   id: string; // the id of the module, for convenience
   code: string | null; // the source code of the module, `null` if external or not yet available
   ast: ESTree.Program; // the parsed abstract syntax tree if available
+  hasDefaultExport: boolean | null; // is there a default export, `null` if external or not yet available
   isEntry: boolean; // is this a user- or plugin-defined entry point
   isExternal: boolean; // for external modules that are referenced but not included in the graph
   isIncluded: boolean | null; // is the module included after tree-shaking, `null` if external or not yet available
@@ -718,7 +734,7 @@ This allows you to inspect the final content of modules before deciding how to r
 
 The returned promise will resolve once the module has been fully transformed and parsed but before any imports have been resolved. That means that the resulting `ModuleInfo` will have empty `importedIds`, `dynamicallyImportedIds`, `importedIdResolutions` and `dynamicallyImportedIdResolutions`. This helps to avoid deadlock situations when awaiting `this.load` in a `resolveId` hook. If you are interested in `importedIds` and `dynamicallyImportedIds`, you should implement a `moduleParsed` hook.
 
-Note that with regard to the `moduleSideEffects`, `syntheticNamedExports` and `meta` options, the same restrictions apply as for the `resolveId` hook: Their values only have an effect if the module has not been loaded yet. Thus, it is very important to use `this.resolve` first to find out if any plugins want to set special values for these options in their `resolveId` hook, and pass these options on to `this.load` if appropriate. The example below showcases how this can be handled to add a proxy module for modules containing a special code comment:
+Note that with regard to the `moduleSideEffects`, `syntheticNamedExports` and `meta` options, the same restrictions apply as for the `resolveId` hook: Their values only have an effect if the module has not been loaded yet. Thus, it is very important to use `this.resolve` first to find out if any plugins want to set special values for these options in their `resolveId` hook, and pass these options on to `this.load` if appropriate. The example below showcases how this can be handled to add a proxy module for modules containing a special code comment. Note the special handling for re-exporting the default export:
 
 ```js
 export default function addProxyPlugin() {
@@ -744,7 +760,16 @@ export default function addProxyPlugin() {
     load(id) {
       if (id.endsWith('?proxy')) {
         const importee = id.slice(0, -'?proxy'.length);
-        return `console.log('proxy for ${importee}'); export * from ${JSON.stringify(importee)};`;
+        // Note that namespace reexports do not reexport default exports
+        let code = `console.log('proxy for ${importee}'); export * from ${JSON.stringify(
+          importee
+        )};`;
+        // We know that while resolving the proxy, importee was already fully
+        // loaded and parsed, so we can rely on hasDefaultExport
+        if (this.getModuleInfo(importee).hasDefaultExport) {
+          code += `export { default } from ${JSON.stringify(importee)};`;
+        }
+        return code;
       }
       return null;
     }
@@ -1142,7 +1167,7 @@ function parentPlugin() {
       }
     }
     // ...plugin hooks
-  }
+  };
 }
 
 function dependentPlugin() {
@@ -1151,20 +1176,19 @@ function dependentPlugin() {
     name: 'dependent',
     buildStart({ plugins }) {
       const parentName = 'parent';
-      const parentPlugin = options.plugins
-              .find(plugin => plugin.name === parentName);
+      const parentPlugin = options.plugins.find(plugin => plugin.name === parentName);
       if (!parentPlugin) {
         // or handle this silently if it is optional
         throw new Error(`This plugin depends on the "${parentName}" plugin.`);
       }
       // now you can access the API methods in subsequent hooks
       parentApi = parentPlugin.api;
-    }
+    },
     transform(code, id) {
       if (thereIsAReasonToDoSomething(id)) {
         parentApi.doSomething(id);
       }
     }
-  }
+  };
 }
 ```

package.json

@@ -64,7 +64,7 @@
     "@rollup/plugin-json": "^4.1.0",
     "@rollup/plugin-node-resolve": "^13.1.3",
     "@rollup/plugin-replace": "^3.0.1",
-    "@rollup/plugin-typescript": "^8.2.5",
+    "@rollup/plugin-typescript": "^8.3.0",
     "@rollup/pluginutils": "^4.1.2",
     "@types/node": "^10.17.60",
     "@types/signal-exit": "^3.0.1",
@@ -100,7 +100,7 @@
     "pretty-bytes": "^5.6.0",
     "pretty-ms": "^7.0.1",
     "requirejs": "^2.3.6",
-    "rollup": "^2.64.0",
+    "rollup": "^2.65.0",
     "rollup-plugin-license": "^2.6.1",
     "rollup-plugin-string": "^3.0.0",
     "rollup-plugin-terser": "^7.0.2",
@@ -111,7 +111,7 @@
     "source-map": "^0.7.3",
     "source-map-support": "^0.5.21",
     "sourcemap-codec": "^1.4.8",
-    "systemjs": "^6.11.0",
+    "systemjs": "^6.12.1",
     "terser": "^5.10.0",
     "tslib": "^2.3.1",
     "typescript": "^4.5.5",

src/ExternalModule.ts

@@ -46,6 +46,7 @@ export default class ExternalModule {
 			get dynamicImporters() {
 				return dynamicImporters.sort();
 			},
+			hasDefaultExport: null,
 			hasModuleSideEffects,
 			id,
 			implicitlyLoadedAfterOneOf: EMPTY_ARRAY,

src/Module.ts

@@ -277,6 +277,13 @@ export default class Module {
 			get dynamicImporters() {
 				return module.dynamicImporters.sort();
 			},
+			get hasDefaultExport() {
+				// This information is only valid after parsing
+				if (!module.ast) {
+					return null;
+				}
+				return 'default' in module.exports || 'default' in module.reexportDescriptions;
+			},
 			hasModuleSideEffects,
 			id,
 			get implicitlyLoadedAfterOneOf() {

src/rollup/types.d.ts

@@ -162,6 +162,7 @@ interface ModuleInfo {
 	dynamicImporters: readonly string[];
 	dynamicallyImportedIdResolutions: readonly ResolvedId[];
 	dynamicallyImportedIds: readonly string[];
+	hasDefaultExport: boolean | null;
 	hasModuleSideEffects: boolean | 'no-treeshake';
 	id: string;
 	implicitlyLoadedAfterOneOf: readonly string[];

test/chunking-form/samples/implicit-dependencies/implicitly-dependent-emitted-entry/_config.js

@@ -73,6 +73,7 @@ module.exports = {
 					dynamicallyImportedIdResolutions: [],
 					dynamicallyImportedIds: [],
 					dynamicImporters: [],
+					hasDefaultExport: false,
 					hasModuleSideEffects: true,
 					id: ID_MAIN,
 					implicitlyLoadedAfterOneOf: [],
@@ -143,6 +144,7 @@ module.exports = {
 					dynamicallyImportedIdResolutions: [],
 					dynamicallyImportedIds: [],
 					dynamicImporters: [],
+					hasDefaultExport: false,
 					hasModuleSideEffects: true,
 					id: ID_DEP,
 					implicitlyLoadedAfterOneOf: [],

test/chunking-form/samples/implicit-dependencies/implicitly-dependent-entry/_config.js

@@ -69,6 +69,7 @@ module.exports = {
 					dynamicallyImportedIdResolutions: [],
 					dynamicallyImportedIds: [],
 					dynamicImporters: [],
+					hasDefaultExport: false,
 					hasModuleSideEffects: true,
 					id: ID_MAIN,
 					implicitlyLoadedAfterOneOf: [],
@@ -139,6 +140,7 @@ module.exports = {
 					dynamicallyImportedIdResolutions: [],
 					dynamicallyImportedIds: [],
 					dynamicImporters: [],
+					hasDefaultExport: false,
 					hasModuleSideEffects: true,
 					id: ID_DEP,
 					implicitlyLoadedAfterOneOf: [],

test/chunking-form/samples/implicit-dependencies/multiple-dependencies/_config.js

@@ -117,6 +117,7 @@ module.exports = {
 					dynamicallyImportedIdResolutions: [],
 					dynamicallyImportedIds: [],
 					dynamicImporters: [],
+					hasDefaultExport: false,
 					hasModuleSideEffects: true,
 					id: ID_MAIN1,
 					implicitlyLoadedAfterOneOf: [],
@@ -236,6 +237,7 @@ module.exports = {
 					dynamicallyImportedIdResolutions: [],
 					dynamicallyImportedIds: [],
 					dynamicImporters: [],
+					hasDefaultExport: false,
 					hasModuleSideEffects: true,
 					id: ID_MAIN2,
 					implicitlyLoadedAfterOneOf: [],
@@ -354,6 +356,7 @@ module.exports = {
 					dynamicallyImportedIdResolutions: [],
 					dynamicallyImportedIds: [],
 					dynamicImporters: [],
+					hasDefaultExport: false,
 					hasModuleSideEffects: true,
 					id: ID_DEP,
 					implicitlyLoadedAfterOneOf: [ID_MAIN1, ID_MAIN2],

test/chunking-form/samples/implicit-dependencies/single-dependency/_config.js

@@ -68,6 +68,7 @@ module.exports = {
 					dynamicallyImportedIdResolutions: [],
 					dynamicallyImportedIds: [],
 					dynamicImporters: [],
+					hasDefaultExport: false,
 					hasModuleSideEffects: true,
 					id: ID_MAIN,
 					implicitlyLoadedAfterOneOf: [],
@@ -138,6 +139,7 @@ module.exports = {
 					dynamicallyImportedIdResolutions: [],
 					dynamicallyImportedIds: [],
 					dynamicImporters: [],
+					hasDefaultExport: false,
 					hasModuleSideEffects: true,
 					id: ID_DEP,
 					implicitlyLoadedAfterOneOf: [ID_MAIN],

test/function/samples/deprecated/manual-chunks-info/_config.js

@@ -111,6 +111,7 @@ module.exports = {
 							],
 							dynamicallyImportedIds: [getId('dynamic')],
 							dynamicImporters: [],
+							hasDefaultExport: false,
 							hasModuleSideEffects: true,
 							id: getId('main'),
 							implicitlyLoadedAfterOneOf: [],
@@ -145,6 +146,7 @@ module.exports = {
 							dynamicallyImportedIdResolutions: [],
 							dynamicallyImportedIds: [],
 							dynamicImporters: [getId('dynamic')],
+							hasDefaultExport: null,
 							hasModuleSideEffects: true,
 							id: 'external',
 							implicitlyLoadedAfterOneOf: [],
@@ -177,6 +179,7 @@ module.exports = {
 							dynamicallyImportedIdResolutions: [],
 							dynamicallyImportedIds: [],
 							dynamicImporters: [],
+							hasDefaultExport: true,
 							hasModuleSideEffects: true,
 							id: getId('lib'),
 							implicitlyLoadedAfterOneOf: [],
@@ -260,6 +263,7 @@ module.exports = {
 							],
 							dynamicallyImportedIds: ['external'],
 							dynamicImporters: [getId('main')],
+							hasDefaultExport: false,
 							hasModuleSideEffects: true,
 							id: getId('dynamic'),
 							implicitlyLoadedAfterOneOf: [],