Feat: add syntheticNamedExports

src/Chunk.ts

@@ -593,6 +593,10 @@ export default class Chunk {
 						else magicString.addSource(new MagicString(rendered));
 					}
 				}
+				module.syntheticExports.forEach(s => {
+					const rendered = s.renderBlock(renderOptions);
+					magicString.addSource(new MagicString(rendered));
+				});
 			}
 			const { renderedExports, removedExports } = module.getRenderedExports();
 			renderedModules[module.id] = {

src/Module.ts

@@ -25,6 +25,7 @@ import { PathTracker, UNKNOWN_PATH } from './ast/utils/PathTracker';
 import ExportShimVariable from './ast/variables/ExportShimVariable';
 import ExternalVariable from './ast/variables/ExternalVariable';
 import NamespaceVariable from './ast/variables/NamespaceVariable';
+import SyntheticNamedExport from './ast/variables/SyntheticNamedExport';
 import Variable from './ast/variables/Variable';
 import Chunk from './Chunk';
 import ExternalModule from './ExternalModule';
@@ -206,6 +207,8 @@ export default class Module {
 	scope!: ModuleScope;
 	sourcemapChain!: DecodedSourceMapOrMissing[];
 	sources = new Set<string>();
+	syntheticExports = new Map<string, SyntheticNamedExport>();
+	syntheticNamedExports: boolean;
 	transformFiles?: EmittedFile[];
 	userChunkNames = new Set<string>();
 	usesTopLevelAwait = false;
@@ -221,12 +224,19 @@ export default class Module {
 	private transformDependencies: string[] = [];
 	private transitiveReexports: string[] | null = null;
 
-	constructor(graph: Graph, id: string, moduleSideEffects: boolean, isEntry: boolean) {
+	constructor(
+		graph: Graph,
+		id: string,
+		moduleSideEffects: boolean,
+		syntheticNamedExports: boolean,
+		isEntry: boolean
+	) {
 		this.id = id;
 		this.graph = graph;
 		this.excludeFromSourcemap = /\0/.test(id);
 		this.context = graph.getModuleContext(id);
 		this.moduleSideEffects = moduleSideEffects;
+		this.syntheticNamedExports = syntheticNamedExports;
 		this.isEntryPoint = isEntry;
 	}
 
@@ -439,9 +449,23 @@ export default class Module {
 
 		// we don't want to create shims when we are just
 		// probing export * modules for exports
-		if (this.graph.shimMissingExports && !isExportAllSearch) {
-			this.shimMissingExport(name);
-			return this.exportShimVariable;
+		if (!isExportAllSearch) {
+			if (this.syntheticNamedExports) {
+				let syntheticExport = this.syntheticExports.get(name);
+				if (!syntheticExport && !this.exports[name]) {
+					const defaultVariable = this.astContext.traceExport('default');
+					syntheticExport = new SyntheticNamedExport(this.astContext, name, defaultVariable as any);
+					this.syntheticExports.set(name, syntheticExport);
+				}
+				if (syntheticExport) {
+					return syntheticExport;
+				}
+			}
+
+			if (this.graph.shimMissingExports) {
+				this.shimMissingExport(name);
+				return this.exportShimVariable;
+			}
 		}
 		return undefined as any;
 	}
@@ -534,6 +558,7 @@ export default class Module {
 		originalSourcemap,
 		resolvedIds,
 		sourcemapChain,
+		syntheticNamedExports,
 		transformDependencies,
 		transformFiles
 	}: TransformModuleJSON & {
@@ -551,6 +576,9 @@ export default class Module {
 		if (typeof moduleSideEffects === 'boolean') {
 			this.moduleSideEffects = moduleSideEffects;
 		}
+		if (typeof syntheticNamedExports === 'boolean') {
+			this.syntheticNamedExports = syntheticNamedExports;
+		}
 
 		timeStart('generate ast', 3);
 
@@ -634,6 +662,7 @@ export default class Module {
 			originalSourcemap: this.originalSourcemap,
 			resolvedIds: this.resolvedIds,
 			sourcemapChain: this.sourcemapChain,
+			syntheticNamedExports: this.syntheticNamedExports,
 			transformDependencies: this.transformDependencies,
 			transformFiles: this.transformFiles
 		};

src/ModuleLoader.ts

@@ -17,6 +17,7 @@ import {
 	errBadLoader,
 	errCannotAssignModuleToChunk,
 	errEntryCannotBeExternal,
+	errExternalSyntheticExports,
 	errInternalIdCannotBeExternal,
 	errInvalidOption,
 	errNamespaceConflict,
@@ -272,6 +273,7 @@ export class ModuleLoader {
 		id: string,
 		importer: string,
 		moduleSideEffects: boolean,
+		syntheticNamedExports: boolean,
 		isEntry: boolean
 	): Promise<Module> {
 		const existingModule = this.modulesById.get(id);
@@ -280,7 +282,13 @@ export class ModuleLoader {
 			return Promise.resolve(existingModule);
 		}
 
-		const module: Module = new Module(this.graph, id, moduleSideEffects, isEntry);
+		const module: Module = new Module(
+			this.graph,
+			id,
+			moduleSideEffects,
+			syntheticNamedExports,
+			isEntry
+		);
 		this.modulesById.set(id, module);
 		this.graph.watchFiles[id] = true;
 		const manualChunkAlias = this.getManualChunk(id);
@@ -321,6 +329,9 @@ export class ModuleLoader {
 				if (typeof sourceDescription.moduleSideEffects === 'boolean') {
 					module.moduleSideEffects = sourceDescription.moduleSideEffects;
 				}
+				if (typeof sourceDescription.syntheticNamedExports === 'boolean') {
+					module.syntheticNamedExports = sourceDescription.syntheticNamedExports;
+				}
 				return transform(this.graph, sourceDescription, module);
 			})
 			.then((source: TransformModuleJSON | ModuleJSON) => {
@@ -370,7 +381,13 @@ export class ModuleLoader {
 			}
 			return Promise.resolve(externalModule);
 		} else {
-			return this.fetchModule(resolvedId.id, importer, resolvedId.moduleSideEffects, false);
+			return this.fetchModule(
+				resolvedId.id,
+				importer,
+				resolvedId.moduleSideEffects,
+				resolvedId.syntheticNamedExports,
+				false
+			);
 		}
 	}
 
@@ -387,7 +404,8 @@ export class ModuleLoader {
 			return {
 				external: true,
 				id: source,
-				moduleSideEffects: this.hasModuleSideEffects(source, true)
+				moduleSideEffects: this.hasModuleSideEffects(source, true),
+				syntheticNamedExports: false
 			};
 		}
 		return resolvedId;
@@ -407,7 +425,7 @@ export class ModuleLoader {
 					: resolveIdResult;
 
 			if (typeof id === 'string') {
-				return this.fetchModule(id, undefined as any, true, isEntry);
+				return this.fetchModule(id, undefined as any, true, false, isEntry);
 			}
 			return error(errUnresolvedEntry(unresolvedId));
 		});
@@ -420,6 +438,7 @@ export class ModuleLoader {
 		let id = '';
 		let external = false;
 		let moduleSideEffects = null;
+		let syntheticNamedExports = false;
 		if (resolveIdResult) {
 			if (typeof resolveIdResult === 'object') {
 				id = resolveIdResult.id;
@@ -429,6 +448,9 @@ export class ModuleLoader {
 				if (typeof resolveIdResult.moduleSideEffects === 'boolean') {
 					moduleSideEffects = resolveIdResult.moduleSideEffects;
 				}
+				if (typeof resolveIdResult.syntheticNamedExports === 'boolean') {
+					syntheticNamedExports = resolveIdResult.syntheticNamedExports;
+				}
 			} else {
 				if (this.isExternal(resolveIdResult, importer, true)) {
 					external = true;
@@ -442,13 +464,18 @@ export class ModuleLoader {
 			}
 			external = true;
 		}
+		if (external && syntheticNamedExports) {
+			syntheticNamedExports = false;
+			this.graph.warn(errExternalSyntheticExports(source, importer));
+		}
 		return {
 			external,
 			id,
 			moduleSideEffects:
 				typeof moduleSideEffects === 'boolean'
 					? moduleSideEffects
-					: this.hasModuleSideEffects(id, external)
+					: this.hasModuleSideEffects(id, external),
+			syntheticNamedExports
 		};
 	}
 

src/ast/variables/SyntheticNamedExport.ts

@@ -0,0 +1,33 @@
+import Module, { AstContext } from '../../Module';
+import { RenderOptions } from '../../utils/renderHelpers';
+import { InclusionContext } from '../ExecutionContext';
+import ExportDefaultVariable from './ExportDefaultVariable';
+import Variable from './Variable';
+
+export default class SyntheticNamedExport extends Variable {
+	context: AstContext;
+	defaultVariable: ExportDefaultVariable;
+	module: Module;
+
+	constructor(context: AstContext, name: string, defaultVariable: ExportDefaultVariable) {
+		super(name);
+		this.context = context;
+		this.module = context.module;
+		this.defaultVariable = defaultVariable;
+	}
+
+	include(context: InclusionContext) {
+		if (!this.included) {
+			this.included = true;
+			this.context.includeVariable(context, this.defaultVariable);
+		}
+	}
+
+	renderBlock(options: RenderOptions) {
+		const _ = options.compact ? '' : ' ';
+		const name = this.getName();
+		const defaultVariable = this.defaultVariable.getName();
+		const output = `${options.varOrConst} ${name}${_}=${_}${defaultVariable}.${this.name};`;
+		return output;
+	}
+}

src/rollup/types.d.ts

@@ -93,6 +93,7 @@ export interface SourceDescription {
 	code: string;
 	map?: SourceMapInput;
 	moduleSideEffects?: boolean | null;
+	syntheticNamedExports?: boolean;
 }
 
 export interface TransformSourceDescription extends SourceDescription {
@@ -109,6 +110,7 @@ export interface TransformModuleJSON {
 	originalSourcemap: ExistingDecodedSourceMap | null;
 	resolvedIds?: ResolvedIdMap;
 	sourcemapChain: DecodedSourceMapOrMissing[];
+	syntheticNamedExports: boolean | null;
 	transformDependencies: string[];
 }
 
@@ -199,6 +201,7 @@ export interface ResolvedId {
 	external: boolean;
 	id: string;
 	moduleSideEffects: boolean;
+	syntheticNamedExports: boolean;
 }
 
 export interface ResolvedIdMap {
@@ -209,6 +212,7 @@ interface PartialResolvedId {
 	external?: boolean;
 	id: string;
 	moduleSideEffects?: boolean | null;
+	syntheticNamedExports?: boolean;
 }
 
 export type ResolveIdResult = string | false | null | undefined | PartialResolvedId;

src/utils/error.ts

@@ -54,7 +54,8 @@ export enum Errors {
 	PLUGIN_ERROR = 'PLUGIN_ERROR',
 	UNRESOLVED_ENTRY = 'UNRESOLVED_ENTRY',
 	UNRESOLVED_IMPORT = 'UNRESOLVED_IMPORT',
-	VALIDATION_ERROR = 'VALIDATION_ERROR'
+	VALIDATION_ERROR = 'VALIDATION_ERROR',
+	EXTERNAL_SYNTHETIC_EXPORTS = 'EXTERNAL_SYNTHETIC_EXPORTS'
 }
 
 export function errAssetNotFinalisedForFileName(name: string) {
@@ -263,6 +264,15 @@ export function errUnresolvedImportTreatedAsExternal(source: string, importer: s
 	};
 }
 
+export function errExternalSyntheticExports(source: string, importer: string) {
+	return {
+		code: Errors.EXTERNAL_SYNTHETIC_EXPORTS,
+		importer: relativeId(importer),
+		message: `External '${source}' can not have syntheticNamedExports`,
+		source
+	};
+}
+
 export function errFailedValidation(message: string) {
 	return {
 		code: Errors.VALIDATION_ERROR,

src/utils/transform.ts

@@ -35,6 +35,7 @@ export default function transform(
 	const emittedFiles: EmittedFile[] = [];
 	let customTransformCache = false;
 	let moduleSideEffects: boolean | null = null;
+	let syntheticNamedExports: boolean | null = null;
 	let trackedPluginCache: { cache: PluginCache; used: boolean };
 	let curPlugin: Plugin;
 	const curSource: string = source.code;
@@ -82,6 +83,9 @@ export default function transform(
 			if (typeof result.moduleSideEffects === 'boolean') {
 				moduleSideEffects = result.moduleSideEffects;
 			}
+			if (typeof result.syntheticNamedExports === 'boolean') {
+				syntheticNamedExports = result.syntheticNamedExports;
+			}
 		} else {
 			return code;
 		}
@@ -193,6 +197,7 @@ export default function transform(
 				originalCode,
 				originalSourcemap,
 				sourcemapChain,
+				syntheticNamedExports,
 				transformDependencies
 			};
 		});

test/chunking-form/samples/synthetic-named-exports/_config.js

@@ -0,0 +1,19 @@
+module.exports = {
+	description: 'simple chunking',
+	options: {
+		input: ['main.js'],
+		plugins: [
+			{
+				resolveId(id) {
+					if (id === './dep1.js') {
+						return {
+							id,
+							syntheticNamedExports: true
+						};
+					}
+					return null;
+				}
+			}
+		]
+	}
+};

test/chunking-form/samples/synthetic-named-exports/_expected/amd/main.js

@@ -0,0 +1,14 @@
+define(function () { 'use strict';
+
+  const d = {
+    fn: 42
+  };
+
+  var fn = d.fn;
+
+  var foo = d.foo;
+
+  console.log(fn);
+  console.log(foo);
+
+});

test/chunking-form/samples/synthetic-named-exports/_expected/cjs/main.js

@@ -0,0 +1,12 @@
+'use strict';
+
+const d = {
+  fn: 42
+};
+
+var fn = d.fn;
+
+var foo = d.foo;
+
+console.log(fn);
+console.log(foo);

test/chunking-form/samples/synthetic-named-exports/_expected/es/main.js

@@ -0,0 +1,10 @@
+const d = {
+  fn: 42
+};
+
+var fn = d.fn;
+
+var foo = d.foo;
+
+console.log(fn);
+console.log(foo);