Feat: add syntheticNamedExports

src/Module.ts

@@ -22,9 +22,11 @@ import TemplateLiteral from './ast/nodes/TemplateLiteral';
 import VariableDeclaration from './ast/nodes/VariableDeclaration';
 import ModuleScope from './ast/scopes/ModuleScope';
 import { PathTracker, UNKNOWN_PATH } from './ast/utils/PathTracker';
+import ExportDefaultVariable from './ast/variables/ExportDefaultVariable';
 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';
@@ -39,7 +41,7 @@ import {
 	RollupWarning,
 	TransformModuleJSON
 } from './rollup/types';
-import { error } from './utils/error';
+import { error, Errors } from './utils/error';
 import getCodeFrame from './utils/getCodeFrame';
 import { getOriginalLocation } from './utils/getOriginalLocation';
 import { makeLegal } from './utils/identifierHelpers';
@@ -206,6 +208,7 @@ export default class Module {
 	scope!: ModuleScope;
 	sourcemapChain!: DecodedSourceMapOrMissing[];
 	sources = new Set<string>();
+	syntheticNamedExports: boolean;
 	transformFiles?: EmittedFile[];
 	userChunkNames = new Set<string>();
 	usesTopLevelAwait = false;
@@ -214,19 +217,28 @@ export default class Module {
 	private ast!: Program;
 	private astContext!: AstContext;
 	private context: string;
+	private defaultExport: ExportDefaultVariable | null | undefined = null;
 	private esTreeAst!: ESTree.Program;
 	private graph: Graph;
 	private magicString!: MagicString;
 	private namespaceVariable: NamespaceVariable | null = null;
+	private syntheticExports = new Map<string, SyntheticNamedExport>();
 	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;
 	}
 
@@ -299,6 +311,21 @@ export default class Module {
 		return allExportNames;
 	}
 
+	getDefaultExport() {
+		if (this.defaultExport === null) {
+			this.defaultExport = undefined;
+			this.defaultExport = this.astContext.traceExport('default') as ExportDefaultVariable;
+			if (!this.defaultExport) {
+				error({
+					code: Errors.SYNTHETIC_NAMED_EXPORTS_NEED_DEFAULT,
+					id: this.id,
+					message: `Modules with 'syntheticNamedExports' need a default export.`
+				});
+			}
+		}
+		return this.defaultExport;
+	}
+
 	getDynamicImportExpressions(): (string | Node)[] {
 		return this.dynamicImports.map(({ node }) => {
 			const importArgument = node.source;
@@ -342,7 +369,7 @@ export default class Module {
 
 	getOrCreateNamespace(): NamespaceVariable {
 		if (!this.namespaceVariable) {
-			this.namespaceVariable = new NamespaceVariable(this.astContext);
+			this.namespaceVariable = new NamespaceVariable(this.astContext, this.syntheticNamedExports);
 			this.namespaceVariable.initialise();
 		}
 		return this.namespaceVariable;
@@ -439,9 +466,25 @@ 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 defaultExport = this.getDefaultExport();
+					if (defaultExport) {
+						syntheticExport = new SyntheticNamedExport(this.astContext, name, defaultExport);
+						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 +577,7 @@ export default class Module {
 		originalSourcemap,
 		resolvedIds,
 		sourcemapChain,
+		syntheticNamedExports,
 		transformDependencies,
 		transformFiles
 	}: TransformModuleJSON & {
@@ -551,6 +595,9 @@ export default class Module {
 		if (typeof moduleSideEffects === 'boolean') {
 			this.moduleSideEffects = moduleSideEffects;
 		}
+		if (typeof syntheticNamedExports === 'boolean') {
+			this.syntheticNamedExports = syntheticNamedExports;
+		}
 
 		timeStart('generate ast', 3);
 
@@ -633,6 +680,7 @@ 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,
@@ -243,7 +244,7 @@ export class ModuleLoader {
 					module.id,
 					(module.resolvedIds[source] =
 						module.resolvedIds[source] ||
-						this.handleMissingImports(await this.resolveId(source, module.id), source, module.id))
+						this.handleResolveId(await this.resolveId(source, module.id), source, module.id))
 				)
 			) as Promise<unknown>[]),
 			...module.getDynamicImportExpressions().map((specifier, index) =>
@@ -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 +404,35 @@ export class ModuleLoader {
 			return {
 				external: true,
 				id: source,
-				moduleSideEffects: this.hasModuleSideEffects(source, true)
+				moduleSideEffects: this.hasModuleSideEffects(source, true),
+				syntheticNamedExports: false
+			};
+		}
+		return resolvedId;
+	}
+
+	private handleResolveId(
+		resolvedId: ResolvedId | null,
+		source: string,
+		importer: string
+	): ResolvedId {
+		return this.handleSyntheticExports(
+			this.handleMissingImports(resolvedId, source, importer),
+			source,
+			importer
+		);
+	}
+
+	private handleSyntheticExports(
+		resolvedId: ResolvedId,
+		source: string,
+		importer: string
+	): ResolvedId {
+		if (resolvedId.external && resolvedId.syntheticNamedExports) {
+			this.graph.warn(errExternalSyntheticExports(source, importer));
+			return {
+				...resolvedId,
+				syntheticNamedExports: false
 			};
 		}
 		return resolvedId;
@@ -407,7 +452,7 @@ 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 +465,7 @@ 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 +475,9 @@ 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;
@@ -448,7 +497,8 @@ export class ModuleLoader {
 			moduleSideEffects:
 				typeof moduleSideEffects === 'boolean'
 					? moduleSideEffects
-					: this.hasModuleSideEffects(id, external)
+					: this.hasModuleSideEffects(id, external),
+			syntheticNamedExports
 		};
 	}
 
@@ -478,13 +528,9 @@ export class ModuleLoader {
 		if (resolution == null) {
 			return (module.resolvedIds[specifier] =
 				module.resolvedIds[specifier] ||
-				this.handleMissingImports(
-					await this.resolveId(specifier, module.id),
-					specifier,
-					module.id
-				));
+				this.handleResolveId(await this.resolveId(specifier, module.id), specifier, module.id));
 		}
-		return this.handleMissingImports(
+		return this.handleResolveId(
 			this.normalizeResolveIdResult(resolution, importer, specifier),
 			specifier,
 			importer

src/ast/variables/NamespaceVariable.ts

@@ -15,11 +15,13 @@ export default class NamespaceVariable extends Variable {
 	private containsExternalNamespace = false;
 	private referencedEarly = false;
 	private references: Identifier[] = [];
+	private syntheticNamedExports: boolean;
 
-	constructor(context: AstContext) {
+	constructor(context: AstContext, syntheticNamedExports: boolean) {
 		super(context.getModuleName());
 		this.context = context;
 		this.module = context.module;
+		this.syntheticNamedExports = syntheticNamedExports;
 	}
 
 	addReference(identifier: Identifier) {
@@ -99,10 +101,17 @@ export default class NamespaceVariable extends Variable {
 		}
 
 		const name = this.getName();
+		const defaultExport = this.syntheticNamedExports ? this.module.getDefaultExport() : undefined;
 
-		const callee = options.freeze ? `/*#__PURE__*/Object.freeze` : '';
-		const membersStr = members.join(`,${n}`);
-		let output = `${options.varOrConst} ${name}${_}=${_}${callee}({${n}${membersStr}${n}});`;
+		let output = `{${n}${members.join(`,${n}`)}${n}}`;
+		if (defaultExport) {
+			output = `/*#__PURE__*/Object.assign(${output}, ${defaultExport.getName()})`;
+		}
+		if (options.freeze) {
+			output = `/*#__PURE__*/Object.freeze(${output})`;
+		}
+
+		output = `${options.varOrConst} ${name}${_}=${_}${output};`;
 
 		if (options.format === 'system' && this.exportName) {
 			output += `${n}exports('${this.exportName}',${_}${name});`;

src/ast/variables/SyntheticNamedExport.ts

@@ -0,0 +1,25 @@
+import Module, { AstContext } from '../../Module';
+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;
+		this.setRenderNames(defaultVariable.getName(), name);
+	}
+
+	include(context: InclusionContext) {
+		if (!this.included) {
+			this.included = true;
+			this.context.includeVariable(context, this.defaultVariable);
+		}
+	}
+}

src/ast/variables/Variable.ts

@@ -49,7 +49,7 @@ export default class Variable implements ExpressionEntity {
 
 	getName(): string {
 		const name = this.renderName || this.name;
-		return this.renderBaseName ? `${this.renderBaseName}.${name}` : name;
+		return this.renderBaseName ? `${this.renderBaseName}${getPropertyAccess(name)}` : name;
 	}
 
 	getReturnExpressionWhenCalledAtPath(
@@ -107,3 +107,7 @@ export default class Variable implements ExpressionEntity {
 		return this.name;
 	}
 }
+
+const getPropertyAccess = (name: string) => {
+	return /^(?!\d)[\w$]+$/.test(name) ? `.${name}` : `[${JSON.stringify(name)}]`;
+};