ModuleLoader.ts

import * as acorn from 'acorn';
import ExternalModule from './ExternalModule';
import Graph from './Graph';
import Module from './Module';
import {
	GetManualChunk,
	HasModuleSideEffects,
	NormalizedInputOptions,
	ResolvedId,
	ResolveIdResult,
	SourceDescription
} from './rollup/types';
import {
	errBadLoader,
	errCannotAssignModuleToChunk,
	errEntryCannotBeExternal,
	errExternalSyntheticExports,
	errInternalIdCannotBeExternal,
	errNamespaceConflict,
	error,
	errUnresolvedEntry,
	errUnresolvedImport,
	errUnresolvedImportTreatedAsExternal
} from './utils/error';
import { readFile } from './utils/fs';
import { isRelative, resolve } from './utils/path';
import { PluginDriver } from './utils/PluginDriver';
import relativeId from './utils/relativeId';
import { resolveId } from './utils/resolveId';
import { timeEnd, timeStart } from './utils/timers';
import transform from './utils/transform';

export interface UnresolvedModule {
	fileName: string | null;
	id: string;
	importer: string | undefined;
	name: string | null;
}

export class ModuleLoader {
	private readonly hasModuleSideEffects: HasModuleSideEffects;
	private readonly indexedEntryModules: { index: number; module: Module }[] = [];
	private latestLoadModulesPromise: Promise<any> = Promise.resolve();
	private readonly manualChunkModules: Record<string, Module[]> = {};
	private nextEntryModuleIndex = 0;

	constructor(
		private readonly graph: Graph,
		private readonly modulesById: Map<string, Module | ExternalModule>,
		private readonly options: NormalizedInputOptions,
		private readonly pluginDriver: PluginDriver
	) {
		this.hasModuleSideEffects = options.treeshake
			? options.treeshake.moduleSideEffects
			: () => true;
	}

	async addEntryModules(
		unresolvedEntryModules: UnresolvedModule[],
		isUserDefined: boolean
	): Promise<{
		entryModules: Module[];
		manualChunkModulesByAlias: Record<string, Module[]>;
		newEntryModules: Module[];
	}> {
		const firstEntryModuleIndex = this.nextEntryModuleIndex;
		this.nextEntryModuleIndex += unresolvedEntryModules.length;
		const loadNewEntryModulesPromise = Promise.all(
			unresolvedEntryModules.map(
				({ id, importer }): Promise<Module> => this.loadEntryModule(id, true, importer)
			)
		).then(entryModules => {
			let moduleIndex = firstEntryModuleIndex;
			for (let index = 0; index < entryModules.length; index++) {
				const { fileName, name } = unresolvedEntryModules[index];
				const entryModule = entryModules[index];
				entryModule.isUserDefinedEntryPoint = entryModule.isUserDefinedEntryPoint || isUserDefined;
				if (fileName !== null) {
					entryModule.chunkFileNames.add(fileName);
				} else if (name !== null) {
					if (entryModule.chunkName === null) {
						entryModule.chunkName = name;
					}
					if (isUserDefined) {
						entryModule.userChunkNames.add(name);
					}
				}
				const existingIndexedModule = this.indexedEntryModules.find(
					indexedModule => indexedModule.module.id === entryModule.id
				);
				if (!existingIndexedModule) {
					this.indexedEntryModules.push({ module: entryModule, index: moduleIndex });
				} else {
					existingIndexedModule.index = Math.min(existingIndexedModule.index, moduleIndex);
				}
				moduleIndex++;
			}
			this.indexedEntryModules.sort(({ index: indexA }, { index: indexB }) =>
				indexA > indexB ? 1 : -1
			);
			return entryModules;
		});
		const newEntryModules = await this.awaitLoadModulesPromise(loadNewEntryModulesPromise);
		return {
			entryModules: this.indexedEntryModules.map(({ module }) => module),
			manualChunkModulesByAlias: this.manualChunkModules,
			newEntryModules
		};
	}

	addManualChunks(manualChunks: Record<string, string[]>): Promise<void> {
		const unresolvedManualChunks: { alias: string; id: string }[] = [];
		for (const alias of Object.keys(manualChunks)) {
			const manualChunkIds = manualChunks[alias];
			for (const id of manualChunkIds) {
				unresolvedManualChunks.push({ id, alias });
			}
		}
		return this.awaitLoadModulesPromise(
			Promise.all(
				unresolvedManualChunks.map(({ id }) => this.loadEntryModule(id, false, undefined))
			).then(manualChunkModules => {
				for (let index = 0; index < manualChunkModules.length; index++) {
					this.addModuleToManualChunk(
						unresolvedManualChunks[index].alias,
						manualChunkModules[index]
					);
				}
			})
		);
	}

	assignManualChunks(getManualChunk: GetManualChunk) {
		const manualChunksApi = {
			getModuleIds: () => this.modulesById.keys(),
			getModuleInfo: this.graph.getModuleInfo
		};
		for (const module of this.modulesById.values()) {
			if (module instanceof Module) {
				const manualChunkAlias = getManualChunk(module.id, manualChunksApi);
				if (typeof manualChunkAlias === 'string') {
					this.addModuleToManualChunk(manualChunkAlias, module);
				}
			}
		}
	}

	async resolveId(
		source: string,
		importer: string | undefined,
		skip: number | null = null
	): Promise<ResolvedId | null> {
		return this.normalizeResolveIdResult(
			this.options.external(source, importer, false)
				? false
				: await resolveId(source, importer, this.options.preserveSymlinks, this.pluginDriver, skip),

			importer,
			source
		);
	}

	private async addModuleSource(id: string, importer: string | undefined, module: Module) {
		timeStart('load modules', 3);
		let source: string | SourceDescription;
		try {
			source = (await this.pluginDriver.hookFirst('load', [id])) ?? (await readFile(id));
		} catch (err) {
			timeEnd('load modules', 3);
			let msg = `Could not load ${id}`;
			if (importer) msg += ` (imported by ${relativeId(importer)})`;
			msg += `: ${err.message}`;
			err.message = msg;
			throw err;
		}
		timeEnd('load modules', 3);
		const sourceDescription =
			typeof source === 'string'
				? { code: source }
				: typeof source === 'object' && typeof source.code === 'string'
				? source
				: error(errBadLoader(id));
		const cachedModule = this.graph.cachedModules.get(id);
		if (
			cachedModule &&
			!cachedModule.customTransformCache &&
			cachedModule.originalCode === sourceDescription.code
		) {
			if (cachedModule.transformFiles) {
				for (const emittedFile of cachedModule.transformFiles)
					this.pluginDriver.emitFile(emittedFile);
			}
			module.setSource(cachedModule);
		} else {
			if (typeof sourceDescription.moduleSideEffects === 'boolean') {
				module.moduleSideEffects = sourceDescription.moduleSideEffects;
			}
			if (typeof sourceDescription.syntheticNamedExports === 'boolean') {
				module.syntheticNamedExports = sourceDescription.syntheticNamedExports;
			}
			module.setSource(
				await transform(sourceDescription, module, this.pluginDriver, this.options.onwarn)
			);
		}
	}

	private addModuleToManualChunk(alias: string, module: Module) {
		if (module.manualChunkAlias !== null && module.manualChunkAlias !== alias) {
			return error(errCannotAssignModuleToChunk(module.id, alias, module.manualChunkAlias));
		}
		module.manualChunkAlias = alias;
		if (!this.manualChunkModules[alias]) {
			this.manualChunkModules[alias] = [];
		}
		this.manualChunkModules[alias].push(module);
	}

	private async awaitLoadModulesPromise<T>(loadNewModulesPromise: Promise<T>): Promise<T> {
		this.latestLoadModulesPromise = Promise.all([
			loadNewModulesPromise,
			this.latestLoadModulesPromise
		]);

		const getCombinedPromise = async (): Promise<void> => {
			const startingPromise = this.latestLoadModulesPromise;
			await startingPromise;
			if (this.latestLoadModulesPromise !== startingPromise) {
				return getCombinedPromise();
			}
		};
		await getCombinedPromise();
		return await loadNewModulesPromise;
	}

	private fetchAllDependencies(module: Module): Promise<unknown> {
		return Promise.all([
			...[...module.sources].map(async source => {
				const resolution = await this.fetchResolvedDependency(
					source,
					module.id,
					(module.resolvedIds[source] =
						module.resolvedIds[source] ||
						this.handleResolveId(await this.resolveId(source, module.id), source, module.id))
				);
				resolution.importers.push(module.id);
				resolution.importers.sort();
			}),
			...module.dynamicImports.map(async dynamicImport => {
				const resolvedId = await this.resolveDynamicImport(
					module,
					dynamicImport.argument,
					module.id
				);
				if (resolvedId === null) return;
				if (typeof resolvedId === 'string') {
					dynamicImport.resolution = resolvedId;
				} else {
					const resolution = (dynamicImport.resolution = await this.fetchResolvedDependency(
						relativeId(resolvedId.id),
						module.id,
						resolvedId
					));
					resolution.dynamicImporters.push(module.id);
					resolution.dynamicImporters.sort();
				}
			})
		]);
	}

	private async fetchModule(
		id: string,
		importer: string | undefined,
		moduleSideEffects: boolean,
		syntheticNamedExports: boolean,
		isEntry: boolean
	): Promise<Module> {
		const existingModule = this.modulesById.get(id);
		if (existingModule instanceof Module) {
			existingModule.isEntryPoint = existingModule.isEntryPoint || isEntry;
			return Promise.resolve(existingModule);
		}

		const module: Module = new Module(
			this.graph,
			id,
			this.options,
			moduleSideEffects,
			syntheticNamedExports,
			isEntry
		);
		this.modulesById.set(id, module);
		this.graph.watchFiles[id] = true;
		await this.addModuleSource(id, importer, module);
		await this.fetchAllDependencies(module);

		for (const name in module.exports) {
			if (name !== 'default') {
				module.exportsAll[name] = module.id;
			}
		}
		for (const source of module.exportAllSources) {
			const id = module.resolvedIds[source].id;
			const exportAllModule = this.modulesById.get(id);
			if (exportAllModule instanceof ExternalModule) continue;
			for (const name in exportAllModule!.exportsAll) {
				if (name in module.exportsAll) {
					this.options.onwarn(errNamespaceConflict(name, module, exportAllModule!));
				} else {
					module.exportsAll[name] = exportAllModule!.exportsAll[name];
				}
			}
		}
		return module;
	}

	private fetchResolvedDependency(
		source: string,
		importer: string,
		resolvedId: ResolvedId
	): Promise<Module | ExternalModule> {
		if (resolvedId.external) {
			if (!this.modulesById.has(resolvedId.id)) {
				this.modulesById.set(
					resolvedId.id,
					new ExternalModule(this.options, resolvedId.id, resolvedId.moduleSideEffects)
				);
			}

			const externalModule = this.modulesById.get(resolvedId.id);
			if (!(externalModule instanceof ExternalModule)) {
				return error(errInternalIdCannotBeExternal(source, importer));
			}
			return Promise.resolve(externalModule);
		} else {
			return this.fetchModule(
				resolvedId.id,
				importer,
				resolvedId.moduleSideEffects,
				resolvedId.syntheticNamedExports,
				false
			);
		}
	}

	private handleResolveId(
		resolvedId: ResolvedId | null,
		source: string,
		importer: string
	): ResolvedId {
		if (resolvedId === null) {
			if (isRelative(source)) {
				return error(errUnresolvedImport(source, importer));
			}
			this.options.onwarn(errUnresolvedImportTreatedAsExternal(source, importer));
			return {
				external: true,
				id: source,
				moduleSideEffects: this.hasModuleSideEffects(source, true),
				syntheticNamedExports: false
			};
		} else {
			if (resolvedId.external && resolvedId.syntheticNamedExports) {
				this.options.onwarn(errExternalSyntheticExports(source, importer));
			}
		}
		return resolvedId;
	}

	private async loadEntryModule(
		unresolvedId: string,
		isEntry: boolean,
		importer: string | undefined
	): Promise<Module> {
		const resolveIdResult = await resolveId(
			unresolvedId,
			importer,
			this.options.preserveSymlinks,
			this.pluginDriver,
			null
		);
		if (
			resolveIdResult === false ||
			(resolveIdResult && typeof resolveIdResult === 'object' && resolveIdResult.external)
		) {
			return error(errEntryCannotBeExternal(unresolvedId));
		}
		const id =
			resolveIdResult && typeof resolveIdResult === 'object' ? resolveIdResult.id : resolveIdResult;

		if (typeof id === 'string') {
			return this.fetchModule(id, undefined, true, false, isEntry);
		}
		return error(errUnresolvedEntry(unresolvedId));
	}

	private normalizeResolveIdResult(
		resolveIdResult: ResolveIdResult,
		importer: string | undefined,
		source: string
	): ResolvedId | null {
		let id = '';
		let external = false;
		let moduleSideEffects = null;
		let syntheticNamedExports = false;
		if (resolveIdResult) {
			if (typeof resolveIdResult === 'object') {
				id = resolveIdResult.id;
				if (resolveIdResult.external) {
					external = true;
				}
				if (typeof resolveIdResult.moduleSideEffects === 'boolean') {
					moduleSideEffects = resolveIdResult.moduleSideEffects;
				}
				if (typeof resolveIdResult.syntheticNamedExports === 'boolean') {
					syntheticNamedExports = resolveIdResult.syntheticNamedExports;
				}
			} else {
				if (this.options.external(resolveIdResult, importer, true)) {
					external = true;
				}
				id = external ? normalizeRelativeExternalId(resolveIdResult, importer) : resolveIdResult;
			}
		} else {
			id = normalizeRelativeExternalId(source, importer);
			if (resolveIdResult !== false && !this.options.external(id, importer, true)) {
				return null;
			}
			external = true;
		}
		return {
			external,
			id,
			moduleSideEffects:
				typeof moduleSideEffects === 'boolean'
					? moduleSideEffects
					: this.hasModuleSideEffects(id, external),
			syntheticNamedExports
		};
	}

	private async resolveDynamicImport(
		module: Module,
		specifier: string | acorn.Node,
		importer: string
	): Promise<ResolvedId | string | null> {
		// TODO we only should expose the acorn AST here
		const resolution = await this.pluginDriver.hookFirst('resolveDynamicImport', [
			specifier,
			importer
		]);
		if (typeof specifier !== 'string') {
			if (typeof resolution === 'string') {
				return resolution;
			}
			if (!resolution) {
				return null;
			}
			return {
				external: false,
				moduleSideEffects: true,
				...resolution
			} as ResolvedId;
		}
		if (resolution == null) {
			return (module.resolvedIds[specifier] =
				module.resolvedIds[specifier] ||
				this.handleResolveId(await this.resolveId(specifier, module.id), specifier, module.id));
		}
		return this.handleResolveId(
			this.normalizeResolveIdResult(resolution, importer, specifier),
			specifier,
			importer
		);
	}
}

function normalizeRelativeExternalId(source: string, importer: string | undefined): string {
	return isRelative(source)
		? importer
			? resolve(importer, '..', source)
			: resolve(source)
		: source;
}