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// This file creates the internal module & binding loaders used by built-in
// modules. In contrast, user land modules are loaded using
// lib/internal/modules/cjs/loader.js (CommonJS Modules) or
// lib/internal/modules/esm/* (ES Modules).
//
// This file is compiled and run by node.cc before bootstrap/node.js
// was called, therefore the loaders are bootstraped before we start to
// actually bootstrap Node.js. It creates the following objects:
//
// C++ binding loaders:
// - process.binding(): the legacy C++ binding loader, accessible from user land
// because it is an object attached to the global process object.
// These C++ bindings are created using NODE_BUILTIN_MODULE_CONTEXT_AWARE()
// and have their nm_flags set to NM_F_BUILTIN. We do not make any guarantees
// about the stability of these bindings, but still have to take care of
// compatibility issues caused by them from time to time.
// - process._linkedBinding(): intended to be used by embedders to add
// additional C++ bindings in their applications. These C++ bindings
// can be created using NODE_MODULE_CONTEXT_AWARE_CPP() with the flag
// NM_F_LINKED.
// - internalBinding(): the private internal C++ binding loader, inaccessible
// from user land unless through `require('internal/test/binding')`.
// These C++ bindings are created using NODE_MODULE_CONTEXT_AWARE_INTERNAL()
// and have their nm_flags set to NM_F_INTERNAL.
//
// Internal JavaScript module loader:
// - NativeModule: a minimal module system used to load the JavaScript core
// modules found in lib/**/*.js and deps/**/*.js. All core modules are
// compiled into the node binary via node_javascript.cc generated by js2c.py,
// so they can be loaded faster without the cost of I/O. This class makes the
// lib/internal/*, deps/internal/* modules and internalBinding() available by
// default to core modules, and lets the core modules require itself via
// require('internal/bootstrap/loaders') even when this file is not written in
// CommonJS style.
//
// Other objects:
// - process.moduleLoadList: an array recording the bindings and the modules
// loaded in the process and the order in which they are loaded.
'use strict';
// This file is compiled as if it's wrapped in a function with arguments
// passed by node::RunBootstrapping()
/* global process, getLinkedBinding, getInternalBinding, primordials */
const {
Error,
Map,
ObjectCreate,
ObjectDefineProperty,
ObjectKeys,
ObjectPrototypeHasOwnProperty,
ReflectGet,
SafeSet,
} = primordials;
// Set up process.moduleLoadList.
const moduleLoadList = [];
ObjectDefineProperty(process, 'moduleLoadList', {
value: moduleLoadList,
configurable: true,
enumerable: true,
writable: false
});
// internalBindingWhitelist contains the name of internalBinding modules
// that are whitelisted for access via process.binding()... This is used
// to provide a transition path for modules that are being moved over to
// internalBinding.
const internalBindingWhitelist = new SafeSet([
'async_wrap',
'buffer',
'cares_wrap',
'config',
'constants',
'contextify',
'crypto',
'fs',
'fs_event_wrap',
'http_parser',
'icu',
'inspector',
'js_stream',
'natives',
'os',
'pipe_wrap',
'process_wrap',
'signal_wrap',
'spawn_sync',
'stream_wrap',
'tcp_wrap',
'tls_wrap',
'tty_wrap',
'udp_wrap',
'url',
'util',
'uv',
'v8',
'zlib'
]);
// Set up process.binding() and process._linkedBinding().
{
const bindingObj = ObjectCreate(null);
process.binding = function binding(module) {
module = String(module);
// Deprecated specific process.binding() modules, but not all, allow
// selective fallback to internalBinding for the deprecated ones.
if (internalBindingWhitelist.has(module)) {
return internalBinding(module);
}
// eslint-disable-next-line no-restricted-syntax
throw new Error(`No such module: ${module}`);
};
process._linkedBinding = function _linkedBinding(module) {
module = String(module);
let mod = bindingObj[module];
if (typeof mod !== 'object')
mod = bindingObj[module] = getLinkedBinding(module);
return mod;
};
}
// Set up internalBinding() in the closure.
let internalBinding;
{
const bindingObj = ObjectCreate(null);
// eslint-disable-next-line no-global-assign
internalBinding = function internalBinding(module) {
let mod = bindingObj[module];
if (typeof mod !== 'object') {
mod = bindingObj[module] = getInternalBinding(module);
moduleLoadList.push(`Internal Binding ${module}`);
}
return mod;
};
}
const loaderId = 'internal/bootstrap/loaders';
const {
moduleIds,
compileFunction
} = internalBinding('native_module');
const getOwn = (target, property, receiver) => {
return ObjectPrototypeHasOwnProperty(target, property) ?
ReflectGet(target, property, receiver) :
undefined;
};
/**
* An internal abstraction for the built-in JavaScript modules of Node.js.
* Be careful not to expose this to user land unless --expose-internals is
* used, in which case there is no compatibility guarantee about this class.
*/
class NativeModule {
/**
* A map from the module IDs to the module instances.
* @type {Map<string, NativeModule>}
*/
static map = new Map(moduleIds.map((id) => [id, new NativeModule(id)]));
constructor(id) {
this.filename = `${id}.js`;
this.id = id;
this.canBeRequiredByUsers = !id.startsWith('internal/');
// The CJS exports object of the module.
this.exports = {};
// States used to work around circular dependencies.
this.loaded = false;
this.loading = false;
// The following properties are used by the ESM implementation and only
// initialized when the native module is loaded by users.
/**
* The C++ ModuleWrap binding used to interface with the ESM implementation.
* @type {ModuleWrap|undefined}
*/
this.module = undefined;
/**
* Exported names for the ESM imports.
* @type {string[]|undefined}
*/
this.exportKeys = undefined;
}
// To be called during pre-execution when --expose-internals is on.
// Enables the user-land module loader to access internal modules.
static exposeInternals() {
for (const [id, mod] of NativeModule.map) {
// Do not expose this to user land even with --expose-internals.
if (id !== loaderId) {
mod.canBeRequiredByUsers = true;
}
}
}
static exists(id) {
return NativeModule.map.has(id);
}
static canBeRequiredByUsers(id) {
const mod = NativeModule.map.get(id);
return mod && mod.canBeRequiredByUsers;
}
// Used by user-land module loaders to compile and load builtins.
compileForPublicLoader() {
if (!this.canBeRequiredByUsers) {
// No code because this is an assertion against bugs
// eslint-disable-next-line no-restricted-syntax
throw new Error(`Should not compile ${this.id} for public use`);
}
this.compileForInternalLoader();
if (!this.exportKeys) {
// When using --expose-internals, we do not want to reflect the named
// exports from core modules as this can trigger unnecessary getters.
const internal = this.id.startsWith('internal/');
this.exportKeys = internal ? [] : ObjectKeys(this.exports);
}
this.getESMFacade();
this.syncExports();
return this.exports;
}
getESMFacade() {
if (this.module) return this.module;
const { ModuleWrap } = internalBinding('module_wrap');
const url = `node:${this.id}`;
const nativeModule = this;
this.module = new ModuleWrap(
url, undefined, [...this.exportKeys, 'default'],
function() {
nativeModule.syncExports();
this.setExport('default', nativeModule.exports);
});
// Ensure immediate sync execution to capture exports now
this.module.instantiate();
this.module.evaluate(-1, false);
return this.module;
}
// Provide named exports for all builtin libraries so that the libraries
// may be imported in a nicer way for ESM users. The default export is left
// as the entire namespace (module.exports) and updates when this function is
// called so that APMs and other behavior are supported.
syncExports() {
const names = this.exportKeys;
if (this.module) {
for (let i = 0; i < names.length; i++) {
const exportName = names[i];
if (exportName === 'default') continue;
this.module.setExport(exportName,
getOwn(this.exports, exportName, this.exports));
}
}
}
compileForInternalLoader() {
if (this.loaded || this.loading) {
return this.exports;
}
const id = this.id;
this.loading = true;
try {
const requireFn = this.id.startsWith('internal/deps/') ?
requireWithFallbackInDeps : nativeModuleRequire;
const fn = compileFunction(id);
fn(this.exports, requireFn, this, process, internalBinding, primordials);
this.loaded = true;
} finally {
this.loading = false;
}
moduleLoadList.push(`NativeModule ${id}`);
return this.exports;
}
}
// Think of this as module.exports in this file even though it is not
// written in CommonJS style.
const loaderExports = {
internalBinding,
NativeModule,
require: nativeModuleRequire
};
function nativeModuleRequire(id) {
if (id === loaderId) {
return loaderExports;
}
const mod = NativeModule.map.get(id);
// Can't load the internal errors module from here, have to use a raw error.
// eslint-disable-next-line no-restricted-syntax
if (!mod) throw new TypeError(`Missing internal module '${id}'`);
return mod.compileForInternalLoader();
}
// Allow internal modules from dependencies to require
// other modules from dependencies by providing fallbacks.
function requireWithFallbackInDeps(request) {
if (!NativeModule.map.has(request)) {
request = `internal/deps/${request}`;
}
return nativeModuleRequire(request);
}
// Pass the exports back to C++ land for C++ internals to use.
return loaderExports;
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