node.js

// Hello, and welcome to hacking node.js!
//
// This file is invoked by node::LoadEnvironment in src/node.cc, and is
// responsible for bootstrapping the node.js core. As special caution is given
// to the performance of the startup process, many dependencies are invoked
// lazily.
//
// Before this file is run, lib/internal/bootstrap/loaders.js gets run first
// to bootstrap the internal binding and module loaders, including
// process.binding(), process._linkedBinding(), internalBinding() and
// NativeModule. And then { internalBinding, NativeModule } will be passed
// into this bootstrapper to bootstrap Node.js core.
'use strict';

(function bootstrapNodeJSCore(process,
                              // bootstrapper properties... destructured to
                              // avoid retaining a reference to the bootstrap
                              // object.
                              { _setupTraceCategoryState,
                                _setupNextTick,
                                _setupPromises, _chdir, _cpuUsage,
                                _hrtime, _hrtimeBigInt,
                                _memoryUsage, _rawDebug,
                                _umask, _initgroups, _setegid, _seteuid,
                                _setgid, _setuid, _setgroups,
                                _shouldAbortOnUncaughtToggle },
                              { internalBinding, NativeModule },
                              triggerFatalException) {
  const exceptionHandlerState = { captureFn: null };
  const isMainThread = internalBinding('worker').threadId === 0;

  function startup() {
    setupTraceCategoryState();

    setupProcessObject();

    // Do this good and early, since it handles errors.
    setupProcessFatal();

    setupProcessICUVersions();

    setupGlobalVariables();

    // Bootstrappers for all threads, including worker threads and main thread
    const perThreadSetup = NativeModule.require('internal/process/per_thread');
    // Bootstrappers for the main thread only
    let mainThreadSetup;
    // Bootstrappers for the worker threads only
    let workerThreadSetup;
    if (isMainThread) {
      mainThreadSetup = NativeModule.require(
        'internal/process/main_thread_only'
      );
    } else {
      workerThreadSetup = NativeModule.require(
        'internal/process/worker_thread_only'
      );
    }

    perThreadSetup.setupAssert();
    perThreadSetup.setupConfig(NativeModule._source);

    if (isMainThread) {
      mainThreadSetup.setupSignalHandlers(internalBinding);
    }

    perThreadSetup.setupUncaughtExceptionCapture(exceptionHandlerState,
                                                 _shouldAbortOnUncaughtToggle);

    NativeModule.require('internal/process/warning').setup();
    NativeModule.require('internal/process/next_tick').setup(_setupNextTick,
                                                             _setupPromises);

    if (isMainThread) {
      mainThreadSetup.setupStdio();
      mainThreadSetup.setupProcessMethods(
        _chdir, _umask, _initgroups, _setegid, _seteuid,
        _setgid, _setuid, _setgroups
      );
    } else {
      workerThreadSetup.setupStdio();
    }

    const perf = internalBinding('performance');
    const {
      NODE_PERFORMANCE_MILESTONE_BOOTSTRAP_COMPLETE,
    } = perf.constants;

    perThreadSetup.setupRawDebug(_rawDebug);
    perThreadSetup.setupHrtime(_hrtime, _hrtimeBigInt);
    perThreadSetup.setupCpuUsage(_cpuUsage);
    perThreadSetup.setupMemoryUsage(_memoryUsage);
    perThreadSetup.setupKillAndExit();

    if (global.__coverage__)
      NativeModule.require('internal/process/write-coverage').setup();

    if (process.env.NODE_V8_COVERAGE) {
      NativeModule.require('internal/process/coverage').setupExitHooks();
    }

    if (process.config.variables.v8_enable_inspector) {
      NativeModule.require('internal/inspector_async_hook').setup();
    }

    const { getOptionValue } = NativeModule.require('internal/options');

    if (getOptionValue('--help')) {
      NativeModule.require('internal/print_help').print(process.stdout);
      return;
    }

    if (getOptionValue('--completion-bash')) {
      NativeModule.require('internal/bash_completion').print(process.stdout);
      return;
    }

    if (isMainThread) {
      mainThreadSetup.setupChildProcessIpcChannel();
    }

    const browserGlobals = !process._noBrowserGlobals;
    if (browserGlobals) {
      // we are setting this here to forward it to the inspector later
      perThreadSetup.originalConsole = global.console;
      setupGlobalTimeouts();
      setupGlobalConsole();
      setupGlobalURL();
      setupGlobalEncoding();
      setupQueueMicrotask();
    }

    if (getOptionValue('--experimental-worker')) {
      setupDOMException();
    }

    // On OpenBSD process.execPath will be relative unless we
    // get the full path before process.execPath is used.
    if (process.platform === 'openbsd') {
      const { realpathSync } = NativeModule.require('fs');
      process.execPath = realpathSync.native(process.execPath);
    }

    Object.defineProperty(process, 'argv0', {
      enumerable: true,
      configurable: false,
      value: process.argv[0]
    });
    process.argv[0] = process.execPath;

    // Handle `--debug*` deprecation and invalidation.
    if (process._invalidDebug) {
      process.emitWarning(
        '`node --debug` and `node --debug-brk` are invalid. ' +
        'Please use `node --inspect` or `node --inspect-brk` instead.',
        'DeprecationWarning', 'DEP0062', startup, true);
      process.exit(9);
    } else if (process._deprecatedDebugBrk) {
      process.emitWarning(
        '`node --inspect --debug-brk` is deprecated. ' +
        'Please use `node --inspect-brk` instead.',
        'DeprecationWarning', 'DEP0062', startup, true);
    }

    const experimentalModules = getOptionValue('--experimental-modules');
    const experimentalVMModules = getOptionValue('--experimental-vm-modules');
    if (experimentalModules || experimentalVMModules) {
      if (experimentalModules) {
        process.emitWarning(
          'The ESM module loader is experimental.',
          'ExperimentalWarning', undefined);
      }
      NativeModule.require('internal/process/esm_loader').setup();
    }

    const { deprecate } = NativeModule.require('internal/util');
    {
      // Install legacy getters on the `util` binding for typechecking.
      // TODO(addaleax): Turn into a full runtime deprecation.
      const { pendingDeprecation } = process.binding('config');
      const utilBinding = internalBinding('util');
      const types = internalBinding('types');
      for (const name of [
        'isArrayBuffer', 'isArrayBufferView', 'isAsyncFunction',
        'isDataView', 'isDate', 'isExternal', 'isMap', 'isMapIterator',
        'isNativeError', 'isPromise', 'isRegExp', 'isSet', 'isSetIterator',
        'isTypedArray', 'isUint8Array', 'isAnyArrayBuffer'
      ]) {
        utilBinding[name] = pendingDeprecation ?
          deprecate(types[name],
                    'Accessing native typechecking bindings of Node ' +
                    'directly is deprecated. ' +
                    `Please use \`util.types.${name}\` instead.`,
                    'DEP0103') :
          types[name];
      }
    }

    // TODO(jasnell): The following have been globals since around 2012.
    // That's just silly. The underlying perfctr support has been removed
    // so these are now deprecated non-ops that can be removed after one
    // major release cycle.
    if (process.platform === 'win32') {
      function noop() {}
      const names = [
        'NET_SERVER_CONNECTION',
        'NET_SERVER_CONNECTION_CLOSE',
        'HTTP_SERVER_REQUEST',
        'HTTP_SERVER_RESPONSE',
        'HTTP_CLIENT_REQUEST',
        'HTTP_CLIENT_RESPONSE'
      ];
      for (var n = 0; n < names.length; n++) {
        Object.defineProperty(global, `COUNTER_${names[n]}`, {
          configurable: true,
          enumerable: false,
          value: deprecate(noop,
                           `COUNTER_${names[n]}() is deprecated.`,
                           'DEP0120')
        });
      }
    }

    perf.markMilestone(NODE_PERFORMANCE_MILESTONE_BOOTSTRAP_COMPLETE);

    perThreadSetup.setupAllowedFlags();

    startExecution();
  }

  // There are various modes that Node can run in. The most common two
  // are running from a script and running the REPL - but there are a few
  // others like the debugger or running --eval arguments. Here we decide
  // which mode we run in.
  function startExecution() {
    // This means we are in a Worker context, and any script execution
    // will be directed by the worker module.
    if (internalBinding('worker').getEnvMessagePort() !== undefined) {
      NativeModule.require('internal/worker').setupChild(evalScript);
      return;
    }

    // To allow people to extend Node in different ways, this hook allows
    // one to drop a file lib/_third_party_main.js into the build
    // directory which will be executed instead of Node's normal loading.
    if (NativeModule.exists('_third_party_main')) {
      process.nextTick(() => {
        NativeModule.require('_third_party_main');
      });
      return;
    }

    // `node inspect ...` or `node debug ...`
    if (process.argv[1] === 'inspect' || process.argv[1] === 'debug') {
      if (process.argv[1] === 'debug') {
        process.emitWarning(
          '`node debug` is deprecated. Please use `node inspect` instead.',
          'DeprecationWarning', 'DEP0068');
      }

      // Start the debugger agent.
      process.nextTick(() => {
        NativeModule.require('internal/deps/node-inspect/lib/_inspect').start();
      });
      return;
    }

    // `node --prof-process`
    // TODO(joyeecheung): use internal/options instead of process.profProcess
    if (process.profProcess) {
      NativeModule.require('internal/v8_prof_processor');
      return;
    }

    // There is user code to be run.
    prepareUserCodeExecution();
    executeUserCode();
  }

  function prepareUserCodeExecution() {
    // If this is a worker in cluster mode, start up the communication
    // channel. This needs to be done before any user code gets executed
    // (including preload modules).
    if (process.argv[1] && process.env.NODE_UNIQUE_ID) {
      const cluster = NativeModule.require('cluster');
      cluster._setupWorker();
      // Make sure it's not accidentally inherited by child processes.
      delete process.env.NODE_UNIQUE_ID;
    }

    // For user code, we preload modules if `-r` is passed
    // TODO(joyeecheung): use internal/options instead of
    // process._preload_modules
    if (process._preload_modules) {
      const {
        _preloadModules
      } = NativeModule.require('internal/modules/cjs/loader');
      _preloadModules(process._preload_modules);
    }
  }

  function executeUserCode() {
    // User passed `-e` or `--eval` arguments to Node without `-i` or
    // `--interactive`.
    // Note that the name `forceRepl` is merely an alias of `interactive`
    // in code.
    // TODO(joyeecheung): use internal/options instead of
    // process._eval/process._forceRepl
    if (process._eval != null && !process._forceRepl) {
      const {
        addBuiltinLibsToObject
      } = NativeModule.require('internal/modules/cjs/helpers');
      addBuiltinLibsToObject(global);
      evalScript('[eval]', wrapForBreakOnFirstLine(process._eval));
      return;
    }

    // If the first argument is a file name, run it as a main script
    if (process.argv[1] && process.argv[1] !== '-') {
      // Expand process.argv[1] into a full path.
      const path = NativeModule.require('path');
      process.argv[1] = path.resolve(process.argv[1]);

      const CJSModule = NativeModule.require('internal/modules/cjs/loader');

      // If user passed `-c` or `--check` arguments to Node, check its syntax
      // instead of actually running the file.
      // TODO(joyeecheung): use internal/options instead of
      // process._syntax_check_only
      if (process._syntax_check_only != null) {
        const fs = NativeModule.require('fs');
        // Read the source.
        const filename = CJSModule._resolveFilename(process.argv[1]);
        const source = fs.readFileSync(filename, 'utf-8');
        checkScriptSyntax(source, filename);
        process.exit(0);
      }

      // Note: this actually tries to run the module as a ESM first if
      // --experimental-modules is on.
      // TODO(joyeecheung): can we move that logic to here? Note that this
      // is an undocumented method available via `require('module').runMain`
      CJSModule.runMain();
      return;
    }

    // Create the REPL if `-i` or `--interactive` is passed, or if
    // stdin is a TTY.
    // Note that the name `forceRepl` is merely an alias of `interactive`
    // in code.
    if (process._forceRepl || NativeModule.require('tty').isatty(0)) {
      const cliRepl = NativeModule.require('internal/repl');
      cliRepl.createInternalRepl(process.env, (err, repl) => {
        if (err) {
          throw err;
        }
        repl.on('exit', () => {
          if (repl._flushing) {
            repl.pause();
            return repl.once('flushHistory', () => {
              process.exit();
            });
          }
          process.exit();
        });
      });

      // User passed '-e' or '--eval' along with `-i` or `--interactive`
      if (process._eval != null) {
        evalScript('[eval]', wrapForBreakOnFirstLine(process._eval));
      }
      return;
    }

    // Stdin is not a TTY, we will read it and execute it.
    readAndExecuteStdin();
  }

  function readAndExecuteStdin() {
    process.stdin.setEncoding('utf8');

    let code = '';
    process.stdin.on('data', (d) => {
      code += d;
    });

    process.stdin.on('end', () => {
      if (process._syntax_check_only != null) {
        checkScriptSyntax(code, '[stdin]');
      } else {
        process._eval = code;
        evalScript('[stdin]', wrapForBreakOnFirstLine(process._eval));
      }
    });
  }

  function setupTraceCategoryState() {
    const { traceCategoryState } = internalBinding('trace_events');
    const kCategoryAsyncHooks = 0;
    let traceEventsAsyncHook;

    function toggleTraceCategoryState() {
      // Dynamically enable/disable the traceEventsAsyncHook
      const asyncHooksEnabled = !!traceCategoryState[kCategoryAsyncHooks];

      if (asyncHooksEnabled) {
        // Lazy load internal/trace_events_async_hooks only if the async_hooks
        // trace event category is enabled.
        if (!traceEventsAsyncHook) {
          traceEventsAsyncHook =
            NativeModule.require('internal/trace_events_async_hooks');
        }
        traceEventsAsyncHook.enable();
      } else if (traceEventsAsyncHook) {
        traceEventsAsyncHook.disable();
      }
    }

    toggleTraceCategoryState();
    _setupTraceCategoryState(toggleTraceCategoryState);
  }

  function setupProcessObject() {
    const EventEmitter = NativeModule.require('events');
    const origProcProto = Object.getPrototypeOf(process);
    Object.setPrototypeOf(origProcProto, EventEmitter.prototype);
    EventEmitter.call(process);
  }

  function setupGlobalVariables() {
    Object.defineProperty(global, Symbol.toStringTag, {
      value: 'global',
      writable: false,
      enumerable: false,
      configurable: true
    });
    global.process = process;
    const util = NativeModule.require('util');

    function makeGetter(name) {
      return util.deprecate(function() {
        return this;
      }, `'${name}' is deprecated, use 'global'`, 'DEP0016');
    }

    function makeSetter(name) {
      return util.deprecate(function(value) {
        Object.defineProperty(this, name, {
          configurable: true,
          writable: true,
          enumerable: true,
          value: value
        });
      }, `'${name}' is deprecated, use 'global'`, 'DEP0016');
    }

    Object.defineProperties(global, {
      GLOBAL: {
        configurable: true,
        get: makeGetter('GLOBAL'),
        set: makeSetter('GLOBAL')
      },
      root: {
        configurable: true,
        get: makeGetter('root'),
        set: makeSetter('root')
      }
    });

    // This, as side effect, removes `setupBufferJS` from the buffer binding,
    // and exposes it on `internal/buffer`.
    NativeModule.require('internal/buffer');

    global.Buffer = NativeModule.require('buffer').Buffer;
    process.domain = null;
    process._exiting = false;
  }

  function setupGlobalTimeouts() {
    const timers = NativeModule.require('timers');
    global.clearImmediate = timers.clearImmediate;
    global.clearInterval = timers.clearInterval;
    global.clearTimeout = timers.clearTimeout;
    global.setImmediate = timers.setImmediate;
    global.setInterval = timers.setInterval;
    global.setTimeout = timers.setTimeout;
  }

  function setupGlobalConsole() {
    const originalConsole = global.console;
    // Setup Node.js global.console.
    const wrappedConsole = NativeModule.require('console');
    Object.defineProperty(global, 'console', {
      configurable: true,
      enumerable: false,
      value: wrappedConsole,
      writable: true
    });
    setupInspector(originalConsole, wrappedConsole);
  }

  function setupGlobalURL() {
    const { URL, URLSearchParams } = NativeModule.require('internal/url');
    Object.defineProperties(global, {
      URL: {
        value: URL,
        writable: true,
        configurable: true,
        enumerable: false
      },
      URLSearchParams: {
        value: URLSearchParams,
        writable: true,
        configurable: true,
        enumerable: false
      }
    });
  }

  function setupGlobalEncoding() {
    const { TextEncoder, TextDecoder } = NativeModule.require('util');
    Object.defineProperties(global, {
      TextEncoder: {
        value: TextEncoder,
        writable: true,
        configurable: true,
        enumerable: false
      },
      TextDecoder: {
        value: TextDecoder,
        writable: true,
        configurable: true,
        enumerable: false
      }
    });
  }

  function setupQueueMicrotask() {
    Object.defineProperty(global, 'queueMicrotask', {
      get: () => {
        process.emitWarning('queueMicrotask() is experimental.',
                            'ExperimentalWarning');
        const { setupQueueMicrotask } =
          NativeModule.require('internal/queue_microtask');
        const queueMicrotask = setupQueueMicrotask(triggerFatalException);
        Object.defineProperty(global, 'queueMicrotask', {
          value: queueMicrotask,
          writable: true,
          enumerable: false,
          configurable: true,
        });
        return queueMicrotask;
      },
      set: (v) => {
        Object.defineProperty(global, 'queueMicrotask', {
          value: v,
          writable: true,
          enumerable: false,
          configurable: true,
        });
      },
      enumerable: false,
      configurable: true,
    });
  }

  function setupDOMException() {
    // Registers the constructor with C++.
    const DOMException = NativeModule.require('internal/domexception');
    const { registerDOMException } = internalBinding('messaging');
    registerDOMException(DOMException);
  }

  function setupInspector(originalConsole, wrappedConsole) {
    if (!process.config.variables.v8_enable_inspector) {
      return;
    }
    const CJSModule = NativeModule.require('internal/modules/cjs/loader');
    const { addCommandLineAPI, consoleCall } = process.binding('inspector');
    // Setup inspector command line API.
    const { makeRequireFunction } =
      NativeModule.require('internal/modules/cjs/helpers');
    const path = NativeModule.require('path');
    const cwd = tryGetCwd(path);

    const consoleAPIModule = new CJSModule('<inspector console>');
    consoleAPIModule.paths =
        CJSModule._nodeModulePaths(cwd).concat(CJSModule.globalPaths);
    addCommandLineAPI('require', makeRequireFunction(consoleAPIModule));
    const config = {};
    for (const key of Object.keys(wrappedConsole)) {
      if (!originalConsole.hasOwnProperty(key))
        continue;
      // If global console has the same method as inspector console,
      // then wrap these two methods into one. Native wrapper will preserve
      // the original stack.
      wrappedConsole[key] = consoleCall.bind(wrappedConsole,
                                             originalConsole[key],
                                             wrappedConsole[key],
                                             config);
    }
    for (const key of Object.keys(originalConsole)) {
      if (wrappedConsole.hasOwnProperty(key))
        continue;
      wrappedConsole[key] = originalConsole[key];
    }
  }

  function noop() {}

  function setupProcessFatal() {
    const {
      executionAsyncId,
      clearDefaultTriggerAsyncId,
      clearAsyncIdStack,
      hasAsyncIdStack,
      afterHooksExist,
      emitAfter
    } = NativeModule.require('internal/async_hooks');

    process._fatalException = (er) => {
      // It's possible that defaultTriggerAsyncId was set for a constructor
      // call that threw and was never cleared. So clear it now.
      clearDefaultTriggerAsyncId();

      if (exceptionHandlerState.captureFn !== null) {
        exceptionHandlerState.captureFn(er);
      } else if (!process.emit('uncaughtException', er)) {
        // If someone handled it, then great.  otherwise, die in C++ land
        // since that means that we'll exit the process, emit the 'exit' event.
        try {
          if (!process._exiting) {
            process._exiting = true;
            process.exitCode = 1;
            process.emit('exit', 1);
          }
        } catch {
          // Nothing to be done about it at this point.
        }
        try {
          const { kExpandStackSymbol } = NativeModule.require('internal/util');
          if (typeof er[kExpandStackSymbol] === 'function')
            er[kExpandStackSymbol]();
        } catch {
          // Nothing to be done about it at this point.
        }
        return false;
      }

      // If we handled an error, then make sure any ticks get processed
      // by ensuring that the next Immediate cycle isn't empty.
      NativeModule.require('timers').setImmediate(noop);

      // Emit the after() hooks now that the exception has been handled.
      if (afterHooksExist()) {
        do {
          emitAfter(executionAsyncId());
        } while (hasAsyncIdStack());
      // Or completely empty the id stack.
      } else {
        clearAsyncIdStack();
      }

      return true;
    };
  }

  function setupProcessICUVersions() {
    const icu = process.binding('config').hasIntl ?
      internalBinding('icu') : undefined;
    if (!icu) return;  // no Intl/ICU: nothing to add here.
    // With no argument, getVersion() returns a comma separated list
    // of possible types.
    const versionTypes = icu.getVersion().split(',');

    for (var n = 0; n < versionTypes.length; n++) {
      const name = versionTypes[n];
      const version = icu.getVersion(name);
      Object.defineProperty(process.versions, name, {
        writable: false,
        enumerable: true,
        value: version
      });
    }
  }

  function tryGetCwd(path) {
    try {
      return process.cwd();
    } catch {
      // getcwd(3) can fail if the current working directory has been deleted.
      // Fall back to the directory name of the (absolute) executable path.
      // It's not really correct but what are the alternatives?
      return path.dirname(process.execPath);
    }
  }

  function wrapForBreakOnFirstLine(source) {
    if (!process._breakFirstLine)
      return source;
    const fn = `function() {\n\n${source};\n\n}`;
    return `process.binding('inspector').callAndPauseOnStart(${fn}, {})`;
  }

  function evalScript(name, body) {
    const CJSModule = NativeModule.require('internal/modules/cjs/loader');
    const path = NativeModule.require('path');
    const cwd = tryGetCwd(path);

    const module = new CJSModule(name);
    module.filename = path.join(cwd, name);
    module.paths = CJSModule._nodeModulePaths(cwd);
    const script = `global.__filename = ${JSON.stringify(name)};\n` +
                   'global.exports = exports;\n' +
                   'global.module = module;\n' +
                   'global.__dirname = __dirname;\n' +
                   'global.require = require;\n' +
                   'return require("vm").runInThisContext(' +
                   `${JSON.stringify(body)}, { filename: ` +
                   `${JSON.stringify(name)}, displayErrors: true });\n`;
    const result = module._compile(script, `${name}-wrapper`);
    if (process._print_eval) console.log(result);
    // Handle any nextTicks added in the first tick of the program.
    process._tickCallback();
  }

  function checkScriptSyntax(source, filename) {
    const CJSModule = NativeModule.require('internal/modules/cjs/loader');
    const vm = NativeModule.require('vm');
    const {
      stripShebang, stripBOM
    } = NativeModule.require('internal/modules/cjs/helpers');

    // Remove Shebang.
    source = stripShebang(source);
    // Remove BOM.
    source = stripBOM(source);
    // Wrap it.
    source = CJSModule.wrap(source);
    // Compile the script, this will throw if it fails.
    new vm.Script(source, { displayErrors: true, filename });
  }

  startup();
});