node/lib/internal/process/execution.js

'use strict';

const path = require('path');

const {
  codes: {
    ERR_INVALID_ARG_TYPE,
    ERR_UNCAUGHT_EXCEPTION_CAPTURE_ALREADY_SET
  }
} = require('internal/errors');

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

// shouldAbortOnUncaughtToggle is a typed array for faster
// communication with JS.
const { shouldAbortOnUncaughtToggle } = internalBinding('util');

function tryGetCwd() {
  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 evalScript(name, body, breakFristLine) {
  const CJSModule = require('internal/modules/cjs/loader');
  if (breakFristLine) {
    const fn = `function() {\n\n${body};\n\n}`;
    body = `process.binding('inspector').callAndPauseOnStart(${fn}, {})`;
  }

  const cwd = tryGetCwd();

  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 (require('internal/options').getOptionValue('--print')) {
    console.log(result);
  }
  // Handle any nextTicks added in the first tick of the program.
  process._tickCallback();
}

const exceptionHandlerState = { captureFn: null };

function setUncaughtExceptionCaptureCallback(fn) {
  if (fn === null) {
    exceptionHandlerState.captureFn = fn;
    shouldAbortOnUncaughtToggle[0] = 1;
    return;
  }
  if (typeof fn !== 'function') {
    throw new ERR_INVALID_ARG_TYPE('fn', ['Function', 'null'], fn);
  }
  if (exceptionHandlerState.captureFn !== null) {
    throw new ERR_UNCAUGHT_EXCEPTION_CAPTURE_ALREADY_SET();
  }
  exceptionHandlerState.captureFn = fn;
  shouldAbortOnUncaughtToggle[0] = 0;
}

function hasUncaughtExceptionCaptureCallback() {
  return exceptionHandlerState.captureFn !== null;
}

function noop() {}

// XXX(joyeecheung): for some reason this cannot be defined at the top-level
// and exported to be written to process._fatalException, it has to be
// returned as an *anonymous function* wrapped inside a factory function,
// otherwise it breaks the test-timers.setInterval async hooks test -
// this may indicate that node::FatalException should fix up the callback scope
// before calling into process._fatalException, or this function should
// take extra care of the async hooks before it schedules a setImmediate.
function createFatalException() {
  return (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 } = 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.
    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;
  };
}

module.exports = {
  tryGetCwd,
  evalScript,
  fatalException: createFatalException(),
  setUncaughtExceptionCaptureCallback,
  hasUncaughtExceptionCaptureCallback
};