debug nodejs package nosync

01_mbrs.js

'use strict';
var fs = require('fs'), assert = require('assert');

function enforceStdio(fd) {
  if (fd !== 0) { throw new Error('Nope, use stdio, stdio rocks!'); }
}

function muchBetterRS(fd) {
  if (muchBetterRS.useBackup) {
    return muchBetterRS.backup.apply(fs, arguments);
  }
  enforceStdio(fd);
  return 0;   // :TODO: implement actual read
};
muchBetterRS.backup = fs.readSync;
muchBetterRS.useBackup = false;
fs.readSync = muchBetterRS;

function selfTest() {
  console.log("I: self-test begins.");
  assert.throws(function () { fs.readSync(42); });
  assert.strictEqual(fs.readSync(0), 0);
  console.log("I: self-test passed.");
}

function noMoreSync() {
  console.log("W: Gonna forbid sync ops!");
  muchBetterRS.useBackup = true;
  var nosync = require('nosync');
  muchBetterRS.useBackup = false;
  console.log("W: No more sync ops now!", nosync);
}

function hello() { console.log('Hello!'); }

setTimeout(selfTest,    100);
setTimeout(hello,       200);
setTimeout(noMoreSync,  200);
setTimeout(hello,       200);
setTimeout(selfTest,    300);

02_output.txt

$ nodejs 01_mbrs.js
I: self-test begins.
I: self-test passed.
Hello!
W: Gonna forbid sync ops!
W: No more sync ops now! {}
Hello!
/tmp/01_mbrs.js:6
  if (fd !== 0) { throw new Error('Nope, use stdio, stdio rocks!'); }
                  ^

Error: Nope, use stdio, stdio rocks!
    at enforceStdio (/tmp/01_mbrs.js:6:25)
    at Object.muchBetterRS [as readSync] (/tmp/01_mbrs.js:13:3)
    at tryReadSync (fs.js:487:20)
    at Object.fs.readFileSync (fs.js:527:19)
    at Object.Module._extensions..js (module.js:578:20)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.require (module.js:497:17)
    at require (internal/module.js:20:19)