Wrap require in Node.js which can resolve relative path call

Question

I'm trying to create a require wrapper to load dependencies, but I found one thing difficult to make it works as the original require function. When the path is a relative one, the wrapper cannot resolve to the correct one since my loader and the caller files are not in a same folder. Here is a simplified description.

index.js
lib/
  loader.js
foo/
  bar.js
  baz.js

index.js

var loader = require('./lib/loader.js'),
    bar = require('./foo/bar.js');
bar(loader);

lib/loader.js

module.exports = function (path) {
  return require(path);
};

foo/bar.js

module.exports = function(loader) {
  var baz = loader('./baz.js');
  console.log(baz);
};

foo/baz.js

module.exports = 'baz';

Obviously, when the index.js is executed, baz.js file cannot be found. Is there any way to resolve to the correct file?

I've found a relative solution but it's not working.

Answer 1

You can use module.require to call require from another module's context, so you could do this by passing that context into the loader method:

lib/loader.js

module.exports = function (moduleContext, path) {
  return moduleContext.require(path);
};

foo/bar.js

module.exports = function(loader) {
  var baz = loader(module, './baz.js');
  console.log(baz);
}

Answer 2

I agree with @JohnnyHK that passing the module context is a cool solution, but I still want to keep the calls simple. Finally I understand the answer I mentioned, and I get what I want.

loader.js

var getCaller, path;

path = require('path');

getCaller = function() {
  var stack, traceFn;
  traceFn = Error.prepareStackTrace;
  Error.prepareStackTrace = function(err, stack) {
    return stack;
  };
  stack = (new Error()).stack;
  Error.prepareStackTrace = traceFn;
  return stack[2].getFileName();
};

module.exports = function(file) {
  var base;
  base = path.dirname(getCaller());
  return require(path.resolve(base, file));
};

The getCaller function use error trace stack to get the filename of the caller of it's caller. I know it's a very tricky approach, and I don't recommend it as a common solution since its compatibility to different versions of Node.js has not been tested.

Note

This loader is used for preparing dependencies, so it doesn't need to iterate node_modules folders. The only two cases are relative path and absolute path, and they can all be correctly processed by this loader.