How to set correct fileName for exceptions thrown from a function in a Function object

Tim Fox timvolpe at
Wed Feb 18 09:40:13 UTC 2015

Hi all,

I'm currently using a CommonJS/npm modules require implementation 
(npm-jvm) with Nashorn.

Roughly, the way it works (and I'm sure you're already familiar with 
this technique) is it takes the JavaScript module and wraps it in a 
Function object:

var body = readScriptAsText();
var args   = ['exports', 'module', 'require', '__filename', '__dirname'];
var func = new Function(args, body);
func.apply(module, [module.exports, module, module.require, 
module.filename, dir]); // Execute it - this works fine

Now let's say the actual module (foomodule.js) we are loading contains this:

module.exports = function() {
     var num = 234;
     num.substr(1, 1); // Will throw TypeError here

I.e. it simply exports a function, which will throw a TypeError when 
it's executed.

When the exported function is executed it does indeed throw a TypeError:

var f = require("foomodule");

f(); // Throws TypeError

Unfortunately the fileName field of the TypeError is set to "<function>" 
not to "foomodule.js", which is unfriendly for the user.

This is understandable as the Function object which wraps the module 
doesn't know about "foomodule.js".

So.. my question is.. how do I tell the Function object that the 
"filename" it should use when exceptions are thrown from it is 

I have tried the following and none work:

var func = new Function(args, body); = "foomodule.js";
func.fileName = "foomodule.js";
func.displayName = "foomodule.js";

Any insights would be greatly appreciated.

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