I'm learning how NodeJS's require() function works to better understand the node ecosystem.

I wrote a script that uses module._pile to pile a script. When I try to require() within the string, it balks... but it seems to have the right paths. What am I doing wrong?

I guess it's worth mentioning I have the json3 module installed in the same directory in ./node_modules/.

The Script

I wrote this script, which works--until I unment the line that's marked.

"use strict";

var json3 = require('json3');

console.log("require.main.filename:", require.main.filename);
console.log("require.main:", require.main);

var module = new module.constructor();
module._pile(`
"use strict";

console.log("require.main.filename:", require.main.filename);
console.log("require.main:", require.main);

// When I unment this, it breaks.  Why?
//var json3 = require('json3');

module.exports = {
  run: function () { console.log("It works!") }
};
`, require.main.paths[0]);

module.exports.run();

Script Output

Here's the output (when the problem code is mented out).

require.main.filename: /home/user/tmp/tmp.js
require.main: Module {
  id: '.',
  exports: {},
  parent: null,
  filename: '/home/user/tmp/tmp.js',
  loaded: false,
  children: 
   [ Module {
       id: '/home/user/tmp/node_modules/json3/lib/json3.js',
       exports: [Object],
       parent: [Circular],
       filename: '/home/user/tmp/node_modules/json3/lib/json3.js',
       loaded: true,
       children: [],
       paths: [Array] } ],
  paths: 
   [ '/home/user/tmp/node_modules',
     '/home/user/node_modules',
     '/home/node_modules',
     '/node_modules' ] }
require.main.filename: /home/user/tmp/tmp.js
require.main: Module {
  id: '.',
  exports: {},
  parent: null,
  filename: '/home/user/tmp/tmp.js',
  loaded: false,
  children: 
   [ Module {
       id: '/home/user/tmp/node_modules/json3/lib/json3.js',
       exports: [Object],
       parent: [Circular],
       filename: '/home/user/tmp/node_modules/json3/lib/json3.js',
       loaded: true,
       children: [],
       paths: [Array] } ],
  paths: 
   [ '/home/user/tmp/node_modules',
     '/home/user/node_modules',
     '/home/node_modules',
     '/node_modules' ] }

Why won't the module within the ad hoc module load?

I'm learning how NodeJS's require() function works to better understand the node ecosystem.

I wrote a script that uses module._pile to pile a script. When I try to require() within the string, it balks... but it seems to have the right paths. What am I doing wrong?

I guess it's worth mentioning I have the json3 module installed in the same directory in ./node_modules/.

The Script

I wrote this script, which works--until I unment the line that's marked.

"use strict";

var json3 = require('json3');

console.log("require.main.filename:", require.main.filename);
console.log("require.main:", require.main);

var module = new module.constructor();
module._pile(`
"use strict";

console.log("require.main.filename:", require.main.filename);
console.log("require.main:", require.main);

// When I unment this, it breaks.  Why?
//var json3 = require('json3');

module.exports = {
  run: function () { console.log("It works!") }
};
`, require.main.paths[0]);

module.exports.run();

Script Output

Here's the output (when the problem code is mented out).

require.main.filename: /home/user/tmp/tmp.js
require.main: Module {
  id: '.',
  exports: {},
  parent: null,
  filename: '/home/user/tmp/tmp.js',
  loaded: false,
  children: 
   [ Module {
       id: '/home/user/tmp/node_modules/json3/lib/json3.js',
       exports: [Object],
       parent: [Circular],
       filename: '/home/user/tmp/node_modules/json3/lib/json3.js',
       loaded: true,
       children: [],
       paths: [Array] } ],
  paths: 
   [ '/home/user/tmp/node_modules',
     '/home/user/node_modules',
     '/home/node_modules',
     '/node_modules' ] }
require.main.filename: /home/user/tmp/tmp.js
require.main: Module {
  id: '.',
  exports: {},
  parent: null,
  filename: '/home/user/tmp/tmp.js',
  loaded: false,
  children: 
   [ Module {
       id: '/home/user/tmp/node_modules/json3/lib/json3.js',
       exports: [Object],
       parent: [Circular],
       filename: '/home/user/tmp/node_modules/json3/lib/json3.js',
       loaded: true,
       children: [],
       paths: [Array] } ],
  paths: 
   [ '/home/user/tmp/node_modules',
     '/home/user/node_modules',
     '/home/node_modules',
     '/node_modules' ] }

Why won't the module within the ad hoc module load?

• javascript
• module
• pilation

Share Improve this question Follow edited Jun 14, 2020 at 12:42 CommunityBot 111 silver badge asked Sep 21, 2017 at 18:57 Sir RobertSir Robert 4,97688 gold badges4545 silver badges6363 bronze badges

Add a ment  | 

1 Answer 1

Sorted by: Reset to default 8 +50

So two things in your code. When you do

var module = new module.constructor();

You loose the original module object, you shouldn't do that. Next to know what the exact issue is, you should have set environment variable NODE_DEBUG=module. This will give you what happens in background. Doing that you get an import message

MODULE 11063: looking for "json3" in []

This means there are no paths set for module loading. So you should add the paths also. Below is the updated code

"use strict";

var json3 = require('json3');
var os = require("os");
console.log("require.main.filename:", require.main.filename);
console.log("require.main:", require.main);

var _module = new module.constructor();
_module.paths = module.paths;

_module._pile(`
"use strict";

// console.log("require.main.filename:", require.main.filename);
// console.log("require.main:", require.main);

//When I unment this, it breaks.  Why?
var json3 = require('json3');

module.exports = {
  run: function () { console.log("It works!") }
};
`, __dirname + "/dynamic_code_loaded_at_run_time.js");

_module.exports.run();

Also the second parameter of _pile is the filename which is being loaded, so you should not provide it a path but a filename. And now you get the correct output

It works!