Support require fallback for strange environments

[bmeck]

See: https://twitter.com/rwaldron/status/430414189413138433

Basically: there is a need to allow non-browserifieds modules to defer to another require function. In this example @rwaldron wanted to use node-serialport from node-webkit's require inside of a browserify bundle.

Solution: --require-fallback $name

Make a CLI option to fallback to an environment's require function if we did not bundle that file.

[andreypopp]

If I understand you correctly, currently you can add a piece of code like this to implement needed functionality:

window.require = function() { return $name.apply(null, arguments); }

because browserify already defers lookup to another function named require if it presents at the time of the bundle execution.

[bmeck]

This is going to be a bit more complex actually:

~ cat b.js
require('X');
~ browserify b.js
Error: module "X" not found from "/.../b.js"

When the flag is enabled we need to defer to $name rather than freak out at bundle time.
Preferably doing this hygienically as well.

[ghost]

This can almost be done with --ignore-missing:

$ echo "require('./x.js')" | browserify --ignore-missing
(function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);throw new Error("Cannot find module '"+o+"'")}var f=n[o]={exports:{}};t[o][0].call(f.exports,function(e){var n=t[o][1][e];return s(n?n:e)},f,f.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
require('./x.js')

},{"./x.js":2}],2:[function(require,module,exports){

},{}]},{},[1])

The problem is that ignore-missing doesn't seem to defer to an existing require call in the environment properly.

[calvinmetcalf]

since all the modules are getting wrapped in function(require,module,exports){} wrappers the call will always get bound to that name, you'd need to have browserify pass the re-call the function at require time, i.e the final step before throwing an error tries window.require

[bmeck]

@calvinmetcalf , just to be clear, we don't always want a global require to be what we defer to some places (mongodb, etc.) do not leave require as a global.

[yuchi]

Shouldn’t this be doable with --excludes? Always if @andreypopp comment is incorrect of course.

[bmeck]

@yuchi unsure what you mean? This all came from @rwaldron being unable to require node-serialport inside of node-webkit.

[yuchi]

Sorry, probably I got this wrong. But the std prelude searches for an already present require function in the outer scope to defer calls to. If you can exclude the incriminated require call you can then use a custom prelude which searches for the correct outer require. An excluded path/module is simply ignored in AOT resolution.

Here for example I had to change the call to the outer require because Titanium’s implementation throws when you call it with more than one argument.

[terinjokes]

As noted, the standard prelude already calls to a global require if a module can't be found. You should be able to implement a global require before including the browserify bundle that delegates to any (sync) source that you want, and have browserify exclude bundling the modules you don't want to bundle.

Does this resolve the issue for everyone?

[moll]

I don't believe there's a way to ignore a whole module with its files currently if you don't have a local copy of it. Something like --external some-module/* tries to glob at compile time and then still fails given a require("some-module/some-file").