Throw an error when require() may have more than one instance of a module in it's cache due to the module being required with inconsitent module name casing.
Usage
npm install --save checkForModuleDuplicates
Check for duplicates (syncchronously):
require('checkForModuleDuplicates')();
Alternatively, you can check periodically:
require('checkForModuleDuplicates').autocheck();
Explanation
If node is running on a filesystem that's case-insensitive (e.g. MacOSX), require() is case-insensitive. At least, in how it resolves to file paths. So require('foo') and require('FOO') will both resolve to the same 'Foo.js' file. However require()'s module caching is case-sensitive, meaning the module instances you get back in that case are different!
(To make matters worse, require() is case-sensitive for built-in modules. require('http') works, but require('Http') throws, thus reinforcing the naive assumption that nodes insures modules are created as singletons.)
This is the intended behavior, by the way. Unfortunately, it can lead to some really nasty bugs. Nasty, because it won't be at all obvious what the underlying cause of the problem is.
For example, I created this module because I wasted 3 hours tracking down a bug
where Sequelize was failing to generate UUIDs. The cause? The
Sequelize.UUIDV4 constant I was passing in to Sequelize came from a different
instance of the Sequelize module and, thus, wasn't actually recognized as
Sequelize.UUIDV4. The fix was to change require('Sequelize') to
require('sequelize'). Everything else worked, however... there was no
indication given that I had inadvertently created a completely different
instance of the module.
So... yeah... fuck that. Never again.