I recently integrated shelljs into one of my projects and mocha started complaining about a global leak with respect to a key property being set on the global object.

I can reproduce the effect in the REPL, i.e. independently of the project in question:

$ node
> var shell = require('shelljs');
undefined
> global.key
undefined
> shell.exec('ls -lad *');
{ code: 0,
  output: ... }
> global.key
'async'

If this is an expected behavior, it might be good to document it in shelljs's README, as it took me a little while to figure out that I hadn't caused the "leak" with a statement in my own code. I imagine it may trip up other folks as well.

Is it a bug perhaps?

By the way, many thanks for creating shelljs. I ran into a situation recently where I just had to have a way to make a synchronous http request. Using shelljs to synchronously invoke another node script which makes the request asynchronously ended up being a far simpler solution than introducing fibers or hand-rolling a C addon.