Changing files rapidly causes build to fail

[Rich-Harris]

I believe this is a regression - fairly sure this used to work. If you hammer Cmd-S (or Ctrl-S, if you're one of those people), it's easy to cause gobble to fall over - something about waiting forever for the first build (aborted by the start of the second one) to finish.

[Rich-Harris]

God, this was a tough one to nail down. Turned out the problem was caused by invalidating the build while a file transformation was taking place - this could cause a queued task to never complete (i.e. neither fulfil nor reject supplied here would ever be called).

It's fixed in 0.7.10, but without a test, so I'll leave this open until I can get round to that.

The smallest test case I could come up with was this:

var gobble = require( 'gobble' );

function block ( input ) {
  var time = Date.now();
  while ( Date.now() - time < 1000 ) {
    // blockety block
  }
  return input;
}

module.exports = gobble([
  gobble( 'src/app' ).exclude( 'bar/**' ),
  gobble( 'src/app/bar' )
]).transform( block );

The src/app and src/app/bar directories contain a file each. Bashing Cmd-S while the block transformation was taking place would generally trigger the bug.