Tried to copy files using streams and pipe and got funny results. Let's
consider following code (highlighted version
https://gist.github.com/3850106 ):
var copy = function(from, to, cb){
var fromStream = fs.createReadStream(from)
fromStream.on('error', cb)
var toStream = fs.createWriteStream(to)
toStream.on('error', cb)
fromStream.on('end', cb)
}
copy('non existing file a', 'non existing dir/file b', function(err){
console.log(err)
})
There are errors in both streams (non existing source file and no parent
directory for destination file) - so, both of them will emit
'error' event, and the callback will be called twice with both errors.
// Error will be reported twice:
//
// { [Error: ENOENT, open 'non existing file a'] errno: 34,
// code: 'ENOENT', path: 'non existing file a' }
// { [Error: ENOENT, open 'non existing dir/file b'] errno: 34,
// code: 'ENOENT', path: 'non existing dir/file b' }
I found the solution by looking at the source of `util.pump` - it does it
by wrapping callback into function that calls callback only once - for the
fist error and ignoring others.
But maybe it would be nice to have a callback for `createXxxStream` or
something like 'ready' or 'success' events to know that it created
successfully?
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