Callback is called before file is copied

[Soulike]

The bug is caused by following code:

ncp/lib/ncp.js

Lines 89 to 109 in 6820b0f

	isWritable(target, function (writable) {
	if (writable) {
	return copyFile(file, target);
	}
	if(clobber) {
	rmFile(target, function () {
	copyFile(file, target);
	});
	}
	if (modified) {
	var stat = dereference ? fs.stat : fs.lstat;
	stat(target, function(err, stats) {
	//if souce modified time greater to target modified time copy file
	if (file.mtime.getTime()>stats.mtime.getTime())
	copyFile(file, target);
	else return cb();
	});
	}
	else {
	return cb();
	}

As we can see, in line 108, cb() can be called before rmFile() and copyFile() finish their jobs. So if target file exists, cb() will be called before file is copied.

The test case below can reproduce the bug:

const destination = path.join(os.tmpdir(), 'bigFile');

ncp(someFile, destination, function (err)
{
    if (err)
    {
        return console.error(err);
    }
    ncp(someFile, destination, function (err)
    {
        if (err)
        {
            return console.error(err);
        }
        fs.readFileSync(destination);    // Error: ENOENT: no such file or directory, open '/tmp/bigFile'
    });
});