I know we have this kind of returns in other parts of the code, but I'd prefer  we have a single return point, it think it makes the code easier to follow and probably extend in case we want to do any other kind of preprocessing.

So instead of 
```js
if (this.env === 'production') {
   return this.fingerprint(tree);
  } else {
    return tree;
}
```

I'd rewrite like 

```js
if (this.env === 'production') {
  tree =  this.fingerprint(tree);
}
return tree;
```

This is mostly personal taste, but to that kind of code feels like GOTO's time ;(.

cc @rjackson @stefanpenner ?