[robocat]

“ Things You Should Never Do: They decided to rewrite the code from scratch.” This is a great general rule.

The rule is situation dependant and some people can break it and succeed: the parent comment was very clearly one of those situations.

The actual risk is that the majority of us think we can break the rule, when it turns out we can’t. But a minority of people/situations can successfully do a complete rewrite, success defined as where the gains abundantly outweigh the pains.

[dannypgh]

My rule is be skeptical of anyone proposing a rewrite who doesn't fully understand the existing system, to such depth that they would feel comfortable refactoring it. Which means anytime someone says "we want to rewrite it because refactoring it is too hard" I tend to not believe them.

There are times when rewrites are less total work, but they're hardly ever "easier" when you account for the cognitive load of making sure the requirements of the rewrite are being accurately captured. Maybe there's an exception if you know the requirements have been drastically simplified, but I doubt that's practically useful.