[dbmikus]

I don't think the OP meant "don't touch old code", but this sentence, to me, implies that "reasons" means good reasons:

> There are reasons for every code and every guard that exists in production.

Sometimes the reasons are not good ones. Maybe that's exactly what the author meant. The rule doesn't read like that to me, though.

And yeah, if you're rewriting something, don't rewrite the whole damn thing! Good code is modular and you should be able to pick it apart and replace components that are causing problems. If it's not causing a problem, don't rewrite it...

However if you're going to be adding features to a section of code (or otherwise working on it a lot), it's a good time to try to understand if you can do a bit of refactoring along the way to clean it up. By default, all code gains code smell over time and also becomes more robust. It's a tight rope to walk.

[dahart]

It is true, sometimes the reasons are not good ones. But, if it is in production, one should assume the reasons are good ones, there's already some evidence. The point is mainly that the burden of proof is on the reader to demonstrate the reasons are not good before modifying it... especially because you're right: code smell is the default product of time. We have to be careful about assuming that code smell indicates something is wrong. My couple of decades of experience is that people assuming reasons aren't good and jumping into modifications is a bigger acute problem than being more conservative than necessary. Accumulating the tower of abstractions is no doubt a problem, but it happens more slowly and is caused by a multitude of bad practices, it rarely breaks production or causes downtime, unlike refactoring too eagerly because of smell or opinion rather than demonstrated necessity. It is indeed a fine line, I completely agree!