[ivanhoe]

The main problem with redundancy is that every time you refactor you need to look for all the occurrences, and sooner or later you'll forget to update the change in one of the places. So in my book redundancy is bad almost always. On the other hand if it's only a few lines without extra dependences, it's often more readable to just repeat them, especially (and it's quite common) when you would need to add extra logic and conditions just to make that little abstraction work.

[ozim]

Let's talk about risk of regression.

Ok I forgot to update some code in one place because I was doing duplicated code. If it is often used place it will be found out quick by QA or users. I kind of have more control over what can break.

On the other hand I made something that is abstract and used in many places in code. I might not be able to tell what will break maybe it will be 5 places maybe none.

In the end you should be able to find similar code in all project files with the tooling. The same with references to abstract code, but abstractions are behind interfaces or are subtypes and it is harder to find in my opinion than doing CTRL-F on all files. Specially with OOP code until you run the program you might not know which method is going to be called.

[ivanhoe]

For me it's a lot about the stress of refactoring: if I know the code is all in one place, I can make sure that I don't break the contract and be fairly relaxed about making my changes. Searching through files, making sure that you've found all the occurrences, reading each of those blocks of code and trying to understand them enough to be sure you're not breaking something is a lot more work, but more importantly it makes me feel very uneasy about refactoring. It's much more stressful because there's more moving parts, you need to be concentrated about a lot more things at once.

[gmueckl]

I always stop and think when I am writing almost identical code multiple times. The kind where everything is the same except for a few data types. Or the kind where every third line is slightly different but you can't switch them around into a single code block guarded by an if.

Trying to DRY would turn this code into a monstrosity (templates - even more interfaces - more ifs than actual logic?). I often find myself forced to let the repetition stand because it is the more obvious code. But it never feels right.