[mmatants]

Rules like DRY or keeping line counts low are based on surface metrics and definitely lead people to over-fit the model based on incomplete information.

Underlying principle of maintainable code is "simply" that it is a concise and flexible expression of knowledge. The "simply" part is in quotation marks because, of course, it takes a good amount of self-awareness and meta-consideration to understand why some ways to express knowledge are better than others. There is also a limit to how "perfect" it can get, because it really depends on the audience too.

This is also why it's OK to let it slide sometimes and move on to more interesting topics - there are diminishing returns on splitting hairs, once broad strokes of good encapsulation and basic readability are applied.

[dllthomas]

DRY is not a surface metric, although it is often misunderstood as one.

The original formulation of DRY was:

"Every piece of knowledge must have a single, unambiguous, authoritative representation within a system."

Elimination of syntactic repetition is not an application of DRY, although application of DRY will often incidentally eliminate syntactic repetition.

[geezerjay]

> Rules like DRY or keeping line counts low are based on surface metrics and definitely lead people to over-fit the model based on incomplete information.

The principles are actually sound, but letting metrics drive the design process is a problem all on its own.

https://en.wikipedia.org/wiki/Goodhart%27s_law