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> as if duplication would be the root of all evil

And instead it gets replaced with the actual root of all evil, complexity.

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To be more specific, incidental complexity.

Many problems have tons of inherent complexity already.

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We still need a way to track that there’s some common pattern in the code. So that when we update one pattern we wonder about the others places in code with the same pattern. Avoiding duplication doesn’t solve that
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My metric for that is "does that code MEAN the same thing" or "does it just look the same". Has worked quite well for me so far. I frequently find myself making a copy of some code rather than adding a parameter (most commonly done with code that would get some flag added)
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Me too ! I don't follow DRY that much, I'm aware that copy pasting is good enough for a few weeks / months to see how things evolve in the future, and do refactor when it's really needed. That said, how do you know if they mean different things ? For GUI code for example, they do mean the same thing, but there's a good chance the code will evolve in the future so premature refactor are wasted time
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GUI code changes as fast as your GUI does. If you have two buttons, call makeButton twice. If they have totally different sizes, don't calculate the size inside makeButton. If tomorrow you want a button and a checkbox, don't call makeButton twice with isCheckbox=true the second time.

Fun fact: Win32 checkboxes are buttons with a bitflag that says they are actually checkboxes.

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Mostly by looking at the calling site where the code is already used and the calling site where I want to reuse it. If both of those mean the same (calculate the tax on x products, for the purpose of applying to the shopping cart, vs for applying to generating reports) then I'll reuse it, if it can be achieved without adding stuff like flags, in most cases. In other cases, it just looks the same (sum some field + calculate a percentage of that, for example, for discounts vs taxes on products) where it's obvious that they don't mean the same. (Though, I do heavily rely on a good type system to deal with future evolutions of that copied code)

TL;DR: Vibes

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This right here.

Here we're loading the customer record and updating their discount %

Here we're loading the broker record and updating their commision %

They will have 99% identical code.

It's possible but exceedingly unlikely we have found 2 things that should be a load_record_and_update_percent(file,id,field,val)

Tomorrow the business logic behind one of those will no longer be a simple % and now you have a real mess.

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> when we update one pattern we wonder about the others places in code with the same pattern. Avoiding duplication doesn’t solve that

It can, that's all about how aggressively you factor and structure your code, eg. combinators make it easy to reuse code in different application patterns without rewriting.

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Exactly!
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Definitely the hallmark of junior. Obsession with code deduplication as the highest pri when it’s quite low among others.
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This is something I've seen repeated time and time again as a criticism of (misused) abstraction and DRY, yet I've never seen ONCE -- and this is not hyperbole, I mean it literally -- a junior making an abstraction with any thought to reuse, generalizing anything, or caring about not repeating code. Most juniors I've worked with are content to just churn new code without paying attention to the codebase at all. This all before the AI deluge, mind you.

Very similar with patterns. I've often read people protesting that juniors overuse design patterns, yet I've seldom seen a junior (mis)use anything more complex than a singleton, and when they use any pattern, it's usually forced upon them by an opinionated Java framework.

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This smells more like the fluidity of what people mean by “junior” more than anything else. Journeymen engineers in their over-engineering phase, or even very “senior” expert programmers can suffer over fitting the product to their own mental model. The most senior judgment is to understand when an abstraction makes sense at a customer level, because that defines the durability of a business-logic abstraction.
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I do agree this happens with the senior overengineering phase, but the comment I replied to mentioned "especially juniors" and I've heard this trope specifically about juniors, with the implication they want to apply what they learned in college, but this hasn't been my experience at all.
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In the early 2000s I often saw juniors and students make staggeringly deep class hierarchies. The equivalent of:

Shape::Polygon::ConvexPolygon::FourSidedConvexPolygon::Square::BlueSquare...

"Intro to OOP" lectures/articles made a deep impression on some people in not quite the right way :)

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