I'd recommend clicking through the headline to watch the talk. Metz talks a lot about types of similarity: similarity by coincidence vs similarity due to an actual semantic or functional equivalence.

Code that is coincidentally similar very often diverges in either the short or long term, and DRYing it up aggressively tends to result in functions that have many boolean parameters that each trigger disjoint sets of behavior - which is a bit of a nightmare to maintain due to the high cognitive overhead of remembering how all the interleaved-but-actually-unrelated behaviors should work.

This outcome is low-cohesion code.

It's a useful concept to be aware of - worth clicking through to the actual content of the talk rather than just the headline.

Hardly iconoclastic, it's a very sensible suggestion.

It would be iconoclastic if the common sense basic approach would be to start with abstraction. It's not, the common sense default is to write possibly duplicate behavior until you actually discover several cases to abstract away, until you bevalop a sensible idea of which functionality unites them and which doesn't carry over all of them.

>Once you have an awkward number of customers (more than five and less than a hundred), maintaining duplicated code that should have been abstracted and modularised will only seem cheap if you don't mind that you burn through even junior employees at a pace

Maintaining the wrong abstraction, or, god help, abstractions, would be even worse.

Code duplication is cheaper than the wrong abstraction. If you have a good abstraction, you should run with it.

If you haven't figured out a good abstraction at 5-100 customers, God help you.

It sounds to me like you are describing a good abstraction. This article does not claim that code duplication is better than any abstraction. It claims that code duplication is better than the wrong abstraction. I'm sure this author would agree that a good abstraction is better than code duplication.

You seem to have experience, I dont mind factoring / unifying logic, when done sensibly with enough history in the trenches. It pains me more whenever a young dev comes in and barks "we must merge these two things!" repeatedly without planning for more than two cases and starting to add more and more boolean variables. Crystal makers. Then the obvious issue comes, the two variants weren't that close and now there's one god class trying to handle all forces in one big state.

I agree that LLMs are naturally anti abstraction machines.. I'm often trying to find way to reverse that.

In my experience, the answer is always "It Depends." That's about the only thing that I can hang "always" on.

It really depends on the exact type of code we're working with, and what our objectives are.

In my case, I often use object inheritance. It's a damn cheap way to DRY. However, when people hear "inheritance," they often think "polymorphism." There's a really big difference between the two, but popular culture has jammed them into one ball, and it's not worth the agita, to try to explain the difference.

But if you are doing optimization, long stacks can be your enemy, and inheritance tends to have long, windy stacks.

In these cases, the copy/pasta method may well be the best approach.

Like I said, "It Depends."

Over-engineering and "abstraction hell" are very much not iconoclastic concepts

i agree with the author. i argue a preference for loose coupling over centralized abstractions. sure it's pleasing to compress the code, but if the use cases actually are sufficiently divergent (as well as bugs and externally driven changes) ultimately it becomes brittle, littered with edge cases behind if fences and both challenging and daunting to change.

ideal case: support libraries and then very simple duplicated code that is easy to read and modify. critically the core control flow should remain duplicated, but simplified by the support libraries.

I think you applied this idea into the era of LLMs but consider an abstraction that takes in multiple god structs for branches it may or may not call in the case you are looking at and has a lot of if conditions that explode in combinatory complexity across a deep call chain. Now the bottle neck is that you need to call this function 144 times a second. That is where you start to have clusters of hot code paths where the latency stacks depending on the angle the god structs come in. Not sure what LLMs do here, I don't vibe code

> I would go as far as to say that any abstraction you can maintain (that is in active maintenance, I mean) is better than code duplication once you are passed a de minimis threshold.

Pretty much everyone arguing for duplication has argued what you are saying, which is wait to see a few instances of it before committing to an abstraction. No one is saying duplicate everything 100 times. So I don't think this discussion was ever iconoclastic.

100% agree. 'Code duplication is far cheaper than the wrong abstraction' is a very good candidate for the worst programming article ever.

My general rule is to start refactoring once you have three copies of the code.

Starting with abstraction when you are only beginning something rarely works well and leads to code bases littered with interfaces having only one implementation.

Abstracting the code when you have two copies does not always pay off, especially when you end up not needeing more than just two copies anyway.

But once you have three copies, it's indeed time to start generalizing.

One of the most challenging kinds of thought to work through with my engineers in professional communication is nuance. For example, they may say something like this, but actually mean "For a particular situation, this is wrong."

The context a decision is evaluated is particularly important for "rules of thumb" like this. There's the rule of 3 (which many senior engineers imparted to me earlier on in my career) - don't refactor until you've actually duplicated it thrice, but even so, what they speak of is a catch-22 that's pretty important to reason about carefully.

On one hand, if you overcorrected on the fear of abstraction, you could easily end up with 500 duplicates that are slightly different and need to be maintained 500 different ways, slowly causing slightly wrong behavior some of the time, data corruption, combinatoric explosion. Surely, once there is such a situation, some degree of abstraction is the only right decision.

On the other hand, if you overcorrected on the fear of duplication early on, you could easily end up with a premature optimization and complexity -- complexity which, most importantly, could be rooted in a gap of understanding of how the code will be used and what direction it may go in over time (often based on which direction the business will go over time).

The only answer that actually works, of course, is "somewhere in the middle." Obviously, that's pretty vague and not very useful. Where, exactly, in the middle IS the right place?

As the years have gone by, I've become more and more steadfast that the answer to that question is and must be an art and not a science. Of course, it must always be rooted in practicality, the actual context of the code around it and where the code/business was in the past and where it will be in the future.

But just as importantly, some of it must be based around beliefs in the face of imperfect information about what you want to invest in for the sake of the technology, the team that develops it, and the business that relies on it. It could be that for your team, your values make it make sense to go a little bit further than "good enough" on normalizing your data modeling, because the way you like to run your business requires that normal form to do the analytics and make decisions productively. It could be that for your team, your values make it make sense to go a little bit further than "good enough" on splitting service boundaries and ensuring clean queues and message passing infrastructure, because you have seasonal spikes where you need to scale up to a ton of load and then scale down after without constantly doing a song and dance or pre-provisioning fragile infrastructure.

But the most common thread there is - art, not a science. Every single decision depends on YOUR team, YOUR business, YOUR needs - and like any art, there is no universal rule or discovery or best practice in the industry that will magically work for your needs without working through the details of whether it appropriately fits your situation or not.

So with that said - I can't really agree with you. At any place I've ever worked with a competent team, maintaining duplicate code is just not that hard and follows the same process for being dealt with. Built a robust test suite that encodes the actual differences and the shared structure. Pull out the pieces that have a good reason to be abstracted and redesign the pieces that encode the true differential structure in a way that is intuitive. Lather rinse repeat. It's always straightforward because it's known - by the time you are doing this process, you've had tons of repetitions and data on what is driving you to develop the abstraction, so when you make the decision, you are making it empirically.

Conversely, I have seen many otherwise competent teams slowed to a halt with premature abstraction. Frameworks that were well intended and reduced duplication, but encoded coupling between components that at a certain point in the businesses progression, fought with reality rather than aided, and all because they were frozen into place before anyone empirically had really clear data about whether the abstraction would be worth it long term. Well intended "clean code" refactors that were meant to solve the old "bad duplication" but instead created a far more difficult to reason about "abstracted base" of code that didn't really solve any of the domain modeling problems and was just as difficult to maintain without introducing buggy behaviors (if not more so) than before.

The biggest problem is that premature abstraction is sexy and fun. There are incentives and dopamine hits from doing it extraneously. But fixing legacy duplication is not fun. And so when it gets done, it tends to get done in a pragmatic way to relieve pain rather than to elicit pleasure. That, I believe is one of the biggest confounding sociological aspects of this whole discussion.

So you centralize 3 liners?

The key lesson is that duplicate code is not necessarily "code duplication" - it was always really about abstraction duplication. If two unrelated variables happen to momentarily share a value, it doesn't mean that value should be made common between them, they are fundamentally different things. It would be a confusing lie and error-prone if the code implied they were the same and that efforts should be made for them to be in sync.

Huh? If anything having lots of customers makes the argument for duplication stronger. The issue is almost always once you get huge and 5 product teams are trying to achieve 5 different goals by using the same overwrought abstraction instead of just copying and decoupling. The abstractions that are actually stable end up becoming libraries or platform team owned systems that no one ever really touches.

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