Unsurprisingly, that goes for just about any idea in software development. I worked in one code base that heard small functions are best, so every function was less than three lines long. You don’t gain anything by replacing `lst.get(0)` with `get_first_item_in_list(lst)` (in fact, understanding becomes much more difficult), but breaking down functions into the smallest units that make sense independently within the business domain can be very helpful, both for understanding and testing.
Otherwise what is better is better and we don't know what we don't know
Having a wrong abstraction means you end up with a class/function/module with a huge amount of configurations through boolean/enum parameters. It's not even clear that all combinations of configurations is even valid. This situation may be simplified by duplicating, and then eliminating code, thus creating more streamlined code for each use case. This may require fixing similar or cross-cutting bugs in multiple places (eg: JSON serialization is stupid, need to hack a workaround), but keeps the business logic changes simple. Maybe a bit more numerous, but the code is able to raise all the scenarios to consider.
Having no abstraction means you may have to change business logic consistently in multiple places, or you have to fix exactly the same misconception (aka a bug) in multiple cases. e.g. tax rate management in a multi-national context. This is also terrible, because you may fix an important problem in one place and forget other places with the same issue. Now you missed 12 potential bugs by fixing one. This can however allow you to discover a true abstraction. Maybe these 12 places should call just one place?
But for code evolving across a team understanding this tension, a bit of duplication while waiting for confirmation that these pieces of code break together and change together is better than just shoving the same 3 if-statements into a function to avoid "line duplication". Concept duplication is more important.
OP is right that code duplication is far cheaper than the wrong abstraction, but the opposite is also true - the right abstraction is far cheaper than code duplication.
Do you want to iterate using for loop or using .iter().step(2).map()?
I would rather have consistency than a mixed bag of levels of abstractions.
This isn't really a good example, assuming both can be used to represent the same thing.
The problem with the wrong abstraction is when your abstraction doesn't let you represent something. Then, because of you've already invested so heavily into it, you start contorting the problem to fit your abstraction and it becomes a shit show.
I don’t think it matters, specially for sort sized loop scopes
But beyond that, any stable abstraction is better than duplicated code.
Usually, some moron decided to copy paste things a few levels up and then the top half of the system metastasized into two parallel universes of broken garbage.
For instance, one might decide to perform auth later in the flow so unauthorized handlers can run and set a “this requires auth” bit that defaults to false, and the other flow could add a forged auth header before the auth step.
Now, the auth handler needs a “allow forged header” flag and a “already authenticated” flag.
I’ve seen that grow to a half dozen cases until massive production dataloss occurred. A buggy client tried to delete something local to their account without specifying a userid as a parameter (this codebase was garbage!) and deleted the something for all users instead.
I can’t remember how the dataloss was “fixed”, but it definitely wasn’t “all requests go through a simple auth check, and all handlers declare/implement their auth requirements in the same way”.
Getting a design approved to require a user id be specified exactly once for account-level operations was fantasy land for that team. (Most hires with any sort of engineering talent bounced in under a year.)
Anyway the “abstractions are hard so copy paste” approach did provide job security for the lifers on that product. I can’t imagine them holding a job elsewhere, but they were completely immune to layoffs (hostage style).
This is a pretty valid approach if you’re an agent hired to perform industrial sabotage, or if you keep replacing keyboards after you knaw through the corner.
Generalizing this in the abstract is a wrong abstraction.
Very true in some sense, but I continue to encourage DRY-bias because I've literally never seen teams duplicate code responsibly and later dedupe it when it's the right time. 95% of the time this sentiment is quoted to justify shipping quick slop and stable reusable bits are never extracted into a shared lib later.
Maybe this is an area where AI can help identify duplicate code though to show opportunities for de-duping
Some previous discussions:
2023 https://news.ycombinator.com/item?id=35927149
2021 https://news.ycombinator.com/item?id=27095503
2020 https://news.ycombinator.com/item?id=23739596
Abstraction is a vague term when used here. Is a shared function an “abstraction”? It’s more like implementation hiding, maybe some data hiding. But you definitely have a dependency on it now.
Acronyms like DRY are for beginners. Once you get good you know when to break the “rules” (and when not to).
At the very least it is not once you're working at the wrong kind of scale.
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.
And in the LLM era the wrong kind of scale appears in different ways; code generated and duplicated without proper abstraction and then maintained by an LLM that cannot be trusted to do the same modification each time it encounters a pattern or to have enough of an overview to slowly rescue duplicated code through good abstractions.
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 past a de minimis threshold.
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.
Hard disagree. When you've had to chase through a change in untold and actually unknown numbers of duplications of code in different permutations and fix them because they are all on fire simultaneously, you'd disagree too. A bad abstraction would at least have had one fire in one place.
If you haven't figured out a good abstraction at 5-100 customers, God help you.
Half of your abstractions are wrong. The hard part is knowing which half.
This is tautological though, it's like saying “starving is much better than eating the wrong food” (for instance: eating quick lime).
Of course you'll always find a way to do things wrong in a way that is costlier than not doing anything.
But also it's very possible to not realise you needed an abstraction until it catches fire in multiple places.
And quite often it's not you that got the codebase to a hundred customers, is it? Sometimes it is a sequence of fresh-faced young developers who didn't have the authority to say "this duplication is bullshit" and were instead compelled to repeat it.
I think a lot of these discussions happen in nice little blog-post vacuums of progressive thinking, where people can go "mmm, object oriented coding obscures intent and clarity, mmm", blog posts with "an X is a Y", "the unreasonable effectiveness of foobar" etc.
In the real world, every duplication that works sticks for good; there is rarely budget to electively replace code that isn't broken. Until one day it doesn't work. And then… how many times is it actually duplicated? How many of the duplicates diverged? How many of these do we no longer need?
This blend of opinion is very naive. Every single project is a business requirement away from having the wrong abstraction in place.
Of course it's a truism if you just say any abstraction that works is a good abstraction.
That is not what I am saying at all. Bullshit abstractions at least let you control the problem. Duplication doesn't.
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."
I agree that LLMs are naturally anti abstraction machines.. I'm often trying to find way to reverse that.
I am a bit of an LLM cynic but I am trying to learn it all, and I have to say I have spent most time trying to work out: how do you explain how a brown-field codebase actually works, in such a way that the LLM won't pervert it through misunderstanding.
It does encourage you towards the "conventional" coding standard for any new project, because you want to use a pattern that it will have seen in its training set.
But for example there are differences of opinion in how wordpress plugins (which have a very complex control flow) should be structured. LLMs are incredible at knowing how WP works, actually, but what is difficult is explaining how your methodology for a large plugin is going to work.
It is a battle — but a useful one because it can be used for, er, studying the comparative belief systems of the LLMs.
Everyone always thinks duplication is fine when you can bill the modifications by the hour. But they never think to understand that the reason they've had so many employees is that they've turned their change process into firefighting all the different versions of the same code and all these young developers burn out from the sheer anxiety of not knowing where all the little fires are.
I once had to rescue a site that had become a victim of its own popularity, that was written by subcontractors who clearly believed that duplication is better than the wrong abstraction.
Until one day, along came a change — MySQL 4 to MySQL 5 — and a significant duplicated query no longer worked due to its new, proper strictness.
The problem was compounded; not only was the broken pattern in hundreds of places where it had sat, stable and predictable, but the pattern was broken because it, itself, was avoidance of another abstraction that would solve it.
They quit: they said they couldn't and wouldn't fix it. It had always worked how they had done it, and it would have to stay on MySQL 4 (which the hosting provider refused to accommodate).
I don't think it helped that they were severely misguided in their understanding of SQL, but the code had become beholden to duplication and then crippled by a new problem in the duplicated pattern.
I had to first find all the contexts in which that pattern appeared (which required me to spend half a day on a bespoke script) and then work out a new pattern and as few variations of it as possible to fix the duplicated code in each place, because there was no proper budget to rewrite the whole thing. And then I sat at my desk, for days, working through each one, figuring out how to change it to fit the slightly different expression of the pattern.
Even a total bullshit abstraction would have saved that client both time and money. And this is only one of dozens of times I've seen small firms simply duplicate and change code that would later become unmaintainable because of a straw breaking a camel's back.
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.
In the real world, duplication happens in an emergent way, there isn't the time each time to judge whether it's really time to just quietly abstract that code, you may not get the permission, budget or window to do it, and if you don't stop the rot really early you are locked into the pattern.
But in one of the scenarios I mention earlier, I earned a chunk of money once fixing an issue that emerged in a subcontractor's four or five line duplication that had ended up rippled through a long-lived codebase. A ground truth (MySQL version) changed, and the pattern broke everywhere, including places where it had evolved.
So I tend towards thinking, yes, any three-line pattern that is likely to appear everywhere should, perhaps, be centralised.
It's certainly worthy of serious consideration. Usually pretty easy to maintain the surface of such an abstraction.
Part of being a good engineer is finding the right balance.
I know engineers who would gladly duplicate code all over the code base to avoid creating a new abstraction.
I know engineers who create polymorphic abstractions for a single caller with a very obvious set of parameters.
So much of wisdom is in finding balance and not being dogmatic about rules.
So code duplication because of abstraction issues is rare. Code duplication because of siloed developers is so much more common.
Basically since moving to a functional approach in typescript I find I do not fight abstractions as I used to when I used classes and inheritance.
it wasn't received well and senior developer told me that 'good developers know exactly what patterns to use all the time before writing any piece of code and that he will clean up my mess'
long story short his refactoring caused what was otherwise a stable system into a complete mess and it reminded me of Nassim Taleb's book
Overengineering, abstractions and premature optimisation are the 3 worst plagues of engineering.
At the same time I’m happy they exist because it means we’ll always have a job.
For $19.95, you can replace your single single point of failure with multiple single points of failure!
But with that in mind, I mostly agree with the article: if it's not a violation of "single source of truth", then abstractions are just a convenience. If it starts being inconvenient, then it's not doing its job and there's no reason to use it. It's a serious code smell if a function needs several flags for custom behavior; that means it's probably the wrong abstraction or violating the single responsibility principle. If there is a legit need for lots of customization, an often-good way to handle is to take a function/functor as an argument for the customization. E.g., rather than `solve(f:double -> double, max_iters = 99, x_abs_tol = 1e-15, x_rel_tol = 1e-15, ...)` you can do `solve(f:double -> double, stopping_criteria: StoppingCriteriaClass)`
This step should also be parameterized by how many times the duplication has occurred. Refactoring preemptively may lead to poor abstractions, but not refactoring after seeing the exact same thing tens of times would also be weird. See also:
Mike's talk argues that code solutions need not be modelled on the real world, and that different data creates different problems, which need different solutions. I can't do the talk justice, but it's had a big impact on me.
Brian's talk is about abstraction generally, and how it's difficult to find the "right" abstraction.
I've always found it odd when even fairly smart engineers sometimes prioritize real-world metaphors over the actual needs of the codebase. Years ago when I was only a few years out of school, I was implementing a connection pool in Rust, and the most reasonable way to implement it was to have the connection hold a weak reference to the pool so that it could get checked back in automatically when dropped. My manager (an extremely experienced engineer) didn't like this idea because "a library holds library books, not the other way around". I didn't feel like this was a compelling reason to design things differently, but he refused to engage with the issue in any way other than through the lens of that metaphor. Eventually the impasse was solved by one of the other managers in my department suggested that while library books don't contain libraries, they do have the name of the library stamped in the back as a reference to where they should be returned, and I guess my manager found this to be a reasonable extension of the analogy. If I were more experienced, maybe I would have recognized that I could find a way to engage with the analogy like the other manager did without ceding the point, but even today I still feel that it was completely bizarre to insist on that as the canonical way to frame things rather than just considering the ramifications of the abstraction in the code and the experience of using the library based on it.
There has been growth since but it's been concentrated into fewer channels and somewhat industrialized.
The Node ecosystem is full of wrong abstractions.
Even better is an old school MPA with progressive enhancement.
Not that I'm immune from choosing the wrong abstraction sometimes. More than once the "other people" was me. We all make mistakes.
It's of course possible to functional-ize segments of logic, but then the question of state mutation must be brought up. How isolated are these changes from other parts of the code / system state. Can this be run in parallel or is it something that must be serial? What potential race conditions exist?
Refactoring code to reduce the number of lines is _compression_, akin to RLE coding.
Refactoring the code to lift conceptually coherent parts is _abstraction_.
Less compression, more abstraction. Then you're fine.
IMO it's easier to inline a bad abstraction than it is to consolidate a bunch of subtly different things that should have been abstracted from the beginning.
But I expect people's opinions on this differ wildly based on their personal experiences. Just my anecdotal take.
On the other hand it is pretty difficult and error prone to consolidate duplicated code which have drifted apart over time.
If in doubt, chose the approach which is simplest and least risk to revert if you discover in the future you made the wrong choice.
I do agree a bad abstraction can cause huge problems. But it’s usually not the kind of abstractions introduced to eliminate code duplication, but the kind of top-down “architecture astronaut” abstractions, where a model is chosen which does not fit the complexity of the problem.
Some of the biggest rabbit holes come from naming conventions not aligning across the business and technology silos. If everyone agrees that Customer has exactly 34 attributes, then it is possible to move to the next step of sharing libraries of types across the team. Getting your POCOs/DTOs 1:1 across the board is when the duplication really starts to melt away.
So... the wrong abstraction, no matter how bad, is better than code duplication?
I agree with you that it’s a truism, but it’s useful advice for people who have a habit of trying too hard to DRY their code. IIRC the author comes from the Ruby world, where DRY was a big thing, and this talk was part of the pendulum swinging back away from this DRY obsession that sometimes just resulted in convoluted code.
Write everything twice quickly becomes write everything 4 times once a new change appears, just as quickly as it becomes write everything 8 times, and so on.
I'm afraid there's no sensible soundbite developers can follow blindly.
Having a lot of if/else in your code is definitely a cost. My weakness isn’t so much the libraries and APIs, but the actual binary - once I have a service that does A very well, and I run into needing A’ I mostly just add in a config line “op_mode = A|A’” and have the else/if chains in the server driving code. Moreso for CLIs that I use myself than production services, but I have added tunables for consistency and replication to datastores to allow new use cases and expand my footprint in the data center.
I would be curious if the previous coders you're talking about actually cited duplication as a good thing. You seem to be implying they are. But almost every instance I've seen of massive code duplication was just from bad programmers shooting from the hip, not from some ideological stance.
Right. But this is a hypothetical, in-a-vacuum situation.
In the real world, your two, three duplicates are in production.
"We really should now de-duplicate this"
"There is not the time or budget, just copy it again; we'll replace all this one day".
It all depends on the amount of duplication and the complexity of the abstraction. Like you said, no generic advice is possible that clearly separates it into "abstract here" and "duplicatehere".
In your example it sounds like we aren't talking about 2-3 places where duplicate code existed that just needed to be refactored into separate units. It sounds more like a complete disregard for abstraction to move on quickly.
If you see duplicate code and have a good understanding how to solve that then it's totally a good thing. The real problem comes in if you add abstractions without knowing wether they will hold up. And this is where the blogpost comes in. In my opinion 2 duplicates are fine, at 3 you should start thinking or implementing an abstraction if you have a good understanding of the code and usecases.
Exactly. The abstraction purists are not working in the messy, dead line driven real world.
A story I like is that in the now lost era of handwriting recognition on PDAs, Jef Raskin concluded that the easiest way to solve the problem was to change handwriting so as to meet the algorithm in the middle.
That is, to find a noticeable simplification of handwriting that people could learn quickly and that eliminated hard-to-process quirks.
I feel I am there with the LLM at the moment, trying to work out what the common ground is.
Wouldn't most large codebases with poor abstractions just have engineers engineer around them with their own solutions? In a large enough codebase you'd have both the bad abstractions and all the not-quite-duplicate implementations ignoring the bad abstraction?
I'm using bad here loosely, it could be buggy, incorrect, incomplete, insufficient and more; while being owned by someone or some team that's a challenge to work with for various reasons (overloaded, under-resourced, overbearing, etc., etc.).
Obviously, yes. But it is my experience that this happens more slowly and that API invocations that break when the abstraction is changed are much easier to identify than broader duplicated patterns of code that span many lines and subtly diverge.
And even then those divergences are better because each wrapper around the abstraction is documenting the problem with it. But the abstraction can at generally be replaced by one with the same API surface.
(Even if you take into account the fact that any API behaviour ultimately gets relied upon even if undocumented. Which is true.)
To be fair my experience is that of a freelancer and contractor who arrives trying to fix things that have been through many such hands. And I think if these developers had it drummed into their head that any attempt at abstraction would be better than copy and paste, these situations would be more knowable.
When that happens there's a major engineering leadership failure currently in progress, even if engineering leadership isn't aware of it.
On the contrary: that's precisely what a bad abstraction would not offer.
Instead it would spread its assumptions to different parts of the system, as every caller, sub-service, etc. would have to change shape to fit in that abstraction's box, however unnatural it is (and we know it would be unnatural, because we already said it's a bad abstraction).
Abstraction is not the same as encapsulation.
But so does duplication, in practice, and it diverges more as it does.
Abstractions are a form of coupling, and coupling can be good, if the components are truly interdependent, and have a well defined domain. The problem with most abstractions, and I’ve seen this time and time again, is that they become brittle, are over used, and the cost of maintaining them grows exponentially with the size of the code base. With the reason for the cost ballooning being the system has disparate components that look interrelated but are absolutely not. Once you give someone a hammer they tend to assume everything is a nail.
The biggest problem, IMHO, is that abstractions are often used where a pattern would be more effective, easier to maintain, and easier to iterate on. And the primary difference between a pattern and an abstraction really comes down to coupling. Patterns remain decoupled, abstractions are tightly coupled.
And to be clear, I will and do use abstractions, when and where they make sense. But only after clear patterns emerge, and it’s been proven that components are truly coupled.
I will gladly die on the hill, that abstractions are measurably worse than duplication an overwhelming amount of the time. They’re often nothing more than a form of premature optimization.
But any abstraction ends up with a signature and a name that can quickly be found in code.
The risk of a long-lived duplication losing its shape and being hard to find is much greater. Especially if the code is going through multiple hands.
I once had to pick up a project — a working, fully functional website. I could see, pretty clearly, the work of several people. All but one of them terrible.
The one was a diligent developer who was fully wrong in their abstraction (in fact significantly) but was consistent in how they used it.
The rest had simply worked around that code, copied and re-copied their own modified duplications and let things lose any shape. The result was error-prone stuff.
Clearly either the budget (or the client's capriciousness — a separate issue and arguably the bigger one) scared away the one guy, who I actually wanted to talk to but could not track down. He possibly had the origin story, and I wanted to know why his particular abstraction, which was at odds with the framework, was there. It was good code in the wrong shape, and it clearly used to do more, and that is interesting.
All the expedient people who had decided to avoid his code and just patch in duplicated pieces around it were the problem. There was no form to their solution at all. And that had clearly happened over some time (because you could see several different code styles)