6 ms·

Reasons Not to Refactor

80 points by chmaynard 2y ago

darioush 2y ago
another reason to not refactor is management will start out supportive of it but some weeks in they will wonder wtf their engineers are doing all day and why aren't they building the new pile of stuff they want built yesterday.
- eyelidlessness 2y ago
  That’s not so much a reason, in my experience, as a frequent default/inertia position. In other words, I expect to start at that default, and challenge it with reasoning, in order to justify a significant refactor.
- svachalek 2y ago
  Refactoring is a terrible project plan. You never want your weekly status to be "refactored some more". Plan your other development work with enough time to refactor as you go.
- lesuorac 2y ago
  The ability to ship small things is I think something really missed in discussion about microservices. Like rather then refactoring the entire application to support a faster cache or something you can just add in another microservice that handles caching of the data. If some way you write the services is poor you can rewrite one of the services a new way and easily evaluate if it's actually a good idea to change the rest or not.
- IshKebab 2y ago
  Don't spend 100% of your time refactoring.
- zingar 2y ago
  I do encounter hostility but what I've realised is that it comes from experience of refactoring being done badly. "We made time for this refactoring thing but it made no difference so now we're not going to 'refactor' anymore". The worst hostility is often from management that used to be technical but never learned how to refactor effectively so they have what they think is justifiable scepticism. s/refactoring/pairing or any other technique that is good in theory but requires skill to implement. I usually find that people without technical background are willing to follow the advice of the developers that work with them, taking the things that work with them into their next roles. If refactoring worked in the beginning they'll be open to it in future, if it didn't work they'll dismiss it. Edit: also - what everyone else said - "refactoring" isn't a business goal, it's one part of achieving the goal. Achieve the goal and no-one cares how you did it. ("add a new button to that widget" isn't a business goal either so there is a tricky aspect of getting management to understand that they should be bringing you problems/goals not solutions)
gavmor 2y ago
Well, yeah, that example decreases symmetry.[0] 0. https://bensguide.substack.com/i/144306439/local-symmetries https://bensguide.substack.com/i/144306439/local-symmetries
lelanthran 2y ago
Simple and brief rules are more successful in practice than long and complicated rules. I feel a briefer and more-to-the-point "When To Refactor" guide is to ask the following questions in the following order and only proceed when you can answer YES to every single question. 1. Do we have test coverage of the use-cases that are affected? 2. Are any non-trivial logic and business changes on the horizon for the code in question? 3. Has the code in question been undergoing multiple modifications in the last two/three/four weeks/months/years? Honestly, if you answer NO to any of the questions above, you're in for a world of hurt and expense if you then proceed to refactor. That last one might seem a bit of a reach, but the reality is that if there is some code in production that has been working unchanged for the last two years, you're wasting your time refactoring it. More importantly, no changes over the last few years means that absolutely no one in the company has in-depth and current knowledge of how that code works, so a refactor is pointless because no one knows what the specific problems actually are.
- andrei_says_ 2y ago
  These are very simple and clear and confirm my own approach to refactoring. Thank you.
- eyelidlessness 2y ago
  One reason I might accept one or more NOs to your questions: Does the refactor support pending work, which isn’t directly related to the refactored code, but benefits from the lessons learned and applied in the refactor… even in some indirect way? This might be providing a clearer pattern you’ll apply to similar new functionality; or it might be providing a new abstraction or even eliminating a failed abstraction which sets that pending work on the right path.
  - AnimalMuppet 2y ago
    Yeah. I did a (very small) refactor. It took, IIRC, four days. When I was done, I could write the new thing I was implementing in 10 new lines that used the newly-refactored existing code.
- 2y ago
karmakaze 2y ago
I have one reason to refactor that's served me well. Does the code exhibit ongoing edge/corner case bugs, which are attributed to the implementation not being factored in the first place? Another sign of this situation is exhaustive test cases which combine factors as they can't reliably be tested in isolation. Distributed logic is another common pattern, where a new feature is made by sprinkling bits of logic here and there, just so, and it all seems to do what's required. You know the kind, where onboarding a new person might lead to the discussion of how this section of your Rube Goldberg contraption works. A fancy way to this world is a poorly designed and maintained home-grown DSL. Continuing to build on such a 'foundation' is madness that spirals to code red situations: stop-the-world, no feature development, until shit gets stable.
PaulHoule 2y ago
The default-oriented answer to #2 is to pass the rows through some function that applies the default to 'loud' if loud is undefined. That's really pretty code and avoids the complex if-statement which is a universal bad smell.
taeric 2y ago
I like these reasons. I will offer some caution on rules for rejecting a proposal. Often times, the number one reason to do something is that there is energy there to do it. If you can take that energy and apply it somewhere else, by all means do so. All too often, suppressing some energy stops all effort.
hylaride 2y ago
Refactoring depends heavily on circumstances. I've seen terrible attempts over my career for all the reasons other people have and will mention here. But I've also seen huge successes. Usually it boils down to "what are you trying to accomplish?" against current code and architecture. I've seen targeted refactors of micro-service code, including language shifts (eg python -> java where threading improved things a lot in that use case), as well as targeted shifts of code to AWS Lambdas, where execution scaling also benefited the use case. But in both examples there was a clear benefit, execution plan, and way to measure success. When you start refactoring large mono-app code bases for nebulous, hard to measure reasons then the risks are much higher (and that's even before scope creep comes into play). This gets even worse if the reason the current code is no longer desirable has reasons (both good and bad) that it is the way it is, and you risk recreating bad code (this was mentioned in the article) into new bad code. Also, migrations to new code can suck if the underlying dependencies, including data(bases) is just as much part of the problem?
BeetleB 2y ago
Everyone talks about refactoring code. What I don't see enough discussion on is refactoring tests. It's a constant battle at work, and I tend to be firm with: "If the test is working, no matter how horrible the (test) code, leave it be."[1] For regular code, we rely on tests to validate our refactors. With test code, we don't have that support. If you have a bunch of tests that could do with a refactor, and your motivation is that you need to write more tests, then set up whatever abstractions you need and write the new tests, but don't touch the existing tests! If you really want, you can overtest: Write new tests with your refactored code that test the same thing as the old ones. It's OK to test the same thing multiple times (when testing is cheap). About a third of the time a coworker looks at my tests and refactors them, he makes an error - the most common one being not testing what the original test meant to test. See, the reason he wanted to refactor was that the original test was hard to follow. And because of that, he failed to interpret it correctly and failed to properly reproduce the test in his refactored code. I then have to code review all his refactors. I have to spend time to figure out what my difficult-to-understand test did, and confirm he didn't introduce bugs. It's very, very tiring. And for what? And he's not a newbie. He's as good at SW as I am. Plenty of experience. If he gets it wrong, I expect most people will get it wrong. With a higher error rate. This is the one case where I say: "Feel free to overcomment." If you took a long time understanding a given test, write out what you learned so that the next time you read it, you know what it does. I'll be happy to code review that. [1] Unless you are the original author of the tests, and they are still fresh in your mind. In that case, refactor all you want.
- kylereeve 2y ago
  When refactoring tests, some form of mutation coverage [0] would be really nice. Verify that the tests break when the underlying code changes. [0] https://en.wikipedia.org/wiki/Mutation_testing https://en.wikipedia.org/wiki/Mutation_testing
  - deleted 2y ago
    [deleted]
- foo_barrio 2y ago
  This is a good point! We've gotten some instances of Chesterson's Fence that some devs casually remove during a "test refactor" that later allowed a regression to make it into prod. I've caught some errors in "test refactoring" from our multiple levels of testing having large overlap with teach other. Our end-to-end tests have a lot of overlap with the integration tests which in turn have a large overlap with unit testing. The unit tests run in a matter of seconds compared to the end-to-end which can take minutes or in some cases hours for our manual testing so the levels of testing also serve as an efficiency for us.
GiorgioG 2y ago
Does anyone really get time to refactor anything these days? Seems like (at least where I'm at), everything is go-go-go, feature work.
- foo_barrio 2y ago
  I try to never ever use the word "refactor" or "clean up" in any of my work items or even commit messages. My boss and other teams I am collaborating with are like clients to me. Restaurant bills typically do not include explicit line items for "dish washing, mopping, grease-trap cleaning, oil disposal, etc." The downside is that other people/teams can appear to work much faster and put you at a disadvantage or even risk of being let go due to this perception. Unfortunately this is where IMO you have to play the game and make sure you toot your own horn to the right people sometimes.
- maccard 2y ago
  If you work in a kitchen, you’re expected to keep the kitchen clean. The trick to that is knowing how to efficiently clear up, and being prepared for the waves when they come. As an engineer it’s no different. If you’re not keeping in top of your own debt, you’re actually falling behind.
- IshKebab 2y ago
  Yeah just do it as part of your work without telling people. You're paid to write software and part of writing software is refactoring.
merb 2y ago
When working with git it’s better to split refactorings, bug fixes and features per commit or merge request (if you squash) else your git history will be not so useful anymore.
gspencley 2y ago
> We often reach a point during refactoring where it seems like there is an easy improvement that applies to almost all cases. It’s usually better not to impose additional abstraction if it only matches “almost” all cases. Need to nit-pick on this one. There are design patterns, depending on your programming paradigm, that enable you to de-dupe the common stuff while allowing for all of those little variances to do their own unique thing without duplicating anything. In OOP the Template Method pattern comes to mind. I would even go so far as to say that the "almost all cases" problem is such a common problem in software development, that the patterns world has come up with various solutions to that which are intended to simplify, not complicate. I'm sure there are concrete examples where there are no good pre-existing solutions, and there are often examples where cures can be worse than the diseases and you need to make a judgement call. But don't give yourself an excuse to duplicate code because you don't know how to de-dupe in the "almost all cases" scenario. That's a very solved problem.
poulsbohemian 2y ago
I spent about a 12 year period of my career doing triage and app performance work. What struck me was how often the core problems were architectural. Either the design was bad from the beginning, or the requirements had changed so dramatically over time (think scaling, for example) that the architecture no longer worked. I bring this up because while I saw a lot of questionable code, at the micro level it really didn't matter. Sure it could have been refactored and improved, but that would have been essentially diminishing returns. Often the improvements that were needed would have been so painful that rather than make them, I watched companies spiral around either throwing hardware at problems or replacing the application entirely because that kind of Bandaid rip was deemed "easier" in the overall politics of the corporate world. So point being - sure, refactor what you can, but don't get too hung up on things that ultimately won't matter.
- jamesfinlayson 2y ago
  > What struck me was how often the core problems were architectural Agreed - I remember at a previous job a new guy turned up and directed a rewrite of an old Perl application into a new Go version. He crowed on and on about how Go was so much faster than Perl but the underlying issue was the original architecture (old one was pinned to a single core and polled a database once a minute, the new one was dispatching requests pulled off a Kafka queue). The old one had been written when the system was handling less than a transaction a minute and the only attempts to fix it were upgrading Perl or various libraries.
bob1029 2y ago
If it won't impact your margins or the customer's willingness to pay for the product then it is difficult to justify. I've been involved with (and responsible for) many "developer aesthetic" refactors over the years. They feel good in the moment but after blowing 2-3 weeks with regression testing, hot patches, etc., you start to wonder if it was all worth it. There is stuff that is properly nasty and needs to be dealt with, but if you are spinning your wheels on things like namespaces being stuck on old company/product names, I would just give it up and move on. The average customer cannot see any of the things that frustrate us unless they are being done very poorly.
- magicalhippo 2y ago
  We've got a lot of 20+ year old code in production, a lot written late at night in a crunch. Much of it's ugly, non-optimal and screams to be ripped out and replaced. But it is working, in areas that see little change and are not overly performance sensitive. So we only do something with it if we need larger changes. Otherwise we leave it be and spend our time being productive elsewhere.
tikhonj 2y ago
> There’s no benefit to improving code that never changes, even if it is highly complex. Only if you don't care about being able to understand and debug the code in the future! And even then it's if you're confident in predicting how much code will or won't need to change, which, well...
- mason55 2y ago
  The point is not to improve it until you actually need to change it. Like you said, you're probably bad at predicting which code is going to need changes in the future, so if it's working now and you don't need to change it then it's a silly risk to try to improve it right now.
patrick451 2y ago
There are two conflicting rules of thumb floating around here 1. If hasn't changed in a long time and no business requirement on the horizon will force it to change, don't refactor. 2. Code is read more than written, so optimize for readability. (1) can only be followed to the detriment of (2), unless you add the condition that the code is also code which developers never need to read and understand to implement other features.
gbuk2013 2y ago
> If we’re embarking on a change that is not really refactoring (for example looking at a bug or an adjustment after a third party change), we can’t fix it with refactoring. Funnily enough I did once fix a bug through refactoring. IIRC it was some intermittent race condition in some async code that I just couldn’t figure out, so I rewrote the code to do the same thing but simpler and the problem disappeared. I was too tired and relieved to continue figuring it out why it was originally broken.
- TiredGuy 2y ago
  Same. Sometimes the best way to fix a bug is to refactor it out of existence.
  - Salgat 2y ago
    And if you're lucky a new hidden bug appears.
- zingar 2y ago
  I suppose theoretically this must have been behaviour change that crept in with the refactoring, that luckily had a good result and not a bad one. I get nervous about things that accidentally work but I definitely relate to being so tired or under too much pressure to move on that I just trust in luck. That said, I would guess that even if the accidental behaviour change didn't occur, the bug would have been much easier to solve after the refactor made the intention of the code clearer.
mont_tag 2y ago
One more consideration is whether a team of people have invested time building a mental map of the current code. Perhaps some rearrangement would be better, faster, clearer, or have some other virtue. But that benefit has to be balanced against invalidating the mental caches of all the other team members. More than once, I've studied code and become adept at maintaining it. Then someone "refactors" everything and I have to invest the effort again. After a few cycles of this, I lose interest in ever seeing the code again. At that point, I can no longer orient a new dev to the code because I'm no longer oriented myself.
- ozim 2y ago
  That is a pain with new guys on team that don’t want to spend time learning the code but rather rewrite it their way so they can understand it. Only problem is that’s ultimately not polite to existing team and hopefully we can filter such people in hiring process but not always.
- zingar 2y ago
  Great point about team mental context! Without knowing the context I would guess that this a bad refactor (away from revealing the intention)... probably including some cases of applying new abstractions that don't fit the real problem. How does that match with your experience? Update: it occurs to me that I have seen complex code (for which people would need a mental map) be simplified so drastically that no-one needs to worry about mental maps. I would much prefer "no-one needs a mental map" over "there's a team with good mental maps".
kevmojay138 2y ago
> Instead of “refactoring” without tests, we can start by writing some tests! I agree with this but I have always struggled with putting it into practice. Good code is easy to test. Often, I want to refactor to make it easy to test.
einpoklum 2y ago
My top reasons not to refactor: 1. My boss won't let me. The usual excuse: "Too risky... there are other priorities... and besides, where are those performance improvements you promised me? We don't pay you to make the code pretty." 2. Boss of group which owns some of the code I need to refactor won't let me: "Too risky... we have other priorities... have your boss bring this up in the next [bogus] meeting" 3. Other developers get panties in a bunch over a tiny refactor (semantically) but which involves changes to names in a lot of files. 4. Knowing that if I'd start this refactor I will not be able to resist another refactor until I'm basically refactoring people's entire code to look quite different.
einpoklum 2y ago
Peeves about the items in the linked post: > 1. The change is not really a refactor Is anything ever really just a refactor, though? > 3. Another refactor is already in progress Ah, but - in large and poorly-maintained codebase, it is always the case that some refactoring is already in progress, likely stalled for weeks, months or years as priorities have shifted without it having been completed. > 4. The code is unlikely to change If the code is unlikely to change, there's a good chance you might want to refactor it out of your repository anyway, into some low-frequency-of-changing library. > There’s no benefit to improving code that never changes Oh, there are lots of benefits to improving code that never changes! And that's because other code _uses_ the code which never changes. And if originally the use is clunky, but you manage to improve it by your refactor, youve' done well indeed. > 5. There are no tests A repository which lacks test coverage is extremely likely to be in dire need of all kinds of refactoring. Waiting until someone (maybe even yourtself) writes tests for most code, before doing anything in the mean time - well, it basically means giving up on yourself. > we can start by writing some tests! Well, that's nice, but - if we do that, then no refactoring would get done, and we'll have to write code based on ugly and unweildy older code, which only adds stuff to refactor later. Plus, who's to say the tests don't fail _already_? :-(
- Fishkins 2y ago
  > Ah, but - in large and poorly-maintained codebase, it is always the case that some refactoring is already in progress, likely stalled for weeks, months or years as priorities have shifted without it having been completed. This is true, and something I also thought of when reading that point. I don't think it's necessarily a counterargument, though. It's probably a better idea to spend your time helping to complete the previous refactor instead of starting your new one. Codebases in which many refactorings are started but not completed can be worse than ones that aren't refactored at all. There could be exceptions if your new changes is very small, localized, and unlikely to interfere with the other changes going on.
  - einpoklum 2y ago
    > It's probably a better idea to spend your time helping to complete > the previous refactor instead of starting your new one That is a fair suggestion - when practicable. Often, it isn't, because of the very reasons which made the old refactor stall in the first place, e.g.: * The target factor of the code was not such a good choice to begin with. * The code in question is critical and any change to it is discouraged or feared. * The code in question is the responsibility of different groups of developers / different departments, and they, or their managers, are not in the mood for collaboration. etc.
madmountaingoat 2y ago
It's all solid advice but that exchange in #5 that the author found delightful, drives me bonkers. If you talk to the people on your team like that, you're not being helpful, you're being an a-hole. I realize its just making a point in the context of the article, but this industry seems to collect pedants, so it seems worth pointing out as an anti-pattern.
- zingar 2y ago
  Article author here, this is a really good point and I can see how that exchange might undermine the point (or even the entire article) for some readers. I think I understand it as fighting fire with fire: that people who are enthusiastic about refactoring without understanding and writing tests are prone to pushing their agenda without really engaging on the substantive points (as in someone who talks "refactoring" without taking in how central automated tests are in the refactoring community). Such a person sometimes needs a confrontational push to go back to the basics on this point.
xg15 2y ago
> “Before we can add tests, we need to refactor.” - “No.” - “Refactoring th–” - “No.” - “Refa–” - “No.” What to do instead: Instead of “refactoring” without tests, we can start by writing some tests! Writing new tests will help us learn about the code. After that, we can come back to refactoring. I assume the author means system tests here? Because it's absolutely possible to have code that is so entangled that it's impossible to write self-contained unit tests before, well, refactoring the code.
- zingar 2y ago
  I mean tests of any kind. The main reason I see for tests not existing is because the engineers don't have the skill to write effective tests fast enough (and after a while in that state, just deciding that tests aren't worth it). The code not being testable is a distant second or third.
deleted 2y ago
[deleted]
coderinsan 2y ago
[dead]

80 points by chmaynard 2y ago

another reason to not refactor is management will start out supportive of it but some weeks in they will wonder wtf their engineers are doing all day and why aren't they building the new pile of stuff they want built yesterday.

eyelidlessness 2y ago
That’s not so much a reason, in my experience, as a frequent default/inertia position. In other words, I expect to start at that default, and challenge it with reasoning, in order to justify a significant refactor.
svachalek 2y ago
Refactoring is a terrible project plan. You never want your weekly status to be "refactored some more". Plan your other development work with enough time to refactor as you go.
lesuorac 2y ago
The ability to ship small things is I think something really missed in discussion about microservices. Like rather then refactoring the entire application to support a faster cache or something you can just add in another microservice that handles caching of the data. If some way you write the services is poor you can rewrite one of the services a new way and easily evaluate if it's actually a good idea to change the rest or not.
IshKebab 2y ago
Don't spend 100% of your time refactoring.
zingar 2y ago
I do encounter hostility but what I've realised is that it comes from experience of refactoring being done badly. "We made time for this refactoring thing but it made no difference so now we're not going to 'refactor' anymore". The worst hostility is often from management that used to be technical but never learned how to refactor effectively so they have what they think is justifiable scepticism. s/refactoring/pairing or any other technique that is good in theory but requires skill to implement. I usually find that people without technical background are willing to follow the advice of the developers that work with them, taking the things that work with them into their next roles. If refactoring worked in the beginning they'll be open to it in future, if it didn't work they'll dismiss it. Edit: also - what everyone else said - "refactoring" isn't a business goal, it's one part of achieving the goal. Achieve the goal and no-one cares how you did it. ("add a new button to that widget" isn't a business goal either so there is a tricky aspect of getting management to understand that they should be bringing you problems/goals not solutions)

gavmor 2y ago

Well, yeah, that example decreases symmetry.[0] 0. https://bensguide.substack.com/i/144306439/local-symmetries https://bensguide.substack.com/i/144306439/local-symmetries

lelanthran 2y ago

Simple and brief rules are more successful in practice than long and complicated rules. I feel a briefer and more-to-the-point "When To Refactor" guide is to ask the following questions in the following order and only proceed when you can answer YES to every single question. 1. Do we have test coverage of the use-cases that are affected? 2. Are any non-trivial logic and business changes on the horizon for the code in question? 3. Has the code in question been undergoing multiple modifications in the last two/three/four weeks/months/years? Honestly, if you answer NO to any of the questions above, you're in for a world of hurt and expense if you then proceed to refactor. That last one might seem a bit of a reach, but the reality is that if there is some code in production that has been working unchanged for the last two years, you're wasting your time refactoring it. More importantly, no changes over the last few years means that absolutely no one in the company has in-depth and current knowledge of how that code works, so a refactor is pointless because no one knows what the specific problems actually are.

andrei_says_ 2y ago
These are very simple and clear and confirm my own approach to refactoring. Thank you.
eyelidlessness 2y ago
One reason I might accept one or more NOs to your questions: Does the refactor support pending work, which isn’t directly related to the refactored code, but benefits from the lessons learned and applied in the refactor… even in some indirect way? This might be providing a clearer pattern you’ll apply to similar new functionality; or it might be providing a new abstraction or even eliminating a failed abstraction which sets that pending work on the right path.
- AnimalMuppet 2y ago
  Yeah. I did a (very small) refactor. It took, IIRC, four days. When I was done, I could write the new thing I was implementing in 10 new lines that used the newly-refactored existing code.
2y ago

karmakaze 2y ago

I have one reason to refactor that's served me well. Does the code exhibit ongoing edge/corner case bugs, which are attributed to the implementation not being factored in the first place? Another sign of this situation is exhaustive test cases which combine factors as they can't reliably be tested in isolation. Distributed logic is another common pattern, where a new feature is made by sprinkling bits of logic here and there, just so, and it all seems to do what's required. You know the kind, where onboarding a new person might lead to the discussion of how this section of your Rube Goldberg contraption works. A fancy way to this world is a poorly designed and maintained home-grown DSL. Continuing to build on such a 'foundation' is madness that spirals to code red situations: stop-the-world, no feature development, until shit gets stable.

PaulHoule 2y ago

The default-oriented answer to #2 is to pass the rows through some function that applies the default to 'loud' if loud is undefined. That's really pretty code and avoids the complex if-statement which is a universal bad smell.

taeric 2y ago

I like these reasons. I will offer some caution on rules for rejecting a proposal. Often times, the number one reason to do something is that there is energy there to do it. If you can take that energy and apply it somewhere else, by all means do so. All too often, suppressing some energy stops all effort.

hylaride 2y ago

Refactoring depends heavily on circumstances. I've seen terrible attempts over my career for all the reasons other people have and will mention here. But I've also seen huge successes. Usually it boils down to "what are you trying to accomplish?" against current code and architecture. I've seen targeted refactors of micro-service code, including language shifts (eg python -> java where threading improved things a lot in that use case), as well as targeted shifts of code to AWS Lambdas, where execution scaling also benefited the use case. But in both examples there was a clear benefit, execution plan, and way to measure success. When you start refactoring large mono-app code bases for nebulous, hard to measure reasons then the risks are much higher (and that's even before scope creep comes into play). This gets even worse if the reason the current code is no longer desirable has reasons (both good and bad) that it is the way it is, and you risk recreating bad code (this was mentioned in the article) into new bad code. Also, migrations to new code can suck if the underlying dependencies, including data(bases) is just as much part of the problem?

BeetleB 2y ago

Everyone talks about refactoring code. What I don't see enough discussion on is refactoring tests. It's a constant battle at work, and I tend to be firm with: "If the test is working, no matter how horrible the (test) code, leave it be."[1] For regular code, we rely on tests to validate our refactors. With test code, we don't have that support. If you have a bunch of tests that could do with a refactor, and your motivation is that you need to write more tests, then set up whatever abstractions you need and write the new tests, but don't touch the existing tests! If you really want, you can overtest: Write new tests with your refactored code that test the same thing as the old ones. It's OK to test the same thing multiple times (when testing is cheap). About a third of the time a coworker looks at my tests and refactors them, he makes an error - the most common one being not testing what the original test meant to test. See, the reason he wanted to refactor was that the original test was hard to follow. And because of that, he failed to interpret it correctly and failed to properly reproduce the test in his refactored code. I then have to code review all his refactors. I have to spend time to figure out what my difficult-to-understand test did, and confirm he didn't introduce bugs. It's very, very tiring. And for what? And he's not a newbie. He's as good at SW as I am. Plenty of experience. If he gets it wrong, I expect most people will get it wrong. With a higher error rate. This is the one case where I say: "Feel free to overcomment." If you took a long time understanding a given test, write out what you learned so that the next time you read it, you know what it does. I'll be happy to code review that. [1] Unless you are the original author of the tests, and they are still fresh in your mind. In that case, refactor all you want.

kylereeve 2y ago
When refactoring tests, some form of mutation coverage [0] would be really nice. Verify that the tests break when the underlying code changes. [0] https://en.wikipedia.org/wiki/Mutation_testing https://en.wikipedia.org/wiki/Mutation_testing
- deleted 2y ago
  [deleted]
foo_barrio 2y ago
This is a good point! We've gotten some instances of Chesterson's Fence that some devs casually remove during a "test refactor" that later allowed a regression to make it into prod. I've caught some errors in "test refactoring" from our multiple levels of testing having large overlap with teach other. Our end-to-end tests have a lot of overlap with the integration tests which in turn have a large overlap with unit testing. The unit tests run in a matter of seconds compared to the end-to-end which can take minutes or in some cases hours for our manual testing so the levels of testing also serve as an efficiency for us.

GiorgioG 2y ago

Does anyone really get time to refactor anything these days? Seems like (at least where I'm at), everything is go-go-go, feature work.

foo_barrio 2y ago
I try to never ever use the word "refactor" or "clean up" in any of my work items or even commit messages. My boss and other teams I am collaborating with are like clients to me. Restaurant bills typically do not include explicit line items for "dish washing, mopping, grease-trap cleaning, oil disposal, etc." The downside is that other people/teams can appear to work much faster and put you at a disadvantage or even risk of being let go due to this perception. Unfortunately this is where IMO you have to play the game and make sure you toot your own horn to the right people sometimes.
maccard 2y ago
If you work in a kitchen, you’re expected to keep the kitchen clean. The trick to that is knowing how to efficiently clear up, and being prepared for the waves when they come. As an engineer it’s no different. If you’re not keeping in top of your own debt, you’re actually falling behind.
IshKebab 2y ago
Yeah just do it as part of your work without telling people. You're paid to write software and part of writing software is refactoring.

merb 2y ago

When working with git it’s better to split refactorings, bug fixes and features per commit or merge request (if you squash) else your git history will be not so useful anymore.

gspencley 2y ago

> We often reach a point during refactoring where it seems like there is an easy improvement that applies to almost all cases. It’s usually better not to impose additional abstraction if it only matches “almost” all cases. Need to nit-pick on this one. There are design patterns, depending on your programming paradigm, that enable you to de-dupe the common stuff while allowing for all of those little variances to do their own unique thing without duplicating anything. In OOP the Template Method pattern comes to mind. I would even go so far as to say that the "almost all cases" problem is such a common problem in software development, that the patterns world has come up with various solutions to that which are intended to simplify, not complicate. I'm sure there are concrete examples where there are no good pre-existing solutions, and there are often examples where cures can be worse than the diseases and you need to make a judgement call. But don't give yourself an excuse to duplicate code because you don't know how to de-dupe in the "almost all cases" scenario. That's a very solved problem.

poulsbohemian 2y ago

I spent about a 12 year period of my career doing triage and app performance work. What struck me was how often the core problems were architectural. Either the design was bad from the beginning, or the requirements had changed so dramatically over time (think scaling, for example) that the architecture no longer worked. I bring this up because while I saw a lot of questionable code, at the micro level it really didn't matter. Sure it could have been refactored and improved, but that would have been essentially diminishing returns. Often the improvements that were needed would have been so painful that rather than make them, I watched companies spiral around either throwing hardware at problems or replacing the application entirely because that kind of Bandaid rip was deemed "easier" in the overall politics of the corporate world. So point being - sure, refactor what you can, but don't get too hung up on things that ultimately won't matter.

jamesfinlayson 2y ago
> What struck me was how often the core problems were architectural Agreed - I remember at a previous job a new guy turned up and directed a rewrite of an old Perl application into a new Go version. He crowed on and on about how Go was so much faster than Perl but the underlying issue was the original architecture (old one was pinned to a single core and polled a database once a minute, the new one was dispatching requests pulled off a Kafka queue). The old one had been written when the system was handling less than a transaction a minute and the only attempts to fix it were upgrading Perl or various libraries.

bob1029 2y ago

If it won't impact your margins or the customer's willingness to pay for the product then it is difficult to justify. I've been involved with (and responsible for) many "developer aesthetic" refactors over the years. They feel good in the moment but after blowing 2-3 weeks with regression testing, hot patches, etc., you start to wonder if it was all worth it. There is stuff that is properly nasty and needs to be dealt with, but if you are spinning your wheels on things like namespaces being stuck on old company/product names, I would just give it up and move on. The average customer cannot see any of the things that frustrate us unless they are being done very poorly.

magicalhippo 2y ago
We've got a lot of 20+ year old code in production, a lot written late at night in a crunch. Much of it's ugly, non-optimal and screams to be ripped out and replaced. But it is working, in areas that see little change and are not overly performance sensitive. So we only do something with it if we need larger changes. Otherwise we leave it be and spend our time being productive elsewhere.

tikhonj 2y ago

> There’s no benefit to improving code that never changes, even if it is highly complex. Only if you don't care about being able to understand and debug the code in the future! And even then it's if you're confident in predicting how much code will or won't need to change, which, well...

mason55 2y ago
The point is not to improve it until you actually need to change it. Like you said, you're probably bad at predicting which code is going to need changes in the future, so if it's working now and you don't need to change it then it's a silly risk to try to improve it right now.

patrick451 2y ago

There are two conflicting rules of thumb floating around here 1. If hasn't changed in a long time and no business requirement on the horizon will force it to change, don't refactor. 2. Code is read more than written, so optimize for readability. (1) can only be followed to the detriment of (2), unless you add the condition that the code is also code which developers never need to read and understand to implement other features.

gbuk2013 2y ago

> If we’re embarking on a change that is not really refactoring (for example looking at a bug or an adjustment after a third party change), we can’t fix it with refactoring. Funnily enough I did once fix a bug through refactoring. IIRC it was some intermittent race condition in some async code that I just couldn’t figure out, so I rewrote the code to do the same thing but simpler and the problem disappeared. I was too tired and relieved to continue figuring it out why it was originally broken.

TiredGuy 2y ago
Same. Sometimes the best way to fix a bug is to refactor it out of existence.
- Salgat 2y ago
  And if you're lucky a new hidden bug appears.
zingar 2y ago
I suppose theoretically this must have been behaviour change that crept in with the refactoring, that luckily had a good result and not a bad one. I get nervous about things that accidentally work but I definitely relate to being so tired or under too much pressure to move on that I just trust in luck. That said, I would guess that even if the accidental behaviour change didn't occur, the bug would have been much easier to solve after the refactor made the intention of the code clearer.

mont_tag 2y ago

One more consideration is whether a team of people have invested time building a mental map of the current code. Perhaps some rearrangement would be better, faster, clearer, or have some other virtue. But that benefit has to be balanced against invalidating the mental caches of all the other team members. More than once, I've studied code and become adept at maintaining it. Then someone "refactors" everything and I have to invest the effort again. After a few cycles of this, I lose interest in ever seeing the code again. At that point, I can no longer orient a new dev to the code because I'm no longer oriented myself.

ozim 2y ago
That is a pain with new guys on team that don’t want to spend time learning the code but rather rewrite it their way so they can understand it. Only problem is that’s ultimately not polite to existing team and hopefully we can filter such people in hiring process but not always.
zingar 2y ago
Great point about team mental context! Without knowing the context I would guess that this a bad refactor (away from revealing the intention)... probably including some cases of applying new abstractions that don't fit the real problem. How does that match with your experience? Update: it occurs to me that I have seen complex code (for which people would need a mental map) be simplified so drastically that no-one needs to worry about mental maps. I would much prefer "no-one needs a mental map" over "there's a team with good mental maps".

kevmojay138 2y ago

> Instead of “refactoring” without tests, we can start by writing some tests! I agree with this but I have always struggled with putting it into practice. Good code is easy to test. Often, I want to refactor to make it easy to test.

einpoklum 2y ago

My top reasons not to refactor: 1. My boss won't let me. The usual excuse: "Too risky... there are other priorities... and besides, where are those performance improvements you promised me? We don't pay you to make the code pretty." 2. Boss of group which owns some of the code I need to refactor won't let me: "Too risky... we have other priorities... have your boss bring this up in the next [bogus] meeting" 3. Other developers get panties in a bunch over a tiny refactor (semantically) but which involves changes to names in a lot of files. 4. Knowing that if I'd start this refactor I will not be able to resist another refactor until I'm basically refactoring people's entire code to look quite different.

einpoklum 2y ago

Peeves about the items in the linked post: > 1. The change is not really a refactor Is anything ever really just a refactor, though? > 3. Another refactor is already in progress Ah, but - in large and poorly-maintained codebase, it is always the case that some refactoring is already in progress, likely stalled for weeks, months or years as priorities have shifted without it having been completed. > 4. The code is unlikely to change If the code is unlikely to change, there's a good chance you might want to refactor it out of your repository anyway, into some low-frequency-of-changing library. > There’s no benefit to improving code that never changes Oh, there are lots of benefits to improving code that never changes! And that's because other code _uses_ the code which never changes. And if originally the use is clunky, but you manage to improve it by your refactor, youve' done well indeed. > 5. There are no tests A repository which lacks test coverage is extremely likely to be in dire need of all kinds of refactoring. Waiting until someone (maybe even yourtself) writes tests for most code, before doing anything in the mean time - well, it basically means giving up on yourself. > we can start by writing some tests! Well, that's nice, but - if we do that, then no refactoring would get done, and we'll have to write code based on ugly and unweildy older code, which only adds stuff to refactor later. Plus, who's to say the tests don't fail _already_? :-(

Fishkins 2y ago
> Ah, but - in large and poorly-maintained codebase, it is always the case that some refactoring is already in progress, likely stalled for weeks, months or years as priorities have shifted without it having been completed. This is true, and something I also thought of when reading that point. I don't think it's necessarily a counterargument, though. It's probably a better idea to spend your time helping to complete the previous refactor instead of starting your new one. Codebases in which many refactorings are started but not completed can be worse than ones that aren't refactored at all. There could be exceptions if your new changes is very small, localized, and unlikely to interfere with the other changes going on.
- einpoklum 2y ago
  > It's probably a better idea to spend your time helping to complete > the previous refactor instead of starting your new one That is a fair suggestion - when practicable. Often, it isn't, because of the very reasons which made the old refactor stall in the first place, e.g.: * The target factor of the code was not such a good choice to begin with. * The code in question is critical and any change to it is discouraged or feared. * The code in question is the responsibility of different groups of developers / different departments, and they, or their managers, are not in the mood for collaboration. etc.

madmountaingoat 2y ago

It's all solid advice but that exchange in #5 that the author found delightful, drives me bonkers. If you talk to the people on your team like that, you're not being helpful, you're being an a-hole. I realize its just making a point in the context of the article, but this industry seems to collect pedants, so it seems worth pointing out as an anti-pattern.

zingar 2y ago
Article author here, this is a really good point and I can see how that exchange might undermine the point (or even the entire article) for some readers. I think I understand it as fighting fire with fire: that people who are enthusiastic about refactoring without understanding and writing tests are prone to pushing their agenda without really engaging on the substantive points (as in someone who talks "refactoring" without taking in how central automated tests are in the refactoring community). Such a person sometimes needs a confrontational push to go back to the basics on this point.

xg15 2y ago

> “Before we can add tests, we need to refactor.” - “No.” - “Refactoring th–” - “No.” - “Refa–” - “No.” What to do instead: Instead of “refactoring” without tests, we can start by writing some tests! Writing new tests will help us learn about the code. After that, we can come back to refactoring. I assume the author means system tests here? Because it's absolutely possible to have code that is so entangled that it's impossible to write self-contained unit tests before, well, refactoring the code.

zingar 2y ago
I mean tests of any kind. The main reason I see for tests not existing is because the engineers don't have the skill to write effective tests fast enough (and after a while in that state, just deciding that tests aren't worth it). The code not being testable is a distant second or third.

deleted 2y ago

[deleted]

coderinsan 2y ago

[dead]