Using go fix to modernize Go code

by todsacerdoti • 5 months ago

432 81 5 months ago

homarp• 5 months ago

I really liked this part:

In December 2024, during the frenzied adoption of LLM coding assistants, we became aware that such tools tended—unsurprisingly—to produce Go code in a style similar to the mass of Go code used during training, even when there were newer, better ways to express the same idea. Less obviously, the same tools often refused to use the newer ways even when directed to do so in general terms such as “always use the latest idioms of Go 1.25.” In some cases, even when explicitly told to use a feature, the model would deny that it existed. [...] To ensure that future models are trained on the latest idioms, we need to ensure that these idioms are reflected in the training data, which is to say the global corpus of open-source Go code.

robviren• 5 months ago

I have run into that a lot which is annoying. Even though all the code compiles because go is backwards compatible it all looks so much different. Same issue for python but in that case the API changes lead to actual breakage. For this reason I find go to be fairly great for codegen as the stability of the language is hard to compete with and the standard lib a powerful enough tool to support many many use cases.

HumblyTossed• 5 months ago

The use of LLMs will lead to homogeneous, middling code.

awesome_dude5• 5 months ago

I'm not sure if that's a criticism or praise - I mean, most people strive for readable code.

cedws• 5 months ago

It does. I’ve been writing Go for long enough, and the code that LLMs output is pretty average. It’s what I would expect a mid level engineer to produce. I still write code manually for stuff I care about or where code structure matters.

Maybe the best way is to do the scaffolding yourself and use LLMs to fill the blanks. That may lead to better structured code, but it doesn’t resolve the problem described above where it generates suboptimal or outdated code. Code is a form of communication and I think good code requires an understanding of how to communicate ideas clearly. LLMs have no concept of that, it’s just gluing tokens together. They litter code with useless comments while leaving the parts that need them most without.

saghm• 5 months ago

You might even say that LLMs are not capable of understanding a brilliant language but we want to use them to build good software. So, the language that we give them has to be easy for them to understand and easy to adopt.

bee_rider• 5 months ago

Do LLMs generate code similar to middling code of a given domain? Why not generate in a perfect language used only by cool and very handsome people, like Fortran, and then translate it to once the important stuff is done?

munk-a4• 5 months ago

Middling code should not exist. Boilerplate code should not exist. For some reason we're suddenly accepting code-gen as SOP instead of building a layer of abstraction on top of the too-onerous layer we're currently building at. Prior generations of software development would see a too-onerous layer and build tools to abstract to a higher level, this generation seems stuck in an idea that we just need tooling to generate all that junk but can continue to work at this level.

meowface• 5 months ago

For a few years, yeah. Eventually it will probably lead to the average quality of code being considerably higher than it was pre-LLMs.

shoo• 5 months ago

middling code, delivered within a tolerable time frame, budget, without taking excessive risk, is good enough for many real-world commercial software projects. homogeneous middling code, written by humans or extruded by machines, is arguably even a positive for the organisation: lots of organisations are more interested in delivery of software projects being predictable, or having a high bus-factor due to the fungibility of the folks (or machines) building and maintaining the code, rather than depending upon excellence.

munk-a4• 5 months ago

PHP went through a similar effort a while back to just clear out places like Stackoverflow of terrible out of date advice (e.g. posts advocating magic_quotes). LLMs make this a slightly different problem because, for the most part, once the bad advice is in the model it's never going away. In theory there's an easier to test surface around how good the advice it's giving is but trying to figure out how it got to that conclusion and correct it for any future models is arcane. It's unlikely that model trainers will submit their RC models to various communities to make sure it isn't lying about those specific topics so everything needs to happen in preparation of the next generation and relying on the hope that you've identified the bad source it originally trained on and that the model will actually prioritize training on that same, now corrected, source.

miki123211• 5 months ago

This is one area where reinforcement learning can help.

The way you should think of RL (both RLVR and RLHF) is the "elicitation hypothesis[1]." In pretraining, models learn their capabilities by consuming large amounts of web text. Those capabilities include producing both low and high quality outputs (as both low and high quality outputs are present in their pretraining corpora). In post training, RL doesn't teach them new skills (see E.G. the "Limits of RLVR"[2] paper). Instead, it "teaches" the models to produce the more desirable, higher-quality outputs, while suppressing the undesirable, low-quality ones.

I'm pretty sure you could design an RL task that specifically teaches models to use modern idioms, either as an explicit dataset of chosen/rejected completions (where the chosen is the new way and the rejected is the old), or as a verifiable task where the reward goes down as the number of linter errors goes up.

I wouldn't be surprised if frontier labs have datasets for this for some of the major languages and packages.

[1] https://www.interconnects.ai/p/elicitation-theory-of-post-tr...

[2] https://limit-of-rlvr.github.io

BiraIgnacio• 5 months ago

I definitely see that with C++ code Not so easy to "fix", though. Or so I think. But I do hope still, as more and more "modern" C++ code gets published

Groxx3• 5 months ago

They're particularly bad about concurrent go code, in my experience - it's almost always tutorial-like stuff, over-simplified and missing error and edge case handling to the point that it's downright dangerous to use... but it routinely slips past review because it seems simple and simple is correct, right? Go concurrency is so easy!

And then you point out issues in a review, so the author feeds it back into an LLM, and code that looks like it handles that case gets added... while also introducing a subtle data race and a rare deadlock.

Very nearly every single time. On all models.

Jyaif2• 5 months ago

a subtle data race and a rare deadlock

That's a langage problem that humans face as well, which golang could stop having (see C++'s Thread Safety annotations).

brightball• 5 months ago

Good use case for Elixir. Apparently it performs best across all programming languages with LLM completions and its concurrency model is ideal too.

https://autocodebench.github.io/

dakolli• 5 months ago

I'd prefer we start nuking the idea of using LLMs to write code, not help it get better. Why don't you people listen to Rob Pike, this technology is not good for us. Its a stain on software and the world in general, but I get it most of ya'll yearn for slop. The masses yearn for slop.

throw432196• 5 months ago

I totally agree. I read threads like this and I just can’t believe people are wasting their time with LLM’s.

whattheheckheck• 5 months ago

The masses yearn to not have to fiddle with bs for rent and food

yawboakye• 5 months ago

battle of my life. several times i’ve had to update my agent instructions to prefer modern and usually better syntax to the old way of doing things. largely it’s worked well for me. i find that making the agents read release notes, and some official blog posts, helps them maintain a healthy and reasonably up-to-date instructions on writing go.

kiernanmcgowan• 5 months ago

Its tooling like this that really makes golang an excellent language to work with. I had missed that rangeint addition to the language but with go fix I'll just get that improvement for free!

Real kudos to the golang team.

jjice• 5 months ago

There have been many situations where I'd rather use another language, but Go's tooling is so good that I still end up writing it in Go. So hard to beat the build in testing, linting, and incredible compilation.

iamcalledrob• 5 months ago

Absolutely.

The Go team has built such trust with backwards compatibility that improvements like this are exciting, rather than anxiety-inducing.

Compare that with other ecosystems, where APIs are constantly shifting, and everything seems to be @Deprecated or @Experimental.

lowmagnet• 5 months ago

I just searched for `for` loops with `:=` within and hand-fixed them. I found a few forms of the for loops and where there was a high number, I used regexp.

This tool is way cooler, post-redesign.

retrodaredevil2• 5 months ago

I think tooling that can modify your source code to make it more modern is really cool stuff. OpenRewrite comes to mind for Java, but nothing comes to the top of my mind for other languages. And heck, I into recently learned about OpenRewrite and I've been writing Java for a long time.

Even though I don't like Go, I acknowledge that tooling like this built right into the language is a huge deal for language popularity and maturity. Other languages just aren't this opinionated about build tools, testing frameworks, etc.

I suspect that as newer languages emerge over the years, they'll take notes from Go and how well it integrates stuff like this.

pjmlp• 5 months ago

Java and .NET IDEs have had this capabilities for years now, even when Eclipse was the most used one there were the tips from Checkstyle, and other similar plugins.

retrodaredevil2• 5 months ago

Yeah I've noticed the IDEs have this ability, but I think tooling outside of IDEs that can be applied in a repeatable way is much better than doing a bunch of mouse clicks in an IDE to change something.

I think the two things that make this a big deal are: callable from the command line (which means it can integrate with CI/CD or AI tools) and like I mentioned, the fact this is built into Go itself.

zhfliz• 5 months ago

python has a number of these via pyupgrade, which are also included in ruff: https://docs.astral.sh/ruff/rules/#pyupgrade-up

silverwind• 5 months ago

eslint had `--fix` since like 10 years, so this is not exactly new.

lelandfe• 5 months ago

Lebab too: https://lebab.github.io/

YesThatTom2• 5 months ago

I can’t find where in the article the author claims it is new (as in original).

In fact, the author shows that this is an evolution of go vet and others.

What’s new, however, is the framework that allows home-grown add ons, which doesn’t have to do everything from scratch.

homebrewer• 5 months ago

Coccinelle for C, used by Linux kernel devs for decades, here's an article from 2009:

https://lwn.net/Articles/315686

Also IDE tooling for C#, Java, and many other languages; JetBrains' IDEs can do massive refactorings and code fixes across millions of lines of code (I use them all the time), including automatically upgrading your code to new language features. The sibling comment is slightly "wrong" — they've been available for decades, not mere years.

Here's a random example:

https://www.jetbrains.com/help/rider/ConvertToPrimaryConstru...

These can be applied across the whole project with one command, rewriting however many problems there are.

Also JetBrains has "structural search and replace" which takes language syntax into account, it works on a higher level than just text like what you'd see in text editors and pseudo-IDEs (like vscode):

https://www.jetbrains.com/help/idea/structural-search-and-re...

https://www.jetbrains.com/help/idea/tutorial-work-with-struc...

For modern .NET you have Roslyn analyzers built in to the C# compiler which often have associated code fixes, but they can only be driven from the IDE AFAIK. Here's a tutorial on writing one:

https://learn.microsoft.com/en-us/dotnet/csharp/roslyn-sdk/t...

nu11ptr• 5 months ago

but nothing comes to the top of my mind for other languages

"cargo clippy --fix" for Rust, essentially integrated with its linter. It doesn't fix all lints, however.

loevborg• 5 months ago

Does anyone have experience transforming a typescript codebase this way? Typescript's LSP server is not powerful enough and doesn't support basic things like removing a positional argument from a function (and all call sites).

Would jscodeshift work for this? Maybe in conjunction with claude?

g947o• 5 months ago

jscodeshift supports ts as a parser, so it should work.

If you want to also remove argument from call sites, you'll likely need to create your own tool that integrates TS Language Service data and jscodeshift.

LLMs definitely help with these codemods quite a bit -- you don't need to manually figure out the details in manipulating AST. But make sure to write tests -- a lot of them -- and come up with a way to quickly fix bugs, revert your change and then iterate. If you have set up the workflow, you may be able to just let LLM automate this for you in a loop until all issues are fixed.

0x696C6961• 5 months ago

Try ast-grep

glitchdout• 5 months ago

ESLint (and typescript-eslint) has the concept of fixers, which updates the source code.

nitnelave• 5 months ago

Rust has clippy nagging you with a bunch of modernity fixes, and sometimes it can autofix them. I learned about a lot of small new features that make the code cleaner through clippy.

kccqzy• 5 months ago

Haskell has had hlint for a very long time. Things like rewriting chained calls of `concat` and `map` into `concatMap`, or just rewriting your boolean expressions like `if a then b else False`.

Mopolo• 5 months ago

In PHP you can use Rector[1]

It's used a lot to migrate old codebases. The tool is using itself to downgrade[2] it so that it can run on older PHP versions to help upgrades.

[1] https://getrector.com

[2] https://github.com/rectorphp/rector-downgrade-php

nzoschke• 5 months ago

Go and its long established conventions and tools continues to be a massive boon to my agentic coding.

We have `go run main.go` as the convention to boot every apps dev environment, with support for multiple work trees, central config management, a pre-migrated database and more. Makes it easy and fast to dev and test many versions of an app at once.

See https://github.com/housecat-inc/cheetah for the shared tool for this.

Then of course `go generate`, `go build`, `go test` and `go vet` are always part of the fast dev and test loop. Excited to add `go fix` into the mix.

hu3• 5 months ago

And the screamingly fast compilation speed is a boon to fast LLM iterations as well.

malklera• 5 months ago

I wonder if you could make a language that is NOT backward compatible if you develop a tool like this alongside it.

suralind• 5 months ago

Self-service analyzers! This will be huge for big libraries and I can imagine heavily used by infra folks (although they could use analyzers already).

latchkey• 5 months ago

biome kind of does this stuff for me in the typescript world. for example, it recommends for...of instead of forEach. paired with ultracite, it really improves my workflow because it is super easy to add to any project, just one dependency. breath of fresh air compared with the eslint ecosystem.

i now have an agents.md file that says to run biome fix after every modification. i end with much nicer code that i don't have to go and fix myself (or resave the file to get biome to run). speeds things up considerably to not have that step in my own workflow.

HALtheWise• 5 months ago

Not even mentioned in the article, my favorite capability is the new `//go:fix inline` directive, which can be applied to a one-line function to make go fix inline it's contents into the caller.

That ends up being a really powerful primitive for library authors to get users off of deprecated functions, as long as the old semantics are concisely expressible with the new features. It can even be used (and I'm hoping someone makes tooling to encourage this) to auto-migrate users to new semver-incompatible versions of widely used libraries by releasing a 1.x version that's implemented entirely in terms of thin wrappers around 2.x functions and go fix will automatically upgrade users when they run it.

rr808• 5 months ago

Incidentally I saw the Wes McKinney podcast who said that Go was the perfect language now because of the fast compile-run cycle with strong types and built in multi thread safety was perfect for Coding Agents. Gave me a whole new interest. https://www.youtube.com/watch?v=1VfzDXeQRhU

Surac• 5 months ago

Not related with go: I recently tried to learn Python beyond the classical example code from the web. After discovering that there are more or less 4 different ways to do a thing with no clear guide what best practice is. I come from C and there one is happy if there is ONE way to do a thing :). Is Go at this stage? Im Intrested in learning Go but not to a point where i need a LLM to determin if my code follows best practice.

notTooFarGone• 5 months ago

go is fairly opinionated and there is very often only one way to do a thing.

For parts where it is not the case see this thread they really work on keeping a fairly simple language. I'd recommend it to anyone tired of python messes

Using go fix to modernize Go code

Related Stories