Can anyone expand on the chromium specifc guidelines on super tiny crates, particularly no nesting of modules/source files?
That feels like the ~2010 era of people saying that functions should be as small as possible. That lead me to reviewing a lot of code where every function was one or two lines and you couldn't actually see what was going on anymore through the layers of unneeded abstraction.
I want to give chrome the benefit of the doubt, but that seems really goofy.
In Cargo-built Rust, a crate is costly in terms of abstraction because it needs its own directory, Cargo.toml, src/ subdir, etc. In the Google build systems I've worked with in the past (and it looks like Chromium follows) they instead put source files in the same directory mixing languages and with finer-grained libraries as they see fit.
Given that a crate is the unit of build parallelization in Rust, there's a benefit to more crates especially when they don't cost much cognitive overhead. You could imagine using crates in the way you'd typically use separate mods in a normal Rust project.
I dug around in their code search to find some examples but didn't see much Rust in there, seems still early. I think https://source.chromium.org/chromium/chromium/src/+/main:tes... has ~4 Rust files that end up separate crates though. (One of them defines a proc macro so even in a Cargo built Rust project it would need to be in its own separate crate, I think!)
You get stricter enforcement of public APIs and dependencies. You can't import anything you haven't declared as a dep, and cycles are impossible. Rustdoc by default shows only your intended public API.
OTOH if you have one crate with lots of modules, it's tempting to import anything anywhere and use pub(crate). Rustdoc needs to be configured to show private items if you want to see internal APIs.
Maybe one or two line functions are a totally different scale than "all source code files in a crate"? So like, one is problematic in a way the other is not. And the guidance is "prefer small," not "always super tiny." See: "Larger crates are allowed" later on. And also see: "Rationale: Fine-grained library targets are recommended in Chromium due to the massive size of our codebase, non-local effects of adding dependencies in the build graph, and to improve performance of parallel compilation and build caching."
It might have to do with optimizing compile times. A crate is the unit of compilation, so small crates increase the likelihood that you won't end up recompiling a lot of unrelated code.
I guess smaller crates and avoiding nested modules could also help optimize for making the code greppable by coding agents without blowing up context windows.
This being Google, I assume everything goes into a single gigantic monorepo that gets thrown at Blaze. If the unit of compilation is the crate, it makes sense for them to prefer that crates are as small as possible.
The granularity of crates shouldn't really impact what kinds of abstractions you build. You can still have as many modules and types as you need, and as big of functions as you need, but its saying you should organize the modules into separate crates instead of one large crate. They even call out the trait coherence rules, saying that you can just make your library bigger instead of forcing a more awkward design in the pursuit of a smaller crate.
I think one benefit of small crates is that it gives you more granularity in linking and dependency graphs, which is especially relevant for rebuilds. At a previous job we had a monolithic "utilities" crate, and this caused problems when you tried to depend on it for the IP address utilities but this brought in the radio frequency utilities. When one of these submodules got an update the versioning would excessively propagate downstream to every consumer. If this was organized as small "net-utils" and "rf-utils" crates then maybe it would not have been as much of an issue.
> Type names should be imported and used unqualified
This just pushes people to have redundant information in types (`IoError` instead of `io::Error`).
Unless a type is widely recognized (like `HashMap`), I prefer to have them fully qualified so I have the contextual meaning for it. If I am working with a generic name like `Source`, what does that mean? I shouldn't have to look up in the imports to understand the code (or only understand it through an LSP).
Reducing imports also reduces unnecessary merge conflicts.
Honestly I think having blanket rules in either direction is a bad idea. Sometimes it makes sense to qualify things, sometimes it's clearer if you don't.
It says below that that in cases of things like `io::Error` it should be used as that though, as in “cases of ambiguities”. It specifically speaks of not using `regex::Regex` but just `Regex` which seems more reasonable to me.
Getters and setters is the one I'm most at disagreement with.
// Mine
let label = Label.text("Hello Wold");
let label_text = label.get_text();
// Theirs
let label = Label.set_text("Hello Wold");
let label_text = label.text();
A method is a way to accomplish a specific task. Emphasis on specific not generic. The getter task is to always return. The setter task is specific. So the method should be the setter - `text`, `color`, `fill`. In Rust the getter can't have same name, so prefix it. Not the other way around.
Their style is pervasive in Rust, such as in the standard library, so I would personally apply a when-in-rome philosophy. FWIW something like `.text("hello")` I would expect to see in a builder-pattern but not in a setter for an object that's already built.
That being said I don't particularly understand your conception of a method. They are both methods. The getter ought to have a shorter name since it is probably called more frequently and because it inherently has less of an impact -- this goes along with the principle that names that demand attention should be larger and easier to notice.
My use case is a TUI framework (https://www.incredible.rs/). The setters configure elements in a chain-able manner. I grappled with the rust convention and decided to go the other way. Rational as mentioned.
But this made me think...
> "The getter ought to have a shorter name since it is probably called more frequently"
This is nice, I have been lurking on google and meta rust projects, mimicking and picking style by prompting LLMs to distill it, taking a look at fmt & clippy configs helps too.
But it wasn't as coherent and reliable from project to project like this guide. Kudos to google on this one !
I'm pretty sure most big software projects (Windows, Linux, Chrome, gcc, LLVM, AAA game engines, ...) are still writing a lot of new C and C++. Pretty much everyone in the embedded world is as well.
As a solo programmer, I still prefer C and C++. In fact, as I've incorporated LLMs in to my workflow, I've been increasingly drawn toward C and its simplicity. A lot of the QoL features of C++ simply aren't needed when you're writing less code manually.
Unfortunately for me, yes. Some companies are very risk adverse and would rather stick with the devil they know. They have no idea what they are sacrificing.
Far from it. Until Rust can read C++ code seamlessly, there will be more code written in C++ than Rust for the foreseeable future. HPC, Finance, AI, Games, Databases, Hardware all continue to be written in C++.
Today I went over a TODO comment from 2007 in a C++ codebase that is still evolving very vividly, year after year. Trust me, for well established projects C++ is there to stay.
C++ seems alive and well in the defense space. The big contractors near me have tons of C++ job postings and I don't think I've seen a single one looking for Rust.
Yes mine is, because they have a huge amount of C++ already and none of it is publicly accessible so security isn't a concern. (Obviously there are many other reasons to prefer Rust, but that is a big one.)
Are you just being snarky, or do you have something more specific to say about something that's choosing C?
Considering that it's been 54 years, and we've yet to find any human being, any at all[1], who can write C without UB, I'd say that writing C in 2026 when there's any other option is basically misconduct and a good case could be made that if the code touches money in any way, then it could be a SOX violation too.
Writing C today is like still writing Cobol. Yes, if you are adding a new type of savings account to your bank, and the rest is in Cobol, then sure write it in Cobol.
Some microcontroller projects may have an ecosystem in C that makes other options harder in practice, but it's still a worthy investment to not use C. There's a reason phone baseband firmwares are moving away from C.
[1] No, not even djb, who people like to bring up.
I really appreciate that they distinguish between library code and application code. Rust gets too much of a bad rap for its complicated generic code, but in most application scenarios you are not writing code nearly that complex or generic.
This is a sub-case of the general one that is narrowing the interpretation of things. A big infinite amount of things can be true or false, only one can be a Rust variant.
I have a huge disagreement here. You should absolutely be using Arc and Rc for any references *that live outside of the call stack.*
Don't do weird crap with lifetimes to try and convince the compiler that what you're doing is ok, just throw Rc/Arc on it and be done with it.
The Rc/Arc advice also applies to C++ IMO, though you use different constructs, std::shared obviously, but there is a strong argument to be made for a std::shared_st or something which is single threaded.
It would not surprise me if this advice comes from experience with C++ where there is no Rc so reference counting is very expensive. Even so, you can greatly reduce the expense by passing things by ref where lifetimes are simple which is the vast majority of the time.
I think using refcounting can allow you to get lazy with your object graphs, throwing referencing to objects around everywhere and then losing the ability to conceptualize who owns what and who is responsible for who (so to speak). Sticking to a stricter ownership graph forces you to be more deliberate with how your types are designed and this can lead to better architecture in the long run.
The good emotions come with the confidence in the engineering quality that it gives you as output (once you overcome the friction, which AI can help you big time to achieve).
Not trying to rain on someone's parade but, the only reason why would care about style guides nowadays is to feed them to our model of choice and let it do what it's supposed to be doing.
So it's not like I am willing to read through this and think to myself "I cannot wait to pick up some new ways of doing things". I'm the general to my agentic army now.
I guess you would code manually every now and then for your own enjoyment but at that point do you care about style guides written for scale?
I'm not sure I really agree with your main point (I think it's probably still important for LLM-generated code to be generally human-understandable, at least if you care about long-term maintainability), but setting that aside to answer this question:
> I guess you would code manually every now and then for your own enjoyment but at that point do you care about style guides written for scale?
I think they're still quite valuable in that case, for a couple reasons:
- When learning a new language (which happens much more frequently when writing code "for pleasure," as it were), "written for scale" guidelines still translate pretty well to "written for oneself" IME. At the very least, they tell you what to expect in code you read, and give you a reasonable starting point as you develop your own taste and stylistic preferences.
- I've noticed some open source projects beginning to institute anti-AI contribution guidelines, and such projects still benefit from codified style guides. Google obviously doesn't fall under this category themselves, but in other language ecosystems, their style guides tend to find use in OSS projects.
Why would they when the class is full of dropouts who, generously, have a 0 percent chance of going "hey, y'know what, that's actually kinda cool! I'm going to change my mind about LLMs being useless" and a 100% chance of going "ur project is total shit and you should feel bad".
First paragraph: “includes guidance on API and implementation design”
It seems to me that if the intent is not just to produce code but also to operate it, having the different pieces behave in a similar, predictable way is kind of nice. Whether the software is written by AI or humans.
This is what we do in my company, give the guidelines to the model. Unfortunately, the model isn't always following them and it's impossible to enforce them manually. There's too much code to review, the code is generally low quality, and is more often than not auto-approved by AI.
Unless you're working on your own project on which you have full control, or you have a strong authority figure in your company who cares about that, it's a lost battle.
It's sad for anyone who love their craft, but tbh I'm not even sure it matters anymore for most projects.
The point of style guides is to optimize for readability despite a cognitively diverse workforce coding in the same repos.
I would think they're probably even more meaningful in an agentic world.
Shitty generals can't review meaningfully review the work of their troops.
On top of that all, I just enjoy programming itself. It's less and less of the meat of a software job over time, but I was coding before I got paid for it, and I'll probably keep coding well after I can get paid for it.
> Shitty generals can't review meaningfully review the work of their troops.
Except that reviewing has become just asking your agent what that piece of code does in english. Reading code has a bit of cognitive load, that we will probably drop it in coming years
Not trying to rain on someone's parade, but the only reason I would care about HN comments nowadays is to feed them to my model of choice and let it generate the contrarian hot takes it's supposed to be generating. So it's not like I am willing to read through this thread and think to myself "I cannot wait to pick up some new ways of complaining about documentation." I'm the Editor-in-Chief to my synthetic pundit army now.
I guess you would type out a comment manually every now and then for your own enjoyment, but at that point do you really care about comments at scale?
---
EDIT (above is a joke) It's very important that every time you find something that is of no use to you, you write a comment explaining that this link is of no interest to you, discouraging people from things you have no interest in. Monoculture for all!
AI bros think you can never look at code and make good software. They're wrong, of course, but they refuse to listen and will probably never listen until the shoddy quality of their work becomes too great to paper over.
Can anyone expand on the chromium specifc guidelines on super tiny crates, particularly no nesting of modules/source files?
That feels like the ~2010 era of people saying that functions should be as small as possible. That lead me to reviewing a lot of code where every function was one or two lines and you couldn't actually see what was going on anymore through the layers of unneeded abstraction.
I want to give chrome the benefit of the doubt, but that seems really goofy.
In Cargo-built Rust, a crate is costly in terms of abstraction because it needs its own directory, Cargo.toml, src/ subdir, etc. In the Google build systems I've worked with in the past (and it looks like Chromium follows) they instead put source files in the same directory mixing languages and with finer-grained libraries as they see fit.
Given that a crate is the unit of build parallelization in Rust, there's a benefit to more crates especially when they don't cost much cognitive overhead. You could imagine using crates in the way you'd typically use separate mods in a normal Rust project.
I dug around in their code search to find some examples but didn't see much Rust in there, seems still early. I think https://source.chromium.org/chromium/chromium/src/+/main:tes... has ~4 Rust files that end up separate crates though. (One of them defines a proc macro so even in a Cargo built Rust project it would need to be in its own separate crate, I think!)
It looks like there's some macro-based import that does import by path, so crate names are generated:
https://source.chromium.org/chromium/chromium/src/+/main:tes...
You get stricter enforcement of public APIs and dependencies. You can't import anything you haven't declared as a dep, and cycles are impossible. Rustdoc by default shows only your intended public API.
OTOH if you have one crate with lots of modules, it's tempting to import anything anywhere and use pub(crate). Rustdoc needs to be configured to show private items if you want to see internal APIs.
Maybe one or two line functions are a totally different scale than "all source code files in a crate"? So like, one is problematic in a way the other is not. And the guidance is "prefer small," not "always super tiny." See: "Larger crates are allowed" later on. And also see: "Rationale: Fine-grained library targets are recommended in Chromium due to the massive size of our codebase, non-local effects of adding dependencies in the build graph, and to improve performance of parallel compilation and build caching."
It might have to do with optimizing compile times. A crate is the unit of compilation, so small crates increase the likelihood that you won't end up recompiling a lot of unrelated code.
I guess smaller crates and avoiding nested modules could also help optimize for making the code greppable by coding agents without blowing up context windows.
This being Google, I assume everything goes into a single gigantic monorepo that gets thrown at Blaze. If the unit of compilation is the crate, it makes sense for them to prefer that crates are as small as possible.
The granularity of crates shouldn't really impact what kinds of abstractions you build. You can still have as many modules and types as you need, and as big of functions as you need, but its saying you should organize the modules into separate crates instead of one large crate. They even call out the trait coherence rules, saying that you can just make your library bigger instead of forcing a more awkward design in the pursuit of a smaller crate.
I think one benefit of small crates is that it gives you more granularity in linking and dependency graphs, which is especially relevant for rebuilds. At a previous job we had a monolithic "utilities" crate, and this caused problems when you tried to depend on it for the IP address utilities but this brought in the radio frequency utilities. When one of these submodules got an update the versioning would excessively propagate downstream to every consumer. If this was organized as small "net-utils" and "rf-utils" crates then maybe it would not have been as much of an issue.
Compilation speed?
> Type names should be imported and used unqualified
This just pushes people to have redundant information in types (`IoError` instead of `io::Error`).
Unless a type is widely recognized (like `HashMap`), I prefer to have them fully qualified so I have the contextual meaning for it. If I am working with a generic name like `Source`, what does that mean? I shouldn't have to look up in the imports to understand the code (or only understand it through an LSP).
Reducing imports also reduces unnecessary merge conflicts.
Honestly I think having blanket rules in either direction is a bad idea. Sometimes it makes sense to qualify things, sometimes it's clearer if you don't.
It says below that that in cases of things like `io::Error` it should be used as that though, as in “cases of ambiguities”. It specifically speaks of not using `regex::Regex` but just `Regex` which seems more reasonable to me.
Getters and setters is the one I'm most at disagreement with.
A method is a way to accomplish a specific task. Emphasis on specific not generic. The getter task is to always return. The setter task is specific. So the method should be the setter - `text`, `color`, `fill`. In Rust the getter can't have same name, so prefix it. Not the other way around.
Their style is pervasive in Rust, such as in the standard library, so I would personally apply a when-in-rome philosophy. FWIW something like `.text("hello")` I would expect to see in a builder-pattern but not in a setter for an object that's already built.
That being said I don't particularly understand your conception of a method. They are both methods. The getter ought to have a shorter name since it is probably called more frequently and because it inherently has less of an impact -- this goes along with the principle that names that demand attention should be larger and easier to notice.
My use case is a TUI framework (https://www.incredible.rs/). The setters configure elements in a chain-able manner. I grappled with the rust convention and decided to go the other way. Rational as mentioned.
But this made me think...
> "The getter ought to have a shorter name since it is probably called more frequently"
So i checked. Rough agent driven counts:
https://github.com/ronilan/incredible-flappy 407 setters and 183 getters.
https://github.com/ronilan/rusticon 546 setters and 5 getters
https://github.com/ronilan/shape-sorting 688 setters and 33 getters.
And in a code editor with a lot of ui configurations based on reusable elements 2865 setters and 206 getters.
In reactive apps on state handlers call on setters with state values. No getters involved...
2 replies →
I think which to use in general Rust code depends on the purpose of your type.
A builder type like `Command` will have unqualified setters and `get_` qualified getters.
For record-like-structs, I think unqualified getters becomes preferred and `set_` qualified setters.
This style is aligned with protocol buffers, which is aligned with the style of protos in C++.
https://protobuf.dev/reference/rust/rust-generated/
This is nice, I have been lurking on google and meta rust projects, mimicking and picking style by prompting LLMs to distill it, taking a look at fmt & clippy configs helps too.
But it wasn't as coherent and reliable from project to project like this guide. Kudos to google on this one !
Much of this is very standard across the Rust ecosystem but it's very helpful to have it all in one place.
At this point, is anybody writing new C or C++? It seems like they are sunset languages even at the big corps.
I'm pretty sure most big software projects (Windows, Linux, Chrome, gcc, LLVM, AAA game engines, ...) are still writing a lot of new C and C++. Pretty much everyone in the embedded world is as well.
As a solo programmer, I still prefer C and C++. In fact, as I've incorporated LLMs in to my workflow, I've been increasingly drawn toward C and its simplicity. A lot of the QoL features of C++ simply aren't needed when you're writing less code manually.
Unfortunately for me, yes. Some companies are very risk adverse and would rather stick with the devil they know. They have no idea what they are sacrificing.
Far from it. Until Rust can read C++ code seamlessly, there will be more code written in C++ than Rust for the foreseeable future. HPC, Finance, AI, Games, Databases, Hardware all continue to be written in C++.
Cloudflare is all in on Rust, it's used everywhere by default, and C++ leftovers are being actively torn down.
Plenty of new C++ going on at my BigCorp employer.
Games, anything that depends on LLVM, GCC, CUDA, SYSCL,....
Ah and Rust's compiler backend dependency on LLVM and in the future GCC as well.
Today I went over a TODO comment from 2007 in a C++ codebase that is still evolving very vividly, year after year. Trust me, for well established projects C++ is there to stay.
C/C++ is still relevant for HPC, where you want to carefully optimize memory management.
Hate to break it to you but Rust is equally capable of doing all the same memory management optimizations.
2 replies →
I've been extracting a lot of verified C from theorem provers recently.
C++ seems alive and well in the defense space. The big contractors near me have tons of C++ job postings and I don't think I've seen a single one looking for Rust.
Do you know if the code bases are of the kind where dynamic memory (among many other features) is disallowed?
1 reply →
Yes mine is, because they have a huge amount of C++ already and none of it is publicly accessible so security isn't a concern. (Obviously there are many other reasons to prefer Rust, but that is a big one.)
grownups with important jobs write C
Are you just being snarky, or do you have something more specific to say about something that's choosing C?
Considering that it's been 54 years, and we've yet to find any human being, any at all[1], who can write C without UB, I'd say that writing C in 2026 when there's any other option is basically misconduct and a good case could be made that if the code touches money in any way, then it could be a SOX violation too.
Writing C today is like still writing Cobol. Yes, if you are adding a new type of savings account to your bank, and the rest is in Cobol, then sure write it in Cobol.
Some microcontroller projects may have an ecosystem in C that makes other options harder in practice, but it's still a worthy investment to not use C. There's a reason phone baseband firmwares are moving away from C.
[1] No, not even djb, who people like to bring up.
12 replies →
I really appreciate that they distinguish between library code and application code. Rust gets too much of a bad rap for its complicated generic code, but in most application scenarios you are not writing code nearly that complex or generic.
The enum-over-bool rule is the one I'd keep even solo, saved me a reversed flag in a cert validator once.
This is a sub-case of the general one that is narrowing the interpretation of things. A big infinite amount of things can be true or false, only one can be a Rust variant.
I have a huge disagreement here. You should absolutely be using Arc and Rc for any references *that live outside of the call stack.*
Don't do weird crap with lifetimes to try and convince the compiler that what you're doing is ok, just throw Rc/Arc on it and be done with it.
The Rc/Arc advice also applies to C++ IMO, though you use different constructs, std::shared obviously, but there is a strong argument to be made for a std::shared_st or something which is single threaded.
It would not surprise me if this advice comes from experience with C++ where there is no Rc so reference counting is very expensive. Even so, you can greatly reduce the expense by passing things by ref where lifetimes are simple which is the vast majority of the time.
I think using refcounting can allow you to get lazy with your object graphs, throwing referencing to objects around everywhere and then losing the ability to conceptualize who owns what and who is responsible for who (so to speak). Sticking to a stricter ownership graph forces you to be more deliberate with how your types are designed and this can lead to better architecture in the long run.
Things like this make me appreciate Gofmt so much
ctrl+c > ctrl+v > into my AGENTS.md for my next rust project /s
no amount of stylistic heterogeneity can make this awful language pleasant
The good emotions come with the confidence in the engineering quality that it gives you as output (once you overcome the friction, which AI can help you big time to achieve).
Not trying to rain on someone's parade but, the only reason why would care about style guides nowadays is to feed them to our model of choice and let it do what it's supposed to be doing.
So it's not like I am willing to read through this and think to myself "I cannot wait to pick up some new ways of doing things". I'm the general to my agentic army now.
I guess you would code manually every now and then for your own enjoyment but at that point do you care about style guides written for scale?
I'm not sure I really agree with your main point (I think it's probably still important for LLM-generated code to be generally human-understandable, at least if you care about long-term maintainability), but setting that aside to answer this question:
> I guess you would code manually every now and then for your own enjoyment but at that point do you care about style guides written for scale?
I think they're still quite valuable in that case, for a couple reasons:
- When learning a new language (which happens much more frequently when writing code "for pleasure," as it were), "written for scale" guidelines still translate pretty well to "written for oneself" IME. At the very least, they tell you what to expect in code you read, and give you a reasonable starting point as you develop your own taste and stylistic preferences.
- I've noticed some open source projects beginning to institute anti-AI contribution guidelines, and such projects still benefit from codified style guides. Google obviously doesn't fall under this category themselves, but in other language ecosystems, their style guides tend to find use in OSS projects.
> I'm the general to my agentic army now.
What have you produced with your agentic army? Would you like to share with the class?
my guess is a lot of heat, some water vapor....
Why would they when the class is full of dropouts who, generously, have a 0 percent chance of going "hey, y'know what, that's actually kinda cool! I'm going to change my mind about LLMs being useless" and a 100% chance of going "ur project is total shit and you should feel bad".
1 reply →
First paragraph: “includes guidance on API and implementation design”
It seems to me that if the intent is not just to produce code but also to operate it, having the different pieces behave in a similar, predictable way is kind of nice. Whether the software is written by AI or humans.
This is what we do in my company, give the guidelines to the model. Unfortunately, the model isn't always following them and it's impossible to enforce them manually. There's too much code to review, the code is generally low quality, and is more often than not auto-approved by AI.
Unless you're working on your own project on which you have full control, or you have a strong authority figure in your company who cares about that, it's a lost battle.
It's sad for anyone who love their craft, but tbh I'm not even sure it matters anymore for most projects.
The point of style guides is to optimize for readability despite a cognitively diverse workforce coding in the same repos.
I would think they're probably even more meaningful in an agentic world.
Shitty generals can't review meaningfully review the work of their troops.
On top of that all, I just enjoy programming itself. It's less and less of the meat of a software job over time, but I was coding before I got paid for it, and I'll probably keep coding well after I can get paid for it.
> Shitty generals can't review meaningfully review the work of their troops.
Except that reviewing has become just asking your agent what that piece of code does in english. Reading code has a bit of cognitive load, that we will probably drop it in coming years
Not trying to rain on someone's parade, but the only reason I would care about HN comments nowadays is to feed them to my model of choice and let it generate the contrarian hot takes it's supposed to be generating. So it's not like I am willing to read through this thread and think to myself "I cannot wait to pick up some new ways of complaining about documentation." I'm the Editor-in-Chief to my synthetic pundit army now.
I guess you would type out a comment manually every now and then for your own enjoyment, but at that point do you really care about comments at scale?
---
EDIT (above is a joke) It's very important that every time you find something that is of no use to you, you write a comment explaining that this link is of no interest to you, discouraging people from things you have no interest in. Monoculture for all!
Are you saying that you don't ever look at the code once it's been generated?
AI bros think you can never look at code and make good software. They're wrong, of course, but they refuse to listen and will probably never listen until the shoddy quality of their work becomes too great to paper over.
Seems very much like your goal was to rain on a parade.