How to write documentation for a Rust crate

https://blog.guillaume-gomez.fr/articles/2020-03-12+Guide+on+how+to+write+documentation+for+a+Rust+crate

by lukastyrychtr • 6 years ago

115 51 6 years ago

jnordwick6• 6 years ago

Why does the rust documentation still suck? It basically only works if you already know what you ate looking for, and still is difficult to read.

Compare the string pages.

Rust: https://doc.rust-lang.org/std/string/struct.String.html

Java: https://docs.oracle.com/en/java/javase/11/docs/api/java.base...

C++: https://en.cppreference.com/w/cpp/string/basic_string

Yes, the cop page probably has some bespoke work on the page, but it still demonstrates ideas that are partially auto generated (and most of that page is auto generated).

* the method and functions aren't sectioned in any useful way. Just a list of functions (solved by adding section and subsection to the doc comments). Methods that create, search, mutate, test, transform, etc should be sectioned off.

* no use of alignment, just blobs of text

* poor use of color. Both java and cpp use color to break up sections and alignment to distinguish different parts of the signature. Rust is just a page of text that is very difficult to scan.

* no summary. Cpp summarizes the group of method before clicking b through to individual listings, while java summarizes each method at the top. This is useful for searching in a page. Rust is once again just a block of text.

* rust also has a unique issue in how to organize traits and other rust specific constructs. It really should have figured this out by now.

I can keep going on the uselessness of the rust docs, and I say this as someone who was involved in the language in the past, and give it a new shot about once a year. But the docs have always sucked compared to other languages.

dijit• 6 years ago

You know. I thought it was just me who was dumb.

I write a fair amount of python and /sometimes/ the docs are confusing; but the rust docs to me are completely useless.

I see people like Jon Gjengset navigating perfectly fine though.

I tend to reach for the examples/ directory, or the tests

vhakulinen• 6 years ago

Why does the rust documentation still suck?

Thats a bit harsh. Yes, the documentation might be (is) a bit hard to read in a sense that its hard to _find_ something from it, but otherwise I've found if quite complete (when it comes to the standard library). Most (if not all) of your points are about the readability of the rendered documentation and not the documentation (content) it self.

jnordwick6• 6 years ago

Yes, almost all my complaints about rust doc is in formatting, sectioning, and grouping. The content is good.

But those display issues make it unusable unless you know what you are already looking for.

henrikeh• 6 years ago

To add another, the C++ reference has an extremely useful section for exploring any piece of documentation: "See also"

Look at this page for `capacity`: https://en.cppreference.com/w/cpp/string/basic_string/capaci...

Immediately, I see what other methods are relevant in this same context. So many languages references are simply enumerations of items in the library, but they don't provide the context needed to actually gain proficiency in the tool and learn incrementally.

trevyn• 6 years ago

To be fair, you’re comparing a 9-year-old language with 25- and 35-year-old languages.

Out of curiosity, is there anything other than the docs that prevents you from working with Rust more?

the8472• 6 years ago

There's an open issue for indices. https://github.com/rust-lang/rust/issues/40273 And various other open issues to improve styling.

I wouldn't call them useless though, clicking the [-] collapses all comments and gives a somewhat useful overview of what's available. It's far from ideal, but still useful.

jasode• 6 years ago

no summary. Cpp summarizes the group of method before clicking b through to individual listings, while java summarizes each method at the top. This is useful for searching in a page. Rust is once again just a block of text.

It looks like Rust docs webpages default to expanded view instead of collapsed view. You can press [-][+] in the upper right hand corner to get a more summarized view that looks more like the cppreference example. Example video :

https://imgur.com/a/EqnzAD3

It doesn't address all your bullet points but that may help give the reader a high level overview.

jnordwick6• 6 years ago

I know, but not even close to the same thing. Those one line summaries that make scanning easy are very useful.

izacus• 6 years ago

And your post doesn't even mention that many of crates, even important ones like crypto, aren't even fully documented and it's very common to just hit the wall of missing entries and no over-arching manual on how the crate should be used.

bpicolo• 6 years ago

I'm kind of intrigued how widely opinions differ here. I consider the Rust docs here dramatically better due to their focus on soft documentation. I can't stand Java docs.

imtringued3• 6 years ago

References are not meant to provide "soft documentation". Guides are supposed to do that.

jnordwick6• 6 years ago

Not even a useful softdoc though. Let's say I need to search then mutate an data structure. There are probably number of ways to do what I need. Right now, it is almost impossible to see what my options are.

And I'm not going to memorize the API either. Sorry.

marcosdumay• 6 years ago

rust also has a unique issue in how to organize traits and other rust specific constructs.

A thousand times this. It doesn't matter how well written and organized that page is, because it's completely irrelevant. The relevant information is all on the traits documentation and other libraries.

Rust could use something similar to hoogle.

rectang• 6 years ago

I agree that the way traits are organized in rustdoc could be improved. It's often hard to find what the capabilities are of a given type because of what we'd call the "yo-yo problem" in OOP: you have to click through multiple levels of the hierarchy to find what you're looking for.

https://en.wikipedia.org/wiki/Yo-yo_problem

OJFord3• 6 years ago

Maybe it's just what you're used to, but I massively prefer the Rust docs for `String` you linked to Java or C++'s.

I think largely for one reason: the sidebar! I just scroll the sidebar for the method I know I want or a method that sounds like what I'm hoping to find, and then click it.

Java & C++ both lack that, it doesn't matter so much with the latter because the page is pretty short, but Java's is huge, and to me totally unnavigable.

tannhaeuser• 6 years ago

Old Java doc (as generated by the original javadoc tool which also inspired other languages I believe) had the kind of navigation you're looking for - it was a boxy HTML frame-based layout so it had to go, but I'm not sure why the default javadoc theme dropped in-page method navigation altogether.

progval• 6 years ago

Why does the rust documentation still suck? It basically only works if you already know what you ate looking for, and still is difficult to read.

You're linking to the reference documentation. Beginners start with the Rust Book, which covers strings: https://doc.rust-lang.org/book/ch08-02-strings.html

Besides, even the reference doc starts with five screenfuls of examples, while the Java and C++ only have two and one respectively.

simion314• 6 years ago

I think Qt documentation is very nice https://doc.qt.io/qt-5/qstring.html

steveklabnik7• 6 years ago

So, I disagree that it "sucks," but what I will say is this: rustdoc has basically been maintained by one or two people over the last ~5 years. It is very hard to contribute to, because it has to use the compiler itself to actually generate the documentation. This means that changing it means changing the compiler, which means a long development cycle. Additionally, this also means working on it isn't really like working on a normal web app. We've tried to get folks to contribute, but they all bounce off. So this means that any improvements we would like to do are really difficult, and there's not a lot of help.

I am hoping that the rust-analyzer work lets us completely fix this, in the same way I was hoping the rls would before, but it's just not ready yet.

quietbritishjim4• 6 years ago

It seems like there is some low-hanging fruit that addresses one of the main complaints of the parent commenter (which I agree with). It would be nice if there was a list of all the methods with just a one line summary of each - like the sidebar but with fractionally more information.

I'm thinking in terms of Doxygen's brief comments vs detailed comments here. Pages typically go (1) class brief comment, (2) list of methods with their brief comments, (3) class detailed comments (including examples), (4) method signatures and detailed comments (linked to from above). Doxygen has many serious problems but I think it gets this bit right.

But a quick glance at the linked std::string::String page suggest that the first sentence of each method's docs already works as a brief summary of its function. I don't know if this is coincidence or deliberate, but if it is deliberate then the page could be reformatted just by changing the documentation system. I'm not saying that's easy, but it's less work than having to add something to every individual function.

jnordwick6• 6 years ago

This means that changing it means changing the compiler,

Wow. What a terrible decision. I'm quite surprised that people actually agreed to that.

I originally said it was shit but I toned it down a little. The information isn't bad, just too difficult to find if you don't already know exactly what you are looking for. You work on rust core so I don't think you are the best person to judge.

The good part is this can mostly be solved by better formatting and adding a top one-one summary section that groups similar functions and traits (creation, mutation, lookup, etc). With just that you could even convince me to ignore the terrible formatting in the lower section.

The general take away is that the docs are too difficult to scan and if you don't already know something exists and its name, the docs aren't very useful.

baby• 6 years ago

IMO golang docs are really really good. You can just click on everything, search the std library easily, find functions you care about easily, etc.

HugoDaniel• 6 years ago

I wish there was something similar to the Haskell Haddock (https://www.haskell.org/haddock/) for Rust.

Something that would automatically generate the signatures and modules entry points/data types. These seem to be very neglected and generally hard to keep up-to-date in the Rust ecosystem.

codetrotter• 6 years ago

I am not familiar with Haddock, as I've barely touched Haskell, but I do write a fair bit of Rust.

Perhaps I am reading your comment wrong, but:

- Generated Rust crate docs include signatures for all of their public functions, and

- Generated Rust crate docs include public enums, public fields of public structs, etc

OJFord3• 6 years ago

What does that do that Rust docs lack?

e.g. here the signatures haven't been written manually... https://doc.rust-lang.org/std/string/struct.String.html

If you click 'src' at the top-right you'll see the full extent of the doc comments that generated it. (You get signatures without any comments.)

dhruvdh• 6 years ago

I don’t know why the experience for the current top commenter has been so poor, but I absolutely love Rust docs, and it never takes me more than a few seconds on the website to find what I am looking for. Perhaps navigating just takes a little getting used to.

If something doesn’t make sense to me I can straight away jump into the source code and make sense of it, from a single click.

I have learned so much about programming just reading the docs for the standard library, or it’s source code. The documentation is one of my favourite things about it the language.

ptato• 6 years ago

What do you mean you don't know? The comment explains his experience a fair bit.

OJFord3• 6 years ago

I don’t know why the experience for the current top commenter

Meta: the experience for readers of your comment would be much better if you'd chosen to reply to that not-now-currently top commenter.

I think almost certainly it was this: https://news.ycombinator.com/item?id=22636726

But that may not be clear at all to later readers if there are many comments here.

asdkhadsj2• 6 years ago

I too find it quite nice. Though when I was starting out I found it exceptionally confusing. Notably the `impl` section towards the bottom. Even today, while I understand that section no problem - I don't usually find it too useful. Likely because the impls in Rust can be a bit weird. Ie Foo might impl `Responder` but only if `Foo` also implements `Serialize`, and those sort of scenarios have happened enough that I usually just ignore the bottom impl section. Not to say that the documentation is incorrect at all, I'm merely explaining how I have "adapted" to scenarios of the past - which could be confusion of my own making.

But.. aside from that, I quite like Rust Docs. I also especially love how I can write tests in them, link to other types and modules like `[Foo]`.

My complaint list for Rust Docs is surprisingly short honestly. Especially since they fixed the slow page loading on huge impl lists.

zelphirkalt• 6 years ago

Well, I guess the most important part of docs is ... examples! Give your users examples, from which they can derive, how to use parts of your library. Those examples also better be explained in natural language as well and not just somewhere in a git repo, so that the user does not need to build a mental model of the ideas of your library first, before being able to understand your examples. Oh and did I mention diagrams would help? As a professional group, we truly suck at documenting things properly.

Many people think, that docs are done once they auto-generated API docs from source code. They are not. That's not something that deserves the name "documentation". Auto-generated API docs are among the last things to turn to, when there is nothing else around or when you already understood the ideas of the library and only need to look up a name of something. That's not only true for Rust, but also for other languages.

quietbritishjim4• 6 years ago

Examples are the most important part of you docs sometimes. There are at least two reasons for visiting docs:

* Want to understand generally how to use a new concept, typically at the class level (or more trickily at the two-or-three-classes level), e.g. how do I create a thread?

* Already familiar with the concept but want to do something specific, typically at the method level, e.g. how to test whether a string starts with a particular prefix?

There was a good post on Hackers News a few months ago breaking down documentation visitors into four categories, so there's at least two more.

I think examples are very important in the first case, typically you want an example led-approach to explaining new concepts. But examples are a lot less important for method-level questions, and are often (not always) totally redundant if you have really clear and precise information about the method and its parameters.

Edit: But just to be clear, I agree that examples are really important and you should definitely put them in your docs (at the class level and above).

Edit 2: Here's the article [1] and HN dicussion [2]. In that terminology, I was distinguishing "explanation" and "reference". The other two types are "tutorial" and "how-to guide".

[1] https://web.archive.org/web/20200312211539/https://www.divio...

[2] https://news.ycombinator.com/item?id=21289832

imtringued3• 6 years ago

You're stumbling over the distinction between "user guide" and "API reference". Both count as documentation but they have completely different goals.

animalnewbie• 6 years ago

I want to thank the rust team- they are extremely dedicated people taking care of the smallest details and giving a compiler and related infrastructure for free. Everyone on the team I've interacted with are amazingly kind and helpful people.

I wish the Reddit community was less of a cancer but I guess it's not the team that's responsible, and also it's reddit after all!

imtringued3• 6 years ago

Does rust-doc make a distinction between a user guide and a reference? A user guide is basically a book that goes over all the general features of the library. A reference provides information about the API of the library.

steveklabnik7• 6 years ago

So, the terminology I've used since around 2013:

* API documentation: stuff like "type signatures"

* Reference documentation: the specification of the language

* Tutorials: long-form text that explains things

I gave a talk about the Bay Area Rust Meetup about this, but it seems like maybe it's lost to history :(

Anyway, rustdoc makes this distinction in a sense because it only provides API documentation, which I believe is what you're calling "reference" documentation. mdbook provides the longer form factor.

Most libraries don't have a language spec, since they're not a language, so they have categories one and three.

devit• 6 years ago

The documentation for crates, modules or struct/enum often contains a "user guide" for the item in question.

I think that's better than a separate book, since in most cases that separate book would never get written.

_bxg1• 6 years ago

+1 to the code examples. Rust's type systems tells you a lot on its own about what you can and cannot do, but it's often unclear as to what you should do. Which struct should I be starting with? Should I be constructing Foo directly or though a utility function provided in a different module? Which of these modules has what I need to do what I came here to do, as opposed to advanced/optional features that most people won't care about?

Even just a single example of the most common use-case does wonders for usability. Even if it's not quite what you need, it tells you about the conventions and gives you things you can maybe swap out with other things in the crate as needed.

joshmarlow2• 6 years ago

One of my personal pet peeves is when library examples don't actually work anymore due to API changes (or typos).

There's actually a really great solution in the Rust ecosystem that I would love to see used more widely - Skeptic [0]. It's a tool that parses markdown, finds Rust and builds it as an auto-generated test. If the example is no longer valid, it breaks your build.

[0] https://github.com/budziq/rust-skeptic

steveklabnik7• 6 years ago

So, to be clear, skeptic helps with extra markdown files you've written. Rustdoc will already do this with every example you write in your API documentation. It's very good though! (mdbook has a similar feature)

joshmarlow2• 6 years ago

Good point - thanks for calling it out!

asdkhadsj2• 6 years ago

Another approach which I've liked in the past to solve this issue is to generate your README's from Rust Source. This has the same net output but the readme lives within Rustdoc.

I think I prefer it living in Rustdoc because then your README is also on docs.rs and whatnot.

But, I can see some downsides with that too. Not every README should be identical to the API docs. Not sure where the balance should sit.

How to write documentation for a Rust crate

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