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Contributing to the Rust Cookbook

The cookbook needs contributors and is intended to be easy to contribute to. Help is welcome.

Building and testing

To start, clone the cookbook from git and navigate to that directory:

git clone https://github.com/rust-lang-nursery/rust-cookbook.git
cd rust-cookbook

Cookbook is built with mdBook, so install that first with Cargo:

cargo install --version 0.3.5 mdbook

To build and view the cookbook locally, run:

mdbook serve

Then open http://localhost:3000 in a web browser to browse the cookbook. Any changes you make to the cookbook source will be automatically rebuilt and visible in the browser, so it can be helpful to keep this window open while editing.

All examples in the cookbook are tested with skeptic, a tool for testing arbitrary markdown documentation in a style similar to rustdoc.

To run the cookbook test suite:

cargo test

Linters

The Rust Cookbook comes with link checking and spell checking linters that run on the continuous integration server. These linters should be run locally before submitting a pull request to ensure there are no dead links or spelling errors made.

To install the link checker, review the documentation for python to install python 3.6 and pip3. Installing link-checker once the dependencies are met is done with pip3.

[sudo] pip3 install link-checker==0.1.0

Alternatively, add the user install directory (probably ~/.local/bin) to your PATH variable and install link-checker for your user.

pip3 install --user link-checker==0.1.0

Checking the links of the book locally first requires the book to be built with mdBook. From the root directory of the cookbook, the following commands run the link checker.

mdbook build
link-checker ./book

The aspell binary provides spell checking. Apt packages provide installation on Debian based operating systems.

[sudo] apt install aspell -y

On other Linux distributions you might also need to install the aspell-en package, or similar.

To check the spelling of the Rust Cookbook locally, run the following command from the root of the Cookbook.

./ci/spellcheck.sh

# or, if you're using a different locale
LANG=en_US.UTF-8 ./ci/spellcheck.sh

If the spell checker finds a misspelled word, you have the opportunity to correct the spelling mistake with the number keys. If the spelling mistake is erroneous, add the word to the dictionary located in ci/dictionary.txt. Pressing a or l will not add the word to the custom dictionary.

If there are no errors, it will just print the local Aspell version and exit.

Finding what to contribute

This project is intended to be simple to contribute to, and to always have obvious next work items available. If at any time there is not something obvious to contribute, that is a bug. Feel free to ask for additional support at the Rust Ecosystem Working Group.

The development process for the cookbook is presently oriented around crates: we decide which crates to represent in the cookbook, then come up with example use cases to write, then write the examples. And those are the three basic, recurring types of contributions needed.

The development process for the cookbook today is tied to the libz blitz, a broader project to improve the Rust crate ecosystem, and the cookbook presently represents the crates under consideration there. The easiest way to find the most immediate work needed for the cookbook is to follow the "What's next" section at the top of that thread, which should at all times link to something to contribute to the cookbook.

Otherwise, look for GitHub issues with the example tag. The simplest way to contribute is to claim one of these examples, and submit a PR adding it. If you do claim one, please leave a comment saying so, so others don't accidentally duplicate your work.

If you have an idea for an example for a specific crate, please suggest it on the relevant tracking issue.

Please do not submit examples for crates not yet represented in the cookbook, unless it is part of the libz blitz crate schedule. Contribution will be open to a broader set of crates in the future. For more about which crates are represented in the cookbook, see "a note about crate representation" in the cookbook.

Adding an example

Adding an example involves:

  • Deciding which section of the book it belongs in
  • Deciding which categories apply to it
  • Adding the example to the section index in intro.md
  • Adding the example to the appropriate section markdown file
  • Updating badges and hyperlinks as needed
  • Writing a useful description of the example

The finished commit will look something like this one.

Examples are presently organized in three ways:

  • Book sections - the cookbook is a book, and is organized like a book in logical sections, like "basics", "encoding", "concurrency".
  • Category tags - each example is tagged with one or more category tags, like "filesystem", "debugging".
  • Crate tags - each example is tagged with one or more crate tags, indicating which crates are represented in the example. Those that use no additional crates are simply tagged 'std'.

For more about the organization of the book see "how to read this book" in the cookbook.

Hopefully your example belongs to an obvious section and categories, but since the cookbook is so new, quite possibly not. Ask on thread.

For most steps you can simply follow the lead of existing examples. The art comes in writing effective examples.

Example guidelines

Examples in the cookbook have these goals and qualities:

  • They can be described by a single sentence that states their utility.
  • They can be read and understood by a complete beginner.
  • They are standalone examples that can be copied into a learner's own workspace and compiled and modified for experimentation.
  • They demonstrate real tasks, such that experienced developers may use it as a reference.
  • They follow best practices and do not take shortcuts.
  • They use consistent error handling.

Title

Examples should have a simple single-sentence title that describes something a typical Rust user typically wants to do.

Generate random numbers with given distribution

Description

Describe traits imported and the methods used. Think about what information supports the use case and might not be obvious to someone new. Keep the description to 1-4 sentences, avoiding explanations outside the scope of the code sample.

Use third person narrative of the code execution, taking the opportunity to link to API documentation. Always use active voice. Hyperlink all references to APIs, either on doc.rust-lang.org/std or docs.rs, and style them as code. Use wildcard version specifiers for crate links.

Any requirements to execute the code that are not apparent, such as passing environment flags, or configuring Cargo.toml should be added after the code sample.

By default, random numbers are generated with uniform distribution. To generate numbers with other distributions you instantiate a distribution, then sample from that distribution using Distribution::sample with help of a random-number generator rand::Rng.

The distributions available are documented here. An example using the Normal distribution is shown below.

Code

Examples are intended to be read by complete beginners, and copied into projects for experimentation. They should follow best practices and not take shortcuts.

The example should have minimal code that doesn't directly support the description of the example. Keep extra functions and types to a minimum.

When an example must handle the possibility of errors, follow the error handling templates in "A note about error handling". Examples always set up error handling correctly and propagate errors with ? (not try!, urwrap, or expect). If there is no need for error handling in the example, prefer main().

Avoid glob imports (*), even for preludes, so that users can see what traits are called. (Some crates might consider using glob imports for preludes best practice, making this awkward.)

Examples should be simple and obvious enough that an experienced dev do not need comments.

Examples should compile without warnings, clippy lint warnings, or panics. The code should be formatted by rustfmt. Hide all error boilerplate and parts of the sample that do not accomplish the subject of the example.

Mark examples that depend on external systems with no_run or remove them if they are not required for the example. Avoid inline comments, preferring explanation in the description.

extern crate rand;

use rand::distributions::{Normal, Distribution};

fn main() {
   let mut rng = rand::thread_rng();
   let normal = Normal::new(2.0, 3.0);
   let v = normal.sample(&mut rng);
   println!("{} is from a N(2, 9) distribution", v)
}

Finally, this book is intended to demonstrate the integration of crates that work well together. We are on the lookout for examples that feature multiple crates sensibly.