Fuchsia Networking welcomes contributions from all. This document defines contribution guidelines where they differ from or refine on the guidelines that apply to Fuchsia as a whole.
Consult the getting started document to set up your development environment.
Consult the contribute changes document for general contribution guidance and project-wide best practices. The remainder of this document describes best practices specific to Fuchsia Networking.
This section is inspired by Flutter's style guide, which contains many general principles that you should apply to all your programming work. Read it. The below calls out specific aspects that we feel are particularly important.
Do not implement features you don‘t need. It is hard to correctly design unused code. This is closely related to the commit sizing advice given above; adding a new data structure to be used in some future commit is akin to adding a feature you don’t need - it is exceedingly hard for your code reviewer to determine if you‘ve designed the structure correctly because they (and you!) can’t see how it is to be used.
You will occasionally encounter behaviour that surprises you or seems wrong. It probably is! Invest the time to find the root cause - you will either learn something, or fix something, and both are worth your time. Do not work around behaviour you don't understand.
Avoid duplicating code whenever possible. In cases where existing code is not exposed in a manner suitable to your needs, prefer to extract the necessary parts into a common dependency.
Avoid unhandled errors and APIs which inherently disallow proper error handling; for a common example, consider fuchsia_async::executor::spawn. spawn inherently precludes error passing (since the flow of execution is severed). In most cases spawn can be replaced with a future that is later included in a select expression (example commit) or simply awaited on directly (example commit).
Do not implicitly discard values. In cases where a return value is unused, always be explicit. In Go, assign unused values to the blank identifier. In Rust, prefer destructuring assignment whenever possible, including when the return value is unit (()). When discarding primitive types where destructuring is not possible, use type annotations:
let _useless_rand: u8 = rand::thread_rng().gen();
Apply the same rules to unused closure parameters.
Prefer type safety over runtime invariant checking. In other words, arrange your abstractions such that they cannot express invalid conditions rather than relying on assertions at runtime.
Write testable code; testable code is modular and its dependencies are easily injected.
Avoid magic numbers.
When writing comments, take a moment to consider the future reader of your comment. Ensure that your comments are complete sentences with proper grammar and punctuation. Note that adding more comments or more verbose comments is not always better; for example, avoid comments that repeat the code they're anchored on.
Documentation comments should be self-contained; in other words, do not assume that the reader is aware of documentation in adjacent files or on adjacent structures. Avoid documentation comments on types which describe instances of the type; for example, AddressSet is a set of client addresses. is a comment that describes a field of type AddressSet, but the type may be used to hold any kind of Address, not just a client's.
Phrase your comments to avoid references that might become stale; for example: do not mention a variable or type by name when possible (certain doc comments are necessary exceptions). Also avoid references to past or future versions of or past or future work surrounding the item being documented; explain things from first principles rather than making external references (including past revisions).
When writing TODOs:
TODO(fxbug.dev/1245):When an implementation is following some specification/document (e.g. RFCs), include a comment with both a quote and citation of the relevant portion(s) of the document near the implementation. The quote lets readers know why something is being done and the citation allows a reader to get more context.
As with code comments, consider the future reader of the error messages emitted by your code. Ensure that your error messages are actionable. For example, avoid test failure messages such as “unexpected value” - always include the unexpected value; another example is “expected to be empty, was non-empty” - this message would be much more useful if it included the unexpected elements.
Always consider: what will the reader do with this message?
Consult the testability rubrics for general guidelines on test-writing and testability reviews on Fuchsia. In Fuchsia Networking, we define the following test classes:
qemu).Consider the following guidelines considering test-writing:
sleep in tests as a means of weak synchronization. Only sleep when strictly necessary (e.g. when polling is required).fuchsia_async::Executor::new_with_fake_time and fake-clock.-count in Go, --gtest_repeat for googletest) and aim for at least 100-1000 runs locally if your test is prone to flakes before merging.Rust test binaries currently don't have an equivalent flag, you may need to resort to a bash loop or equivalent to get repeated runs. See #65218.
Commits should be arranged for ease of reading; that is, incidental changes such as code movement or formatting changes should be committed separately from actual code changes.
Commits should always be focused. For example, a commit could add a feature, fix a bug, or refactor code, but not a mixture.
Commits should be thoughtfully sized; avoid overly large or complex commits which can be logically separated, but also avoid overly separated commits that require code reviews to load multiple commits into their mental working memory in order to properly understand how the various pieces fit together. If your changes require multiple commits, consider whether those changes warrant a design doc or RFC.
Commit messages should be concise but self-contained (avoid relying on issue references as explanations for changes) and written such that they are helpful to people reading in the future (include rationale and any necessary context).
Avoid superfluous details or narrative.
Commit messages should consist of a brief subject line and a separate explanatory paragraph in accordance with the following:
The body may be omitted if the subject is self-explanatory; e.g. when fixing a typo. The git book contains a Commit Guidelines section with much of the same advice, and the list above is part of a blog post by Chris Beams.
Commit messages should make use of issue tracker integration. See Commit-log message integration in the monorail documentation.
When using issue tracker integration, don't omit necessary context that may also be included in the relevant issue (see “Commit messages should be concise but self-contained” above). Many issues are Google-internal, and any given issue tracker is not guaranteed to be usable at the time that the commit history is read.
Commit messages should never contain references to any of:
Adding a Test: line to the commit message is encouraged. A Test: line should:
For example: Test: Added new unit tests. `fx test netstack-gotests` .
fx setRun the following command to build all tests and their dependencies:
fx set core.x64 --with //src/connectivity/network:tests
If you're working on changes that affect fdio and third_party/go, add:
--with //sdk/lib/fdio:tests --with //third_party/go:go_stdlib_tests