From edee52fa577ad3143777644d9b5e764b4e0a837d Mon Sep 17 00:00:00 2001 From: Aleksey Kladov Date: Sun, 2 Aug 2020 14:37:27 +0200 Subject: reorg docs --- docs/dev/style.md | 211 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 211 insertions(+) create mode 100644 docs/dev/style.md (limited to 'docs/dev/style.md') diff --git a/docs/dev/style.md b/docs/dev/style.md new file mode 100644 index 000000000..0a85b4a55 --- /dev/null +++ b/docs/dev/style.md @@ -0,0 +1,211 @@ +Our approach to "clean code" is two-fold: + +* We generally don't block PRs on style changes. +* At the same time, all code in rust-analyzer is constantly refactored. + +It is explicitly OK for a reviewer to flag only some nits in the PR, and then send a follow-up cleanup PR for things which are easier to explain by example, cc-ing the original author. +Sending small cleanup PRs (like renaming a single local variable) is encouraged. + +# Scale of Changes + +Everyone knows that it's better to send small & focused pull requests. +The problem is, sometimes you *have* to, eg, rewrite the whole compiler, and that just doesn't fit into a set of isolated PRs. + +The main things to keep an eye on are the boundaries between various components. +There are three kinds of changes: + +1. Internals of a single component are changed. + Specifically, you don't change any `pub` items. + A good example here would be an addition of a new assist. + +2. API of a component is expanded. + Specifically, you add a new `pub` function which wasn't there before. + A good example here would be expansion of assist API, for example, to implement lazy assists or assists groups. + +3. A new dependency between components is introduced. + Specifically, you add a `pub use` reexport from another crate or you add a new line to the `[dependencies]` section of `Cargo.toml`. + A good example here would be adding reference search capability to the assists crates. + +For the first group, the change is generally merged as long as: + +* it works for the happy case, +* it has tests, +* it doesn't panic for the unhappy case. + +For the second group, the change would be subjected to quite a bit of scrutiny and iteration. +The new API needs to be right (or at least easy to change later). +The actual implementation doesn't matter that much. +It's very important to minimize the amount of changed lines of code for changes of the second kind. +Often, you start doing a change of the first kind, only to realise that you need to elevate to a change of the second kind. +In this case, we'll probably ask you to split API changes into a separate PR. + +Changes of the third group should be pretty rare, so we don't specify any specific process for them. +That said, adding an innocent-looking `pub use` is a very simple way to break encapsulation, keep an eye on it! + +Note: if you enjoyed this abstract hand-waving about boundaries, you might appreciate +https://www.tedinski.com/2018/02/06/system-boundaries.html + +# Crates.io Dependencies + +We try to be very conservative with usage of crates.io dependencies. +Don't use small "helper" crates (exception: `itertools` is allowed). +If there's some general reusable bit of code you need, consider adding it to the `stdx` crate. + +# Minimal Tests + +Most tests in rust-analyzer start with a snippet of Rust code. +This snippets should be minimal -- if you copy-paste a snippet of real code into the tests, make sure to remove everything which could be removed. +There are many benefits to this: + +* less to read or to scroll past +* easier to understand what exactly is tested +* less stuff printed during printf-debugging +* less time to run test + +It also makes sense to format snippets more compactly (for example, by placing enum definitions like `enum E { Foo, Bar }` on a single line), +as long as they are still readable. + +## Order of Imports + +We separate import groups with blank lines + +```rust +mod x; +mod y; + +// First std. +use std::{ ... } + +// Second, external crates (both crates.io crates and other rust-analyzer crates). +use crate_foo::{ ... } +use crate_bar::{ ... } + +// Then current crate. +use crate::{} + +// Finally, parent and child modules, but prefer `use crate::`. +use super::{} +``` + +Module declarations come before the imports. +Order them in "suggested reading order" for a person new to the code base. + +## Import Style + +Items from `hir` and `ast` should be used qualified: + +```rust +// Good +use ra_syntax::ast; + +fn frobnicate(func: hir::Function, strukt: ast::StructDef) {} + +// Not as good +use hir::Function; +use ra_syntax::ast::StructDef; + +fn frobnicate(func: Function, strukt: StructDef) {} +``` + +Avoid local `use MyEnum::*` imports. + +Prefer `use crate::foo::bar` to `use super::bar`. + +## Order of Items + +Optimize for the reader who sees the file for the first time, and wants to get a general idea about what's going on. +People read things from top to bottom, so place most important things first. + +Specifically, if all items except one are private, always put the non-private item on top. + +Put `struct`s and `enum`s first, functions and impls last. + +Do + +```rust +// Good +struct Foo { + bars: Vec +} + +struct Bar; +``` + +rather than + +```rust +// Not as good +struct Bar; + +struct Foo { + bars: Vec +} +``` + +## Variable Naming + +We generally use boring and long names for local variables ([yay code completion](https://github.com/rust-analyzer/rust-analyzer/pull/4162#discussion_r417130973)). +The default name is a lowercased name of the type: `global_state: GlobalState`. +Avoid ad-hoc acronyms and contractions, but use the ones that exist consistently (`db`, `ctx`, `acc`). +The default name for "result of the function" local variable is `res`. +The default name for "I don't really care about the name" variable is `it`. + +## Collection types + +We prefer `rustc_hash::FxHashMap` and `rustc_hash::FxHashSet` instead of the ones in `std::collections`. +They use a hasher that's slightly faster and using them consistently will reduce code size by some small amount. + +## Preconditions + +Function preconditions should generally be expressed in types and provided by the caller (rather than checked by callee): + +```rust +// Good +fn frbonicate(walrus: Walrus) { + ... +} + +// Not as good +fn frobnicate(walrus: Option) { + let walrus = match walrus { + Some(it) => it, + None => return, + }; + ... +} +``` + +## Premature Pessimization + +Avoid writing code which is slower than it needs to be. +Don't allocate a `Vec` where an iterator would do, don't allocate strings needlessly. + +```rust +// Good +use itertools::Itertools; + +let (first_word, second_word) = match text.split_ascii_whitespace().collect_tuple() { + Some(it) => it, + None => return, +} + +// Not as good +let words = text.split_ascii_whitespace().collect::>(); +if words.len() != 2 { + return +} +``` + +## Documentation + +For `.md` and `.adoc` files, prefer a sentence-per-line format, don't wrap lines. +If the line is too long, you want to split the sentence in two :-) + +## Commit Style + +We don't have specific rules around git history hygiene. +Maintaining clean git history is encouraged, but not enforced. +We use rebase workflow, it's OK to rewrite history during PR review process. + +Avoid @mentioning people in commit messages and pull request descriptions(they are added to commit message by bors). +Such messages create a lot of duplicate notification traffic during rebases. -- cgit v1.2.3 From e96bfd812a0f883bc9aa6b5ebe3b0a712c860487 Mon Sep 17 00:00:00 2001 From: Aleksey Kladov Date: Sun, 2 Aug 2020 14:59:18 +0200 Subject: Tweak style wording --- docs/dev/style.md | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) (limited to 'docs/dev/style.md') diff --git a/docs/dev/style.md b/docs/dev/style.md index 0a85b4a55..1c68f5702 100644 --- a/docs/dev/style.md +++ b/docs/dev/style.md @@ -67,7 +67,8 @@ as long as they are still readable. ## Order of Imports -We separate import groups with blank lines +Separate import groups with blank lines. +Use one `use` per crate. ```rust mod x; @@ -92,7 +93,7 @@ Order them in "suggested reading order" for a person new to the code base. ## Import Style -Items from `hir` and `ast` should be used qualified: +Qualify items from `hir` and `ast`. ```rust // Good @@ -144,7 +145,7 @@ struct Foo { ## Variable Naming -We generally use boring and long names for local variables ([yay code completion](https://github.com/rust-analyzer/rust-analyzer/pull/4162#discussion_r417130973)). +Use boring and long names for local variables ([yay code completion](https://github.com/rust-analyzer/rust-analyzer/pull/4162#discussion_r417130973)). The default name is a lowercased name of the type: `global_state: GlobalState`. Avoid ad-hoc acronyms and contractions, but use the ones that exist consistently (`db`, `ctx`, `acc`). The default name for "result of the function" local variable is `res`. @@ -152,12 +153,12 @@ The default name for "I don't really care about the name" variable is `it`. ## Collection types -We prefer `rustc_hash::FxHashMap` and `rustc_hash::FxHashSet` instead of the ones in `std::collections`. +Prefer `rustc_hash::FxHashMap` and `rustc_hash::FxHashSet` instead of the ones in `std::collections`. They use a hasher that's slightly faster and using them consistently will reduce code size by some small amount. ## Preconditions -Function preconditions should generally be expressed in types and provided by the caller (rather than checked by callee): +Express function preconditions in types and force the caller to provide them (rather than checking in callee): ```rust // Good @@ -205,7 +206,7 @@ If the line is too long, you want to split the sentence in two :-) We don't have specific rules around git history hygiene. Maintaining clean git history is encouraged, but not enforced. -We use rebase workflow, it's OK to rewrite history during PR review process. +Use rebase workflow, it's OK to rewrite history during PR review process. Avoid @mentioning people in commit messages and pull request descriptions(they are added to commit message by bors). Such messages create a lot of duplicate notification traffic during rebases. -- cgit v1.2.3