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doc: update contributing and coding style
* Update `CONTRIBUTING.md` * Add `CODE_STYLE.md`
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| # Code style | ||
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| This is a description of a coding style that every contributor **must** follow. | ||
| Please, read the whole document before you start pushing code. | ||
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| ## Generics | ||
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| All trait bounds should be written in `where`: | ||
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| ```rust | ||
| // GOOD | ||
| pub fn new<N, T, P, E>(user_id: i32, name: N, title: T, png_sticker: P, emojis: E) -> Self | ||
| where | ||
| N: Into<String>, | ||
| T: Into<String>, | ||
| P: Into<InputFile>, | ||
| E: Into<String>, | ||
| { ... } | ||
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| // BAD | ||
| pub fn new<N: Into<String>, | ||
| T: Into<String>, | ||
| P: Into<InputFile>, | ||
| E: Into<String>> | ||
| (user_id: i32, name: N, title: T, png_sticker: P, emojis: E) -> Self { ... } | ||
| ``` | ||
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| ```rust | ||
| // GOOD | ||
| impl<T> Trait for Wrap<T> | ||
| where | ||
| T: Trait | ||
| { ... } | ||
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| // BAD | ||
| impl<T: Trait> Trait for Wrap<T> { ... } | ||
| ``` | ||
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| ## Use `Self` where possible | ||
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| When referring to the type for which block is implemented, prefer using `Self`, rather than the name of the type: | ||
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| ```rust | ||
| impl ErrorKind { | ||
| // GOOD | ||
| fn print(&self) { | ||
| Self::Io => println!("Io"), | ||
| Self::Network => println!("Network"), | ||
| Self::Json => println!("Json"), | ||
| } | ||
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| // BAD | ||
| fn print(&self) { | ||
| ErrorKind::Io => println!("Io"), | ||
| ErrorKind::Network => println!("Network"), | ||
| ErrorKind::Json => println!("Json"), | ||
| } | ||
| } | ||
| ``` | ||
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| ```rust | ||
| impl<'a> AnswerCallbackQuery<'a> { | ||
| // GOOD | ||
| fn new<C>(bot: &'a Bot, callback_query_id: C) -> Self | ||
| where | ||
| C: Into<String>, | ||
| { ... } | ||
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| // BAD | ||
| fn new<C>(bot: &'a Bot, callback_query_id: C) -> AnswerCallbackQuery<'a> | ||
| where | ||
| C: Into<String>, | ||
| { ... } | ||
| } | ||
| ``` | ||
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| **Rationale:** `Self` is generally shorter and it's easier to copy-paste code or rename the type. | ||
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| ## Deriving traits | ||
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| Derive `Debug`, `Clone`, `Copy`, `PartialEq`, `Eq` and `Hash` for public types when possible (in this order). | ||
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| **Rationale:** these traits can be useful for users and can be implemented for most types. | ||
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| Derive `Default` when there is a reasonable default value for the type. | ||
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| ## Full paths for logging | ||
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| Always write `tracing::<op>!(...)` instead of importing `use tracing::<op>;` and invoking `<op>!(...)`. | ||
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| ```rust | ||
| // GOOD | ||
| tracing::warn!("Everything is on fire"); | ||
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| // BAD | ||
| use tracing::warn; | ||
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| warn!("Everything is on fire"); | ||
| ``` | ||
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| **Rationale:** | ||
| - Less polluted import blocks | ||
| - Uniformity | ||
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| ## `&str` -> `String` conversion | ||
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| Prefer using `.to_string()` or `.to_owned()`, rather than `.into()`, `String::from`, etc. | ||
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| **Rationale:** uniformity, intent clarity. | ||
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| ## Order of imports | ||
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| ```rust | ||
| // First core, alloc and/or std | ||
| use core::fmt; | ||
| use std::{...}; | ||
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| // Second, external crates (both crates.io crates and other rust-analyzer crates). | ||
| use crate_foo::{ ... }; | ||
| use crate_bar::{ ... }; | ||
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| // If applicable, the current sub-modules | ||
| mod x; | ||
| mod y; | ||
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| // Finally, the internal crate modules and submodules | ||
| use crate::{}; | ||
| use super::{}; | ||
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| // Re-exports are treated as item definitions rather than imports, so they go | ||
| // after imports and modules. Use them sparingly. | ||
| pub use crate::x::Z; | ||
| ``` | ||
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| ## Import Style | ||
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| When implementing traits from `core::fmt`/`std::fmt` import the module: | ||
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| ```rust | ||
| // GOOD | ||
| use core::fmt; | ||
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| impl fmt::Display for RenameError { | ||
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { .. } | ||
| } | ||
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| // BAD | ||
| impl core::fmt::Display for RenameError { | ||
| fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result { .. } | ||
| } | ||
| ``` | ||
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| ## If-let | ||
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| Avoid the `if let ... { } else { }` construct if possible, use `match` instead: | ||
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| ```rust | ||
| // GOOD | ||
| match ctx.expected_type.as_ref() { | ||
| Some(expected_type) => completion_ty == expected_type && !expected_type.is_unit(), | ||
| None => false, | ||
| } | ||
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| // BAD | ||
| if let Some(expected_type) = ctx.expected_type.as_ref() { | ||
| completion_ty == expected_type && !expected_type.is_unit() | ||
| } else { | ||
| false | ||
| } | ||
| ``` | ||
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| Use `if let ... { }` when a match arm is intentionally empty: | ||
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| ```rust | ||
| // GOOD | ||
| if let Some(expected_type) = this.as_ref() { | ||
| // Handle it | ||
| } | ||
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| // BAD | ||
| match this.as_ref() { | ||
| Some(expected_type) => { | ||
| // Handle it | ||
| }, | ||
| None => (), | ||
| } | ||
| ``` |
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