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Sync Rust style guide with BaseGL repo

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@ -10,6 +10,15 @@ programmer burden; there is usually only _one way_ to lay out code correctly.
<!-- MarkdownTOC levels="2,3" autolink="true" -->
- [Code Formatting](#code-formatting)
- [Line Width](#line-width)
- [Imports](#imports)
- [Sections](#sections)
- [Vertical Spacing](#vertical-spacing)
- [Multi-Line Expressions](#multi-line-expressions)
- [Vertical Alignment](#vertical-alignment)
- [Spacing](#spacing)
- [Impl Definitions](#impl-definitions)
- [Getters and Setters](#getters-and-setters)
- [Naming](#naming)
- [Package Structure and Naming](#package-structure-and-naming)
- [The Public API](#the-public-api)
@ -31,16 +40,368 @@ programmer burden; there is usually only _one way_ to lay out code correctly.
This section explains the rules for visually laying out your code. They provide
a robust set of guidelines for creating a consistent visual to the code.
Primary formatting is dealt with using the Rust formatting tool
['rustfmt'](https://rust-lang.github.io/rustfmt/), which enforces rules around
whitespace, line-wrapping, and alignment. The Enso repository contains the main
[`.rustfmt.toml`](../.rustfmt.toml) configuration file, and this is what should
be used for all new Rust projects.
Code style is _far_ more than just the visual formatting of the code, especially
as formatting can often be automated. According to the documentation of rustfmt,
"formatting code is a mostly mechanical task which takes both time and mental
effort." While, in many cases, the programmer can be relieved of this burden
through use of an automated formatter, it is sometimes the case that such a tool
imposes _more_ cognitive load in programmers. With rustfmt, programmers tend to
have to refactor long lines to use variables, and move code to specific modules
or sections lest rustfmt produce code that is hard to read and write. Thus, it
is very important to write code in such a way that we can be proud of its
quality.
All files must be formatted using `rustfmt` before commit, and this should be
set up as either a precommit hook, or using functionality for automatic
formatting in your editor. To quickly format code, it can be run via `cargo`
using the `cargo fmt` command.
Due to the fact that `rustfmt` doesn't support multiple of our requirements, we
have created a guide for how to format Rust code for this project. Please read
it carefully.
We hope that, in the future, `rustfmt` will come to support many of the things
described below, but even so, many portions of this guide will need to be
handled manually.
### Line Width
Each line in the source file should be of a maximum of 80 characters of text.
This includes comments.
### Imports
The imports section at the top of a file should be separated into four groups.
These groups should be sorted in alphabetical order and are divided as follows:
```rust
// Group 1: sub-module definitions.
// Group 2: prelude-like imports.
// Group 3: local-crate imports.
// Group 4: external imports.
```
Please look at the following by way of example:
```rust
pub mod display_object;
use crate::prelude::*;
use crate::closure;
use crate::data::opt_vec::OptVec;
use crate::dirty;
use crate::system::web::group;
use nalgebra::Matrix4;
use nalgebra::Vector3;
```
### Sections
Rust source files should be divided into sections, with a header placed before
the definition of each new concept in a file.
By the term "concept," we are referring primarily to a structure with a set of
related implementations. However if the related implementations rely on some
simple helper structs, these may also be defined in the same section. A section
should have a header as follows.
```rust
// ===================
// === SectionName ===
// ===================
```
Additionally, the code in each section should further be divided into
sub-sections that group relevant functionality within the section. The header
for a sub-section is as follows.
```rust
// === SubSectionName ===
```
At least one section should be defined in every file.
#### An Example of Using Sections
Here is a large-scale example of how sections should be used in source files.
```rust
// =================
// === AxisOrder ===
// =================
/// Defines the order in which particular axis coordinates are processed. Used
/// for example to define the rotation order in `DisplayObject`.
pub enum AxisOrder {XYZ,XZY,YXZ,YZX,ZXY,ZYX}
impl Default for AxisOrder {
fn default() -> Self {Self::XYZ}
}
// =================
// === Transform ===
// =================
/// Defines the order in which transformations (scale, rotate, translate) are
/// applied to a particular object.
pub enum TransformOrder {
ScaleRotateTranslate,
ScaleTranslateRotate,
RotateScaleTranslate,
RotateTranslateScale,
TranslateRotateScale,
TranslateScaleRotate
}
impl Default for TransformOrder {
fn default() -> Self { Self::ScaleRotateTranslate }
}
// =============================
// === HierarchicalTransform ===
// =============================
pub struct HierarchicalTransform<OnChange> {
transform : Transform,
transform_matrix : Matrix4<f32>,
origin : Matrix4<f32>,
matrix : Matrix4<f32>,
pub dirty : dirty::SharedBool<OnChange>,
pub logger : Logger,
}
impl<OnChange> HierarchicalTransform<OnChange> {
pub fn new(logger:Logger, on_change:OnChange) -> Self {
let logger_dirty = logger.sub("dirty");
let transform = default();
let transform_matrix = Matrix4::identity();
let origin = Matrix4::identity();
let matrix = Matrix4::identity();
let dirty = dirty::SharedBool::new(logger_dirty,on_change);
Self {transform,transform_matrix,origin,matrix,dirty,logger}
}
}
// === Getters ===
impl<OnChange> HierarchicalTransform<OnChange> {
pub fn position(&self) -> &Vector3<f32> {
&self.transform.position
}
pub fn rotation(&self) -> &Vector3<f32> {
&self.transform.rotation
}
...
}
// === Setters ===
impl<OnChange:Callback0> HierarchicalTransform<OnChange> {
pub fn position_mut(&mut self) -> &mut Vector3<f32> {
self.dirty.set();
&mut self.transform.position
}
pub fn rotation_mut(&mut self) -> &mut Vector3<f32> {
self.dirty.set();
&mut self.transform.rotation
}
...
}
```
### Vertical Spacing
We use the following rules for the amount of vertical space separating various
constructs in the source:
- 2 blank lines after the imporst
- 2 blank lines before each section
- 1 blank line before and after sub-section
- 1 blank line before functions / structures / impls
- 1 blank line at the end of the file
### Multi-Line Expressions
In an ideal world, all expressions in the code should be a single line. This is
because multi-line expressions are usually hard to read, and because they can
introduce lots of noise in the code. In the vast majority of cases, the presence
of a multi-line expression indicates that the code needs refactoring.
Please try to refactor portions of multi-line expressions to well-named
variables, and divide them up to a set of single-line expressions.
#### Multi-Line Expression Examples
The following is an example of poorly formatted code:
```rust
pub fn new() -> Self {
let shape_dirty = ShapeDirty::new(logger.sub("shape_dirty"),
on_dirty.clone());
let dirty_flag = MeshRegistryDirty::new(logger.sub("mesh_registry_dirty"),
on_dirty);
Self { dirty_flag, dirty_flag }
}
```
The following is an example of the same code properly formatted:
```rust
pub fn new() -> Self {
let sub_logger = logger.sub("shape_dirty");
let shape_dirty = ShapeDirty::new(sub_logger,on_dirty.clone());
let sub_logger = logger.sub("mesh_registry_dirty");
let dirty_flag = MeshRegistryDirty::new(sub_logger,on_dirty);
Self {shape_dirty,dirty_flag}
}
```
### Vertical Alignment
In order to create a visual flow to our code that aids readability, the
following constructs should be aligned vertically where possible:
- Assignment operators (`=`)
- Type operators (`:`)
- Match arrows (`=>`)
- Similar parameters or types
#### A Vertical Alignment Example
The following is an example of a function that correctly uses the vertical
alignment rules above:
```rust
impl Printer for GlobalVarStorage {
fn print(&self, builder:&mut Builder) {
match self {
Self::ConstStorage => build!(builder,"const"),
Self::UniformStorage => build!(builder,"uniform"),
Self::InStorage (qual) => build!(builder,"in" ,qual),
Self::OutStorage (qual) => build!(builder,"out",qual),
}
}
}
```
### Spacing
The following spacing rules are _also_ employed in order to create a visual flow
to our code to aid readability:
- The type operator is not spaced: `fn test(foo:String, bar:Int) { ... }`
- Commas between complex expressions (including the argument list) are spaced
- Commas between simple elements are not spaced: `Result<Self,Error>`
- Arguments to functions are not spaced: `build(builder,"out",qual)`
- Operators are always spaced: `let foo = a + b * c;`
#### Spacing Examples as Function Definitions
The following function definitions are all good examples of correct use of
spacing.
```rust
pub fn new<Dom:Str>(dom:Dom, logger:Logger) -> Result<Self,Error> {
...
}
```
```rust
pub fn new<Dom:Str>(dom:Dom, logger:Logger) -> Result<Self,Error> {
...
}
```
```rust
pub fn new<Dom:Str>
(dom:Dom, logger:Logger, on_dirty:OnDirty) -> Result<Self,Error> {
...
}
```
```rust
pub fn new<Dom:Str>
(dom:Dom, logger:Logger, on_dirty:OnDirty, on_remove:OnRemove)
-> Result<Self,Error> {
...
}
```
```rust
pub fn new<Dom:Str>
( dom : Dom
, logger : Logger
, on_dirty : OnDirty
, on_remove : OnRemove
, on_replace : OnReplace
) -> Result<Self,Error> {
...
}
```
Long `where` clauses are formatted this way:
```rust
pub fn new<D,L>(dom:D, logger:L) -> Result<Self,Error>
where D:AsRef<str>, L:IsLogger {
...
}
```
Or, in case they are really long, this way:
```rust
pub fn new<D,L>(dom:D, logger:L) -> Result<Self,Error>
where D:AsRef<str>
L:IsLogger
... {
...
}
```
### Impl Definitions
In order to aid in fast discovery of the header of an impl definition, we use
the following style. In all cases, the `where` block should be placed after a
line break.
```rust
// No constraints
impl<T> Printer for Option<T> {
...
}
```
```rust
// Some constraints
impl<T:Printer>
Printer for Option<T> {
...
}
```
```rust
// Constraints in where block
impl<T> Printer for Option<T>
where T: Printer {
...
}
```
### Getters and Setters
We have the following rules for getters and setters in our codebase.
- Getters do not have the `get_` prefix, while setters do have the `set_`
prefix.
- If a setter is provided, a `mut` accessor should be provided as well.
Correct examples for the definition of getters and setters can be found below:
```rust
fn field(&self) -> &Type {
&self.field
}
fn field_mut(&mut self) -> &mut Type {
&mut self.field
}
fn set_field(&mut self, val:Type) {
*self.field_mut = val;
}
```
## Naming
Enso has some fairly simple general naming conventions, though the sections