Style Guide

Style Guide for Rust in Polkadot

• Indent using tabs
• Never have spaces before a non-whitespace character starts
• Follow-on lines are only ever a single indent from the original line.

fn long_simple_calculation(some_long_variable_a: i8, some_long_variable_b: i8) -> bool {
	let x = some_long_variable_a * some_long_variable_b
		- some_long_variable_b / some_long_variable_a
		+ sqrt(some_long_variable_a) - sqrt(some_long_variable_b);
	x > 10
}

- Indent level should follow open parens/brackets, but should be collapsed to the smallest number of levels actually used:

fn calculate(some_long_variable_a: f32, some_long_variable_b: f32, some_long_variable_c: f32) -> f32 { (-some_long_variable_b + sqrt( // two parens open, but since we close them both on the same line, only one indent level is used some_long_variable_b * some_long_variable_b - 4 * some_long_variable_a * some_long_variable_c // both closed here at beginning of line, so back to the original indent level )) / (2 * some_long_variable_a) }

- `where` is indented, and its items are indented one further
- Long arg lists or function calls are indented similarly to code blocks, and once one param is indented in such a way, all others should be, too. Run-on parameter lists are also acceptable for single-line run-ons of basic function calls.

fn foo( really_long_parameter_name_1: SomeLongTypeName, really_long_parameter_name_2: SomeLongTypeName, shrt_nm_1: u8, shrt_nm_2: u8 ) { // Complex line (not just a function call, also a let statement). Full structure. let (a, b) = bar( really_long_parameter_name_1, really_long_parameter_name_2, shrt_nm_1, shrt_nm_2 ); // Long, simple function call that fits onto two lines. Inline with a run-on. waz(really_long_parameter_name_1, really_long_parameter_name_2, shrt_nm_1, shrt_nm_2); // Short function call. Inline. baz(a, b); }

- Always end last item of a multi-line comma-delimited set with `,` when legal:

struct Point { x: T, y: T, // <-- Multiline comma-delimited lists end with a trailing , }

// Single line comma-delimited items do not have a trailing , enum Meal { Breakfast, Lunch, Dinner };

- Avoid trailing `;`s where unneeded.

if condition { return 1 // <-- no ; here }

- `match` arms may be either blocks or have a trailing `,` but not both.
- Blocks should not be used unnecessarily.

match meal { Meal::Breakfast => "eggs", Meal::Lunch => { check_diet(); recipe() } // Meal::Dinner => { return Err("Fasting") } // WRONG Meal::Dinner => return Err("Fasting"), }