• Quickstart
• Overview
• Motivation
  • Reducing AST Churn
    • whitespace
    • arrow-parens
    • one var
• Install
  • Prettier
  • with SolHint
• License

Quickstart

See the dappspec format for additional style guide directives

Prettier & Plugin+Config

Warning A Major Semver release for prettier is upcoming, ensure you are using compatible versions

npm i -D prettier@^2 prettier-plugin-solidity@latest prettier-config-solidity@latest  --save-exact

create prettier.config.js file

'use strict';
const prettierConfig = require('prettier-config-solidity');
module.exports = prettierConfig;

Editorconfig

# Stop the editor from looking for .editorconfig files in the parent directories
# root = true

[*]
# Non-configurable Prettier behaviors
charset = utf-8
insert_final_newline = true
# Caveat: Prettier won’t trim trailing whitespace inside template strings, but your editor might.
# trim_trailing_whitespace = true

# Configurable Prettier behaviors
# (change these if your Prettier config differs)
end_of_line = lf
indent_style = space
indent_size = 2
max_line_length = 80

# Solidity
# https://github.com/sambacha/prettier-config-solidity
[*.sol]
indent_size = 4
indent_style = space

# Ignore fixtures and vendored files
[{dist,artifacts,vendor,test,fixtures,tests,cache,__snapshot__,}/**]
charset = unset
end_of_line = unset
indent_size = unset
indent_style = unset
insert_final_newline = unset
trim_trailing_spaces = unset

Style Convention

Example:

• Changes unit to unit256

unformatted

    function swapExactETHForTokens(uint amountOutMin, address[] calldata path, address to, uint deadline)
        external
        override
        payable
        ensure(deadline)
        returns (uint[] memory amounts)
    {

formatted

    function swapExactETHForTokens(
        uint256 amountOutMin,
        address[] calldata path,
        address to,
        uint256 deadline
    ) external payable override ensure(deadline) returns (uint256[] memory amounts) {
        require(path[0] == WETH, "UniswapV2Router: INVALID_PATH");

Overview

Prettier configuration for Solidity

Motivation

This configuration is optimized to reduce diff churn and improve AST results.

The following rules are employed, with specific reasonings to their choice (source: airbnb style guide):

printWidth

The behavior of printWidth is located here: prettier-solidity/prettier-plugin-solidity/blob/b504261047d0019c924d53a2b9ab0738b1e05703/src/nodes/FunctionDefinition.js#L99

See more here prettier-plugin-solidity/issues/474#issuecomment-823670541

whitespace

source@airbnb/javascript#whitespace--in-braces

• 19.12 Add spaces inside curly braces. eslint: object-curly-spacing

// bad
const foo = { clark: 'kent' };

// good
const foo = { clark: 'kent' };

arrow-parens

• 8.4 Always include parentheses around arguments for clarity and consistency. eslint: arrow-parens

source@airbnb/javascript#arrows--one-arg-parens

Why? Minimizes diff churn when adding or removing arguments.

// bad
[1, 2, 3].map((x) => x * x);

// good
[1, 2, 3].map((x) => x * x);

// bad
[1, 2, 3].map(
  (number) =>
    `A long string with the ${number}. It’s so long that we don’t want it to take up space on the .map line!`,
);

// good
[1, 2, 3].map(
  (number) =>
    `A long string with the ${number}. It’s so long that we don’t want it to take up space on the .map line!`,
);

// bad
[1, 2, 3].map((x) => {
  const y = x + 1;
  return x * y;
});

// good
[1, 2, 3].map((x) => {
  const y = x + 1;
  return x * y;
});

one var

• 13.2 Use one const or let declaration per variable or assignment. eslint: one-var

Why? It’s easier to add new variable declarations this way, and you never have to worry about swapping out a ; for a , or introducing punctuation-only diffs. You can also step through each declaration with the debugger, instead of jumping through all of them at once.

ref:eslint/rules/one-var

// bad
const items = getItems(),
  goSportsTeam = true,
  dragonball = 'z';

// bad
// (compare to above, and try to spot the mistake)
const items = getItems(),
  goSportsTeam = true;
dragonball = 'z';

// good
const items = getItems();
const goSportsTeam = true;
const dragonball = 'z';

20.2 Additional trailing comma: Yup. eslint: comma-dangle

Why? This leads to cleaner git diffs. Also, transpilers like Babel will remove the additional trailing comma in the transpiled code which means you don’t have to worry about the trailing comma problem in legacy browsers.

// bad - git diff without trailing comma
const hero = {
     firstName: 'Florence',
-    lastName: 'Nightingale'
+    lastName: 'Nightingale',
+    inventorOf: ['coxcomb chart', 'modern nursing']
};

// good - git diff with trailing comma
const hero = {
     firstName: 'Florence',
     lastName: 'Nightingale',
+    inventorOf: ['coxcomb chart', 'modern nursing'],
};

8.6 Enforce the location of arrow function bodies with implicit returns. eslint: implicit-arrow-linebreak

// bad
(foo) => bar;

(foo) => bar;

// good
(foo) => bar;
(foo) => bar;
(foo) => bar;

Install

Prettier

npm i -D prettier prettier-plugin-solidity@latest prettier-config-solidity  --save-exact

npm i -D prettier prettier-plugin-solidity@latest prettier-config-solidity  --save-exact --legacy-peer-deps

or

yarn add -D prettier prettier-plugin-solidity@latest prettier-config-solidity  --save-exact

with SolHint

npm install --save-dev solhint solhint-plugin-prettier prettier prettier-plugin-solidity --save-exact

{
  "plugins": ["prettier"],
  "rules": {
    "prettier/prettier": "error"
  }
}

License

SPDX-License-Identifier: Apache-2.0