CYF ESLint Configuration

A standard ESLint configuration for all CYF examples/projects.

Versioning

This configuration uses SemVer, interpreted as follows:

• Patch release (x.y.z -> x.y.z+1): bugfixes and tooling updates mean that code that previously passed linting should continue to pass after the update.

• Minor release (x.y.z -> x.y+1.0): a change to an existing rule means that code that previously failed linting may now pass, or a new configuration means that code that previously passed linting should continue to pass.

• Major release (x.y.z -> x+1.0.0): a new rule, or a change to an existing rule, means that code that previously passed linting will not pass any more.

Please bear these definitions in mind when reporting any bugs.

Usage

Install this package along with ESLint itself:

npm install --save-dev eslint @codeyourfuture/eslint-config-standard

Then create an ESLint config file and add this config:

const cyf = require("@codeyourfuture/eslint-config-standard");

module.exports = [...cyf.configs.standard];

or using ES module syntax:

import cyf from "@codeyourfuture/eslint-config-standard";

export default [...cyf.configs.standard];

Alternatively, for a slightly more permissive set of rules, you can use cyf.configs.lax.

You can also call cyf.configure with some rules to add/override your own settings:

export default [...cyf.configure({
  // ...
})];

Principles

1. Errors only - don't teach learners to ignore any output, all rules should either be "error" or "off"
2. Maximise consistency - where there are options (e.g. braces for single-line statements, parentheses around arrow function parameters), be consistent with the non-optional cases
3. Minimise change set size - keep commits small so learners can focus on the important changes

Rules

This config starts from the ESLint and Stylistic recommended rules then adds the following:

Configuration	Rule	Setting	Principles/rationale
standard, lax	@stylistic/arrow-parens		2, 3
standard, lax	@stylistic/brace-style	"1tbs", { "allowSingleLine": false }
standard, lax	@stylistic/comma-dangle	"always-multiline"	3
standard	@stylistic/indent	"tab", { "SwitchCase": 1 }	Tabs are more accessible
standard	@stylistic/linebreak-style	"unix"
standard, lax	@stylistic/no-trailing-spaces
standard, lax	@stylistic/object-curly-spacing	"always"
standard, lax	@stylistic/operator-linebreak	"before"
standard, lax	@stylistic/quote-props	"as-needed"	3
standard, lax	@stylistic/quotes	"double", { "avoidEscape": true, "allowTemplateLiterals": false }	More likely to need ' inside a string than "
standard, lax	@stylistic/semi		Learners shouldn't have to memorise the ASI rules
standard, lax	curly		2
standard, lax	no-unused-vars	{ "ignoreRestSiblings": true }
standard, lax	no-var		Stick with let and const for more predictable behaviour

Development

You can clone this repo and run npm install to install the development dependencies. Two scripts are provided:

• lint: uses the version of ESLint installed as a dev dependency to lint index.js against its own rules.

• test:examples: runs bin/examples.sh to test the configuration against the pass.js and fail.js examples in examples/. pass.js contains code that should pass linting according to the configuration, fail.js contains code that should fail linting.

• test:install: runs bin/test.sh to create a package, installs ESLint (version defined by the required environment variable ESLINT_VERSION) and the current version of this configuration, then checks that there are no version conflicts and lints index.js. E.g. ESLINT_VERSION=9 npm run test will test that this configuration works with the latest version of ESLint 9.