Eslint-config-topcoder NPM

eslint-config-topcoder

This package contains ESLint configs for applications:

nodejs v7 (backend application)
nodejs v7 with babel (backend application written in babel)
react

It contains plugins:

eslint-plugin-babel - ESLint rules for babel
eslint-plugin-react - ESLint rules for react
eslint-plugin-lodash - ESLint rules for lodash (underscore is forbidden)
eslint-plugin-import - ESLint plugin with rules that help validate proper imports

Installation

Nodejs

npm install --save-dev eslint-config-topcoder

Configure .eslintrc

{
  "extends": "eslint-config-topcoder/nodejs"
}

Nodejs + babel

npm install --save-dev eslint-config-topcoder eslint-plugin-babel@^4.0.0 babel-eslint@^7.1.1

Configure .eslintrc

{
  "extends": "eslint-config-topcoder/nodejs-babel"
}

React

npm install --save-dev eslint-config-topcoder eslint-plugin-babel@^4.0.0 eslint-plugin-react@^6.8.0 babel-eslint@^7.1.1

Configure .eslintrc

{
  "extends": "eslint-config-topcoder/react"
}

Add scripts to package.json

"scripts": {
  "lint": "eslint .",
  "lint:fix": "npm run lint -- --fix"
}

Run scripts with -s flag

  npm run lint -s
  npm run lint:fix -s

General notes

It's not allowed to disable rules. The purpose of this config is to keep consistent styles in all topcoder projects.
However some exception are allowed.
You can disable rules in configuration/setup files.
Example:
```
app.use((err, req, res, next) => { // eslint-disable-line no-unused-vars
   res.json({
     error: err.message
   });
});
```
ExpressJS requires to create a function with 4 parameters for error handling, but it may happen that we don't use some parameters.
Following example is not allowed, because socket can be removed.
```
io.on('connection', (socket) => { // eslint-disable-line no-unused-vars
  winston.info('socket connection established');
});
```
magic-numbers Following magic numbers are allowed: -1, 0, 1.
In some cases you can disable this rule:

Math computations

const avg = (foo + bar) / 2; // eslint-disable-line magic-numbers

Unit tests
Unit tests usually contain hard-coded data, and magic-numbers can be problematic.

In following cases it's not allowed to disable magic-numbers
bad

res.status(400);
res.json({error: 'some validation error'});

good

import HttpStatus from 'http-status';

res.status(HttpStatus.BAD_REQUEST);
res.json({error: 'some validation error'});

bad

if (foo.status === 1) {

}

good

const ACTIVE_STATUS = 1;

if (foo.status === ACTIVE_STATUS) {

}

You should disable only using inline commands:
bad (all rules are disabled)
```
// eslint-disable-line
```
good (only 1 rule is disabled)
```
// eslint-disable-line magic-numbers
```
Exceptions for import/no-unresolved
It's allowed to add exceptions if you use aliases (mostly React).
For example:
```
'import/no-unresolved': [2, { ignore: ['^components/', '^containers/', '^services/', '^layouts/'] }]
```

Config for unit tests

If test directory contains unit tests, you should create test/.eslintrc and extend the base config.
Example:

{
  "extends" : "../.eslintrc",
  "env"     : {
    "mocha" : true
  },
  "globals": {
    "expect": true,
  },
  "rules": {
    // allow chai asserts like `expect(foo).to.be.true`
    "no-unused-expressions": 0,
    "no-magic-numbers": 0,
    "max-lines": 0,
  }
}