@balena/lint/README.md

Balena.io eslint & prettier wrapper

@balena/lint
==========

`@balena/lint` is a linter & formatter based on [eslint](https://eslint.org/) and [prettier](https://github.com/prettier/prettier) to detect style errors based on balena.io coding guidelines.

Overview
--------

`@balena/lint` uses balena's `.eslintrc.js` and `.prettierrc`.
If a `.eslintrc.js` is found in the to-be-linted project
directory or its parents then the rules found in it will be merged with the default `@balena/lint` ones.
Another way to to override the default balena lint rules is by specifying a configuration
file with the `-f` parameter.

## Files checked

By default`.ts` and `.tsx` files are linted. You can also specify additional file extensions to be parse by using the -e option.
Eg: "-e js -e jsx"

## Prettier

You can reference the prettier configuration file to your consumer project
from `./config/.prettierrc`.

Usage
-----

You can use this module as:

1. A standalone project by installing it with `npm install -g @balena/lint`:

  ```
  kostas@macbook:~/balena/test$ balena-lint src/
    ✓ src/test.ts

    ✓ Ok! » 0 errors and 0 warnings in 1 file
  ```

2. A development dependency in `package.json` with ```npm install --save-dev @balena/lint```. Then
  you can use the module in your build/testing process:

  ```
  package.json
  ------------
  ...
  "scripts": {
    "lint": "balena-lint src/ && echo \"Done!\""
  },
  ...

  kostas@macbook:~/balena/test$ npm run lint

  > test@1.0.0 lint /Users/kostas/balena/test
  > balena-lint src/ && echo "Done!"

    ✓ src/test.ts

    ✓ Ok! » 0 errors and 0 warnings in 1 file

    Done!

  ```

3. A development dependency, that will get picked up by your IDE/Editor eslint/prettier.

Manually create these config files in your project root:

`.eslintrc.js`

```js
{
  "extends": [
    "./node_modules/@balena/lint/config/.eslintrc.js"
  ]
}
```

For prettier config create `.prettierrc.js`

```js
const fs = require('fs');

module.exports = JSON.parse(fs.readFileSync('./node_modules/@balena/lint/config/.prettierrc', 'utf8'));
```

Rules that require type information
-----------------------------------

Some linting rules such as `no-floating-promises` require Typescript type information.
To enable these rules, use the `-t` option to point to your project's `tsconfig.json`
file, if any. Without the `-t` option, those rules will be disabled but may still print
a warning message such as:  
`Warning: The 'no-floating-promises' rule requires type information.`  
To prevent this warning message from being printed, override the rules by creating a
`.eslintrc.js` file as described in the previous sections. For example:

```json
{
    "extends": "./node_modules/@balena/lint/config/.eslintrc.js",
    "rules": {
        "no-floating-promises": false
    }
}
```

Support
-------

If you're having any problem, please [raise an issue](https://github.com/balena-io-modules/node-balena-lint/issues/new) on GitHub and the balena.io team will be happy to help.

Tests
-----

Run the test suite by doing:

```sh
$ npm install && npm test
```

Contribute
----------

- Issue Tracker: [github.com/balena-io-modules/node-balena-lint/issues](https://github.com/balena-io-modules/node-balena-lint/issues)
- Source Code: [github.com/balena-io-modules/node-balena-lint](https://github.com/balena-io-modules/node-balena-lint)

Before submitting a PR, please make sure that you include tests, and that `npm run lint` runs without a warning.

License
-------

The project is licensed under the Apache 2.0 license.