Z-Brain ESLint Rules

Custom ESLint (TypeScript) rules that are being used in Z-Brain projects. Some of them are project-specific, some are helpful anywhere.

Notice: If you have any propositions feel free to make an issue or create a pull request.

How to use

Installing

yarn add @z-brain/eslint-plugin-z-brain
or
npm i -s @z-brain/eslint-plugin-z-brain

Adding to .eslintrc

The plugin import and adding the recommended rule set.

module.exports = {
    env: {
        es6: true,
    },
    extends: ["plugin:@z-brain/z-brain/recommended"],
    parser: "@typescript-eslint/parser",
    parserOptions: {
        project: ["./tsconfig.json"],
        sourceType: "module",
        ecmaVersion: "es2019",
    },
    plugins: ["@z-brain/z-brain"],
};

Configuring specific rules:

module.exports = {
  rules: {
    '@z-brain/z-brain/empty-array-check-with-absent-length': 'warn',
  },
};

Rules

empty-array-check-with-absent-length

Short description:

Protects against forgotten '.length' when checking an array for emptiness

Detailed description:

The condition result being never changed according to current typings. Add .length or if you're writing a check for a falsy-value please add an appropriate type to the array definition.

Examples

See all cases & examples in the unit tests.

function foo(ids: number[]) {
  if (ids.length) return; // GOOD
  if (ids) return;        // BAD
}

// GOOD
function foo(ids: number[] | null | undefined) {
  if (ids) return;
}
function foo(ids: number[] | boolean) {
  if (ids) return;
}
function foo(ids?: number[]) {
  if (ids) return;
}

// BAD
function foo(ids: number[]) {
  if (ids) return; // in accordance with typings 'ids' is always trusty-value 
}

Helpful links

• AST explorer

Articles

• Simplest rule: Create a custom eslint rule with typescript
• More details: How I learned to love the AST
• The most complex article: How to write an ESLint plugin in TypeScript

Documentation & repos

• Awesome official guide @typescript-eslint/experimental-utils · GitHub
• Lots of good & simple examples: eslint-plugin-nestjs-typed package - GitHub
• Official ESLint custom rules guide
• Description of all packages in @typescript-eslint · GitHub
• Using the Compiler API · microsoft/TypeScript Wiki · GitHub
• More about type checking via TS Compiler API

Development notes

Quick Start

cd /Users/volumes/code/z-brain
git clone [email protected]:z-brain/eslint-plugin-z-brain.git
cd eslint-plugin-z-brain
yarn install

How to use NodeJS version from the .nvmrc

1. Install NVM

2. Use .nvmrc file one of the next ways:

   • Execute nvm use in the project root directory
   • Install NVM Loader and your .nvmrc will be loaded automatically when you open the terminal.

How to make a build

yarn run build

How to run lint

Notice: linter isn't configured yet

• Just show problems yarn run lint
• Fix problems if it is possible yarn run lint:fix

How to run tests

• All tests

  yarn run test
yarn run test:watch

• Specific tests

  yarn run test src/my.spec.ts
yarn run test:watch src/my.spec.ts

How to build and publish NPM package

NPM Token: npm_UVqN......qTww

CI configuration details here: .github/workflows/npmpublish.yml

yarn run ci \
&& npm version patch -m 'Update package version version to %s' \
&& npm publish --access public \
&& git push --no-verify && git push --tags --no-verify

How to build package to local installation

1. yarn run build
2. Then you can install a local package build from the root repo dir (not dist) path file:.../eslint-plugin-z-brain.

Author

| Anton Korniychuk | | :---: |