@typescript-eslint/eslint-plugin

What is @typescript-eslint/eslint-plugin?

The @typescript-eslint/eslint-plugin package is an ESLint plugin that contains a set of ESLint rules that are specifically designed for TypeScript code. It helps in identifying and reporting on patterns found in TypeScript code, and it can be used to enforce a wide range of coding standards and conventions.

What are @typescript-eslint/eslint-plugin's main functionalities?

Type-aware linting

This feature allows for rules that require type information. For example, the 'strict-boolean-expressions' rule ensures that boolean expressions are clear and error-free by considering the types involved in the expression.

/* eslint @typescript-eslint/strict-boolean-expressions: 'error' */
function isTruthy(value: any): boolean {
  return Boolean(value);
}

Code style enforcement

Enforces naming conventions for everything from variables to type parameters. This example enforces camelCase naming for variables.

/* eslint @typescript-eslint/naming-convention: ['error', { 'selector': 'variable', 'format': ['camelCase'] }] */
let myVariable = 1;

Accessibility checks

This feature requires functions and methods to explicitly define their return type to improve code readability and maintainability.

/* eslint @typescript-eslint/explicit-function-return-type: 'warn' */
function add(x: number, y: number) {
  return x + y;
}

Other packages similar to @typescript-eslint/eslint-plugin

eslint-plugin-react

This package provides linting rules for React and JSX. It's similar to @typescript-eslint/eslint-plugin in that it extends ESLint's capabilities to a specific language extension, but it focuses on React rather than TypeScript.

eslint-plugin-vue

This package is designed for linting Vue.js templates and scripts. Like @typescript-eslint/eslint-plugin, it provides additional rules that are specific to the Vue.js framework, complementing the standard ESLint rules.

eslint-plugin-import

This plugin provides a set of rules that help ensure proper imports, exports, and module structure. While it's not specific to TypeScript, it complements @typescript-eslint/eslint-plugin by enforcing best practices in module usage.

README

ESLint Plugin TypeScript

Installation

Make sure you have TypeScript and @typescript-eslint/parser installed, then install the plugin:

npm i @typescript-eslint/eslint-plugin --save-dev

It is important that you use the same version number for @typescript-eslint/parser and @typescript-eslint/eslint-plugin.

Note: If you installed ESLint globally (using the -g flag) then you must also install @typescript-eslint/eslint-plugin globally.

Usage

Add @typescript-eslint/parser to the parser field and @typescript-eslint to the plugins section of your .eslintrc configuration file:

{
  "parser": "@typescript-eslint/parser",
  "plugins": ["@typescript-eslint"]
}

Then configure the rules you want to use under the rules section.

{
  "parser": "@typescript-eslint/parser",
  "plugins": ["@typescript-eslint"],
  "rules": {
    "@typescript-eslint/rule-name": "error"
  }
}

You can also enable all the recommended rules for our plugin. Add plugin:@typescript-eslint/recommended in extends:

{
  "extends": ["plugin:@typescript-eslint/recommended"]
}

You can also use eslint:recommended with this plugin. Add both eslint:recommended and plugin:@typescript-eslint/eslint-recommended:

{
  "extends": [
    "eslint:recommended",
    "plugin:@typescript-eslint/eslint-recommended",
    "plugin:@typescript-eslint/recommended"
  ]
}

If you want to use rules which require type information, you will need to specify a path to your tsconfig.json file in the "project" property of "parserOptions".

{
  "parser": "@typescript-eslint/parser",
  "parserOptions": {
    "project": "./tsconfig.json"
  },
  "plugins": ["@typescript-eslint"],
  "rules": {
    "@typescript-eslint/restrict-plus-operands": "error"
  }
}

See @typescript-eslint/parser's README.md for more information on the available "parserOptions".

Note: Make sure to use eslint --ext .js,.ts since by default eslint will only search for .js files.

Usage with Prettier

Install eslint-config-prettier to disable our code formatting related rules:

{
  "extends": [
    "plugin:@typescript-eslint/recommended",
    "prettier",
    "prettier/@typescript-eslint"
  ]
}

Note: Make sure you have eslint-config-prettier@4.0.0 or newer.

Usage with Airbnb

Airbnb has two configs, a base one eslint-config-airbnb-base and one that includes rules for React eslint-config-airbnb.

First you'll need to install the config according to the instructions in one of the links above. npx install-peerdeps --dev eslint-config-airbnb or npx install-peerdeps --dev eslint-config-airbnb-base should work if you are using npm 5+.

Then you should add airbnb (or airbnb-base) to your extends section of .eslintrc. You might also want to turn on plugin:@typescript-eslint/recommended as well to enable all of the recommended rules.

{
  "extends": ["airbnb-base", "plugin:@typescript-eslint/recommended"]
}

Note: You can use Airbnb's rules alongside Prettier, see Usage with Prettier

Supported Rules

Key: :heavy_check_mark: = recommended, :wrench: = fixable, :thought_balloon: = requires type information

Name	Description	:heavy_check_mark:	:wrench:	:thought_balloon:
@typescript-eslint/adjacent-overload-signatures	Require that member overloads be consecutive	:heavy_check_mark:
@typescript-eslint/array-type	Requires using either T[] or Array<T> for arrays	:heavy_check_mark:	:wrench:
@typescript-eslint/await-thenable	Disallows awaiting a value that is not a Thenable			:thought_balloon:
@typescript-eslint/ban-ts-ignore	Bans “// @ts-ignore” comments from being used
@typescript-eslint/ban-types	Enforces that types will not to be used	:heavy_check_mark:	:wrench:
@typescript-eslint/camelcase	Enforce camelCase naming convention	:heavy_check_mark:
@typescript-eslint/class-name-casing	Require PascalCased class and interface names	:heavy_check_mark:
@typescript-eslint/consistent-type-definitions	Consistent with type definition either interface or type	:heavy_check_mark:	:wrench:
@typescript-eslint/explicit-function-return-type	Require explicit return types on functions and class methods	:heavy_check_mark:
@typescript-eslint/explicit-member-accessibility	Require explicit accessibility modifiers on class properties and methods	:heavy_check_mark:
@typescript-eslint/func-call-spacing	Require or disallow spacing between function identifiers and their invocations		:wrench:
@typescript-eslint/generic-type-naming	Enforces naming of generic type variables
@typescript-eslint/indent	Enforce consistent indentation	:heavy_check_mark:	:wrench:
@typescript-eslint/interface-name-prefix	Require that interface names be prefixed with I	:heavy_check_mark:
@typescript-eslint/member-delimiter-style	Require a specific member delimiter style for interfaces and type literals	:heavy_check_mark:	:wrench:
@typescript-eslint/member-naming	Enforces naming conventions for class members by visibility
@typescript-eslint/member-ordering	Require a consistent member declaration order
@typescript-eslint/no-angle-bracket-type-assertion	Enforces the use of as Type assertions instead of <Type> assertions	:heavy_check_mark:
@typescript-eslint/no-array-constructor	Disallow generic Array constructors	:heavy_check_mark:	:wrench:
@typescript-eslint/no-empty-function	Disallow empty functions
@typescript-eslint/no-empty-interface	Disallow the declaration of empty interfaces	:heavy_check_mark:
@typescript-eslint/no-explicit-any	Disallow usage of the any type	:heavy_check_mark:	:wrench:
@typescript-eslint/no-extra-parens	Disallow unnecessary parentheses		:wrench:
@typescript-eslint/no-extraneous-class	Forbids the use of classes as namespaces
@typescript-eslint/no-floating-promises	Requires Promise-like values to be handled appropriately.			:thought_balloon:
@typescript-eslint/no-for-in-array	Disallow iterating over an array with a for-in loop			:thought_balloon:
@typescript-eslint/no-inferrable-types	Disallows explicit type declarations for variables or parameters initialized to a number, string, or boolean	:heavy_check_mark:	:wrench:
@typescript-eslint/no-magic-numbers	Disallows magic numbers
@typescript-eslint/no-misused-new	Enforce valid definition of new and constructor	:heavy_check_mark:
@typescript-eslint/no-namespace	Disallow the use of custom TypeScript modules and namespaces	:heavy_check_mark:
@typescript-eslint/no-non-null-assertion	Disallows non-null assertions using the ! postfix operator	:heavy_check_mark:
@typescript-eslint/no-object-literal-type-assertion	Forbids an object literal to appear in a type assertion expression	:heavy_check_mark:
@typescript-eslint/no-parameter-properties	Disallow the use of parameter properties in class constructors	:heavy_check_mark:
@typescript-eslint/no-require-imports	Disallows invocation of require()
@typescript-eslint/no-this-alias	Disallow aliasing this
@typescript-eslint/no-triple-slash-reference	Disallow /// <reference path="" /> comments	:heavy_check_mark:
@typescript-eslint/no-type-alias	Disallow the use of type aliases
@typescript-eslint/no-unnecessary-qualifier	Warns when a namespace qualifier is unnecessary		:wrench:	:thought_balloon:
@typescript-eslint/no-unnecessary-type-assertion	Warns if a type assertion does not change the type of an expression		:wrench:	:thought_balloon:
@typescript-eslint/no-unused-vars	Disallow unused variables	:heavy_check_mark:
@typescript-eslint/no-use-before-define	Disallow the use of variables before they are defined	:heavy_check_mark:
@typescript-eslint/no-useless-constructor	Disallow unnecessary constructors
@typescript-eslint/no-var-requires	Disallows the use of require statements except in import statements	:heavy_check_mark:
@typescript-eslint/prefer-for-of	Prefer a ‘for-of’ loop over a standard ‘for’ loop if the index is only used to access the array being iterated
@typescript-eslint/prefer-function-type	Use function types instead of interfaces with call signatures		:wrench:
@typescript-eslint/prefer-includes	Enforce includes method over indexOf method		:wrench:	:thought_balloon:
@typescript-eslint/prefer-namespace-keyword	Require the use of the namespace keyword instead of the module keyword to declare custom TypeScript modules	:heavy_check_mark:	:wrench:
@typescript-eslint/prefer-readonly	Requires that private members are marked as readonly if they're never modified outside of the constructor		:wrench:	:thought_balloon:
@typescript-eslint/prefer-regexp-exec	Prefer RegExp#exec() over String#match() if no global flag is provided			:thought_balloon:
@typescript-eslint/prefer-string-starts-ends-with	Enforce the use of String#startsWith and String#endsWith instead of other equivalent methods of checking substrings		:wrench:	:thought_balloon:
@typescript-eslint/promise-function-async	Requires any function or method that returns a Promise to be marked async			:thought_balloon:
@typescript-eslint/require-array-sort-compare	Enforce giving compare argument to Array#sort			:thought_balloon:
@typescript-eslint/restrict-plus-operands	When adding two variables, operands must both be of type number or of type string			:thought_balloon:
@typescript-eslint/semi	Require or disallow semicolons instead of ASI		:wrench:
@typescript-eslint/type-annotation-spacing	Require consistent spacing around type annotations	:heavy_check_mark:	:wrench:
@typescript-eslint/unbound-method	Enforces unbound methods are called with their expected scope			:thought_balloon:
@typescript-eslint/unified-signatures	Warns for any two overloads that could be unified into one by using a union or an optional/rest parameter