typescript-eslint

https://typescript-eslint.io/
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typescript-eslint is a toolkit that enables ESLint, Prettier, and other tools to work with...
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### Install typescript-eslint with Bun

Source: https://typescript-eslint.io/packages/typescript-eslint

Install the package using the Bun package manager.

```bash
bun add typescript-eslint
```

--------------------------------

### Install dependencies with Bun

Source: https://typescript-eslint.io/getting-started

Install the required packages for ESLint, TypeScript, and typescript-eslint using Bun.

```bash
bun add --save-dev eslint @eslint/js typescript typescript-eslint
```

--------------------------------

### Install dependencies with Bun

Source: https://typescript-eslint.io/getting-started/legacy-eslint-setup

Install the required ESLint, TypeScript, and parser packages using Bun.

```bash
bun add --dev @typescript-eslint/parser @typescript-eslint/eslint-plugin eslint typescript
```

--------------------------------

### Install dependencies with npm

Source: https://typescript-eslint.io/getting-started/legacy-eslint-setup

Install the required ESLint, TypeScript, and parser packages using npm.

```bash
npm install --save-dev @typescript-eslint/parser @typescript-eslint/eslint-plugin eslint typescript
```

--------------------------------

### Install dependencies with pnpm

Source: https://typescript-eslint.io/getting-started

Install the required packages for ESLint, TypeScript, and typescript-eslint using pnpm.

```bash
pnpm add --save-dev eslint @eslint/js typescript typescript-eslint
```

--------------------------------

### Install dependencies with npm

Source: https://typescript-eslint.io/getting-started

Install the required packages for ESLint, TypeScript, and typescript-eslint using npm.

```bash
npm install --save-dev eslint @eslint/js typescript typescript-eslint
```

--------------------------------

### Install typescript-eslint with pnpm

Source: https://typescript-eslint.io/packages/typescript-eslint

Install the package using the pnpm package manager.

```bash
pnpm add typescript-eslint
```

--------------------------------

### Install dependencies with pnpm

Source: https://typescript-eslint.io/getting-started/legacy-eslint-setup

Install the required ESLint, TypeScript, and parser packages using pnpm.

```bash
pnpm add --save-dev @typescript-eslint/parser @typescript-eslint/eslint-plugin eslint typescript
```

--------------------------------

### Install dependencies with Yarn

Source: https://typescript-eslint.io/getting-started/legacy-eslint-setup

Install the required ESLint, TypeScript, and parser packages using Yarn.

```bash
yarn add --dev @typescript-eslint/parser @typescript-eslint/eslint-plugin eslint typescript
```

--------------------------------

### Implement a rule to ban for-of loops over enums

Source: https://typescript-eslint.io/developers/custom-rules

This example demonstrates using the TypeScript type checker to identify if a node in a for-of loop is an enum. It retrieves parser services, gets the type at the node's location, and checks the symbol flags.

```typescript
import { ESLintUtils } from '@typescript-eslint/utils';  

import * as ts from 'typescript';  

  

export const rule = createRule({  

  create(context) {  

    return {  

      ForOfStatement(node) {  

        // 1. Grab the parser services for the rule  

        const services = ESLintUtils.getParserServices(context);  

  

        // 2. Find the TS type for the ES node  

        const type = services.getTypeAtLocation(node.right);  

  

        // 3. Check the TS type's backing symbol for being an enum  

        if (type.symbol.flags & ts.SymbolFlags.Enum) {  

          context.report({  

            messageId: 'loopOverEnum',  

            node: node.right,  

          });  

        }  

      },  

    };  

  },  

  meta: {  

    docs: {  

      description: 'Avoid looping over enums.',  

    },  

    messages: {  

      loopOverEnum: 'Do not loop over enums.',  

    },  

    type: 'suggestion',  

    schema: [],  

  },  

  name: 'no-loop-over-enum',  

  defaultOptions: [],  

});
```

--------------------------------

### Basic createProjectService usage

Source: https://typescript-eslint.io/packages/project-service

A minimal example showing how to initialize the service and open a client file.

```typescript
import { createProjectService } from '@typescript-eslint/project-service';  

  

const { service } = createProjectService();  

  

service.openClientFile('index.ts');
```

--------------------------------

### Initialize and use Project Service

Source: https://typescript-eslint.io/packages/project-service

Demonstrates how to create a project service instance, open a file, and retrieve its TypeScript program.

```typescript
import { createProjectService } from '@typescript-eslint/project-service';  

  

const filePathAbsolute = '/path/to/your/project/index.ts';  

const { service } = createProjectService();  

  

service.openClientFile(filePathAbsolute);  

  

const scriptInfo = service.getScriptInfo(filePathAbsolute)!;  

const program = service  

  .getDefaultProjectForFile(scriptInfo.fileName, true)!  

  .getLanguageService(true)  

  .getProgram()!;
```

--------------------------------

### TSNamespaceExportDeclaration example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Example of a namespace export declaration.

```typescript

export as namespace X;  


```

--------------------------------

### TSModuleDeclarationModuleWithStringIdNotDeclared Example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Example of a string module declaration that is not declared.

```typescript
module 'foo' {}
```

--------------------------------

### Example ESLint configuration for v6

Source: https://typescript-eslint.io/blog/announcing-typescript-eslint-v6-beta

An example .eslintrc.cjs file demonstrating the updated configuration structure for projects using typed linting in v6.

```javascript
module.exports = {  

  extends: [  

    'eslint:recommended',  

    'plugin:@typescript-eslint/recommended',  

    'plugin:@typescript-eslint/recommended-requiring-type-checking',  

    'plugin:@typescript-eslint/recommended-type-checked',  

    'plugin:@typescript-eslint/stylistic-type-checked',  

  ],  

  plugins: ['@typescript-eslint'],  

  parser: '@typescript-eslint/parser',  

  parserOptions: {  

    project: './tsconfig.json',  

    project: true,  

    tsconfigRootDir: __dirname,  

  },  

  root: true,  

};
```

--------------------------------

### Example usage of createProgram

Source: https://typescript-eslint.io/packages/typescript-estree

Shows how to use createProgram to initialize a program instance and pass it to parseAndGenerateServices.

```javascript
const tsESTree = require('@typescript-eslint/typescript-estree');  
  
const program = tsESTree.createProgram('tsconfig.json');  
const code = `const hello: string = 'world';`;  
const { ast, services } = parseAndGenerateServices(code, {  
  filePath: '/some/path/to/file/foo.ts',  
  loc: true,  
  program,  
  range: true,  
});
```

--------------------------------

### TSModuleDeclarationModuleWithStringIdDeclared Examples

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Examples of string module declarations that are declared.

```typescript
declare module 'foo' {}

declare module 'foo';
```

--------------------------------

### Basic eslint.config.js setup

Source: https://typescript-eslint.io/blog/announcing-typescript-eslint-v7

A minimal configuration file using typescript-eslint to enable recommended ESLint and typescript-eslint rules.

```javascript
// @ts-check  

  

import js from '@eslint/js';  

import tseslint from 'typescript-eslint';  

  

export default tseslint.config(  

  js.configs.recommended,  

  ...tseslint.configs.recommended,  

);
```

--------------------------------

### TSModuleDeclarationModuleWithIdentifierId module example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Example of a legacy module declaration.

```typescript
module A {}
```

--------------------------------

### FunctionDeclarationWithName example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

A basic example of a normal function declaration.

```typescript
function f() {}
```

--------------------------------

### ExportNamedDeclaration specifiers property example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Example of exported specifiers.

```typescript
export { a, b };
```

--------------------------------

### ExportNamedDeclaration declaration property example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Example of an exported declaration.

```typescript
export const x = 1;
```

--------------------------------

### ExportNamedDeclarationWithSource example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Example of exporting names from another module.

```typescript
export { a, b } from 'mod';  
```

--------------------------------

### ExportNamedDeclarationWithoutSourceWithSingle Example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Example of exporting a single named declaration.

```typescript

export const x = 1;  



```

--------------------------------

### FileSpecifier Examples

Source: https://typescript-eslint.io/packages/type-utils/type-or-value-specifier

Examples of using FileSpecifier to match types or values by name, optionally restricted by file path.

```json
{ "from": "file", "name": "Props" }
```

```json
{ "from": "file", "name": "Props", "path": "file.tsx" }
```

--------------------------------

### TSModuleDeclarationNamespace id property example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Examples of module declaration identifiers.

```typescript
namespace A {} namespace A.B.C {} module 'a' {}
```

--------------------------------

### createProjectService()

Source: https://typescript-eslint.io/packages/project-service

Creates a new Project Service instance, as well as metadata on its creation. This is the main entry point for using the project service.

```APIDOC
## createProjectService()

### Description
Creates a new Project Service instance, as well as metadata on its creation.

### Function Signature
function createProjectService(settings?): ProjectServiceAndMetadata;

### Parameters
- **settings** (CreateProjectServiceSettings) - Optional - Settings to create a new Project Service instance.

### Returns
- **ProjectServiceAndMetadata** - A new Project Service instance, as well as metadata on its creation.

### Example
```ts
import { createProjectService } from '@typescript-eslint/project-service';

const { service } = createProjectService();

service.openClientFile('index.ts');
```
```

--------------------------------

### ExportNamedDeclaration attributes property example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Example usage of the attributes property.

```typescript
export { foo } from 'mod' with { type: 'json' };
```

--------------------------------

### Correct await using usage

Source: https://typescript-eslint.io/rules/await-thenable

This example demonstrates the correct usage of using for synchronous disposables and await using for asynchronous disposables.

```typescript
function makeSyncDisposable(): Disposable {  

  return {  

    [Symbol.dispose](): void {  

      // Dispose of the resource  

    },  

  };  

}  

  

async function shouldNotAwait() {  

  using resource = makeSyncDisposable();  

}  

  

function makeAsyncDisposable(): AsyncDisposable {  

  return {  

    async [Symbol.asyncDispose](): Promise<void> {  

      // Dispose of the resource asynchronously  

    },  

  };  

}  

  

async function shouldAwait() {  

  await using resource = makeAsyncDisposable();  

}  
```

--------------------------------

### TSModuleDeclarationGlobal kind example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Example showing the different kinds of module declarations.

```typescript
namespace Foo {} 
^^^^^^^^^ 
module 'foo' {} 
^^^^^^ 
global {} 
^^^^^^
```

--------------------------------

### TSModuleDeclarationGlobal global example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Example of the global property usage in a module declaration.

```typescript
declare global {}
```

--------------------------------

### Install typescript-eslint v8 for Flat Config

Source: https://typescript-eslint.io/blog/announcing-typescript-eslint-v8-beta

Use this command to install the v8 beta version when using ESLint flat configuration.

```bash
npm i typescript-eslint@rc-v8 --save-dev
```

--------------------------------

### FunctionDeclarationWithName expression property example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Example demonstrating the expression property for an ArrowFunctionExpression.

```typescript
(() => 1)
```

--------------------------------

### FunctionDeclarationWithName declare property example

Source: https://typescript-eslint.io/packages/typescript-estree/ast-spec

Example demonstrating the declare property for a TSDeclareFunction.

```typescript
declare function foo() {}
```
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