@typescript-eslint/scope-manager

What is @typescript-eslint/scope-manager?

The @typescript-eslint/scope-manager package is part of the TypeScript ESLint project. It is used to generate TypeScript-aware scope information for ESLint. This scope information is essential for linting TypeScript codebases, as it understands TypeScript-specific features like types and interfaces, which are not present in regular JavaScript.

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

Scope Analysis

The package analyzes the scope of variables and types within TypeScript code. It helps in identifying where variables are defined and how they are being used, which is crucial for linting and avoiding errors like variable shadowing or undeclared variables.

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TypeScript-specific Scope Handling

It extends ESLint's scope analysis capabilities to understand TypeScript-specific constructs such as interfaces, types, and enums, which are not part of the standard JavaScript language.

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Integration with ESLint

The scope manager is designed to work seamlessly with ESLint, allowing developers to use ESLint's rule set for TypeScript code. It provides the necessary scope information to ESLint rules so they can operate on TypeScript code as they would on JavaScript code.

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Other packages similar to @typescript-eslint/scope-manager

eslint-scope

eslint-scope is a package that performs scope analysis for JavaScript code. It is used by ESLint to determine the variables and their references within the code. Unlike @typescript-eslint/scope-manager, it does not have built-in support for TypeScript-specific features.

ts-morph

ts-morph is a TypeScript compiler API wrapper that provides an easier way to interact with the TypeScript compiler. It includes features for analyzing and manipulating TypeScript code, which can be used for tasks similar to scope analysis. However, it is a more general-purpose tool and not specifically tailored for ESLint integration.

typescript-eslint-parser

typescript-eslint-parser is a parser that allows ESLint to lint TypeScript code. It is an older package that has been deprecated in favor of @typescript-eslint/parser, which works in conjunction with @typescript-eslint/scope-manager to provide linting capabilities for TypeScript code.

README

TypeScript Scope Manager

This is a fork of eslint-scope, enhanced to support TypeScript functionality. You can view the original licence for the code here.

This package is consumed automatically by @typescript-eslint/parser. You probably don't want to use it directly.

Getting Started

You can find our Getting Started docs here

Installation

$ yarn add -D typescript @typescript-eslint/scope-manager
$ npm i --save-dev typescript @typescript-eslint/scope-manager

API

analyze(tree, options)

Analyses a given AST and returns the resulting ScopeManager.

interface AnalyzeOptions {
  /**
   * Known visitor keys.
   */
  childVisitorKeys?: Record<string, string[]> | null;

  /**
   * Which ECMAScript version is considered.
   * Defaults to `2018`.
   * `'latest'` is converted to 1e8 at parser.
   */
  ecmaVersion?: EcmaVersion | 1e8;

  /**
   * Whether the whole script is executed under node.js environment.
   * When enabled, the scope manager adds a function scope immediately following the global scope.
   * Defaults to `false`.
   */
  globalReturn?: boolean;

  /**
   * Implied strict mode (if ecmaVersion >= 5).
   * Defaults to `false`.
   */
  impliedStrict?: boolean;

  /**
   * The identifier that's used for JSX Element creation (after transpilation).
   * This should not be a member expression - just the root identifier (i.e. use "React" instead of "React.createElement").
   * Defaults to `"React"`.
   */
  jsxPragma?: string;

  /**
   * The identifier that's used for JSX fragment elements (after transpilation).
   * If `null`, assumes transpilation will always use a member on `jsxFactory` (i.e. React.Fragment).
   * This should not be a member expression - just the root identifier (i.e. use "h" instead of "h.Fragment").
   * Defaults to `null`.
   */
  jsxFragmentName?: string | null;

  /**
   * The lib used by the project.
   * This automatically defines a type variable for any types provided by the configured TS libs.
   * For more information, see https://www.typescriptlang.org/tsconfig#lib
   *
   * Defaults to the lib for the provided `ecmaVersion`.
   */
  lib?: Lib[];

  /**
   * The source type of the script.
   */
  sourceType?: 'script' | 'module';

  /**
   * Emit design-type metadata for decorated declarations in source.
   * Defaults to `false`.
   */
  emitDecoratorMetadata?: boolean;
}

Example usage:

import { analyze } from '@typescript-eslint/scope-manager';
import { parse } from '@typescript-eslint/typescript-estree';

const code = `const hello: string = 'world';`;
const ast = parse(code, {
  // note that scope-manager requires ranges on the AST
  range: true,
});
const scope = analyze(ast, {
  ecmaVersion: 2020,
  sourceType: 'module',
});

References

• https://eslint.org/docs/developer-guide/scope-manager-interface
• https://github.com/eslint/eslint-scope

Contributing

See the contributing guide here