@typescript-eslint/visitor-keys

What is @typescript-eslint/visitor-keys?

The @typescript-eslint/visitor-keys package provides an enumeration of TypeScript ESTree AST node types and their respective visitor keys. It is primarily used in the context of ESLint plugins and custom rules development to traverse the AST (Abstract Syntax Tree) of TypeScript code and analyze or manipulate the code structure.

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

AST Node Traversal

This code demonstrates how to use the visitor keys from the package to traverse an AST node and its children recursively. The `traverseAST` function takes a node and a visitor object that contains methods corresponding to node types. It uses the visitor keys to determine which properties of a node to traverse.

const visitorKeys = require('@typescript-eslint/visitor-keys');

function traverseAST(node, visitor) {
  if (visitor[node.type]) {
    visitor[node.type](node);
  }

  const keys = visitorKeys[node.type] || [];
  keys.forEach((key) => {
    const value = node[key];
    if (Array.isArray(value)) {
      value.forEach(child => traverseAST(child, visitor));
    } else if (value && typeof value === 'object') {
      traverseAST(value, visitor);
    }
  });
}

Other packages similar to @typescript-eslint/visitor-keys

eslint-visitor-keys

This package provides a list of visitor keys for traversing the AST of JavaScript code. It is similar to @typescript-eslint/visitor-keys but is tailored for JavaScript rather than TypeScript. It is used by ESLint to work with its own rules and plugins.

babel-types

While not a direct equivalent, babel-types is part of the Babel ecosystem and provides definitions for various AST node types, builders, and assertion methods. It can be used to traverse and manipulate ASTs for both JavaScript and TypeScript, offering a broader scope compared to @typescript-eslint/visitor-keys.

estraverse

Estraverse is a simple and flexible library for traversing and replacing nodes in an ECMAScript AST. It is not TypeScript-specific but can be used with JavaScript ASTs. It provides a similar traversal functionality but does not rely on a predefined set of visitor keys.

README

TypeScript-ESTree Visitor Keys

Visitor keys used to help traverse the TypeScript-ESTree AST

Contributing

See the contributing guide here

Changelog

5.26.0 (2022-05-23)

Bug Fixes

• ast-spec: add SpreadElement to ArrayExpression.elements (#5025) (9f3121b)
• eslint-plugin: [member-delimiter-style] autofixer result is not as expected when comments after the delimiter with option delimiter: 'none' (#5029) (ed7b5f6)
• eslint-plugin: [member-delimiter-style] autofixer result is not as expected with option delimiter: 'none' (#5023) (9e97a11)
• eslint-plugin: [prefer-readonly] correct issue with anonymus functions (#4974) (952e2f0), closes #2590

Features

• [4.7] support instantiation expressions (#4938) (79fbc77)
• [4.7] support optional variance annotation (#4831) (7e7b24c)
• typescript-estree: extends constraints for infer (#4830) (8cbbcc3)