ast-types-x

library1.18.0jsnpmunverified

ast-types-x is a JavaScript library providing an efficient, modular, and Esprima-compatible implementation of the Mozilla Parser API's abstract syntax tree (AST) type hierarchy. It serves as a foundational tool for working with JavaScript ASTs, enabling robust static analysis, code transformation, and code generation. The current stable version is 1.18.0, released in August 2024, indicating active maintenance and feature development, such as recent additions for `PrivateIdentifier` and `decorators`. Key differentiators include its comprehensive understanding of the AST type system, facilitating advanced node iteration and traversal mechanisms, and its builder API for programmatically constructing AST nodes. It aims to offer complete control over AST manipulation through primitives like `getFieldNames` and `getFieldValue`, alongside a powerful `visit` abstraction for tree traversal, making it suitable for complex code analysis and manipulation tasks. It ships with TypeScript types, enhancing developer experience in TypeScript projects.

type-stubs serialization

npm install ast-types-x

github ↗package ↗

INSTALL

IMPORT

SIG · AST-TYPES-X

ast-types-x

type-stubsjavascriptv1.18.0

Install

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Import

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Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

namedTypes

✓ import { namedTypes } from 'ast-types-x';

✗ const namedTypes = require('ast-types-x').namedTypes;

Primary way to access AST type definitions for checking and assertion. Uses named export.

builders

✓ import { builders } from 'ast-types-x';

✗ const builders = require('ast-types-x').builders;

Used for programmatically constructing AST nodes (e.g., `b.identifier('foo')`). Uses named export.

visit

✓ import { visit } from 'ast-types-x';

✗ const visit = require('ast-types-x').visit;

The main entry point for AST traversal. Uses named export.

{ getFieldNames, getFieldValue }

✓ import { getFieldNames, getFieldValue } from 'ast-types-x';

✗ const getFieldNames = require('ast-types-x').getFieldNames;

Low-level utilities for inspecting AST node fields, including default values. Uses named exports.

Demonstrates creation of AST nodes using the builders API and type checking using the namedTypes API, asserting the structure of a simple 'if' statement.

import assert from 'assert'; import { namedTypes as n, builders as b } from 'ast-types-x'; // Create an identifier node for 'foo' var fooId = b.identifier('foo'); // Create an if statement: if (foo) { foo(); } var ifFoo = b.ifStatement(fooId, b.blockStatement([ b.expressionStatement(b.callExpression(fooId, [])) ])); // Assertions to check node types and structure assert.ok(n.IfStatement.check(ifFoo)); assert.ok(n.Statement.check(ifFoo)); assert.ok(n.Node.check(ifFoo)); assert.ok(n.BlockStatement.check(ifFoo.consequent)); assert.strictEqual( ifFoo.consequent.body[0].expression.arguments.length, 0 ); assert.strictEqual(ifFoo.test, fooId); assert.ok(n.Expression.check(ifFoo.test)); assert.ok(n.Identifier.check(ifFoo.test)); assert.ok(!n.Statement.check(ifFoo.test)); console.log('AST node creation and type checking successful!');

Debug

Known issues

breakingAs new ECMAScript features are introduced, the structure of AST nodes (e.g., `ClassDeclaration`, `ClassProperty`) might change with new properties being added (like `decorators` or `PrivateIdentifier`). Code relying on exact AST shape or missing properties might break.

fix

Always use `ast-types-x`'s type checking (`n.NodeType.check()`) and field iteration (`eachField`) utilities for robust code that adapts to new AST structures. Avoid hardcoding assumptions about property existence.

affects: >=1.0.0

gotchaMixing CommonJS `require()` with ESM `import` statements can lead to issues, especially with default exports or interop. `ast-types-x` is primarily designed for ESM usage as shown in its documentation.

fix

Prefer `import ... from 'ast-types-x'` syntax in modern Node.js environments. If using CommonJS, ensure you're correctly accessing named exports (e.g., `require('ast-types-x').namedTypes`).

affects: >=1.0.0

gotchaWhen manipulating AST nodes, direct mutation of properties might lead to unexpected behavior or issues with subsequent traversals if not managed carefully. The library provides helpers, but explicit copying might be needed for immutable-like operations.

fix

For safe node transformation, consider creating new nodes or using the provided traversal utilities (like `visit`) which often provide mechanisms to return new nodes or manage transformations. If manually copying, use `eachField` to ensure all fields and default values are correctly transferred.

affects: >=1.0.0

Errors

Common errors & fixes

TypeError: Cannot read properties of undefined (reading 'check')

Attempting to use `n.NodeType.check()` on a type that doesn't exist or is incorrectly accessed from `namedTypes`.

fix

Ensure the AST node type you are checking (`NodeType`) is a valid and exported type from `ast-types-x`'s `namedTypes` object (e.g., `n.IfStatement`, `n.Identifier`). Double-check spelling and case sensitivity.

TypeError: The requested module 'ast-types-x' does not provide an export named '...' (e.g., 'namedTypes')

Incorrectly importing a symbol that is not a named export from `ast-types-x` or trying to use `require()` for ESM-only exports.

fix

Verify that the symbol you are trying to import (e.g., `namedTypes`, `builders`, `visit`) is indeed a named export. Ensure your environment is configured for ESM if using `import` statements, or use correct CommonJS access if in a CJS module.

Error: `visit` called with an object that has no `type` property, or `visit` was called with a null or undefined object.

`ast-types-x`'s `visit` function requires a valid AST node object (with a `type` property) as its first argument.

fix

Ensure that the first argument passed to `visit` is a well-formed AST node object. Check for `null`, `undefined`, or plain JavaScript objects that lack the required `type` property.

Upgrade

Version history

1.18.0latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

47 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/pionxzh/ast-types-x ↗

packagehttps://www.npmjs.com/package/ast-types-x ↗