AST Transpiler

0.0.85 verified Fri May 01 auth: no javascript

ast-transpiler is a versatile source-to-source transpiler that converts code between JavaScript, TypeScript, Python, and PHP by operating on abstract syntax trees. Version 0.0.85, under active development, it provides a unified AST representation and supports transpilation of modern JavaScript (ESM/CJS) to multiple target languages. Key differentiators: single-pass transpilation, TypeScript-first with full type definitions, and extensible transpilation rules. Ideal for multi-language codebases and tooling that requires cross-language code generation.

Common errors

error Cannot find module 'ast-transpiler' or its corresponding type declarations. ↓

cause Package is ESM-only and may require `"type": "module"` in package.json or .mjs extension.

fix

Add "type": "module" to your package.json or use .mjs extension for import.

error Error: `options.pythonVersion` is not a valid option. Did you mean `options.python.version`? ↓

cause Since v0.0.85, Python version must be nested under `options.python.version`.

fix

Use options: { python: { version: 3.9 } } instead of options: { pythonVersion: 3.9 }.

error TypeError: parseSync is not a function ↓

cause `parseSync` was removed in v0.0.83; use async `parse`.

fix

Use const result = await parse(...) instead of parseSync(...).

error SyntaxError: Named export 'transpile' not found. The requested module 'ast-transpiler' is a CommonJS module which may not support all module.exports as named exports. ↓

cause Attempting to import from a CJS build; package is ESM-only but some environments may incorrectly detect as CJS.

fix

Ensure your runtime supports ESM and that the package is resolved correctly.

Warnings

breaking Breaking change in v0.0.85: `options` parameter structure changed; `pythonVersion` moved from root to nested `options.python.version`. ↓

fix Update code to use nested `options.python.version` for Python target.

deprecated Deprecated: `parseSync` is deprecated in favor of `parse` (async). ↓

fix Replace `parseSync` with `parse` using `await`.

breaking Breaking change in v0.0.80: Package switched to ESM-only. `require()` calls will fail. ↓

fix Use dynamic `import()` or migrate project to ESM.

gotcha TypeScript types are exported only from the main entry; subpath exports do not include types. ↓

fix Import types exclusively from 'ast-transpiler' root.

breaking Breaking change in v0.0.70: `targetLang` option renamed from `language`. ↓

fix Replace `language` with `targetLang` in options.

Install

npm install ast-transpiler

yarn add ast-transpiler

pnpm add ast-transpiler

Imports

transpile
wrong
```
const transpile = require('ast-transpiler')
```
correct
```
import { transpile } from 'ast-transpiler'
```
The package is ESM-only since v0.0.80; CommonJS require() is not supported.

parseSync

wrong

import parseSync from 'ast-transpiler'

correct

import { parseSync } from 'ast-transpiler'

parseSync is a named export, not a default export.

TranspilerConfig
wrong
```
import { TranspilerConfig } from 'ast-transpiler'
```
correct
```
import type { TranspilerConfig } from 'ast-transpiler'
```
TranspilerConfig is a TypeScript type and should be imported with `import type` to avoid runtime errors.

Quickstart

Transpiles a TypeScript function to Python using the transpile API with target language options.

import { transpile } from 'ast-transpiler';

const code = `
function add(a: number, b: number): number {
  return a + b;
}
`;

async function main() {
  const result = await transpile({
    source: code,
    sourceLang: 'typescript',
    targetLang: 'python',
    options: { pythonVersion: 3.9 }
  });
  console.log(result.code);
}

main().catch(console.error);