rs-module-lexer

library2.8.0jsnpmunverified

rs-module-lexer is an ES module parser built with Rust, offering a drop-in compatible output data structure with `es-module-lexer`. Currently at version 2.8.0, it maintains an active release cadence with frequent minor updates. Its key differentiator is the ability to directly parse TypeScript (TS/TSX) and JSX files, unlike `es-module-lexer` which necessitates a prior transformation step. Powered by SWC, this library collapses the transform and parse steps into a single API call, streamlining module analysis in bundlers and build tools. It's designed for scenarios requiring fast and accurate identification of imports and exports across various JavaScript and TypeScript syntaxes, providing a consistent API and data format.

type-stubs http-networking web-framework serialization data

npm install rs-module-lexer

github ↗package ↗

INSTALL

IMPORT

SIG · RS-MODULE-LEXER

rs-module-lexer

type-stubsjavascriptv2.8.0

Install

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Import

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Disk

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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.

parseAsync

✓ import { parseAsync } from 'rs-module-lexer'

✗ const { parseAsync } = require('rs-module-lexer')

The primary asynchronous API for parsing, recommended for most use cases, especially in Node.js environments. Since v2.1.1.

parse

✓ import { parse } from 'rs-module-lexer'

✗ const { parse } = require('rs-module-lexer')

The synchronous API for parsing. Use `parseAsync` when possible to avoid blocking the event loop.

ModuleInfo

✓ import type { ModuleInfo } from 'rs-module-lexer'

TypeScript type for the output structure of a parsed module, aligning with es-module-lexer's data shape.

Demonstrates parsing multiple TypeScript and JavaScript files asynchronously, showcasing import and export extraction.

import { parseAsync } from 'rs-module-lexer'; async function analyzeCode() { const tsCode = ` import { useState, useEffect } from 'react'; import { someUtil } from './utils'; export const MyComponent = () => { const [count, setCount] = useState(0); useEffect(() => { console.log('Count:', count); }, [count]); return <div>Hello</div>; }; export function helper() { /* ... */ } `; const { output } = await parseAsync({ input: [ { filename: 'my-component.tsx', code: tsCode, }, { filename: 'another-file.js', code: 'import { foo } from "bar";', } ], }); // Accessing the results for 'my-component.tsx' const myComponentResult = output[0]; console.log('Imports for my-component.tsx:', myComponentResult.imports); console.log('Exports for my-component.tsx:', myComponentResult.exports); // Accessing the results for 'another-file.js' const anotherFileResult = output[1]; console.log('Imports for another-file.js:', anotherFileResult.imports); } analyzeCode().catch(console.error);

Debug

Known issues

breakingWhen migrating from `es-module-lexer`, the API signature changes from a direct return of `[imports, exports, facade, hasModuleSyntax]` to an object `{ output }` where `output` is an array of results, each containing these properties. You must destructure `output[0]` (or the relevant index) to access the parsing results for a single file.

fix

Change `const [imports, exports] = parse(code)` to `const { output } = await parseAsync({ input: [{ filename, code }] }); const { imports, exports } = output[0];`

affects: >=2.0.0

gotchaThe `parseAsync` method expects an array of input objects, each with a `filename` and `code` property. The `filename` extension (`.ts`, `.tsx`, `.js`, `.jsx`) is crucial for `rs-module-lexer` to correctly auto-detect the syntax and parse the file.

fix

Always provide a `filename` with the correct extension in the input object: `parseAsync({ input: [{ filename: 'component.tsx', code: '...' }] })`

affects: >=2.0.0

breakingVersion 2.0.0 introduced support for the 'import with' syntax (e.g., `import json from 'source' with { type: 'json' }`) and export object destructing. While aligning with `es-module-lexer` and modern ES module syntax, this might alter parsing results for code leveraging these features compared to `rs-module-lexer` versions prior to 2.0.0.

fix

No direct fix needed, but be aware of parsing behavior changes if upgrading from pre-2.0.0 versions and using these specific syntaxes.

affects: >=2.0.0

gotchaUnlike `es-module-lexer`, `rs-module-lexer` does not require an `init()` call before parsing. Directly import and use `parse` or `parseAsync`.

fix

Remove any `await init` or `init()` calls when migrating from `es-module-lexer` to `rs-module-lexer`.

affects: >=2.0.0

Errors

Common errors & fixes

TypeError: parse is not a function

Attempting to use `parse` without destructuring it from the module, or using CommonJS `require` instead of ES module `import`.

fix

Ensure you are using `import { parse, parseAsync } from 'rs-module-lexer'` for ES modules, or verify your environment supports top-level await for dynamic imports.

Property 'output' does not exist on type '{ imports: Import[]; exports: Export[]; facade: boolean; hasModuleSyntax: boolean; }[]'

Incorrectly assuming the `parseAsync` return value is directly the `imports`/`exports` array, or not accessing the individual file results from the `output` array.

fix

The result of `parseAsync` is an object `{ output: [...] }`. You need to access `result.output[index]` to get the parsing details for a specific file. For a single input file, use `const { output: [firstFileResult] } = await parseAsync(...)`.

Parsing error or incorrect import/export detection for TS/TSX/JSX files.

The `filename` property in the input object was missing or had an incorrect file extension, preventing `rs-module-lexer` from correctly detecting the syntax.

fix

Always provide a `filename` with the accurate extension (e.g., `.ts`, `.tsx`, `.jsx`) in the input object passed to `parseAsync` or `parse`.

Upgrade

Version history

2.8.0latest on npm

Audit

Dependencies

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Agent activity

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Resources

githubhttps://github.com/fz6m/rs-module-lexer ↗

packagehttps://www.npmjs.com/package/rs-module-lexer ↗