babel-file-loader

2.0.0 verified Sat Apr 25 auth: no javascript

Load files into memory for parsing and traversal with Babylon/Babel. Version 2.0.0 is the latest stable release, published as part of the babel-multi-file project. It provides async and sync methods to resolve file paths from import declarations and load parsed File objects, enabling multi-file Babel plugin analysis. Key differentiators: integrates directly with Babel's visitor pattern and File representation, offering low-level control over file resolution and parsing.

Common errors

error Error [ERR_REQUIRE_ESM]: require() of ES Module not supported ↓

cause Using require('babel-file-loader') in a CommonJS context.

fix

Use dynamic import: const { loadImportSync } = await import('babel-file-loader'); or switch your project to ES modules.

error SyntaxError: Unexpected token 'export' ↓

cause Using ES module syntax in a .js file without type:module or .mjs extension.

fix

Rename the file to .mjs or add "type": "module" to your package.json.

error TypeError: path.traverse is not a function ↓

cause Attempting to traverse the path object directly instead of the File object's path property returned by loadImportSync.

fix

Use file.path.traverse({...}) where file is the return value of loadImportSync.

error Error: Cannot find module 'babylon' ↓

cause Missing peer dependency for Babylon parser.

fix

Install babylon: npm install babylon@latest

Warnings

breaking Version 2.0.0 is a complete rewrite from the previous babel-file-loader package (v1). API changed entirely: sync methods now return objects instead of using callbacks, and all functions are async/sync variants. ↓

fix Upgrade to v2.0.0 and adapt code to use new sync/async naming (e.g., loadImportSync instead of callback-based loadImport).

gotcha The package is ESM-only (type: module). Using require() or CommonJS will fail with ERR_REQUIRE_ESM. ↓

fix Use dynamic import() inside CommonJS, or switch to ES module context. For Babel plugins, ensure your plugin file uses .mjs or "type": "module" in package.json.

gotcha loadImportSync may throw if the import path cannot be resolved or parsed; always wrap in try/catch inside visitor functions. ↓

fix Wrap calls in try/catch blocks to prevent Babel plugin from crashing.

deprecated The underlying Babylon parser is deprecated in favor of @babel/parser. This package still uses Babylon; may break with newer Babel versions. ↓

fix Consider using @babel/traverse and @babel/core's programmatic API for multi-file analysis.

gotcha All async functions (e.g., loadImport, loadFile) are not exported as promises; they use callback-style? The docs mention Async/Sync variants but actual async behavior is unclear. ↓

fix Prefer sync variants (loadImportSync) for use inside Babel visitors; async functions may not work as expected.

Install

npm install babel-file-loader

yarn add babel-file-loader

pnpm add babel-file-loader

Imports

loadImportSync

wrong

const loadImportSync = require('babel-file-loader').loadImportSync

correct

import { loadImportSync } from 'babel-file-loader'

Package ships ES modules; named exports only, no default export. Use ESM import syntax.

loadFileSync

wrong

import loadFileSync from 'babel-file-loader'

correct

import { loadFileSync } from 'babel-file-loader'

Default import is incorrect; all exports are named.

resolveFilePathSync
wrong
```
const { resolveFilePathSync } = require('babel-file-loader')
```
correct
```
import { resolveFilePathSync } from 'babel-file-loader'
```
CommonJS require is not supported in the ESM distribution; use dynamic import or ES module context.

Quickstart

Shows how to use loadImportSync inside a Babel plugin visitor to load and parse the file referenced by an import declaration.

import { loadImportSync } from 'babel-file-loader';

export default function() {
  return {
    visitor: {
      ImportDeclaration(path) {
        try {
          const file = loadImportSync(path);
          console.log('Loaded file:', file.opts.filename);
        } catch (e) {
          console.error('Failed to load import:', e.message);
        }
      }
    }
  };
}