babel-plugin-rewire-exports

2.3.0 verified Sat Apr 25 auth: no javascript

Babel plugin for stubbing ES6/ES2015 module exports in tests. Version 2.3.0 (stable, last release 2021) allows rewriting exported values in importing modules without modifying module internals. Unlike babel-plugin-rewire, it keeps imports and local variables intact. It generates rewire/stub functions (rewire for default, rewire$name for named exports, and restore). Works with Babel 7 (use 0.x for Babel 6), supports browser and Node ESM, and bundles with Webpack, Rollup, SystemJS, and CommonJS via env preset. Release cadence: infrequent, no recent updates.

Common errors

error Error: Plugin babel-plugin-rewire-exports requires @babel/core but was not found. ↓

cause Missing @babel/core peer dependency.

fix

Run npm install --save-dev @babel/core babel-plugin-rewire-exports

error TypeError: Cannot assign to read only property 'message' of object '#<Object>' ↓

cause Attempting to rewire a constant export without unsafeConst option.

fix

Add "unsafeConst": true to plugin options, or change export to let/var.

error SyntaxError: Unexpected token $ ↓

cause Using node <8.5.0 or browser without ESM support for rewire$name identifier.

fix

Upgrade Node or use a bundler that supports the plugin's output.

Warnings

breaking v2.0.0: Functions are rewritten as variables. Export default function foo() {} becomes var foo = function foo() {}; export { foo as default }; ↓

fix In tests, access the function via the variable export, not the original function declaration. Use rewire$default for default exports.

deprecated v1.3.0: Constant exports behavior changed. Constants can't be rewired within the module; only the exported binding is mutable. ↓

fix If relying on rewiring const inside the module, use unsafeConst option or upgrade to >=1.3.0 and export as let/var.

gotcha Plugin must be placed before @babel/plugin-transform-modules-commonjs when targeting CommonJS. ↓

fix In .babelrc, order: ["babel-plugin-rewire-exports", "@babel/plugin-transform-modules-commonjs"]

gotcha Default export rewiring: rewire() stub replaces the default export, but the original default is kept and can be restored via restore(). ↓

fix Use rewire(stub) for default exports, not named import default.

gotcha If the module already has top-level identifiers named rewire or restore, the generated stubs are renamed to rewire$default and restore$rewire. ↓

fix Check for name collisions and use the renamed stubs accordingly.

Install

npm install babel-plugin-rewire-exports

yarn add babel-plugin-rewire-exports

pnpm add babel-plugin-rewire-exports

Imports

rewire (default export stub)
wrong
```
import rewire from './my-module'
```
correct
```
import { rewire } from './my-module'
```
The plugin exports rewire as a named export, not default. It replaces the default export of the module.
rewire$name (named export stub)
wrong
```
import { rewire_name } from './my-module'
```
correct
```
import { rewire$name } from './my-module'
```
For named exports, the stub is rewire$<exportName>. The dollar sign is part of the identifier.
restore
wrong
```
import restore from './my-module'
```
correct
```
import { restore } from './my-module'
```
restore is a named export from the transformed module, not default.

Quickstart

Shows basic setup and usage: rewire a named export, restore original.

// .babelrc
{
  "plugins": ["babel-plugin-rewire-exports"]
}

// text.js
export let message = 'Hello world!';

// logger.js
import {message} from './text.js';
export default function log() {
  console.log(message);
}

// test.js
import {rewire$message, restore} from './text.js';
import log from './logger.js';

log(); // 'Hello world!'
rewire$message('stubbed');
log(); // 'stubbed'
restore();
log(); // 'Hello world!'