rollup-plugin-ephemeral

0.0.1 verified Mon Apr 27 auth: no javascript

A Rollup plugin for creating virtual modules that behave like real files, useful for testing or generating modules on-the-fly. Version 0.0.1 is the initial unstable release. Different from @rollup/plugin-virtual in that ephemeral modules are treated as real file modules by Rollup, affecting resolution and caching behavior. This package ships TypeScript types and supports ESM only.

Common errors

error Error [ERR_REQUIRE_ESM]: require() of ES Module /path/to/rollup-plugin-ephemeral/index.js not supported. ↓

cause The package is ESM-only, but the project is using CommonJS require() to load the plugin.

fix

Switch to dynamic import: const ephemeral = await import('rollup-plugin-ephemeral'); or configure your project as ESM.

error TypeError: ephemeral is not a function ↓

cause Importing the default export incorrectly, e.g., using named import where only default export exists.

fix

Use: import ephemeral from 'rollup-plugin-ephemeral'; Do not use named import: import { ephemeral } from 'rollup-plugin-ephemeral';

Warnings

breaking ESM-only: rollup-plugin-ephemeral uses native ES modules. Using require() will throw MODULE_NOT_FOUND. ↓

fix Use import syntax and ensure your project is configured for ESM (e.g., type: module in package.json).

gotcha Virtual modules created by this plugin are treated as real files by Rollup's resolveId hook, which may affect caching and watch mode behavior differently than @rollup/plugin-virtual. ↓

fix If you need standard virtual module behavior, use @rollup/plugin-virtual instead.

gotcha The plugin does not support side effects via a separate options object; all arguments are positional. Pass only id and code. ↓

fix Call ephemeral('id', 'code') with exactly two string arguments.

Install

npm install rollup-plugin-ephemeral

yarn add rollup-plugin-ephemeral

pnpm add rollup-plugin-ephemeral

Imports

ephemeral

wrong

const ephemeral = require('rollup-plugin-ephemeral')

correct

import ephemeral from 'rollup-plugin-ephemeral'

This package is ESM-only; CommonJS require() will fail.

ephemeral (named export)

wrong

import { default as ephem } from 'rollup-plugin-ephemeral'

correct

import { ephemeral } from 'rollup-plugin-ephemeral'

The package only exports a default function; named import is not available.

ephemeral (type import)

wrong

import { RollupPluginEphemeralOptions } from 'rollup-plugin-ephemeral'

correct

import type { RollupPluginEphemeralOptions } from 'rollup-plugin-ephemeral'

Types are only available as type-only imports to avoid runtime side effects.

Quickstart

Shows basic usage: create a virtual module entry.js that exports a constant, then bundle with Rollup and output the generated code.

import ephemeral from 'rollup-plugin-ephemeral';
import { rollup } from 'rollup';

const bundle = await rollup({
  input: 'entry.js',
  plugins: [
    ephemeral('entry.js', 'export const answer = 42;'),
  ],
});
const { output } = await bundle.generate({ format: 'es' });
console.log(output[0].code);