Registry / testing / rollup-plugin-memfs

rollup-plugin-memfs

library4.0.1-alpha.0jsnpmunverified

A Rollup plugin that uses an in-memory filesystem (memfs) as the file system backend, enabling unit testing of Rollup builds without writing to disk. Current version is 4.0.1-alpha.0. It replaces Rollup's default file system with a memfs instance, allowing deterministic tests and fast iteration. Key differentiators: works with memfs v4, supports Promise-based memfs API, and is TypeScript-native. Compared to alternatives like rollup-plugin-mock-fs, this plugin integrates directly with memfs's Volume for fine-grained virtual file control.

testing devops

npm install rollup-plugin-memfs

package ↗

INSTALL

IMPORT

SIG · ROLLUP-PLUGIN-MEMF

rollup-plugin-memfs

testingjavascriptv4.0.1-alpha.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 18–223 runs

build_error

glibc

node 18–223 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

memfsPlugin

✓ import { memfsPlugin } from 'rollup-plugin-memfs'

✗ const memfsPlugin = require('rollup-plugin-memfs')

Package is ESM-only since v4. CommonJS require will fail.

createFs

✓ import createFs from 'memfs/lib/promises'

✗ import { createFs } from 'memfs'

The createFs function is a default export from memfs/lib/promises, not a named export from 'memfs'.

Volume

✓ import { Volume } from 'memfs'

✗ import Volume from 'memfs'

Volume is a named export from 'memfs'.

Creates an in-memory filesystem with memfs, uses it as Rollup's file system, and generates a bundle without touching disk.

import { Volume } from 'memfs'; import createFs from 'memfs/lib/promises'; import { memfsPlugin } from 'rollup-plugin-memfs'; import { rollup } from 'rollup'; const vol = Volume.fromJSON({ '/input.js': 'export default 42;' }); const memfs = createFs(vol); async function build() { const bundle = await rollup({ input: '/input.js', plugins: [memfsPlugin(memfs)] }); const { output } = await bundle.generate({ format: 'es' }); console.log(output[0].code); // 'var input = 42; export { input as default };' } build();

Debug

Known issues

breakingPackage renamed from 'rollup-plugin-memfs' to 'rollup-plugin-memfs' (no change, but major version bump to 4 changes API).

fix

Update import to ESM: import { memfsPlugin } from 'rollup-plugin-memfs'. No more default export.

affects: >=4.0.0

deprecatedmemfs v3 is deprecated; memfs v4 changes the filesystem API.

fix

Use memfs v4 and its Promise-based API: import createFs from 'memfs/lib/promises'.

affects: >=4.0.0

gotchaThe plugin requires memfs as a peer dependency, but it is not listed in package.json dependencies.

fix

Install memfs separately: npm install memfs

affects: >=1.0.0

gotchaRollup's onwarn option may ignore file system errors that are caught by memfs.

fix

Set onwarn to log warnings: onwarn(warning, defaultHandler) => { console.warn(warning.message); }

affects: >=0.0.0

Errors

Common errors & fixes

Error: Cannot find module 'rollup-plugin-memfs'

Package is ESM-only; using require() instead of import.

fix

Switch to ESM: use import or set type:"module" in package.json.

TypeError: memfsPlugin is not a function

Incorrect import: default import used when only named export exists.

fix

Use named import: import { memfsPlugin } from 'rollup-plugin-memfs'.

Error: ENOENT: no such file or directory, open '/index.js'

The file path does not exist in the memfs volume.

fix

Add the file to the volume: vol.fromJSON({'/index.js': 'content'}).

Upgrade

Version history

4.0.1-alpha.0latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

6 hits · last 30 days

node

Resources

packagehttps://www.npmjs.com/package/rollup-plugin-memfs ↗