privatenumber / fs-require

Create a require() function from any file-system. Great for in-memory fs testing!

fs-require

Create a require() function from any file-system.

Pass in a virtual file-system for in-memory testing without writing to disk.

Features

• 💞 Works well with memfs!
• 🪄 Resolves implicit entry index and implicit extensions js and json
• 🗺 Resolves relative and absolute paths
• 📍 __dirname & __filename
• ✅ require.resolve() & require.cache
• 👻 Mocks fs within fsRequire
• 👣 Call stack shows paths with fs-require:// protocol

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🚀 Install

npm i fs-require

🙋‍♀️ Why?

Using fs-require with memfs is a great combination for writing tests that interact with the file-system.

Testing functionality that interacts with the file-system can be brittle because they expect a clean slate and can also be dangerous if the path is wrong. Creating a virtual file-system with memfs and testing its contents with fsRequire makes it secure and fast!

👨‍🏫 Usage

import { Volume } from 'memfs'
import { createFsRequire } from 'fs-require'

// Create a virtual fs from JSON
const virtualFs = Volume.fromJSON({
    '/hello-world.js': `
        module.exports = function () {
            return 'Hello world!'
        }
    `
})

// Create fsRequire
const fsRequire = createFsRequire(virtualFs)

// Import virtual module
const helloWorld = fsRequire('/hello-world')

console.log(helloWorld()) // Hello world!

⚙️ API

createFsRequire(fs, options?)

Returns a fsRequire(modulePath) function that resolves from the file-system passed in.

fs

Type: FileSystem

Required

The file-system to resolve requires from.

options

options.fs

Type: boolean | FileSystem

Code executed the virtual file-system may require('fs') and this may either pose as a security concern or yield inconsistent results as the virtual file won't not accessible through the actual fs module.

By default require('fs') is shimmed to the file-system passed into createFsRequire.

To disable this behavior and resolve to the real fs module, set this to true.

You can also pass in a different file-system too.

fsRequire(modulePath)

modulePath

Type: string

Required

Path to the module you want to "require". Mocks Node.js require.

fsRequire.resolve(modulePath)

modulePath

Type: string

Required

Path to the module you want to "resolve". Mocks Node.js require.resolve.

fsRequire.cache

Type: Record<string, Module>

An object that contains the cache for modules that have been loaded so far. The key is the absolute path to the module, and the value is the module instance. Mocks Node.js require.cache.

To re-load a module that has already been loaded, you can delete the cache the same way you would in Node.js:

delete fsRequire.cache[fsRequire.resolve('/some-module.js')]

💁‍♂️ FAQ

Can it resolve case insensitive paths?

Case sensitivity in paths is a file-system concern so it would depend on the fs passed in. For example, macOS (native fs) is case insensitive. memfs is case sensitive.

👨‍👩‍👧 Related

• fs-monkey - By the same author of memfs. Patches the global require to access a virtual fs.