alloy / juse

A Jest script transformer backed FUSE implementation

Juse: A Jest script transformer backed FUSE implementation, which allows you to access the FS with files transformed in place by Jest’s script transformer.

⚠️ This is just a proof-of-concept. It is slow, naive, and unpolished.

Install

Install dependencies:

git clone https://github.com/alloy/juse.git
cd juse
yarn install

Configure FUSE kernel extension once:

yarn fuse-native is-configured
false
sudo yarn fuse-native configure

Build code:

yarn build

Usage

Mount a jest configured project:

cd my-project
mkdir /tmp/my-project-mount-point
node path/to/juse/index.js /tmp/my-project-mount-point

Now files that would be transformed by jest in your project will be transformed in place when accessing them. E.g. for a TS file like:

import { NativeModules } from "react-native"
const { Emission } = NativeModules

import { Sentry } from "react-native-sentry"

// AREmission sets this to "" if not configured, which is falsy in JS so this conditional is fine.
if (Emission.sentryDSN) {
  Sentry.config(Emission.sentryDSN).install()
}

…accessing it like so:

cat /tmp/my-project-mount-point/a-file-in-your-project.ts

…will show:

var _reactNative = require("react-native");

var _reactNativeSentry = require("react-native-sentry");

var Emission = _reactNative.NativeModules.Emission;

if (Emission.sentryDSN) {
  _reactNativeSentry.Sentry.config(Emission.sentryDSN).install();
}
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TODO

• Read source files non-block, unlike what the ScriptTransformer does. Unsure what Jest offers.
• Fill build cache ahead of time. Unsure what Jest offers.
• Use Jest’s platform aware resolver to check if files should be transformed.
• Rename file extnames to .js