UX: npm 5 error, yarn is not picked

Description

I could not create a React Native app on my machine and it was not clear why. Apparently it is package manager issues.

create-react-native-app MyRnApp
Creating a new React Native app in /Users/bestander/work/MyRnApp.

Using package manager as npm with npm interface.
Installing packages. This might take a couple minutes.
Installing react-native-scripts...

npm notice created a lockfile as package-lock.json. You should commit this file.
npm WARN react-redux@5.0.6 requires a peer of react@^0.14.0 || ^15.0.0-0 || ^16.0.0-0 but none was installed.

+ react-native-scripts@1.8.1
added 423 packages in 18.72s

*******************************************************************************
ERROR: npm 5 is not supported yet
*******************************************************************************

It looks like you're using npm 5 which was recently released.

Create React Native App doesn't work with npm 5 yet, unfortunately. We
recommend using npm 4 or yarn until some bugs are resolved.

You can follow the known issues with npm 5 at:
https://github.com/npm/npm/issues/16991

*******************************************************************************

[09:43:27] bestander:~/work $ cat MyRnApp/package.json
{
  "name": "MyRnApp",
  "version": "0.1.0",
  "private": true,
  "devDependencies": {
    "react-native-scripts": "1.8.1"
  }
}

Expected Behavior

1. npm@5 problem is printed in yellow (as warning) and I had no idea that I have a corrupt installation with no clear way to recover it. If the error is colored red and there is a guide how to recover (update npm, switch to yarn etc) it would work better for beginners like me

2. Would it be better to check for npm@5 issue before starting to bootstrap the project?

3. I have yarn installed but it was not picked by the app by default I guess because it checks whether yarn is installed using

var result = _crossSpawn2.default.sync('yarnpkg', ['--version'], { stdio: 'ignore' });

Not all Yarn installations register yarnpkg bin.

Environment

Please run these commands in the project folder and fill in their results:

• npm ls react-native-scripts: react-native-scripts@1.8.1
• npm ls react-native: react-native@0.50.3
• npm ls expo: expo@23.0.6
• node -v: v8.1.2
• npm -v: 5.0.3
• yarn --version: 1.2.0
• watchman version: watchman: command not found

Also specify:

1. Operating system: Mac OS X
2. Phone/emulator/simulator & version: 11

Reproducible Demo

create-react-native-app MyRnApp

[bestander]

Yeah, looks like this was because my local setup has only yarn bin exposed to PATH. I checked brew and install script expose both yarn and yarnpkg.

I’ll close the task

[bestander]

Hm weird, yarnpkg binary is in the bin folder https://github.com/yarnpkg/yarn/tree/master/bin