Install via yarn returns prompt to use yarn.

[JoshStrobl]

• VSCode Version: git (67cd925)
• OS Version: Linux goliath 4.13.12-32.current #1 SMP Wed Nov 8 19:07:57 UTC 2017 x86_64 GNU/Linux

Steps to Reproduce:

1. Run yarn (installed globally) during build
2. See output

+ yarn
yarn install v1.3.2
$ node build/npm/preinstall.js
*** Please use yarn to install dependencies

The + before yarn merely denotes during our build what command is being run and is not part of the command itself. Running yarn as a replacement for npm install as per #38481

Further notes:

• Yes, this is a clean build. All builds are done in a new, clean build environment (so we can have reproducible builds).

[JoshStrobl]

If I remove lines 15 to 18 on build/npm/preinstall.js it goes about installing the dependencies as expected.

[joaomoreno]

What's the value of npm_execpath in https://github.com/Microsoft/vscode/blob/master/build/npm/preinstall.js#L15 ?

[JoshStrobl]

undefined is the value of npm_execpath, both in our build env and outside it (host).

NPM for us: usr/bin/npm: symbolic link to ../lib/node_modules/npm/bin/npm-cli.js, where this is provided by our nodejs package: Package nodejs has file /usr/lib/node_modules/npm/bin/npm-cli.js

[joaomoreno]

While executing build/npm/preinstall.js, as part of yarn install, can you find any environment variable which points to yarn as being the package manager used, instead of npm?

Simply add the following to preinstall.js to find out:

console.log(process.env);
process.exit(1);

[JoshStrobl]

Not sure why my test code earlier was reporting it as undefined. Regardless, value is /usr/lib64/node_modules/yarn/bin/yarnpkg when I do console.log(process.env['npm_execpath']);

Seems to fail because it's checking for yarn.js and not the executable yarnpkg (we build our yarn and ship it as a package).