preinstall script breaks pnp installation silently in yarn workspaces

[bugzpodder]

clone https://github.com/bradfordlemley/cra-monorepo-examples
use plug-n-play: yarn --pnp
goto a apps/cra-app1
add a preinstall script:

+++ b/apps/cra-app1/package.json
@@ -5,13 +5,14 @@
   "dependencies": {
     "react": "^16.2.0",
     "react-dom": "^16.2.0",
-    "react-scripts": "2.0.0-next.b2fd8db8"
+    "react-scripts": "2.0.4"
   },
   "scripts": {
     "start": "react-scripts start",
     "build": "react-scripts build",
     "test": "react-scripts test --env=jsdom",
-    "eject": "react-scripts eject"
+    "eject": "react-scripts eject",
+    "preinstall": "node -e 'if(!/yarn\\.js$/.test(process.env.npm_execpath))throw new Error(\"Use yarn install\")'"
   },
   "browserslist": {
     "development": [

run yarn in workspace root, see no obivous errors
run yarn app1 see react-scripts not found
run yarn app2 and it works fine.

@arcanis

[bugzpodder]

This is super annoying, I have another directory that doesn't have the executables (ie babel/eslint) working and I have no idea why. need to remove stuff from package.json piece by piece until I find the culprit.

it appears to be caused by postinstall scripts (node-sass, cypress, etc). --ignore-scripts doesn't really work for some reason. Deleting these dependencies make it work.

[arcanis]

Woops - we automatically unplug the packages that have {pre/post}install scripts (since otherwise they would get built inside the cache, which could lead to cache corruptions). I forgot to prevent this from happening with workspaces.