macOS default ENV vars - RCT_NO_LAUNCH_PACKAGER

I have a very (I think) simple GitHub Actions workflow file.


name: CI
on:
  push:
    branches:
    - master

jobs:
  beta:
    name: Beta
    runs-on: macOS-latest

    strategy:
      matrix:
        destination: ['platform=iOS Simulator,OS=13.1,name=iPhone 8']
        xcode: ['/Applications/Xcode_11.6.app/Contents/Developer']
        node-version: [14.6.0]

    steps:
      - name: Checkout Repo
        uses: actions/checkout@master
      - name: Check env
        run: |
          echo "SHELL:${SHELL} RCT_NO_LAUNCH_PACKAGER:${RCT_NO_LAUNCH_PACKAGER}"

RCT_NO_LAUNCH_PACKAGER is set to 1 when this workflow is evaluated in GitHub Actions and I am not doing it. I confirmed with a bare demo/test repo here.

To be clear, I can understand why a CI environment might set that particular var for the sake of a React Native app. But I could have saved myself a few days of debugging and head scratching if I had known that GH Actions was setting this var that impacts the React Native metro bundler behavior in Xcode’s Start Packager Build Phase.

I can find no documentation explaining that this variable would have any value. Is there documentation on the list of macOS default ENV vars? Debugging this took a while and it would be great to have a better understanding of what other ENV vars may be getting set so I don’t lose my mind next time I encounter a similar, “works on localhost, behaving different in GitHub Actions”, behavior like this.

I realize now I can just run env in a macOS build. Seems worthwhile to just do that and look at everything there.