define-shared-variables.yml

name: Define shared variables to be reused by callable workflow

on:
  workflow_call:
    inputs:
      shared-variables:
        required: false
        type: string

jobs:
  run:
    runs-on: ubuntu-20.04
    
    steps:
      - uses: actions/checkout@v3
        name: Checkout Base
        with:
          fetch-depth: 0

      - name: Export variables to JSON
        id: varsStep
        uses: actions/github-script@v6
        with:
          script: |
            const envVarsFromInputs = `${{ inputs.shared-variables }}`;
            const sharedVariablesObject = envVarsFromInputs ? JSON.parse(envVarsFromInputs) : {};

            function exportVariable(name, value) {
              sharedVariablesObject[name] = value;
            }

            switch('${{ github.event_name }}') {
              case 'pull_request': {
                exportVariable('HEAD_SHA', '${{ github.event.pull_request.head.sha }}');
                exportVariable('CURRENT_BRANCH', '${{ github.head_ref }}');
                exportVariable('BASE_BRANCH', '${{ github.base_ref }}');
                exportVariable('NX_BASE', 'origin/${{ github.base_ref }}');
                exportVariable('NX_HEAD', 'origin/${{ github.head_ref }}');
                exportVariable('NX_BRANCH', '${{ github.head_ref }}');
                break;
              }
              case 'workflow_dispatch':
              case 'push': {
                exportVariable('HEAD_SHA', '${{ github.sha }}');
                exportVariable('CURRENT_BRANCH', '${{ github.ref_name }}');
                exportVariable('BASE_BRANCH', '${{ github.ref_name }}');
                exportVariable('NX_HEAD', 'origin/${{ github.ref_name }}');
                exportVariable('NX_BRANCH', '${{ github.ref_name }}');
                break;
              }
            }

            core.setOutput('value', JSON.stringify(sharedVariablesObject));
            Object.entries(sharedVariablesObject).forEach(([name, value]) => {
              core.exportVariable(name, value);
            });

      - name: Export composed variables to JSON
        id: sharedVarsStep
        uses: actions/github-script@v6
        env:
          DEPENDENCIES_CACHE_KEY: ${{ runner.os }}-build-cache-node-modules-${{ hashFiles('**/package-lock.json') }}
          DEPENDENCIES_RESTORE_KEY: ''

        with:
          script: |
            const fileName = 'temp/variables.json';
            const fs = require('fs');
            const path = require('path')
            const sharedVariablesObject = ${{ steps.varsStep.outputs.value }};
            const stepEnvVariables = ${{ toJson(env) }};
            const mergedVariables = { ...sharedVariablesObject, ...stepEnvVariables };
            fs.mkdirSync(path.dirname(fileName), { recursive: true })
            fs.writeFileSync(fileName, JSON.stringify(mergedVariables));
            core.setOutput('value', JSON.stringify(mergedVariables));

      - name: Save success targets
        uses: actions/cache/save@v3
        with:
          path: 'temp/variables.json'
          key: shared-variables-${{ github.run_id }}-${{ github.run_attempt }}

      - name: Display variables
        uses: actions/github-script@v6
        with:
          script: |
            console.log(${{ steps.sharedVarsStep.outputs.value }});