check_existing.yml

- task: Bash@3
  displayName: 'Check if Package Exists'
  inputs:
    targetType: 'inline'
    script: |
      set -e

      
      # Configure default organization and project
      az devops configure --defaults organization=$(System.TeamFoundationCollectionUri) project=$(System.TeamProject)

      # Authenticate with Azure DevOps
      az devops login --token $(System.AccessToken)


      # Attempt to download the package
      az artifacts universal download \
        --feed "$(feedName)" \
        --name "$(packageName)" \
        --version "$(packageVersion)" \
        --path "$(Build.ArtifactStagingDirectory)/temp_download"

      RESULT=$?

      if [ $RESULT -eq 0 ]; then
        echo "Package exists."
        echo "##vso[task.setvariable variable=PackageExists]true"
      else
        echo "Package does not exist or an error occurred."
        echo "##vso[task.setvariable variable=PackageExists]false"
      fi

      # Clean up temporary files
      rm -rf "$(Build.ArtifactStagingDirectory)/temp_download"

      set -e  # Re-enable exit on error
  env:
    SYSTEM_ACCESSTOKEN: $(System.AccessToken)

conditionally_push.yml

- task: UniversalPackages@0
  displayName: 'Publish Universal Package'
  inputs:
    command: 'publish'
    publishDirectory: '$(Build.ArtifactStagingDirectory)'
    feedsToUsePublish: 'internal'
    vstsFeedPublish: 'YourFeedID'
    vstsFeedPackagePublish: '$(packageName)'
    packagePublishVersion: '$(packageVersion)'
  condition: ne(variables['PackageExists'], 'true')