Azure Pipelines $Build.SourcesDirectory listing empty directory

Question

I have azure debug pipeline that looks like below. I use $(Build.SourcesDirectory) azure variable to list content of my repository. Unfortunately, for some reason the content of SourcesDirectory is empty. Why? What am I doing wrong? I remember that it used to work.

pool:
  vmImage: ubuntu-latest

stages:
- stage: Debug
  displayName: Debug
  jobs:
  - deployment: Debug
    displayName: Debug
    strategy:
      runOnce:
        deploy:
          steps:
            - task: CmdLine@2
              displayName: Debug
              inputs:
                script: |
                  echo 'Build.SourcesDirectory'
                  echo $(Build.SourcesDirectory)
                  ls -l $(Build.SourcesDirectory)

Answer 1

I still don't know the reason behind why it didn't work in first place (I guess some pipeline permissions or settings that I don't have/know) but, I found the fix that worked for me.

I had to add checkout: self step (docs) before my debug task.

pool:
  vmImage: ubuntu-latest

stages:
- stage: Debug
  displayName: Debug
  jobs:
  - deployment: Debug
    displayName: Debug
    strategy:
      runOnce:
        deploy:
          steps:
            # The Fix!
            - checkout: self
            - task: CmdLine@2
              displayName: Debug
              inputs:
                script: |
                  echo 'Build.SourcesDirectory'
                  echo $(Build.SourcesDirectory)
                  ls -l $(Build.SourcesDirectory)