Powershell error inside azure release pipeline yaml

Question

I converted Azure release pipeline classic pipeline to yaml with yamlzr Powershell command is failing inside yaml file:

You cannot call a method on a null-valued expression in powershell inside azure release pipeline yaml

$branch = $env:build_sourceBranch.substring($env:build_sourceBranch.indexOf('/', 5) + 1)

1. I tried to use Build.SourceBranchName built-in variable but not working.

2. I tried to map it

 env:
            BUILD_SOURCEBRANCH: $(Build.SourceBranchName)

I got (Line: 162, Col: 13): A mapping was not expected eror.

Answer 1

I can reproduce the issue with your script (lowercase variable) when using Ubuntu-latest agent in pipeline.

In DevOps Variable names are transformed to uppercase, and the characters "." and " " are replaced by "_". So the variable should be $env:BUILD_SOURCEBRANCH. See Define and modify your variables in a script

The problem is that Linux is case sensitive. It cannot identify the lowercase variable $env:build_sourceBranch in Linux. We need to use The uppercase variable $env:BUILD_SOURCEBRANCH when using Linux agent (Ubuntu-latestfor example).

So the correct script when using "Ubuntu-latest" would be like this:

$branch = $env:BUILD_SOURCEBRANCH.substring($env:BUILD_SOURCEBRANCH.indexOf('/', 5) + 1)

Alternately, we can use the Windows-latest agent with the lowercase variable $env:build_sourceBranch.

For example:

trigger: none

pool:
  vmImage: Windows-latest

steps:
- task: PowerShell@2
  inputs:
    targetType: 'inline'
    script: |
      $branch = $env:build_sourceBranch.substring($env:build_sourceBranch.indexOf('/', 5) + 1)
      
      Write-Host "branch :" $branch