Azure DevOps - Set a Build variable using another variable (nested/composed variables) - azure-devops

Question

In Azure DevOps I have a Pipeline variable "package version" and I set it using 0.1.3$(Rev:.r)-alpha .
I use that variable to replace the "Version" in the .net core project file.
In the Build tasks the dotnet build give me this error:
so I assume the Pipeline variable cannot use a nested variable.
There is a nother way or a different syntax to do it?
[Edit]
The nested variables should work.
I think the error was the dotnet pack using Automatic package versioning set to "Use the build number" that contain the wrong $(rev:.r) (lowercase!).
Using a custom string for Version in the VS project file gives noise on VS (error if the file is open, warning otherwise) and now the Pipeline Build give me an error on dotnet nuget restore because of the invalid Version.
I decided to use a simple clean version, <Version>0.1.2</Version>, that I can choose and document.
Then I want to find a way to read it in the build pipeline and create a custom variable attaching the Build Revision:
0.1.2$(Rev:.r) => 0.1.2.123
That is the result I want.
I found this: https://marketplace.visualstudio.com/items?itemName=tmarkovski.projectversionasvariable
I'm using it with the default settings.
I'm using the variables it creates to compose a new variable, "package version":
and I use that in the nuget pack task:
but it does not work.
The resulting variable still contain "$(Rev:.r)" not parsed.
I'll try to use again the "Automatic package versioning" and create the build number in the Options...
[Edit 2]
Set the build version number in the Pipeline Build Options worked.
It's not the optimal solution because the Build Number is not parsed and looks awful.
[Solution]
$(Rev:.r) is not available outside Build / Options.
I used $(Build.BuildNumber) and I'm able to create a composed variable:
$(Version.MajorMinor).$(Build.BuildNumber)-alpha
Build.BuildNumber is valorized in Build/Options: $(Build.DefinitionVersion)$(Rev:.r)
Version.MajorMinor is created by the Project Version As Build Variable add-on.
I don't know how to obtain the same result without using a third party component.

Answer 1

I'm glad my extension helped and thanks for the nice review. If you want more control and have a little time to spend to play with PowerShell, you can easily achieve what you want in two steps, without using third party extensions.
Read and parse the .csproj file as XML
Set build variables
Here are couple of links on reading XML files and working with build variables, it's actually pretty easy.
https://www.business.com/articles/powershell-read-xml-files/
VSTS: Pass build/release variables into Powershell script task
[xml]$XmlDocument = Get-Content -Path $env:project_file
echo $XmlDocument.Project.PropertyGroup.Version
https://learn.microsoft.com/en-us/azure/devops/pipelines/process/variables?view=vsts&tabs=yaml%2Cbatch
Write-Host '##vso[task.setvariable variable=package_version;issecret=true]0.1.2.'
Note: my answer wouldn't fit in a comment, I had to post an answer.