conditionnally select nuget package during build - azure-devops

Question

Our build environment is VSTS pipeline and our development environment is visual studio.
We are using dev branches (or feature branches) and we have a main branch (master branch).
As piece of code are getting stable and don't need much debug, We are now willing to split our projects into nuget packages.
As long as we are in dev or feature branch, we want to generate and use the -alpha nuget package to test and use the latest code.
But as soon as we are doing a pull request to the master branch, we want to use the stable nuget package.
Of course, without having to manually go to the nuget package manager and update every nuget package before committing;
Said differently, every project in a dev branch should automatically build with the -alpha version of each nuget package and the build of the master branch should be with the stable version of the package.
How can we create a vsts pipeline to achieve this

Answer 1

conditionnally select nuget package during build
You could add a task (powershell or batch) to modify the nuget.config or the project file to update the package version with condition.
steps:
- powershell: |
# Write your PowerShell commands here.
update the package version in the nuget.config or project file.
displayName: 'Update package version'
condition: and(succeeded(), eq(variables['Build.Reason'], 'PullRequest'))

Answer 2

You create two (build) pipelines:
Dev / Feature you name it -> gets triggered by your feature/* branches and publishes your -aplpha nuget package
Stable / Prod -> gets triggered by pull requests into the main branch and publishes the stable nuget package
I personally don't have much experience with YAML, yet, but in the classic pipeline editor you can easily add tasks. Each pipeline should roughly be looking like this:
Some more details:
Missing on the screen shot is the important trigger part. You can also edit that in the classic pipeline editor in the "trigger" tab. There you choose your feature branch setting (e.g. feature/*) and exclude the master on the feature pipeline.
Converting all to YAML should be straight forward via the "View YAML" feature in the classic web editor.
Depending on your private setup you might need extra steps like NuGet auth if you use a private NuGet server etc..