Is it possible to use a variable in the ref property of resources:repository for Azure DevOps YAML? - azure

Question

I have two AzureDevOps Git branches:
master
feature/mybranch
I have a multi-stage build pipeline defined in yaml, where some of the steps are templated into separate .yml files.
In my outer azure-pipelines.yml I reference a repository where my template .yml's live:
resources:
repositories:
- repository: templates
type: git
name: MyProject/MyRepo
when I'm building in the 'master' branch everything is good as by default the repository will look in refs/heads/master.
when I'm working in the feature branch and I want to test experimental changes to my template .yml files, I don't want it to fetch them from the master branch, I want it to use the files from the branch I am working in.
The following works and allows me to do this:
resources:
repositories:
- repository: templates
type: git
name: MyProject/MyRepo
ref: refs/heads/feature/mybranch
However, when I merge this back to master, I obviously don't want 'ref:' still pointing at the feature branch, so I'd like to generate the value of 'ref:' dynamically with a variable.
I've tried using ref: $(Build.SourceBranch) where $(Build.SourceBranch) should expand to 'refs/heads/feature/mybranch'
But it doesn't work. Error:
62638: "/azure-pipelines.yml: Could not get the latest source version for repository MySolution hosted on Azure Repos using ref refs/heads/$(Build.SourceBranch)."

Answer 1

Instead of referencing the repo in resources, use inline checkout as described here
https://learn.microsoft.com/en-us/azure/devops/pipelines/repos/multi-repo-checkout?view=azure-devops#checking-out-a-specific-ref
- checkout: git://MyProject/MyRepo#features/tools
And this yaml element allows use of template expressions using variables, parameters e.g.
- checkout: git://${{ variables.repoName}}#${{ variables.branchRef }}
OR
- checkout: git://${{ parameters.repoName}}#${{ parameters.branchRef }}
And you can change that dynamically
Or the other alternative is use script task as below
- script: |
# note checkout: git://$(System.TeamProject)/${{ parameters.repoName }}#${{ parameters.repoRef }} this does not work if this task is run multiple times in same pipeline
# see here for more details :https://developercommunity.visualstudio.com/t/checkout-fails-with-an-error-occurred-while-loadin/1005991#T-N1270459
repoDir=$(Agent.BuildDirectory)/${{ parameters.repoName }}
/bin/rm -rf $repoDir
url_with_token=$(echo $(System.CollectionUri) | sed -e "s/https\:\/\//https\:\/\/$(System.AccessToken)\#/g")
git clone $url_with_token/$(System.TeamProject)/_git/${{ parameters.repoName }} $repoDir
cd $repoDir
git fetch origin '${{ parameters.repoRef }}':'localBranch'
git checkout localBranch
name: clone_script
displayName: Checkout using script ${{ parameters.repoName }}#${{ parameters.repoRef }}
I have added above as a template and its usage in a gist, to make it re-usable easily.
Hope that helps
https://gist.github.com/scorpionlion/1773d08b62ca5875cc2fd6dcdd0394d2

Answer 2

Is it possible to use a variable in the ref property of
resources:repository for Azure DevOps YAML?
For this question, the answer is Yes, it's possible.
About why you receive that error message, just is the variable($(Build.SourceBranch)) you used is incorrect. You should use $(Build.SourceBranchName).
As normal, for ref, we should input master or any other feature branches. Such as
ref: refs/heads/master
This may make you thought that this is same with the value of $(Build.SourceBranch). It looks same, I know, but different. In fact, for server, it will read the exactly branch name not the branch path, which we can clearly figure out with the classic editor type:
According with classic editor type, we can know here we should input the exactly branch name.
So, as the Predefined variables defined, the value of $(Build.SourceBranch) is the branch path, but for $(Build.SourceBranchName), it's represent a exactly branch name.
So, if you want to execute successfully, you need to use : $(Build.SourceBranchName). And it's worked on my side.
Hope this also can help you stay away from the error message.
Edit:
The complete script which is worked for me is:
resources:
repositories:
- repository: templates
type: git
name: MyApp/MyconApp
ref: $(Build.SourceBranchName)

Answer 3

The azure docs state
Variables can't be used to define a repository in a YAML statement.
So that seems to place some limitations on what you can do here. Perhaps there is a workaround that still allows you to do what you want.