How do you properly use Azure DevOps functions in a variable template? - function

Question

How can I use the Azure DevOps counter function in a variable template?
Up until now, I have been using the counter function to set a variable in an pipeline and the value has been set as expected - it started at 1 and has incremented every time I run the pipeline.
Variable template - /Variables/variables--code--build-and-deploy-function-app.yml
variables:
- name: major
value: '1'
- name: minor
value: '0'
- name: patch
value: $[counter(format('{0}.{1}-{2}', variables['major'], variables['minor'], variables['Build.SourceBranchName']), 1)]
- name: branch
${{ if eq( variables['Build.SourceBranchName'], 'master' ) }}:
value: ''
${{ if ne( variables['Build.SourceBranchName'], 'master' ) }}:
value: -${{ variables['Build.SourceBranchName'] }}
However, after moving the exact same variables in to a variable template, the value of counter is the literal value specified in the template.
Digging further in to the documentation for templates, I found some words on template expression functions, together with an example of how to use a functon -
You can use general functions in your templates. You can also use a few template expression functions.
Given that counter is listed on the page that the link above refers to, I assumed I would be able to use it. However, no matter what I've tried, I can't get it to work. Here are a few examples -
${{ counter('${{ format('{0}.{1}-{2}', variables['major'], variables['minor'], variables['Build.SourceBranchName']) }}', 1) }}
${{ counter(format('{0}.{1}-{2}', variables['major'], variables['minor'], variables['Build.SourceBranchName']), 1) }}
$[counter('${{ format('{0}.{1}-{2}', variables['major'], variables['minor'], variables['Build.SourceBranchName']) }}', 1)]
What am I doing wrong?
Update
My variable template is as above, an here is how I use it in the pipeline -
pr: none
trigger: none
variables:
- template: ../Variables/variables--code--build-and-deploy-function-app.yml
name: ${{ variables.major }}.${{ variables.minor }}.${{ variables.patch }}${{ variables.branch }}
The expanded pipeline obtained from logs after a run is as follows -
pr:
enabled: false
trigger:
enabled: false
variables:
- name: major
value: 1
- name: minor
value: 0
- name: patch
value: $[counter(format('{0}.{1}-{2}', variables['major'], variables['minor'], variables['Build.SourceBranchName']), 1)]
- name: branch
value: -CS-805
name: 1.0.$[counter(format('{0}.{1}-{2}', variables['major'], variables['minor'], variables['Build.SourceBranchName']), 1)]-CS-805
As can be seen from the extended pipeline, the patch variable isn't being evaluated, resulting in the name containing the literal value -

Answer 1

I inserted the same variables into the template and the patch variable works as expected. It seems that your counter is correct.
Here are my sample, you could refer to it:
Template Yaml: build.yml
variables:
- name: major
value: '1'
- name: minor
value: '0'
- name: patch
value: $[counter(format('{0}.{1}-{2}', variables['major'], variables['minor'], variables['Build.SourceBranchName']), 1)]
Azure-Pipelines.yml
name: $(patch)
trigger:
- none
variables:
- template: build.yml
pool:
vmImage: 'windows-latest'
steps:
- script: echo $(patch)
displayName: 'Run a one-line script'
In order to make the result more intuitive, I set patch variable to build name.
Here is the result:
Update:
Test with $(varname) and it could work as expected.
trigger:
- none
variables:
- template: build.yml
name: $(major).$(minor)-$(patch)$(branch)
Result:
The $(varname) means runtime before a task executes.