Azure Pipelines YAML: Unexpected value 'variables' - azure

Question

I'm using Azure Pipelines as a part of Azure DevOps.
I'm trying to define variables in my template file, because I need to use the same value multiple times.
This is my stage-template.yml:
parameters:
- name: param1
type: string
- name: param2
type: string
variables:
var1: path/${{ parameters.param2 }}/to-my-file.yml
stages:
- stage: Deploy${{ parameters.param2 }}
displayName: Deploy ${{ parameters.param1 }}
jobs:
...
When trying to use this pipeline, I get an error message:
/stage-template.yml (Line: 7, Col: 1): Unexpected value 'variables'
Why is this not working? What did I do wrong?

Answer 1

You can't have variables in a template that is included as a stage, job or step template (i.e. included below a stages, jobs or steps element in a pipeline). You can only use variables in a variable template.
The documentation sadly is not really clear about that.
Including a stage template
# pipeline-using-stage-template.yml
stages:
- stage: stage1
[...]
# stage template reference, no 'variables' element allowed in stage-template.yml
- template: stage-template.yml
Including a variable template
# pipeline-using-var-template.yml
variables:
# variable template reference, only variables allowed inside the template
- template: variables.yml
steps:
- script: echo A step.
If you are using a template to include variables in a pipeline, the included template can only be used to define variables.
https://learn.microsoft.com/en-us/azure/devops/pipelines/process/templates?view=azure-devops#variable-reuse

Answer 2

you cant have parameters in the pipeline, only in the templateReferences:
name: string # build numbering format
resources:
pipelines: [ pipelineResource ]
containers: [ containerResource ]
repositories: [ repositoryResource ]
variables: # several syntaxes, see specific section
trigger: trigger
pr: pr
stages: [ stage | templateReference ]
if you want to use variables in templates you have to use proper syntax:
parameters:
- name: param1
type: string
- name: param2
type: string
stages:
- stage: Deploy${{ parameters.param2 }}
displayName: Deploy ${{ parameters.param1 }}
variables:
var1: path/${{ parameters.param2 }}/to-my-file.yml
jobs:
...

Answer 3

This works for me:
In your parent yaml:
stages:
- stage: stage1
displayName: 'stage from parent'
jobs:
- template: template1.yml
parameters:
param1: 'somevalueforparam1'
inside template1:
parameters:
param1: ''
param2: ''
jobs:
- job: job1
workspace:
clean: all
displayName: 'Install job'
pool:
name: 'yourpool'
variables:
- name: var1
value: 'value1'