Access output from looped stages in devops pipelines

Question

Baiscally I have the following workflow:

• For each configured item, run a stage which does stuff, and outputs a string into a variable

• After all prioir stages have elapsed, send a notification to teams/slack whatever with all collected variables.

Or as vastly simplified pipeline in part as pseudocode:

stages:
  - ${{ each stage in parameters.branchInfo }}:
  - stage: ${{stage.name}}
      displayName: Do stuff for ${{ stage.name }}
      dependsOn: []
      jobs:
        - job: foo
          displayName: Perform Foo
          steps:
            - checkout: ${{ stage.name }}
              displayName: Clone ${{ stage.name }}
              fetchDepth: 0
              lfs: true
              persistCredentials: true
              clean: true            
          
            - task: PythonScript@0
              inputs:
                scriptSource: 'filePath'
                scriptPath: './doo_foo.py'
 - stage: report
     displayName: Report success
      # TODO: something like this?  dependsOn: ${{ each stage in parameters.fooList }}
      jobs:
      - job: 
        displayName: Perform Branching
        steps:
          - task: Bash@3
            displayName: 'Notify someone'
            inputs:
              targetType: 'inline'
              script: |
                # pseudocode
                ${{ each stage in parameters.fooList }} 
                  echo $[ stageDependencies.{stage.name}.foo.outputs['{stage.name}.myVar'] ]
                {{ endfor }}
                             

where doo_foo.py, does this:

print(f'##vso[task.setvariable variable=myVar]myFancyValue')

How can this be done?

Answer 1

You can use variables from previous stages, but you cannot use variables from looped stages in devops pipelines.

TODO: something like this? dependsOn: ${{ each stage in parameters.fooList }}

In Azure DevOps, the dependsOn keyword doesn’t support looping through a list of parameters.

The most nearby way is to use object type parameters like below:

parameters:
  - name: fooList
    type: object
    default:
      - stage1
      - stage2
    values:
      - stage1
      - stage2
      - stage3 

stages:
- stage: stage1
  ...

- stage: stage2
  dependsOn: []
  ...

- stage: stage3
  dependsOn: []
  ...

- stage: report
  dependsOn: ${{ parameters.fooList }}

However, to map variables from previous stage, you need to define the variable with isOutput=true, and map the variable in with detail stage name, cannot use parameter stage name.

- stage: one
  jobs:
  - job: A
    steps:
    - task: Bash@3
      inputs:
          filePath: 'script-a.sh'
      name: setvar
    - bash: |
       echo "##vso[task.setvariable variable=skipsubsequent;isOutput=true]true"
      name: skipstep

- stage: two
  jobs:
  - job: B
    variables:
      - name: skipMe
        value: $[ stageDependencies.one.A.outputs['skipstep.skipsubsequent'] ]

You can check the doc Use outputs in a different stage for the details.

Hence, you have to define the stage explicitly in last report stage if you want to get all variable output in previous stages:

- stage: report
  dependsOn: # define the stage name explicitly
  - stage1
  - stage2
  jobs:
  - job: job3
    variables:
    - name: skipMe
      value: $[ stageDependencies.stage1.job1.outputs['skipstep.skipsubsequent'] ]
    - name: newtestvar
      value: $[ stageDependencies.stage2.job2.outputs['setvar.testvar'] ]
    steps:
      - bash: |
          echo $(skipMe)
          echo $(newtestvar)

PS: if you prefer to use python script to define the variable, use format with isOutput=true: print(f'##vso[task.setvariable variable=myVar;isOutput=true]myFancyValue')