Azure Pipelines: Passing Variables Between Stages

In my last post I wrote about Azure Pipelines: Passing Variables Between Jobs, and in this let's see how we can pass variables between stages in Azure Pipelines.

Let's say we need to pass a variable from StageA to StageB.

trigger:
- main
 
pool:
  vmImage: ubuntu-latest
 
stages:
- stage: StageA
  displayName: Stage A
  variables:
    someVariable: ''
  jobs:  
  - job: JobA
    displayName: Job A
    steps:    
    # Create output variable and set value
    - script: |
        echo "##vso[task.setvariable variable=stageAVariable;isOutput=true]someValue"
      name: outputVariable
      displayName: Output Variable
 
- stage: StageB
  displayName: Stage B
  variables:
    # Map the output variable from Stage A into Stage B
    stageBVariable: $[ stageDependencies.StageA.JobA.outputs['outputVariable.stageAVariable'] ]
  jobs:  
  - job: JobB
    displayName: Job B
    steps:
    # stageBVariable has the value set in JobA
    - script: |
        echo $(stageBVariable)
      name: printUpdatedVariable
      displayName: Print Updated Variable

Note how StageA.JobA.outputVariable is outputting the variable using isOutput=true. And then StageB is getting it mapped via stageDependencies. 

When we have multiple stages in a pipeline, by default, they run sequentially in the order in which they are defined in the YAML file. So in the above use case where we have 2 stages, we don't explicitly need to use dependsOn. 

Now let's add another Step: StageC.

trigger:
- main
 
pool:
  vmImage: ubuntu-latest
 
stages:
- stage: StageA
  displayName: Stage A
  variables:
    someVariable: ''
  jobs:  
  - job: JobA
    displayName: Job A
    steps:
    # Create output variable      
    - script: |
        echo "##vso[task.setvariable variable=stageAVariable;isOutput=true]someValue"
      name: outputVariable
      displayName: Output Variable
 
- stage: StageB
  displayName: Stage B
  variables:
    # Map the output variable from Stage A into Stage B
    stageBVariable: $[ stageDependencies.StageA.JobA.outputs['outputVariable.stageAVariable'] ]
  jobs:  
  - job: JobB
    displayName: Job B
    steps:
    # stageBVariable has the value set in JobA
    - script: |
        echo $(stageBVariable)
      name: printUpdatedVariable
      displayName: Print Updated Variable
 
- stage: StageC
  displayName: Stage C
  # Need to explictely depend on Stage A
  dependsOn: 
  - StageA
  - StageB
  variables:
    # Map the output variable from Stage A into Stage C
    stageCVariable: $[ stageDependencies.StageA.JobA.outputs['outputVariable.stageAVariable'] ]
  jobs:  
  - job: JobC
    displayName: Job C
    steps:
    # stageCVariable has the value set in JobA
    - script: |
        echo $(stageCVariable)
      name: printUpdatedVariable
      displayName: Print Updated Variable

Here especially for StageC, we need to explicitly depend on StageA. You might skip it thinking they run sequentially meaning StageA -> StageB -> StageC, so technically StageC is depending on StageA.  But unfortunately depending just on the previous stage is not enough. You need to explicitly declare the dependency on the stage from which you are mapping the variable from.

Hope this helps.

Happy Coding.

Regards,

Jaliya