How to pass complex DevOps pipeline template parameter to script

Question

In an Azure DevOps pipeline template, I am declaring a parameter as an array/sequence

parameters:
  mySubscription: ''
  myArray: []

steps:
- AzureCLI@2
  inputs:
    azureSubscription: ${{ parameters.mySubscription }}
    scriptType: pscore
    scriptPath: $(Build.SourcesDirectory)/script.ps1
    arguments: '-MyYAMLArgument ${{ parameters.myArray }}'

Value for the parameter is then passed from pipeline definition as

steps:
- template: myTemplate.yml
  parameters:
    mySubscription: 'azure-connection'
    myArray:
    - field1: 'a'
      field2: 'b'
    - field1: 'aa'
      field2: 'bb'

My problem is I can't pass that array as-is in YAML syntax (kind of ToString()) to be able to consume and treat that array from PowerShell in my template. When trying to run this pipeline, I get the following error: /myTemplate.yml (Line: X, Col: X): Unable to convert from Array to String. Value: Array. The line/column referenced in the error message correspond to arguments: '-MyYAMLArgument ${{ parameters.myArray }}' from my template.

I also tried to map the parameter as an environment for my script

- AzureCLI@2
  inputs:
    azureSubscription: ${{ parameters.mySubscription }}
    scriptType: pscore
    scriptPath: $(Build.SourcesDirectory)/script.ps1
    arguments: '-MyYAMLArgument $Env:MY_ENV_VAR'
  env:
    MY_ENV_VAR: ${{ parameters.myArray }}

This does not work too: /myTemplate.yml (Line: X, Col: Y): A sequence was not expected. That time line/column refers to MY_ENV_VAR: ${{ parameters.myArray }}.

Does anyone ever faced a similar requirement to pass complex types (here an array/sequence of object) defined from the pipeline definition to a PowerShell script? If so, how did you achieve it?

Answer 1

You can now convert these types of parameters to String using the convertToJson function in an ADO pipeline:

parameters:
  - name: myParameter
    type: object
    default:
        name1: value1
        name2: value2

...

- task: Bash@3
  inputs:
    targetType: inline
    script: |
      echo "${{ convertToJson(parameters.myParameter) }}"

# or in Python:
- task: PythonScript@0
  inputs:
    scriptSource: inline
    script: |
      import json
      d = json.loads('''${{ convertToJson(parameters.myParameter) }}''')
      print(f"##vso[task.setvariable variable=MY_VAR]{d.get('name2')}")

ref: https://developercommunity.visualstudio.com/t/allow-type-casting-or-expression-function-from-yam/880210

convertToJson: https://learn.microsoft.com/en-us/azure/devops/pipelines/process/expressions?view=azure-devops#converttojson