YAML Parser error on Azure DevOps Pipeline

Question

I'm getting the following error on my azure devop pipeline, it seems to relate towards parameters loop but despite writing the script multiple different ways I can't seem to get rid of it. YAML validators and my YAML linter don't detect an issue.

/azure-pipelines.yml (Line: 1, Col: 12): Unexpected value ''

Below is my code, it uses a template as well, which I will include beneath it.

azure-pipelines.yml

parameters:
steps:
- ${{ each project in parameters.projects }}:
  - task: UsePythonVersion@0
    displayName: 'Setting python version to 3.7'
    inputs:
      versionSpec: '3.7'
      architecture: 'x64'

  - script: |
      pushd '$(System.DefaultWorkingDirectory)/${{ project }}'
      pip install -r requirements.txt
    displayName: 'Install prerequisites'

  - task: ArchiveFiles@2
    displayName: 'Archive files'
    inputs:
      rootFolderOrFile: '$(System.DefaultWorkingDirectory)/${{ project }}'
      includeRootFolder: false
      archiveFile: '$(System.DefaultWorkingDirectory)/${{ project }}.zip'

  - task: PublishBuildArtifacts@1
    inputs:
      PathtoPublish: '$(System.DefaultWorkingDirectory)/${{ project }}.zip'
      artifactName: 'drop'

  - task: AzureResourceManagerTemplateDeployment@3
    displayName: 'ARM Template deployment: Resource Group scope'
    
    inputs:
      azureResourceManagerConnection: $(serviceConnectionName)
      subscriptionId: $(subscriptionId)
      resourceGroupName: $(resourceGroupName)
      location: $(resourceGroupLocation)
      csmFile: 'deployment_template.json'
      overrideParameters: '-appName ${{ project }} -storageAcctName $(storageAcctName)  -hostingPlanName $(hostingPlanName)'

  - task: AzureFunctionApp@1
    inputs:
      azureSubscription: $(serviceConnectionName)
      appType: functionAppLinux
      appName: ${{ project }}
      package: '$(System.DefaultWorkingDirectory)/${{ project }}.zip'

Template - deploy-functions.yml

trigger:
  - main

variables:
  - group: 'AzFunctionsAppVariableGroup'
    
pool:
  vmImage: ubuntu-18.04
  
steps:
- template: azure-pipelines.yml
  parameters:
    projects:
    - ProjectName1

Answer 1

If I throw your azure-pipelines.yml into the pipeline editor in Azure DevOps, it marks the line ending of parameters: with the warning

"Incorrect type. Expected "array"."

I didn't work with templates on pipelines so far, but from the MS doc page , it seems that you need to specify the parameters that you are passing like so:

#azure-pipelines.yml

parameters:
- name: projects
  type: object #object, since you are passing a list of strings
steps:
- ${{ each project in parameters.projects }}:
#...

Answer 2

It's suggested that you could enable the feature of YAML template editor with picture below and process the test.