Extend a job's dependsOn in a template - azure-devops

Question

I'm creating a template in which I pass a job list. In this template, I add a "pre" job to the job list, and then add all jobs. I'd like to be able to add a dependency on the "pre" job to all jobs in the job list, without breaking any dependencies between the jobs in the joblist parameter. My template looks something like this:
parameters:
- name: Jobs
type: jobList
jobs:
- job: prejob
steps:
- powershell: |
Write-Host "This is my prejob"
- ${{ each job in parameters.Jobs }}:
- ${{ each pair in job }}:
${{ if and(ne(pair.key, 'steps'),ne(pair.key, 'dependsOn')) }}:
${{ pair.key }}: ${{ pair.value }}
dependsOn: 'prejob'
steps:
- ${{ job.steps }}
now this of course overwrites the dependsOn of the jobs passed.
What can I change in the template so I can join the passed job dependencies with the prejob job? The join expression joins 2 arrays, but my prejob text is not an array, and I'm not sure the dependsOn property of a job is always an array.

Answer 1

Please try this:
parameters:
- name: Jobs
type: jobList
jobs:
- job: prejob
steps:
- powershell: |
Write-Host "This is my prejob"
- ${{ each job in parameters.Jobs }}:
- ${{ each pair in job }}:
${{ if and(ne(pair.key, 'steps'),ne(pair.key, 'dependsOn')) }}:
${{ pair.key }}: ${{ pair.value }}
dependsOn:
- 'prejob'
- ${{ if job.dependsOn }}:
- ${{ job.dependsOn }}
steps:
- ${{ job.steps }}
In that way you should be able to make dependency to prejob and keep dependencies from jobs.