Checking for null object type parameter in Azure YAML

Question

I'm setting up a build template and can't figure out the syntax for an optional object type parameter. In my pipeline I'm calling the template like this:

stages:
- template: aspnet-core.yml@templates
  parameters:
    database:
      name: 'SomeDatabase'
      server: 'SomeServer'

I have the parameter defined like this in the template:

parameters:
  database: null

I want to do a check like this in the template so I can run a task conditionally:

- ${{ if ne('${{ parameters.database }}', null) }}:

However, it's not liking the keyword null in the if statement, and I don't know how to represent the fact that it wasn't passed in. What are my options here?

Answer 1

I've found another solution to that, you can work with the length of the incoming object. If the object is empty, it's length is 0

parameters:
  - name: myObject
    type: object
    default: []
  
steps:
  - ${{ if not(eq(length(parameters.myObject), 0)) }}:
      - script: |
          echo "hello world"
        displayName: "next task"

Answer 2

You can use below expression to check if a parameter is empty. For below example

- ${{if parameters.database}}:

Below is my testing template and azure-pipeline.yml.

the script task will only get executed when database is evaluated to true. I tested and found database: "" and database: will be evalutated to false. If it is defined as database: {}, it will be evaluated to true.

Template: deploy-jobs.yaml

parameters:
  database: {}

stages:
- stage: buildstage
  pool: Hosted VS2017

  jobs:
  - job: secure_buildjob
    steps:
    - ${{if parameters.database}}:
      - script: echo "will run if database is not empty"
        displayName: 'Base: Pre-build'

azure-pipeline.yml:

stages:
- template: deploy-jobs.yaml
  parameters:
    database: ""

To execute some tasks if database is empty you can use below statement:

 steps:
    - ${{if not(parameters.database)}}:
      - script: echo "will run if database is empty"
        displayName: 'Base: Pre-build'