Partial override of object type parameter with default values

In ADO, I want to partially override object type parameter using templates.

For example:

main.yml

parameters:
   - name: person 
     type: object 
     default:
        first_name: "Jane"
        last_name: "Doe"
        role: "Student"

- template: templates/template.yml 
  parameters:
      person: ${{parameters.person}}

template.yml

parameters:
   - name: person
     type: object

Here, I want to send object parameter, person, only with role: "Teacher" like this, and in template.yml, person object's first_name is "Jane" and last_name is "Doe", but role will be "Teacher". Is this possible?

project.yml

extends: 
   template: template/main/main.yml
   parameters: 
      person:
         role: "Teacher"

I tried the code above, but in template-yml, it could not parse first_name or last_name.

You cannot partially override an object parameter in the pipelines via passing part of the elements directly.

As a workaround, you can replace the role with your target value when pass the parameter to your template.

The main.yml:

trigger: none

pool:
  vmImage: ubuntu-latest

parameters:
- name: person
  type: object
  default:
    first_name: "Jane"
    last_name: "Doe"
    role: "Student"

steps:
- script: |
    echo "${PERSON}"
  env:
    PERSON: ${{ convertToJson(parameters.person) }}

- template: templates/template.yml
  parameters:
    person_update:
      ${{each pair in parameters.person}}:
        ${{if and( eq(pair.key, 'role'), eq(pair.value, 'student' )) }}:
          ${{pair.key}}: 'Teacher'
        ${{else}}:
          ${{pair.key}}: ${{pair.value}}

The template.yml:

parameters:
- name: person_update
  type: object
  default: {}

steps:
- script: |
    echo "${PERSON}"
  env:
    PERSON: ${{ convertToJson(parameters.person_update) }}

Result: