Azure DevOps Pipeline variables format usage

Question

I am having an issue with the variables in Azure DevOps pipelines. I can not effectively use them in an if statement or as a placeholder in a value argument.

This is a related question but the answer does not work for me.

I have defined a variable like this in the top level pipeline .yml file.

variables:
- name: artifact_source
  readonly: true
  value: 'ecu'

- name: artifact_getter
  readonly: true
  value: 'get_artifacts_ecu.yaml'

And in a lower level template file i want to use them like this:

    # Get binaries
    - template: $(artifact_getter)
      parameters:
        variant: ${{ parameters.variant }}

Gives me this error: File /.azuredevops/template/$(artifact_getter) not found in repository.

or

jobs:
  - job: ${{ parameters.variant }}
    pool: ${{ parameters.pool }}
    steps:

    # Clean checkout
    - checkout: self
      clean: true

    # Get binaries
    - ${{ if eq( $(artifact_source), 'ecu') }}:
      - template: get_artifacts_ecu.yml
        parameters:
          variant: ${{ parameters.variant }}

This gives an error: Unrecognized value: '$'. Located at position 5 within expression: eq( $(artifact_source), 'ecu'). For more help, refer to https://go.microsoft.com/fwlink/?linkid=842996

I am wondering about what format i should use to get the value of the variable here. I see different forms how to reference variables:

${{ variables.artifact_source }}
$[variables.var]
$env:artifact_source
$(artifact_source)  # only one working for variables

Also documented here. But i can only get $(name) to work, but not in my case.

How can i use variables to switch to a different template?

Answer 1

In the Expressions document, it mentions as part of an expression, you may access variables using one of two syntaxes:

• Index syntax: variables['MyVar']
• Property dereference syntax: variables.MyVar

So, you can use eq(variables['artifact_source'], 'ecu') or eq(variables.artifact_source, 'ecu') here.

# Get binaries
- ${{ if eq(variables['artifact_source'], 'ecu') }}:
  - template: get_artifacts_ecu.yml
    parameters:
      variant: ${{ parameters.variant }}

or

# Get binaries
- ${{ if eq(variables.artifact_source, 'ecu') }}:
  - template: get_artifacts_ecu.yml
    parameters:
      variant: ${{ parameters.variant }}