Cannot convert value "System.String" to type "System.Boolean"

Question

I am trying to put a variable inside a parameter in the pipeline yml for the Azure DevOps. I am trying to do it like so:

variables:
  myArg: true

- template: my-custom-template.yml@myrep
  parameters:
    myArg: $[ eq(variables.argVal, 'true') ]

But I am getting the error:

$[ eq(variables.argVal, 'true') ]

Cannot process argument transformation on parameter | 'myArg'. Cannot convert value "System.String" to type | "System.Boolean". Boolean parameters accept only Boolean values and | numbers, such as $True, $False, 1 or 0.

Instead of the $[ eq(variables.argVal, 'true') ] I tried the ${{ eq(variables.argVal, 'true') }} and the $( eq(variables.argVal, 'true') ). All gave the same error.

So, could someone help me to understand what is the correct way to convert a variable to a boolean parameter in Azure DevOps pipeline yml, please?

Answer 1

You can't use parameters with runtime expressions ($[]). Parameters are resolved at template compilation time, before runtime expressions can be evaluated. You should use compilation expressions, ${{}}