how to run a conditional step in Azure devOps?

I'm building my pipelines in the Microsoft devOps forge. I would like to make the test pipeline to export the coverage as an artifact. I run my pipeline on a matrix of python version. I would like to run the exportation only for Python 3.8. How can I specify that a step is conditional ?

Here is my test.yaml file:

trigger:
  branches:
    include:
      - main

pool:
  vmImage: windows-latest
strategy:
  matrix:
    Python37:
      python.version: "3.7"
    Python38:
      python.version: "3.8"
    Python39:
      python.version: "3.9"
    Python310:
      python.version: "3.10"
    Python311:
      python.version: "3.11"

steps:
  - task: UsePythonVersion@0
    inputs:
      versionSpec: "$(python.version)"
    displayName: "Use Python $(python.version)"
  - script: python -m pip install nox
    displayName: "Install dependencies"
  - script: nox -s test
    displayName: "Test with pytest"
  - task: PublishBuildArtifacts@1 # this one should be executed only for Python 3.8
    displayName: "Publish coverage"
    inputs:
      pathToPublish: "./htmlcov/"
      artifactName: "coverage"

To accomplish this would recommend leveraging an ADO expression to load the task only if the variable version is 3.8. This is different then a condition as the condition will always load the task and skip it if the condition is not met.

- ${{ if eq(variable.python.version, '3.8')}} :     
  - task: PublishBuildArtifacts@1 
    displayName: "Publish coverage"
    inputs:
       pathToPublish: "./htmlcov/"
       artifactName: "coverage"

Here is a blog post going into the details between the two.

The equivalent of the GitHub action "if" statement is "condition". it can be placed to add execution conditions on jobs, tasks or stages.

in this example to publish the artefact only for version 3.8 use the condition with the following statement:

- task: PublishBuildArtifacts@1 
    condition: eq(variable["python.version"], "3.8")
    displayName: "Publish coverage"
    inputs:
      pathToPublish: "./htmlcov/"
      artifactName: "coverage"

more information can be found in Azure condition documentation.

Be aware that the variable is called using the $[]syntax to be interpreted at run-time. more information about variable syntax can be found here